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An inclination towards renewable energy resources has been increased due to the requirement of clean environment and to satisfy the increasing power demand for the long run. A grid connected system requires the availability of a transformer in its power conversion stages that provides galvanic isolation between the grid and the power system. But inclusion of transformer results in making the system bulky and more expensive. In this paper different transformer-less PV inverter topologies are analyzed by comparing their efficiency, leakage current and THD of load current using MATLAB/Simulink environment. In order to achieve maximum power, maximum power point tracking (P&O algorithm) is used. From the simulation results, modified HB-ZVR is found to have minimum leakage current and constant common mode voltage with higher efficiency. Also, the hardware results are obtained for modified HB-ZVR topology.
Control Method for Unified Power Quality Conditioner Using Fuzzy Based Nine-S...IJERA Editor
A nine-switch power converter having two sets of out-put terminals was recently proposed in place of the
traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already
been proven to have certain advantages, in addition to its component saving topological feature. Despite these
advantages, the nine-switch converter has so far found limited applications due to its many perceived
performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained
phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nineswitch
power conditioner is proposed here that virtually “converts” most of these topological short comings into
interesting performance advantages. Aiming further to reduce its switching losses, an appropriate discontinuous
modulation scheme is proposed and studied here in detail to doubly ensure that maxi-mal reduction of
commutations is achieved. With an appropriately designed control scheme then incorporated, the nine-switch
converter is shown to favorably raise the overall power quality in experiment, hence justifying its role as a
power conditioner at a reduced semiconductor cost.
A Novel Control Method for Unified Power Quality Conditioner Using Nine-Switc...IJERA Editor
A nine-switch power converter having two sets of out-put terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually “converts” most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maxi-mal reduction of commutations is achieved. With an appropriately designed control scheme then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in experiment, hence justifying its role as a power conditioner at a reduced semiconductor cost.
Lclr filter design and modelling for harmonic mitigation in interconnected mi...eSAT Journals
Abstract Today many people are attracted towards distribution generation (DG) because of low energy cost power supply, local generation, highly reliable system, supply with good power quality. Increasing attention and investment in renewable energy that is DG energy sources give rise to rapid development of high penetration renewable energy sources like solar energy, wind energy, hydro energy. Out of this most important and best is the solar energy. There are multiple ways to interface PV arrays with the power grid, but in there is problem of power quality. Today’s important concern of the power system is the power quality in case of renewable energy sources. The power quality improvement in the interconnected micro grid systems and grid interconnection with Distribution Generation (DGs) is the challenging task and to overcome the power quality problem passive filters are the best and cost effective solution. In this paper the LCLR filter is implemented between inverter and grid. The complete system consists of photovoltaic cell (PV), DC-DC boost converter, DC-AC inverter, LCLR filter and the grid. This paper also consists of complete MATLAB simulation of PV cell, DC-DC boost converter and inverter with LCLR filter. Key Words: Renewable energy, PV module, DC-DC boost converter, DGs, LCLR filter, power quality, micro grid (MG) and THD
Voltage Regulation with Hybrid RES based Distributed Generation in the for Ac...IJMTST Journal
In this paper adaptive zone-based Volt/VAR management is proposed, which coordinates active
participation of DGs with conventional voltage regulation equipment. To achieve a flexible and scalable
solution while minimizing complexity and requirements for data-handling capability, DG management
systems are integrated with decentralized parts of the Volt/VAR management system in smaller
geographical zones. Coordination of DGs with conventional voltage regulation equipment is based on
predefined control hierarchies. However, to reduce requirements for data handling capability, the distribution
grid is divided into zones with individual voltage regulation and reactive support schemes. To add flexibility
and scalability, these zones can be combined into larger zones with a common Volt/VAR management
scheme. This is referred to as adaptive zoning. The results indicate that the control schemes successfully
restore voltage to within limits after disturbance of grid conditions. Adaptive zoning effectively reduces
system complexity and requirements for data handling capability, while still ensuring a grid-wide solution.
The proposed concept is implemented to hybrid RES method the simulation results are presented by using
Matlab/Simulink platform.
Hybrid energy storage system control analogous to power quality enhancement o...IJECEIAES
Increasing nonlinear loads and power electronic converters lead to various power quality issues in microgrids (MGs). The interlinking converters (ILCs) can participate in these systems to harmonic control and power quality enhancement. However, ILC participation deteriorates the dc link voltage, system stability, and storage lifetime due to oscillatory current phenomena. To address these problems, a new control strategy for a hybrid energy storage system (HESS) is proposed to eliminate the adverse effects of the harmonic control operation of ILC. Specifically, battery and super-capacitor (SC) are used as HESSs that provide low and high power frequency load, respectively. The proposed strategy tries to compensate the current oscillation imposed by ILC with fuzzy control of HESS. In this method, a proportional-resonant (PR) controller integrated with harmonic compensator (HC) is employed to control the ILC for power quality enhancement and oscillatory current elimination. The main advantages of the proposed strategy are to reduce DGs power fluctuations, precise DC bus voltage regulation for generation and load disturbances, improved grid power quality under nonlinear load and transition conditions. The performance of the proposed method for isolated and grid-connected modes is verified using simulation studies in the MATLAB software environment.
This paper displays a Fly Back Converter idea to straightforwardly incorporate cascaded flyback converter. The flyback-converter finds a way between DC-source and DC Motor-load. This work covenants with the modeling, simulation, and application of a Fuzzy Logic controlled (FLC) - Cascaded Fly back Converter (CFLB) system. This work recommends FLC to control Parallel cascaded fly-back converter to fabricate essential DC voltage from the input supply voltage. The yield of CFLB is controlled utilizing closed loop configuration. Closed loop PI & Fuzzy logic controlled CFLB systems are simulated and their results are related. The outcomes signify that the FLC based system gave a superior response than the P.I. controlled CFLB system. The FLC controlled CFLB system has benefits like decreased steady state error and enhanced time domain-response.
An inclination towards renewable energy resources has been increased due to the requirement of clean environment and to satisfy the increasing power demand for the long run. A grid connected system requires the availability of a transformer in its power conversion stages that provides galvanic isolation between the grid and the power system. But inclusion of transformer results in making the system bulky and more expensive. In this paper different transformer-less PV inverter topologies are analyzed by comparing their efficiency, leakage current and THD of load current using MATLAB/Simulink environment. In order to achieve maximum power, maximum power point tracking (P&O algorithm) is used. From the simulation results, modified HB-ZVR is found to have minimum leakage current and constant common mode voltage with higher efficiency. Also, the hardware results are obtained for modified HB-ZVR topology.
Control Method for Unified Power Quality Conditioner Using Fuzzy Based Nine-S...IJERA Editor
A nine-switch power converter having two sets of out-put terminals was recently proposed in place of the
traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already
been proven to have certain advantages, in addition to its component saving topological feature. Despite these
advantages, the nine-switch converter has so far found limited applications due to its many perceived
performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained
phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nineswitch
power conditioner is proposed here that virtually “converts” most of these topological short comings into
interesting performance advantages. Aiming further to reduce its switching losses, an appropriate discontinuous
modulation scheme is proposed and studied here in detail to doubly ensure that maxi-mal reduction of
commutations is achieved. With an appropriately designed control scheme then incorporated, the nine-switch
converter is shown to favorably raise the overall power quality in experiment, hence justifying its role as a
power conditioner at a reduced semiconductor cost.
A Novel Control Method for Unified Power Quality Conditioner Using Nine-Switc...IJERA Editor
A nine-switch power converter having two sets of out-put terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually “converts” most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maxi-mal reduction of commutations is achieved. With an appropriately designed control scheme then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in experiment, hence justifying its role as a power conditioner at a reduced semiconductor cost.
Lclr filter design and modelling for harmonic mitigation in interconnected mi...eSAT Journals
Abstract Today many people are attracted towards distribution generation (DG) because of low energy cost power supply, local generation, highly reliable system, supply with good power quality. Increasing attention and investment in renewable energy that is DG energy sources give rise to rapid development of high penetration renewable energy sources like solar energy, wind energy, hydro energy. Out of this most important and best is the solar energy. There are multiple ways to interface PV arrays with the power grid, but in there is problem of power quality. Today’s important concern of the power system is the power quality in case of renewable energy sources. The power quality improvement in the interconnected micro grid systems and grid interconnection with Distribution Generation (DGs) is the challenging task and to overcome the power quality problem passive filters are the best and cost effective solution. In this paper the LCLR filter is implemented between inverter and grid. The complete system consists of photovoltaic cell (PV), DC-DC boost converter, DC-AC inverter, LCLR filter and the grid. This paper also consists of complete MATLAB simulation of PV cell, DC-DC boost converter and inverter with LCLR filter. Key Words: Renewable energy, PV module, DC-DC boost converter, DGs, LCLR filter, power quality, micro grid (MG) and THD
Voltage Regulation with Hybrid RES based Distributed Generation in the for Ac...IJMTST Journal
In this paper adaptive zone-based Volt/VAR management is proposed, which coordinates active
participation of DGs with conventional voltage regulation equipment. To achieve a flexible and scalable
solution while minimizing complexity and requirements for data-handling capability, DG management
systems are integrated with decentralized parts of the Volt/VAR management system in smaller
geographical zones. Coordination of DGs with conventional voltage regulation equipment is based on
predefined control hierarchies. However, to reduce requirements for data handling capability, the distribution
grid is divided into zones with individual voltage regulation and reactive support schemes. To add flexibility
and scalability, these zones can be combined into larger zones with a common Volt/VAR management
scheme. This is referred to as adaptive zoning. The results indicate that the control schemes successfully
restore voltage to within limits after disturbance of grid conditions. Adaptive zoning effectively reduces
system complexity and requirements for data handling capability, while still ensuring a grid-wide solution.
The proposed concept is implemented to hybrid RES method the simulation results are presented by using
Matlab/Simulink platform.
Hybrid energy storage system control analogous to power quality enhancement o...IJECEIAES
Increasing nonlinear loads and power electronic converters lead to various power quality issues in microgrids (MGs). The interlinking converters (ILCs) can participate in these systems to harmonic control and power quality enhancement. However, ILC participation deteriorates the dc link voltage, system stability, and storage lifetime due to oscillatory current phenomena. To address these problems, a new control strategy for a hybrid energy storage system (HESS) is proposed to eliminate the adverse effects of the harmonic control operation of ILC. Specifically, battery and super-capacitor (SC) are used as HESSs that provide low and high power frequency load, respectively. The proposed strategy tries to compensate the current oscillation imposed by ILC with fuzzy control of HESS. In this method, a proportional-resonant (PR) controller integrated with harmonic compensator (HC) is employed to control the ILC for power quality enhancement and oscillatory current elimination. The main advantages of the proposed strategy are to reduce DGs power fluctuations, precise DC bus voltage regulation for generation and load disturbances, improved grid power quality under nonlinear load and transition conditions. The performance of the proposed method for isolated and grid-connected modes is verified using simulation studies in the MATLAB software environment.
This paper displays a Fly Back Converter idea to straightforwardly incorporate cascaded flyback converter. The flyback-converter finds a way between DC-source and DC Motor-load. This work covenants with the modeling, simulation, and application of a Fuzzy Logic controlled (FLC) - Cascaded Fly back Converter (CFLB) system. This work recommends FLC to control Parallel cascaded fly-back converter to fabricate essential DC voltage from the input supply voltage. The yield of CFLB is controlled utilizing closed loop configuration. Closed loop PI & Fuzzy logic controlled CFLB systems are simulated and their results are related. The outcomes signify that the FLC based system gave a superior response than the P.I. controlled CFLB system. The FLC controlled CFLB system has benefits like decreased steady state error and enhanced time domain-response.
This paper presents a droop control technique for equal power sharing in islanded microgrid. In this study, the proposed controller is based on the frequency droop method, is applied to a robust droop controller in parallel connected inverters. The previous robust droop controller deals with voltage droop method. A modification has been formed against this controller by adding a fuzzy logic controller with the frequency droop method. The only sharing error which is concentrated in this paper is the error in sharing the rated frequency among the inverters. By adapting fuzzy in the robust droop, it tries to eliminate the frequency error, hence that the frequency reference of the inverters keeps maintain at 50Hz. A derivation of generalized models of a single-phase parallel-connected inverter system is shown. The simulation results show that the proposed controller with FLC is able to improve the stability of frequency reference and the performance of power sharing between the inverters under the inductive line impedance.
Mitigation of Power Quality Issues by Nine Switches UPQC Using PI & ANN with ...IJERA Editor
A nine-switch power converter having two sets of output terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually ―converts‖ most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, Harmonics, Voltage Sag & Swell an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maximal reduction of commutations is achieved. With an appropriately designed control scheme with PI and ANN with Hysteresis controller then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in Simulation, hence justifying its role as a power conditioner at a reduced cost.
Mitigation of Power Quality Issues by Nine Switches UPQC Using PI & ANN with ...MABUSUBANI SHAIK
Abstract—A nine-switch power converter having two sets of output terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually “converts” most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, Harmonics, Voltage Sag & Swell an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maximal reduction of commutations is achieved. With an appropriately designed control scheme with PI and ANN with Hysteresis controller then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in Simulation, hence justifying its role as a power conditioner at a reduced cost.
Index Terms—Discontinuous pulse-width modulation, nine switch converter, power conditioner, power quality.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Comparison of PI and ANN Control Techniques for Nine Switches UPQC to Improve...MABUSUBANI SHAIK
Abstract: This paper presents a comprehensive review on the UPQC to reinforce power quality. Typically this can be often speculated to gift a broad outline on the varied possible intelligent controls used with UPQC. The most purpose of a UPQC is to control on voltage flicker/unbalance, reactive power and harmonics. In different words, the UPQC has the potential of up power quality at the purpose of installation on power industrial power systems. The appliance of computing is growing quick within the
space of power electronics and drives. From olden days to now days we are using twelve switches used in back to back configuration. But now we are using nine switches instead of 12 switches. In 9 switch UPQC converters given the most useful benefits compared to 12 switches power converter. The nine switches UPQC converter gets the best results by using of two methods. They are one is PI controller technique and other one is ANN controller technique. By contrast PI and ANN, ANN is better than PI for power quality enhancement and voltage sag and voltage swell mitigations. The factitious neural network
(ANN) is taken into account as a replacement tool to style management electronic equipment for power-quality (PQ) devices. A whole simulation study is administrated to analysis the performance of the ANN controller and compares its performance with the quality PI controller results. The nine-switch convertor has already been proved to possess sure benefits, additionally to its part saving topological feature. Despite these benefits, the nine-switch convertor has thus far found restricted applications because of its several perceived performance tradeoffs like requiring associate degree outsized dc-link capacitance, restricted amplitude sharing, and unnatural part shift between its 2 sets of output terminals. Rather than acceptive these tradeoffs as limitations, a nine-switch power conditioner is projected here that nearly ―converts‖ most of those topological short comings into
fascinating performance benefits. Aiming more to cut back its switch losses, Harmonics, Voltage Sag & Swell associate degree acceptable discontinuous modulation theme is projected and studied here thoroughly to doubly make sure that top reduction of commutations is achieved. With associate degree suitably designed management theme with PI and ANN with physical
phenomenon controller then incorporated, the nine-switch convertor is shown to favorably raise the general power quality in Simulation, thus justifying its role as an influence conditioner at a reduced value.
Keywords: ANN, Active Power Filters, PI Controller, Nine Switch Converter, Power Quality, UPQC.
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Various Resonant Converters for high voltage and high power applications have been designed. Different Topologies of LLC, LCC, and CLL Resonant Converters have been simulated and compared for the same input voltage. The simulation was done at a very high frequency. The Output Power and the Efficiency of all the three Resonant Converters were calculated.With the results, it has been proved that LCC Resonant Converters were very much suited to give an output voltage of around 62 Kilovolts with a output power of 20 kilowatts.
Design and implementation of a series switching SPSI for PV cell to use in ca...journalBEEI
A carrier-based grid synchronous method is proposed to develop the system efficiency, phase and power quality of the inverter output waves. The operating principle of a single-phase phase synchronous inverter (SPSI) is introduced, with proper synchronous paid to the switching-frequency synchronizing voltage made by the interleaved process, as well as actual mitigation approaches. In the construction of the SPSI, input and output filters are electrically coupled with the two sides of an inverter. The inverter power electronic switches and other electrical components are operated by carrier-based grid synchronous controller (CBGSC) with PWM regulator. The SPSI is designed and implemented with the Toshiba 40WR21 IGBT, Digital Microcontroller pulse controller (DMPC) and 4N35 Optocoupler with a fundamental frequency of 50Hz. The other parameters are considered as load resistance, =11Ω, duty cycle, 85%, carrier frequency, 2.5kHz and input DC voltage, ± 340V. In addition, LCL lowpass grid filters are used to convert squire wave to sine wave with required phase and frequency. Finally, the simulated and experimental results obtained with a carrier-based grid synchronous SPSI experimental prototype are exposed for justification, showing the phase error of 55% improvement, reduced 11% of THD and the conversion efficiency of 97.02% highly predicted by the proposed design technique to improve the microgrid system.
Battery energy storage systems are becoming more and more popular solution in the household applications, especially, in combination with renewable energy sources. The bidirectional AC-DC power electronic converter have great impact to the overall efficiency, size, mass and reliability of the storage system. This paper reviews the literature that deals with high efficiency converter technologies for connecting low voltage battery energy storage to an AC distribution grid. Due to low voltage of the battery isolated bidirectional AC-DC converter or a dedicated topology of the non isolated converter is required. Review on single stage, two stage power converters and integrated solutions are done in the paper.
New Hybrid Structure Based on Improved Switched Inductor Z-Source and Paralle...IJPEDS-IAES
Nowadays, more and more distributed generations and renewable energy
sources, such as wind, solar and tidal power, are connected to the public grid
by the means of power inverters. They often form microgrids before being
connected to the public grid. Due to the availability of high current power
electronic devices, it is inevitable to use several inverters in parallel for highpower
and/or low-cost applications. So, inverters should beconnected in
parallel to provide system redundancy and high reliability, which are
important for critical customers. In this paper, the modeling, designing and
stability analysis of parallel-connected three-phaseinverters are derived for
application in renewable energy systems. To enlarge voltage adjustability,
the proposed inverter employs an improved switched inductor Z-source
impedance network to couple the main circuit and the power source.
Compared with the classical Z-source inverter (ZSI) and switched inductor
Z-source inverter (SL-ZSI), the proposed inverter significantly increases the
voltage boost inversion ability and also can increase the power capacity and
the reliability of inverter systems. The proposed topology and its
performances are validated using simulation results which are obtained in
Matlab/Simulink.
An electric vehicle (EV) can be charged wirelessly through an inductively coupled power transfer system where the system resonates the inductive coupling coil at the operating frequency by means of a compensation network. However, the resonant behaviour implies overcurrent in the inverter MOSFETs during uncoupled and high load resistor conditions, which affect to the inverter MOSFETs failure whenever the current exceeds their maximum current rating. Therefore, this paper presents a CLL/S detuned compensation network for EV wireless charging application to limit the inverter current during the uncoupled state and open circuit load conditions. The proposed compensation consists of a series capacitor and parallel inductor at the primary side and series capacitor at the secondary side. By using Kirchhoff Voltage Law (KVL) analysis, the primary side is detuned to inductive behaviour to ensure zero voltage switching (ZVS), and the secondary side remains at natural resonant tuning. From the simulation analysis, the slight increase of the parallel inductor value at the primary side can limit of the inverter current at uncoupled and high load resistor conditions. The proposed system also offers higher efficiency than the series-series detuned compensation and slightly lower than the double-sided LCC compensation network at different coupling factor.
LOAD FREQUENCY CONTROL IN TWO AREA NETWORK INCLUDING DGIAEME Publication
Automatic Generation Control (AGC) is associate integral a part of Energy Management
System. This paper deals with the automatic generation control of interconnected multi area grid
network. The first purpose of the AGC is to balance the full system generation against system load
and losses so the specified frequency and power interchange with neighboring systems are
maintained. Any pair between generation and demand causes the system frequency to deviate from
regular worth. So high frequency deviation could result in system collapse. This necessitates
associate correct and quick acting controller to take care of constant nominal frequency. The
limitations of the conventional controls are slow and lack of efficiency in handling system nonlinearity.
This leads to develop a control technique for AGC. In this paper both conventional and
PI viz. Proportional Integral controller approach of automatic generation control has been
examined. PI based AGC has been used for all optimization purposes. System performance has
been evaluated at various disturbances such as, load disturbances, grid disturbances and both load
and grid disturbances. Various responses due to conventional and proposed PI based AGC
controllers have been compared at load disturbances, grid disturbances and both load and grid
disturbances.
The long established battery chargers are having many drawbacks such as prominent ripple charging current, less efficiency and bulky in size. To overcome these drawbacks of conventional battery charger, several charging circuits have been proposed and inevitability force to design a high-performance battery charger with small in size and improved efficiency. In this paper solar photovoltaic system based half-bridge series–parallel resonant converter (HBSPRC) charger is proposed for battery interface. The converter is designed to abolish low and high-frequency ripple currents and thus take full advantage of the life of secondary battery circuit. This is achieved by designing converter switches turn on at zero current and zero voltage with switching frequency greater than that of resonance frequency which leads to freewheeling diodes need not have very fast reverse-recovery characteristics. The performance of the power converters depends upon the control method adopted; in this work fuzzy logic controller is used for controlling the output voltage of HBSPRC. The fuzzy control scheme for the HBSPR converter has been designed and validated in hardware implementation of HBSPRC switching technique. From the results, it is found that the proposed battery charging system which reduces the switching loss and voltage stress across the power switches which increases the efficiency of the converter.
To eliminate the adverse effect from parameter variations as well as distorted grid conditions, a current control scheme of an LCL-filtered grid-connected inverter using a discrete integral sliding mode control (ISMC) and resonant compensation is presented. The proposed scheme is constructed based on the cascaded multiloop structure, in which three control loops are composed of grid-side current control, capacitor voltage control, and inverter-side current control. An active damping to suppress the resonance caused by LCL filter can be effectively realized by means of the inverter-side feedback control loop. Furthermore, the seamless transfer operation between the grid-connected mode and islanded mode is achieved by the capacitor voltage control loop. To retain a high tracking performance and robustness of the ISMC as well as an excellent harmonic compensation capability of the resonant control (RC) scheme at the same time, two control methods are combined in the proposed current controller. As a result, the proposed scheme yields a high quality of the injected grid currents and fast dynamic response even under distorted grid conditions. Furthermore, to reduce the number of sensors, a discrete-time reduced-order state observer is introduced. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.
Analysis of Six Active Power Control Strategies of Interconnected Grids with ...Power System Operation
In this paper, the generator angle stability of several active power control schemes of a
voltage-source converter (VSC)-based high-voltage DC (HVDC) is evaluated for two interconnected
AC systems. Excluding frequency control, there has been no detailed analysis of interconnected grids
depending upon the converter power control, so six different types of active power control of the
VSC-HVDC are defined and analyzed in this paper. For each TSO (transmission system operator),
the applicable schemes of two kinds of step control and four kinds of ramp-rate control with a droop
characteristic are included in this research. Furthermore, in order to effectively evaluate the angle
stability, the Generators-VSC Interaction Factor (GVIF) index is newly implemented to distinguish
the participating generators (PGs) group which reacts to the converter power change. As a result,
the transient stabilities of the two power systems are evaluated and the suitable active power control
strategies are determined for two TSOs. Simulation studies are performed using the PSS®E program
to analyze the power system transient stability and various active power control schemes of the
VSC-HVDC. The results provide useful information indicating that the ramp-rate control shows a
more stable characteristic than the step-control for interconnected grids; thus, a converter having a
certain ramp-rate slope similar to that of the other generator shows more stable results in several cases.
Enhanced dynamic performance of grid feeding distributed generation under va...IJECEIAES
Controlling weak grid-connected systems is very challenging. In transient, frequency and voltage oscillations may lead to voltage and/or frequency stability problems and finally lead to system collapse. During steady-state operation and at the point of common coupling (PCC), voltage degradation and grid voltage background harmonics restrict the inverter's functionality, reduce the power flow capability and cause poor power quality. With weak grid connection, grid impedance variance will contaminate the voltage waveform by harmonics and augment the resonance, destabilizing the inverter operation. In this paper, complete mathematical modeling is carried out and state feedback-plus-integral control is implemented to support the stabilization of the system. The proposed controller is adopted to provide a smooth transient under sudden load change by controlling the injected grid current under different grid inductance values. Furthermore, the proposed control is used to reduce the order and size of the inverter output filter while maintaining system stability. The proposed control has been compared with the conventional proportional integral (PI) controller under different scenarios to validate its effectiveness and to strengthen its implementation as a simple controller for distributed generator applications.
This paper presents a droop control technique for equal power sharing in islanded microgrid. In this study, the proposed controller is based on the frequency droop method, is applied to a robust droop controller in parallel connected inverters. The previous robust droop controller deals with voltage droop method. A modification has been formed against this controller by adding a fuzzy logic controller with the frequency droop method. The only sharing error which is concentrated in this paper is the error in sharing the rated frequency among the inverters. By adapting fuzzy in the robust droop, it tries to eliminate the frequency error, hence that the frequency reference of the inverters keeps maintain at 50Hz. A derivation of generalized models of a single-phase parallel-connected inverter system is shown. The simulation results show that the proposed controller with FLC is able to improve the stability of frequency reference and the performance of power sharing between the inverters under the inductive line impedance.
Mitigation of Power Quality Issues by Nine Switches UPQC Using PI & ANN with ...IJERA Editor
A nine-switch power converter having two sets of output terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually ―converts‖ most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, Harmonics, Voltage Sag & Swell an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maximal reduction of commutations is achieved. With an appropriately designed control scheme with PI and ANN with Hysteresis controller then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in Simulation, hence justifying its role as a power conditioner at a reduced cost.
Mitigation of Power Quality Issues by Nine Switches UPQC Using PI & ANN with ...MABUSUBANI SHAIK
Abstract—A nine-switch power converter having two sets of output terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually “converts” most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, Harmonics, Voltage Sag & Swell an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maximal reduction of commutations is achieved. With an appropriately designed control scheme with PI and ANN with Hysteresis controller then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in Simulation, hence justifying its role as a power conditioner at a reduced cost.
Index Terms—Discontinuous pulse-width modulation, nine switch converter, power conditioner, power quality.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Comparison of PI and ANN Control Techniques for Nine Switches UPQC to Improve...MABUSUBANI SHAIK
Abstract: This paper presents a comprehensive review on the UPQC to reinforce power quality. Typically this can be often speculated to gift a broad outline on the varied possible intelligent controls used with UPQC. The most purpose of a UPQC is to control on voltage flicker/unbalance, reactive power and harmonics. In different words, the UPQC has the potential of up power quality at the purpose of installation on power industrial power systems. The appliance of computing is growing quick within the
space of power electronics and drives. From olden days to now days we are using twelve switches used in back to back configuration. But now we are using nine switches instead of 12 switches. In 9 switch UPQC converters given the most useful benefits compared to 12 switches power converter. The nine switches UPQC converter gets the best results by using of two methods. They are one is PI controller technique and other one is ANN controller technique. By contrast PI and ANN, ANN is better than PI for power quality enhancement and voltage sag and voltage swell mitigations. The factitious neural network
(ANN) is taken into account as a replacement tool to style management electronic equipment for power-quality (PQ) devices. A whole simulation study is administrated to analysis the performance of the ANN controller and compares its performance with the quality PI controller results. The nine-switch convertor has already been proved to possess sure benefits, additionally to its part saving topological feature. Despite these benefits, the nine-switch convertor has thus far found restricted applications because of its several perceived performance tradeoffs like requiring associate degree outsized dc-link capacitance, restricted amplitude sharing, and unnatural part shift between its 2 sets of output terminals. Rather than acceptive these tradeoffs as limitations, a nine-switch power conditioner is projected here that nearly ―converts‖ most of those topological short comings into
fascinating performance benefits. Aiming more to cut back its switch losses, Harmonics, Voltage Sag & Swell associate degree acceptable discontinuous modulation theme is projected and studied here thoroughly to doubly make sure that top reduction of commutations is achieved. With associate degree suitably designed management theme with PI and ANN with physical
phenomenon controller then incorporated, the nine-switch convertor is shown to favorably raise the general power quality in Simulation, thus justifying its role as an influence conditioner at a reduced value.
Keywords: ANN, Active Power Filters, PI Controller, Nine Switch Converter, Power Quality, UPQC.
International Journal of Engineering Research and DevelopmentIJERD Editor
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Various Resonant Converters for high voltage and high power applications have been designed. Different Topologies of LLC, LCC, and CLL Resonant Converters have been simulated and compared for the same input voltage. The simulation was done at a very high frequency. The Output Power and the Efficiency of all the three Resonant Converters were calculated.With the results, it has been proved that LCC Resonant Converters were very much suited to give an output voltage of around 62 Kilovolts with a output power of 20 kilowatts.
Design and implementation of a series switching SPSI for PV cell to use in ca...journalBEEI
A carrier-based grid synchronous method is proposed to develop the system efficiency, phase and power quality of the inverter output waves. The operating principle of a single-phase phase synchronous inverter (SPSI) is introduced, with proper synchronous paid to the switching-frequency synchronizing voltage made by the interleaved process, as well as actual mitigation approaches. In the construction of the SPSI, input and output filters are electrically coupled with the two sides of an inverter. The inverter power electronic switches and other electrical components are operated by carrier-based grid synchronous controller (CBGSC) with PWM regulator. The SPSI is designed and implemented with the Toshiba 40WR21 IGBT, Digital Microcontroller pulse controller (DMPC) and 4N35 Optocoupler with a fundamental frequency of 50Hz. The other parameters are considered as load resistance, =11Ω, duty cycle, 85%, carrier frequency, 2.5kHz and input DC voltage, ± 340V. In addition, LCL lowpass grid filters are used to convert squire wave to sine wave with required phase and frequency. Finally, the simulated and experimental results obtained with a carrier-based grid synchronous SPSI experimental prototype are exposed for justification, showing the phase error of 55% improvement, reduced 11% of THD and the conversion efficiency of 97.02% highly predicted by the proposed design technique to improve the microgrid system.
Battery energy storage systems are becoming more and more popular solution in the household applications, especially, in combination with renewable energy sources. The bidirectional AC-DC power electronic converter have great impact to the overall efficiency, size, mass and reliability of the storage system. This paper reviews the literature that deals with high efficiency converter technologies for connecting low voltage battery energy storage to an AC distribution grid. Due to low voltage of the battery isolated bidirectional AC-DC converter or a dedicated topology of the non isolated converter is required. Review on single stage, two stage power converters and integrated solutions are done in the paper.
New Hybrid Structure Based on Improved Switched Inductor Z-Source and Paralle...IJPEDS-IAES
Nowadays, more and more distributed generations and renewable energy
sources, such as wind, solar and tidal power, are connected to the public grid
by the means of power inverters. They often form microgrids before being
connected to the public grid. Due to the availability of high current power
electronic devices, it is inevitable to use several inverters in parallel for highpower
and/or low-cost applications. So, inverters should beconnected in
parallel to provide system redundancy and high reliability, which are
important for critical customers. In this paper, the modeling, designing and
stability analysis of parallel-connected three-phaseinverters are derived for
application in renewable energy systems. To enlarge voltage adjustability,
the proposed inverter employs an improved switched inductor Z-source
impedance network to couple the main circuit and the power source.
Compared with the classical Z-source inverter (ZSI) and switched inductor
Z-source inverter (SL-ZSI), the proposed inverter significantly increases the
voltage boost inversion ability and also can increase the power capacity and
the reliability of inverter systems. The proposed topology and its
performances are validated using simulation results which are obtained in
Matlab/Simulink.
An electric vehicle (EV) can be charged wirelessly through an inductively coupled power transfer system where the system resonates the inductive coupling coil at the operating frequency by means of a compensation network. However, the resonant behaviour implies overcurrent in the inverter MOSFETs during uncoupled and high load resistor conditions, which affect to the inverter MOSFETs failure whenever the current exceeds their maximum current rating. Therefore, this paper presents a CLL/S detuned compensation network for EV wireless charging application to limit the inverter current during the uncoupled state and open circuit load conditions. The proposed compensation consists of a series capacitor and parallel inductor at the primary side and series capacitor at the secondary side. By using Kirchhoff Voltage Law (KVL) analysis, the primary side is detuned to inductive behaviour to ensure zero voltage switching (ZVS), and the secondary side remains at natural resonant tuning. From the simulation analysis, the slight increase of the parallel inductor value at the primary side can limit of the inverter current at uncoupled and high load resistor conditions. The proposed system also offers higher efficiency than the series-series detuned compensation and slightly lower than the double-sided LCC compensation network at different coupling factor.
LOAD FREQUENCY CONTROL IN TWO AREA NETWORK INCLUDING DGIAEME Publication
Automatic Generation Control (AGC) is associate integral a part of Energy Management
System. This paper deals with the automatic generation control of interconnected multi area grid
network. The first purpose of the AGC is to balance the full system generation against system load
and losses so the specified frequency and power interchange with neighboring systems are
maintained. Any pair between generation and demand causes the system frequency to deviate from
regular worth. So high frequency deviation could result in system collapse. This necessitates
associate correct and quick acting controller to take care of constant nominal frequency. The
limitations of the conventional controls are slow and lack of efficiency in handling system nonlinearity.
This leads to develop a control technique for AGC. In this paper both conventional and
PI viz. Proportional Integral controller approach of automatic generation control has been
examined. PI based AGC has been used for all optimization purposes. System performance has
been evaluated at various disturbances such as, load disturbances, grid disturbances and both load
and grid disturbances. Various responses due to conventional and proposed PI based AGC
controllers have been compared at load disturbances, grid disturbances and both load and grid
disturbances.
The long established battery chargers are having many drawbacks such as prominent ripple charging current, less efficiency and bulky in size. To overcome these drawbacks of conventional battery charger, several charging circuits have been proposed and inevitability force to design a high-performance battery charger with small in size and improved efficiency. In this paper solar photovoltaic system based half-bridge series–parallel resonant converter (HBSPRC) charger is proposed for battery interface. The converter is designed to abolish low and high-frequency ripple currents and thus take full advantage of the life of secondary battery circuit. This is achieved by designing converter switches turn on at zero current and zero voltage with switching frequency greater than that of resonance frequency which leads to freewheeling diodes need not have very fast reverse-recovery characteristics. The performance of the power converters depends upon the control method adopted; in this work fuzzy logic controller is used for controlling the output voltage of HBSPRC. The fuzzy control scheme for the HBSPR converter has been designed and validated in hardware implementation of HBSPRC switching technique. From the results, it is found that the proposed battery charging system which reduces the switching loss and voltage stress across the power switches which increases the efficiency of the converter.
To eliminate the adverse effect from parameter variations as well as distorted grid conditions, a current control scheme of an LCL-filtered grid-connected inverter using a discrete integral sliding mode control (ISMC) and resonant compensation is presented. The proposed scheme is constructed based on the cascaded multiloop structure, in which three control loops are composed of grid-side current control, capacitor voltage control, and inverter-side current control. An active damping to suppress the resonance caused by LCL filter can be effectively realized by means of the inverter-side feedback control loop. Furthermore, the seamless transfer operation between the grid-connected mode and islanded mode is achieved by the capacitor voltage control loop. To retain a high tracking performance and robustness of the ISMC as well as an excellent harmonic compensation capability of the resonant control (RC) scheme at the same time, two control methods are combined in the proposed current controller. As a result, the proposed scheme yields a high quality of the injected grid currents and fast dynamic response even under distorted grid conditions. Furthermore, to reduce the number of sensors, a discrete-time reduced-order state observer is introduced. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.
Analysis of Six Active Power Control Strategies of Interconnected Grids with ...Power System Operation
In this paper, the generator angle stability of several active power control schemes of a
voltage-source converter (VSC)-based high-voltage DC (HVDC) is evaluated for two interconnected
AC systems. Excluding frequency control, there has been no detailed analysis of interconnected grids
depending upon the converter power control, so six different types of active power control of the
VSC-HVDC are defined and analyzed in this paper. For each TSO (transmission system operator),
the applicable schemes of two kinds of step control and four kinds of ramp-rate control with a droop
characteristic are included in this research. Furthermore, in order to effectively evaluate the angle
stability, the Generators-VSC Interaction Factor (GVIF) index is newly implemented to distinguish
the participating generators (PGs) group which reacts to the converter power change. As a result,
the transient stabilities of the two power systems are evaluated and the suitable active power control
strategies are determined for two TSOs. Simulation studies are performed using the PSS®E program
to analyze the power system transient stability and various active power control schemes of the
VSC-HVDC. The results provide useful information indicating that the ramp-rate control shows a
more stable characteristic than the step-control for interconnected grids; thus, a converter having a
certain ramp-rate slope similar to that of the other generator shows more stable results in several cases.
Enhanced dynamic performance of grid feeding distributed generation under va...IJECEIAES
Controlling weak grid-connected systems is very challenging. In transient, frequency and voltage oscillations may lead to voltage and/or frequency stability problems and finally lead to system collapse. During steady-state operation and at the point of common coupling (PCC), voltage degradation and grid voltage background harmonics restrict the inverter's functionality, reduce the power flow capability and cause poor power quality. With weak grid connection, grid impedance variance will contaminate the voltage waveform by harmonics and augment the resonance, destabilizing the inverter operation. In this paper, complete mathematical modeling is carried out and state feedback-plus-integral control is implemented to support the stabilization of the system. The proposed controller is adopted to provide a smooth transient under sudden load change by controlling the injected grid current under different grid inductance values. Furthermore, the proposed control is used to reduce the order and size of the inverter output filter while maintaining system stability. The proposed control has been compared with the conventional proportional integral (PI) controller under different scenarios to validate its effectiveness and to strengthen its implementation as a simple controller for distributed generator applications.
Control strategies for seamless transfer between the grid-connected and isla...IJECEIAES
Design of control strategies for Distributed generation systems is very important to achieve smoother transition between the grid connected and islanding modes of operation. The transition between these two modes of operation should be seamless, without any severe transients during the changeover. In this paper, two different control strategies namely inverter output current control and indirect grid current control for the seamless transfer between the modes of operation has been explored for the suitability. The design and analysis of the cascaded control loops based on Proportional Integral (PI) controller has been dealt in detail for both inverter output current control and indirect grid current control strategy. Control parameters are designed using the control system toolbox in MATLAB. A 10kW grid connected microgrid system has been designed and simulated in MATLAB/Simulink and the results are presented under grid connected operation, islanding operation and the transition between the modes considering fault condition in the grid side. The simulation studies are carried out using both the control strategies and the results are presented to validate the design methodology.
A Novel Control Method for Unified Power Quality Conditioner Using Nine-Switc...IJERA Editor
A nine-switch power converter having two sets of out-put terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually “converts” most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maxi-mal reduction of commutations is achieved. With an appropriately designed control scheme then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in experiment, hence justifying its role as a power conditioner at a reduced semiconductor cost.
An Adaptive Virtual Impedance Based Droop Control Scheme for Parallel Inverte...IAES-IJPEDS
This paper presents an adaptive virtual impedance based droop control
scheme for parallel inverter operation in low voltage microgrid. Because it is
essential to achieve power sharing between inverters in microgrid, various
droop control schemes have been proposed. In practice, the line impedance
between inverters and the point of common coupling (PCC) in microgrid are
not always equal. This imbalance in line impedance often results in a reactive
power mismatch among inverters. This problem has been solved by
introducing a virtual impedance loop in the conventional droop control
scheme. However, the reactive power sharing performance of this method is
still deteriorated when the line impedances change during operation. To
overcome such a problem, a new control scheme that is based on a virtual
impedance loop and an impedance estimation scheme is proposed.
To monitor the changes in line impedances, the impedance estimator is
implemented by using the output voltages and currents of inverters as well as
the voltages at the PCC. To compensate for the reactive power mismatch due
to the line impedance changes, the estimated line impedance is fed to the
virtual impedance loop in which it adjusts the virtual impedance value.
Comparative simulation results with the conventional ones verify the
effectiveness of the proposed adaptive virtual impedance based droop control
scheme.
This paper presents a thorough control structure of the distributed generators inside the microgrid during both grid-connected and islanded operation modes. These control structures of the DGs voltage source inverters are implemented in synchronous reference frame (SRF) and controlled using linear PI controllers. By implementing the control structures, the desired real and reactive power can be efficiently transferred to the local loads and the utility load by the microgrid generating units. A modified droop control technique is introduced to facilitate the microgrid performance during both modes of operation. The active and reactive power sharing of the load demand between the utility grid and the microgrid can be performed by this drop control technique during the islanded mode. The system performance during intentional islanding event and utility load increase is investigated. The effectiveness of the offered control structures is confirmed through simulation results during both modes of operation.
Line and Grid Impedance Impact on the Performances of a Parallel Connected Mo...IAES-IJPEDS
With the rising fuel cost, increasing demand of power and the concerns for global climate change, the use of clean energy make the connection of power electronics building bloc in the heart of the current research. The high output current applications make the parallel connection of modular inverters to be a solution for the use of low power building block inverters where the output power cannot be handled by a single inverter configuration. In this context, average-modeling using average phase–leg technique allows the n-parallel connected inverters to be analyzed accurately and rapidly without requiring the complexity of the full switched inverter topology. The obtained analytical solution along with the equivalent circuit model makes easier the design of the control loop. The analytical solution of the n-parallel connected inverters shows the impact of the line and grid impedance on the performance of the overall system. The impact of this coupling has to be investigated such that the main feature of paralleling inverters is guaranteed and that the inverter mode of operation will not be compromised. The main advantage of paralleling inverters can be lost for a certain coupling impedance considerations.
Power quality is a concern for utility and grid operators due to a large penetration of intermittent and stochastic renewable power generation sources. One of the major concerns, when designing and controlling grid-feeding photovoltaic (PV) inverters is meeting the grid requirements. International grid requirements demand low-voltage ride-through (LVRT) capability and maintaining grid functionality during fault conditions. This paper presents a comprehensive review for several control techniques to assure the LVRT capability of grid-feeding converters as well as discussing their respective advantages and limitations in detail. Areas for further research are identified afterwards. Finally, the conclusion gives a brief summary and critique of the findings.
Improved Virtual Synchronous Generator Control to Analyse and Enhance the Tra...Kashif Mehmood
In recent years, the integration of renewable energy resource (RES) into the power system is growing rapidly, and
it is necessary to analyse and evaluate the effect of RES on transient stability of the power system. In this paper, centre of
inertia (COI) concept is implemented to analyse and evaluate the integration effects of an auxiliary damping control (ADC) based
virtual synchronous generator (VSG) consisting an improved governor. The impact of VSG integration is divided into synchronous
generator (SG) linked parts and COI associated parts. Due to VSG integration into the power system, the significant elements
which disturb the COI dynamic motion and rotor dynamics of SG are examined in detail. Different cases are considered to evaluate
the effectiveness of the proposed method, i.e., VSG’s different integrating location and different power capacities. It is observed
in simulation results that COI dynamic motion and rotor dynamics of SG are positively affected by VSG integration and transient
stability improves significantly
This paper deals with controlling a grid-connected dual-active bridge multilevel inverter for renewable energy integration. The concept of direct power control is integrated with model predictive control algorithm, which is termed as predictive direct power control, to control the real and reactive power injected into the power grid. The proposed multilevel inverter allows more options of feasible voltage vectors for switching vector selections in order to generate multilevel outputs, and thereby obtaining high power quality in the power grid. By using the predictive direct power control, simulation results show that the proposed multilevel inverter produces lower power ripple and manage to achieve currents with low total harmonic distortion which are well within the IEEE standard. The modeling and simulation of the system are implemented and validated by MATLAB Simulink software.
A NOVEL CONTROL STRATEGY FOR POWER QUALITY IMPROVEMENT USING ANN TECHNIQUE FO...IJERD Editor
The proposed system presents power-control strategies of a Micro grid-connected hybrid generation
system with versatile power transfer. This hybrid system allows maximum utilization of freely available
renewable energy sources like wind and photovoltaic energies. For this, an adaptive MPPT algorithm along with
standard perturbs and observes method will be used for the system.
The inverter converts the DC output from non-conventional energy into useful AC power for the
connected load. This hybrid system operates under normal conditions which include normal room temperature
in the case of solar energy and normal wind speed at plain area in the case of wind energy. However, designing
an optimal micro grid is not an easy task, due to the fact that primary energy carriers are changeable and
uncontrollable, as is the demand. Traditional design and optimization tools, developed for controlled power
sources, cannot be employed here. Simulation methods seem to be the best solution.
The dynamic model of the proposed system is first elaborated in the stationary reference frame and
then transformed into the synchronous orthogonal reference frame. The transformed variables are used in
control of the voltage source converter as the heart of the interfacing system between DG resources and utility
grid. By setting an appropriate compensation current references from the sensed load currents in control circuit
loop of DG, the active, reactive, and harmonic load current components will be compensated with fast dynamic
response, thereby achieving sinusoidal grid currents in phase with load voltages, while required power of the
load is more than the maximum injected power of the DG to the grid. In addition, the proposed control method
of this paper does not need a phase-locked loop in control circuit and has fast dynamic response in providing
active and reactive power components of the grid-connected loads.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Improving Distribution Feeders for Photovoltaic Generation by Loop Power Cont...IJMER
Now a day’s solar power plants are more reliable, because no fuel and reduced CO2 emission. But the solar power generation system do not work in all weather conditions, it is power generated only solar radiation time .To overcome this problem by using (pv)). In fuel cell power generation there will be no problems, where as in fuel cell power distribution systems have some problems like overloading the distribution feeders. In this project to overcome this overloading by using Loop Power Controller (LPC).The loop power controller to control real power and reactive power flow by adjusting voltage ratio and phase shift. Daily loading unbalance is determined by analyzing (pv) power generation recording by using SCADA system and load profile based on Data Automation System (DAS).The loop power controller can improve controllability, operational flexibility and reduce power loss of the distribution system. The Loop Power Controller (LPC) is based on the MATLAB/ SIMULINK.
Power Quality Improvement at Distribution Level for Grid Connected Renewable ...IJERA Editor
The non-linear load current harmonics may result in voltage harmonics and can create a serious PQ problem in
the power system network. Active power filters (APF) are extensively used to compensate the load current
harmonics and load unbalance at distribution level. This results in an additional hardware cost. However, in this
project it has incorporated the features of APF in the conventional inverter interfacing renewable with the grid,
without any additional hardware cost. Here, the main idea is the maximum utilization of inverter rating which is
most of the time underutilized due to intermittent nature of RES. The grid-interfacing inverter can effectively be
utilized to perform the four important functions they are to transfer active power harvested from the renewable
resources (wind, solar, etc.), load reactive power demand support, current harmonics compensation at PCC and
current unbalance and neutral current compensation in case of 3-phase 4-wire system. Moreover, with adequate
control of grid-interfacing inverter, all the four objectives can be accomplished either individually or
simultaneously. The PQ constraints at the PCC can therefore be strictly maintained within the utility standards
without additional hardware cost.
With such a control, the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear
unbalanced load at point of common coupling appears as balanced linear load to the grid. This new control
concept is demonstrated with extensive MATLAB/Simulink simulation studies
The use of distributed generation (DG) within distribution systems has increased for the last two decades due to worldwide increase in demand for electricity and governmental policy change from “conventional” energy to “green” energy. High levels of penetration of DG have many significant benefits but also come with many drawbacks such as voltage drop and power losses. This study presents the impact of DG at different locations in a distribution feeder in terms of the feeder voltage profile. A radial distribution system is simulated using PSCAD/EMTDC simulation software while changing the size and location of DG in the system. The obtained results are used for better understanding on the impact of DG on voltage profile in radial distribution feeder.
اگر نیاز به دریافت گواهی ایزو برای دارالترجمه هستید و یا می خواهید برای شرکت خود گواهی اصلی ایزو را با توجه به حوزه کاری خود دریافت کنید ما در بخش ترجمه گواهی ایزو یکسری مطالب با ارزش از نحوه آشنایی با استانداردها و اصالت گواهی ایزو را در این فایل برای شما منتشر کرده ایم پس با ما همراه باشید
ترجمه فیلم از جمله خدماتی است که به صورت متمرکز توسط دارالترجمه پارسیس تجزیه و تحلیل شده و با استفاده تلاش مترجمان انجام خواهد شد
هر کشوری یک سنت متفاوت از ترجمه فیلم ها را به طور عمده در اختیار دارد .صنعت دوبله و زیر نویس مجموعه ای به هم پیوسته از ترجمه فیلم است , زیرا هر فیلمی که ترجمه می گردد نیاز به دوبله و یا زیرنویس خواهد داشت .
تکنیک ترجمه فیلم مختص تمامی فیلم هاو کلیپ ها کوتاه و بلند است , از سریال گرفته تا مجموعه تلوزیونی , در همه این موارد تصمیم به انتخاب حالت ترجمه به هیچ وجه خود سرانه نیست و نخواهد بود .
ممکن است فیلم به دو زبان مختلف ترجمه شود که همه این موارد بستگی به فرهنگ های منبع در یک زمینه بین المللی است .
انواع ترجمه فیلم
دو نوع عمده از ترجمه فیلم وجود دارد:
1-دوبله کردن فیلم
2-زیرنویس کردن فیلم
هر کدام از آنها متن اصلی را به زبان مبدا ترجمه خواهد کرد , در ترجمه فیلم , صنعت دوبله به عنوان متدی شناخته شده است که به شدت محتوای فیلم را از نظر مخاطب تحت تاثیر قرار داده و حتی تکنیک تحرک دهانی بازیگران در این ترجمه ها باید بگونه ای باشد تا یک ترجمه دقیق و سلیس ارائه شود .
از سوی دیگر، زیرنویس، یعنی ارائه یک ترجمه از گفتار زبان مبدأ به زبان مقصد که به شکل زیرنویس های هماهنگ شده ارائه می گردد، معمولا در پایین صفحه، قالبی است که متن به متن ترجمه ها نوشته می شود , این باعث میشود مخاطب را تحت تاثیر و تجزیه , تحلیل فیلم کند .
لیست کامل دارالترجمه رسمی در تهران بروز ترین آمار مربوط به سال 1398
در این بین دارالترجمه رسمی پارسیس با کد 966 نیز درج شده است جهت کسب اطلاعات بیشتر با دارالترجمه ما تماس بگیرید
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ترجمه چینی به عنوان زبانی که در جهان بیشترین جمعیت را دارد در هر موضوعی در دارالترجمه چینی پارسیس انجام خواهد شد
آشنایی بیشتر با خدمات ترجمه چینی
کشور چین از جمله کشور های پیشرو در صنعت , نرخ جمعیتی در جهان حکم یک رهبر را ایفا میکند , چین امروزه به عنوان یک بازار تاثیر گذار برای شرکت های تجاری دولتی و شخصی به دنبال جذب مخاطبین بیشتر در سراسر جهان است .
یکی از سریع ترین راه های دستیابی موثر به بازار چین استفاده از متخصصانی است که فرهنگ و زبان چینی را درک کرده و همراه شما باشند لذا خدمات ترجمه چینی در موضوعات مختلفی قابل ارائه خواهد بود که به ترتیب آن ها را نام خواهیم برد .
ترجمه عربی، مانند دیگر زبانها نیازمند داشتن تجربه کافی و بالایی میباشد تا بتوان یک متن خوب و روان و با تاثیرگذاری بالا را ترجمه کرده و تحویل داد.
ترجمه عربی به انواع زبانها امکان پذیر است و شما قادر خواهید بود زبان عربی را به تمام زبانهای زنده دنیا ترجمه کنید و یا اینکه زبانهای دیگر را به زبان عربی بازگردانید، اما باید در نظر داشته باشید، متنی خوب و مورد قبول است که به صورت حرفهای ترجمه شده باشد و به دست مترجمان مورد اعتماد و دارای اعتبار سپرده شده باشد تا مشکلاتی نظیر نامفهوم بودن، به هم ریختگی و … در کلمات و جملات متن دیده نشود.
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ما در دارالترجمه روسی ترجمه روسی به فارسی و ترجمه فارسی به روسی را انجام میدهیم برای کسب اطلاعات بیشتر به سایت زیر مراجعه نمایید
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ترجمه آلمانی در دارالترجمه آلمانی پارسیس توسط مترجم تخصصی و رسمی و مترجم شفاهی انجام می شود , در ترجمه آلمانی خدمات ما به صورت فوری چند ساعته و چند روزه انجام خواهد شد برای کسب اطلاعات بیشتر به سایت ما مراجعه نمایید
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ترجمه رمان به عنوان یک اثر روایی از داستان نثر است که کلمه به کلمه به صورت کاملا دقیق توسط دارالترجمه پارسیس انجام میگردد
ترجمه رمان های معرف از جمله رمان دون کیشوت و یا رمان رمان آنا کارِنینا در دارالترجمه پارسیس
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ترجمه مقاله فرانسه ترجمه مقاله فرانسوی توسط دارالترجمه فرانسوی پارسیس انجام می شود , در صورتی که نیاز به ترجمه مقاله به زبان فارسی دارید کافیست از طریق سایت دارالترجمه فرانسوی پارسیس درخواست ترجمه فرانسه داده و منتظر اعلام هزینه و زمان باشید , ما با استفاده از مترجم تخصصی زبان فرانسوی در دپارتمان ترجمه فرانسه قادریم متون شما را ترجمه کنیم https://parsistrans.com
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ترجمه آنلاین به کابران این امکان را ارائه میدهند که کیفیت وسرعت تضمین شده به صورت کاملا رایگان باشد,آشنایی با 10 ابزار ترجمه آنلاین به صورت کاملا رایگان
امروزه عرصه جهانی بیشتر شبیه دهکده جهانی وب می باشد , جهان امروز درگیر ارتباطات مداوم و اجباری با اینترنت شده و لذا باید بتواند به طور موثر در زمان واقعی با یکدیگر ارتباط برقرار کنند.
با همکاری دارالترجمه رسمی پارسیس و دارالترجمه پارت
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هر کشوری یک سنت متفاوت از ترجمه فیلم ها را به طور عمده در اختیار دارد .صنعت دوبله و زیر نویس مجموعه ای به هم پیوسته از ترجمه فیلم است , زیرا هر فیلمی که ترجمه می گردد نیاز به دوبله و یا زیرنویس خواهد داشت
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استخدام کارآموز دارالترجمه با تضمین 100 درصدی استخدام دائم به همراه قرارداد یکساله در دارالترجمه رسمی پارسیس
کاراموز دارالترجمه و فرم زن نیاز مند همکاری موادم با مترجم حضوری در دارالترجمه رسمی پارسیس است , به این معنی است که فرم زن با تسلط خود قادر است متون دریافتی ترجمه شده از مترجم را در قالب فرم ترجمه رسمی انجام دهد برای کسب اطلاعات بیشتر بر روی سایت دارالترجمه رسمی پارسیس مراجعه نمایید
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ترجمه کتاب توسط دارالترجمه رسمی پارسیس توسط مترجمان تخصصی و نخبه انجام می شود
ما قادریم کتاب های شما را به هر زبانی از جمله انگلیسی , آلمانی ,ترکی , ژاپنی را ترجمه تخصصی کنید برای کسب اطلاعات بیشتر به سایت دارالترجمه رسمی ما مراجعه نمایید
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دانلود ترجمه انگلیسی به فارسی مهاجرت به اوکراین
دارالترجمه انگلیسی پارسیس یک نمونه مقاله انگلیسی را به فارسی در خصوص قانون مهاجرت به اوکراین منتشر کرده که توسط مترجم انگلیسی ترجمه شده است .
جهت دانلود کامل ترجمه انگلیسی به فارسی کلیک کنید
yon.ir/C3qIK
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ترجمه تخصصی انگلیسی در دارالترجمه تخصصی انگلیسی پارسیس توسط مترجم تخصصی انگلیسی قابل انجام است برای کسب اطلاعات بیشتر بر روی لینک زیر کلیک کنید
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The Roman Empire A Historical Colossus.pdfkaushalkr1407
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1. Modeling and design of a multivariable control system for
multi-paralleled grid-connected inverters with LCL filter
Ali Akhavan a
, Hamid Reza Mohammadi a,⇑
, Josep M. Guerrero b
a
University of Kashan, Kashan, Iran
b
Aalborg University, Aalborg, Denmark
a r t i c l e i n f o
Article history:
Received 8 March 2017
Received in revised form 14 June 2017
Accepted 21 July 2017
Keywords:
Multi-paralleled inverters
Active damping
Coupling effect
LCL filter
a b s t r a c t
The quality of injected current in multi-paralleled grid-connected inverters is a matter of concern. The
current controlled grid-connected inverters with LCL filter are widely used in the distributed generation
(DG) systems due to their fast dynamic response and better power features. However, designing a reliable
control system for grid-connected inverters with LCL filter is complicated. Firstly, overcoming to system
resonances due to LCL filters is a challenging task, intrinsically. This could become worse as number of
paralleled grid-connected inverters increased. In order to deal with resonances in the system, damping
methods such as passive or active damping is necessary. Secondly and perhaps more importantly, paral-
leled grid-connected inverters in a microgrid are coupled due to grid impedance. Generally, the coupling
effect is not taken into account when designing the control systems. In consequence, depending on the
grid impedance and the number of paralleled inverters, the inverters installed in a microgrid do not
behave as expected. In other words, with a proper control system, a single inverter is stable in grid-
connected system, but goes toward instability with parallel connection of other inverters. Therefore, con-
sideration of coupling effect in the multi-paralleled grid-connected inverters is vital. Designing control
systems for multi-paralleled grid-connected inverters becomes much more difficult when the inverters
have different characteristics such as LCL filters and rated powers. In this paper, the inverters with differ-
ent characteristics in a microgrid are modeled as a multivariable system. The comprehensive analysis is
carried out and the coupling effect is described. Also, the control system design for multi-paralleled grid-
connected inverters with LCL filter is clarified and a dual-loop active damping control with capacitor cur-
rent feedback is designed. Finally, the proposed multivariable control system for a microgrid with three-
paralleled grid-connected inverters with LCL filter is validated by simulation.
Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction
Renewable energy is harvested from nature, it is clean and free.
However, it is widely accepted that renewable energy is not a
panacea that comes without challenges. As an interface between
the distributed generation (DG) plants and the grid, the grid-
connected inverters are essential to convert all kinds of generated
power into a high quality AC power and inject it into the grid reli-
ably [1]. The inverters installed in microgrids are generally voltage
source inverters with an output filter. Nowadays, the LCL filter is
considered to be a preferred choice for attenuation of switching
frequency harmonics in the injected grid current compared with
the L filter [2,3]. Because of using smaller reactive elements, the
cost and weight of the inverter system are reduced when using
LCL filter. However, due to the resonance of the LCL filter, damping
methods are needed for the grid-connected inverters to stabilize
the system [4]. Passive and active methods for damping the reso-
nance of the LCL filter have been extensively discussed in literature
[5–8]. Active damping is preferred to passive damping due to its
high efficiency and flexibility of the conversion.
The quality of the grid injected current is very important in the
grid-connected systems. International standards regulate the con-
nection of inverters to the grid and limit the harmonic content of
the injected current. IEEE std. 1547-2003 [9] gives the limitation
of the injected grid current harmonics. If the harmonic content of
the injected current exceeds the standard limits, it is required to
disconnect the inverter from the grid. Thus, the LCL filters are
implemented to prevent the grid from being polluted with switch-
ing harmonics. Therefore, designing adequate control system for
grid-connected inverters with LCL filter is a matter of concern.
http://dx.doi.org/10.1016/j.ijepes.2017.07.016
0142-0615/Ó 2017 Elsevier Ltd. All rights reserved.
⇑ Corresponding author at: Department of Electrical and Computer Engineering,
University of Kashan, Ravand Blvd., P.O. Box, 8731753153 Kashan, Iran.
E-mail address: mohammadi@kashanu.ac.ir (H.R. Mohammadi).
Electrical Power and Energy Systems 94 (2018) 354–362
Contents lists available at ScienceDirect
Electrical Power and Energy Systems
journal homepage: www.elsevier.com/locate/ijepes
: کن ترجمه خودتhttps://freepaper.me/t/250851
2. A more difficulty is appeared when multi-paralleled grid-
connected inverters are coupled due to the grid impedance Zg. In
this condition, the inverters influence each other as a result. All
inverters in Fig. 1, share the voltage in the point of common cou-
pling (PCC) Vpcc and are able to modify this voltage by injecting
their currents [10]. It should be noted that, if the grid impedance
was ideally considered to be zero, the coupling effect would not
exist because the voltage in the PCC would always be Vg. Depend-
ing on the number of paralleled inverters and the grid impedance
Zg, the inverters installed in a microgrid might not behave as
expected. In other words, with proper control system, a single
inverter is stable in grid-connected system, but goes toward insta-
bility with parallel connection of other inverters. Therefore, consid-
eration of coupling effect in the multi-paralleled grid-connected
inverters is very important and microgrid should be modeled as
a multivariable system.
Many literatures with regard to active damping strategies are
published [11–18]. However, their analyses are done for single
grid-connected inverter. In consequence, coupling effect among
inverters due to grid impedance is not considered and the stability
and performance of the inverter in a microgrid might be ques-
tioned. In [10], authors have been modeled the N-paralleled invert-
ers in a PV power plant as a multivariable system. However, all
inverters are assumed to be the same including their hardware,
software, rated powers, LCL filters and reference injected currents.
It is widely accepted that this assumption is not valid in the real
microgrid since different sources such as photovoltaic panels, wind
turbines and fuel cells with different inverters, LCL filters and ref-
erence injected currents may be collected in a microgrid. Also, in
case of PV power plants as considered in [10], even though the
same panels and inverters are used, the reference current of each
inverter may be different due to partial shadow. In [19], a robust
control strategy for a grid-connected multi-bus microgrid contain-
ing several inverter-based DG units is proposed. However, only
compensation of positive and negative sequence current compo-
nents using Lyapunov function and sliding mode method is
discussed. In [20], a back to back (B2B) converter connection is pro-
posed to provide a reliable interface, while it can provide isolation
between utility and microgrids.
In this paper, modeling and control of three-paralleled grid-
connected inverters with different characteristics are described.
In fact, the LCL filter parameters, rated powers and also, reference
injected currents of the inverters are considered to be different.
For this task, all inverters are modeled as a multivariable system
in order to modeling the coupling effect among inverters due to
grid impedance. Also, dual-loop active damping control using the
capacitor current feedback as inner loop [5] is chosen for its simple
and effective implementation. Due to single phase application, the
proportional and resonant (PR) controllers are considered for con-
trol system.
This paper is organized as follows. In Section 2, modeling and
control of a single grid-connected inverter is described. In Section 3,
modeling and control of the three-paralleled grid-connected
inverters with different characteristics in a microgrid are analyzed.
In Section 4, controller design regarding to PR controllers for the
multivariable system that is modeled in previous section is
described. In Section 5, the theoretical study is validated through
simulation in MATLAB software. Finally, Section 6, concludes this
paper.
2. Modeling and control of a single grid-connected inverter
In this section, the modeling and control of a single grid-
connected inverter with LCL filter is described. Although, this issue
has already been addressed in available literatures [11–17], the
goal is to get the reader familiarized with the methodology used
along this paper.
A generic structure of the LCL-filtered grid-connected inverter is
shown in Fig. 2. The LCL filter consists of an inverter-side inductor
L1, a filter capacitor C, and a grid-side inductor L2. Parasitic resis-
tances are neglected in order to simplicity.
Z1 ¼ L1 Á s; Z2 ¼ L2 Á s; Z3 ¼
1
C3 Á s
; Zg ¼ Lg Á s ð1Þ
In this figure, Vdc is the input DC voltage, Vinv is the output volt-
age of the inverter bridge, i1, ig, iC are inverter-side current, grid-
side current and capacitor current, respectively. Also, Gi(s) is the
current regulator and iC is fed back to damp the LCL filter reso-
nance. At the PCC, the grid is modeled by its Thevenin equivalent
circuit for simplicity, consisting of a voltage source Vg in series with
grid impedance Zg. Gd(s) is the transfer function which combines
the computational delay, the PWM delay, and the sampler [10].
GdðsÞ ¼
1 À 0:5 Á s Á Ts
ð1 þ 0:5 Á s Á TsÞ2
ð2Þ
where Ts refers to the sampling period.
Vdc_1
Vdc_2
Vdc_n
VSC_1
VSC_2
VSC_n
Z11 Z21
Z31
Z12 Z22
Z32
Z1n Z2n
Z3n
i11 i21
i31
i12 i22
i32
i1n i2n
i3n
Vg
Zg
VpccVinv_1
Vinv_2
Vinv_n
ig
Fig. 1. Typical multi-paralleled grid-connected inverters.
Vdc
VSC
Z1 Z2
Z3
ig
ic
Vg
Zg
VpccVinv
i1
PWM
( )dG s ( )iG s refiPWMK
igic
Fig. 2. Configuration of a single grid-connected inverter with LCL filter.
A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362 355
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3. With the aforementioned model, the linearized model of the
single grid-connected inverter with LCL filter in s-domain can be
derived as shown in Fig. 3(a). In this figure, KPWM is the propor-
tional controller in the inner loop. Considering Fig. 3(a), adequate
controller design is quite complicate due to interacting loops and
complexity of the system. To simplify the design procedure, an
equivalent model containing decoupled regulating loops would
be desirable. The model in Fig. 3(a) can be simplified by adding
capacitor voltage (vC) to output signal of the transfer function
KPWM, and by replacing feedback signal iC with i1-ig. In this way,
the equivalent model of the system will be obtained as shown in
Fig. 3(b). Now, the design procedure can be done considering
decoupled loops. It is well known that the cut-off frequency of
the inner loop must be higher than the outer loop.
3. Modeling and control of multi-paralleled grid-connected
inverters
3.1. System description
A set of N-paralleled LCL-filtered grid-connected inverters is
shown in Fig. 1. The dynamics of these inverters are coupled due
to the grid impedance. The equivalent circuit for current control
design of the N-paralleled inverters of Fig. 1 is shown in Fig. 4,
where Z1i (with i = 1 . . . N), Z2i and Z3i are the inverter-side inductor
impedances, the grid-side inductor impedances and the capacitor
impedances, respectively. Moreover, i1i, i2i and i3i are the inverter
side current, the grid side current and the capacitor current,
respectively. vZ3i is the capacitor voltage and vinv i is the inverter
output voltage, all for i-th inverter. Also, ig is the grid injected
current.
3.2. Modeling
Multivariable control loops corresponding to the three-
paralleled grid-connected inverters with LCL filter coupled due to
the grid impedance in a microgrid are shown in Fig. 5. This is the
Multiple Input Multiple Output (MIMO) version of the Single Input
Single Output (SISO) control loop of Fig. 3(b). In this figure, Gi is the
matrix transfer function that contains the controllers Gi(s); Gd is
the diagonal matrix transfer function that contains the delay trans-
fer function Gd(s); KPWM is the matrix transfer function of the inner
loop regulators; GðsÞ is the matrix transfer function representing
the relation between the inverter-side currents i1i and inverter out-
put voltages vinv i. Due to coupling effect, this matrix transfer func-
tion contains diagonal and non-diagonal elements which will be
obtained in the next step.
3.3. Calculation of the matrix transfer function GðsÞ
Matrix transfer function GðsÞ is represented in (3). This matrix
has non-diagonal elements since each inverter output voltage
vinv i influences the output current of other inverters. The elements
of the matrix transfer function GðsÞ are calculated through the
superposition and Thevenin equivalent circuit theorems.
i1n ¼ GðsÞ Â vinv
i11
i12
:::
i1n
2
6
6
6
4
3
7
7
7
5
¼
G11 G12 ::: G1n
G21 G22 ::: G2n
::: ::: ::: :::
Gn1 Gn2 ::: Gnn
2
6
6
6
4
3
7
7
7
5
Â
vinv1
vinv2
:::
vinv n
2
6
6
6
4
3
7
7
7
5
ð3Þ
Fig. 3. (a) Block diagram of the dual-loop control strategy based on capacitor current feedback. (b) Simplified block diagram of the aforementioned dual-loop control strategy.
Fig. 4. The equivalent circuit of the N-paralleled inverters.
356 A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362
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4. The diagonal elements are regarded as the transfer functions
between the inverter-side current and its own output voltage.
Accordingly, G11, for example, can be calculated if grid voltage
and all the inverter output voltages vinv i are supposed to be zero
except vinv 1. For this purpose, the auxiliary circuit of Fig. 6 is
derived from Fig. 4. In this circuit, the output current is i11 and
the only voltage source is vinv 1. Therefore the diagonal element
G11, can be directly obtained. Similarly, other elements of the
matrix transfer function GðsÞ can be calculated as presented in
Appendix A.
4. Control system design
4.1. Design of controller for multivariable system
In order to determine the interaction between loops of a MIMO
system, relative gain array (RGA) method can be used [21]. The
RGA of a non-singular square matrix GðsÞ is defined as
K ¼ Gð0Þ Á ÂGð0ÞÀT
ð4Þ
where ÁÂ denotes element-by-element multiplication and Gð0Þ is
the matrix GðsÞ in the steady-state condition (x = 0).
The RGA is a square matrix which has some unique properties,
i.e. the sum of its rows as its columns are equal to 1. If diagonal ele-
ments of the RGA matrix be close to unity, the system is diagonally
dominant. In other words, interaction of loops in the system is rel-
atively low and each output can be controlled by one input. On
other hand, in MIMO systems with severe interaction, each output
is related to the all inputs. In fact, RGA is an index which shows
degree of interaction in a MIMO system. Since in the described
control loop only matrix transfer function GðsÞ has non-diagonal
elements, therefore, the RGA of this matrix should be calculated.
By using the parameters listed in Table 1, the matrix transfer
function Gð0Þ which contains the transfer functions in the Appen-
dix A, is calculated as:
Gð0Þ ¼
1:7757 À0:3738 À0:2804
À0:3738 2:7103 À0:4673
À0:2804 À0:4673 2:1495
2
6
4
3
7
5 ð5Þ
Z11 Z21
Z31
i11
Vinv_1
Z22
Z12 Z32
Z23
Zg
Z13 Z33
Fig. 6. Auxiliary circuit of the three-paralleled inverters provided that grid voltage
and all the converter voltages vinv i are zero except vinv 1.
Table 1
Parameters of the inverters and grid.
Parameters of the inverter 1
Input DC voltage, Vdc 1 360 V
Inverter-side impedance L11 = 330 mH
Z11 (R11, L11) R11 = 0.2 O
Grid-side impedance L21 = 330 mH
Z21 (R21, L21) R21 = 0.3 O
Impedance of filter capacitor C31 = 10 mF
Z31 (R31, C31) R31 = 0.2 O
Sampling frequency 30 kHz
Switching frequency 10 kHz
Rated power 5 kVA
Parameters of the inverter 2
Input DC voltage, Vdc 2 360 V
Inverter-side impedance L12 = 1 mH
Z12 (R12, L12) R12 = 0.1 O
Grid-side impedance L22 = 1 mH
Z22 (R22, L22) R22 = 0.2 O
Impedance of filter capacitor C32 = 13 mF
Z32 (R32, C32) R32 = 0.3 O
Sampling frequency 30 kHz
Switching frequency 10 kHz
Rated power 5 kVA
Parameters of the inverter 3
Input DC voltage, Vdc 3 360 V
Inverter-side impedance L13 = 600 mH
Z13 (R13, L13) R13 = 0.3 O
Grid-side impedance L23 = 200 mH
Z23 (R23, L23) R23 = 0.1 O
Impedance of filter capacitor C33 = 10 mF
Z33 (R33, C33) R33 = 0.2 O
Sampling frequency 30 kHz
Switching frequency 10 kHz
Rated power 10 kVA
Parameters of the grid
Grid Voltage, Vg (RMS) 220 V
Fundamental frequency f0 50 Hz
Grid impedance Lg = 1.3 mH
Zg (Rg, Lg) Rg = 0.1 O
Fig. 5. Multivariable control loops for three-paralleled grid-connected inverters.
A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362 357
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5. Therefore, the RGA matrix can be easily calculated as follows:
K ¼ Gð0Þ Á ÂGð0ÞÀT
¼
1:0654 À0:0374 À0:0280
À0:0374 1:0841 À0:0467
À0:0280 À0:0467 1:0748
2
6
4
3
7
5 ð6Þ
According to the calculated RGA matrix, diagonal elements are
close to unity and non-diagonal elements are close to zero. Hence,
if cut-off frequency of each main loop designed as high as possible,
the interaction of loops can be neglected. It should be noted that
with this assumption, the coupling due to the grid impedance
remains because any diagonal elements of matrix GðsÞ; for example
G11, includes the elements of other inverters such as Z12, Z22, Z13,
Z23 and etc. (see Appendix A). However, if in another case study,
the diagonal elements of the RGA matrix be far from unity and
there is severe interaction in the system, the pre-compensator
matrix can be used to reduce the interaction [21].
Corresponding control system for designing the inner loop and
outer loop controllers for Inverter 1 is shown in Fig. 7. In this fig-
ures, G11 is the first diagonal elements of GðsÞ. It should be noted
that, block diagrams of control system for Inverter 2 and Inverter
3 are not shown due to similarity. For example, to achieving the
block diagram of control system for Inverter 2, G11 should be
replaced by G22 (second diagonal elements of GðsÞ) and KPWM1
should be replaced by KPWM2. Also, blocks that are related to capac-
itor (C31) and grid-side inductor (L21) of Inverter 1, should be
replaced by capacitor and grid-side inductor of Inverter 2 (i.e. C32
and L22, respectively).
4.2. PR controllers
For a three phase converter, a simple PI controller which is
designed in the dq rotating reference frame, achieves infinite loop
gain and consequently zero steady state error at the fundamental
frequency. However, this method is not applicable to single-
phase converters, because there is only one phase variable avail-
able. The dq transformation requires a minimum of two orthogonal
variables [22,23]. Hence, in single phase applications, it is common
to use PR controller as (7) due to its high gain at the fundamental
frequency.
GPRðsÞ ¼ kp þ
krs
s2 þ x2
0
ð7Þ
where x0 ¼ 2  p  f0 and f0 is the fundamental frequency.
PR controller and also inner loop proportional controller for each
control system should be designed using bode diagram and consid-
ering phase margin and cut-off frequency constraints. At first, inner
loop proportional controller should be designed and then outer
loop PR controller can be designed. It is well known that the cut-
off frequency of the inner loop must be higher than outer loop.
4.3. Design the parameters of the controllers
In this paper, a proportional controller is used as inner loop con-
troller to enhance the cut-off frequency of the inner loop. The loop
gain of the inner loop for inverter 1 control system, which shown in
Fig. 7, can be easily obtained as
GinnerðsÞ ¼ GdðsÞ Á KPWM1 Á G11ðsÞ ð8Þ
If inner loop cut-off frequency defined as xinner, then propor-
tional controller can be achieved as:
jGinnerjs¼jxinner
¼ jGdðsÞ Á KPWM1 Á G11ðsÞjs¼jxinner
¼ 1 ) KPWM1
¼
1
jGdðsÞ Á G11ðsÞjs¼jxinner
ð9Þ
Afterward, in order to obtain the parameters of PR controller,
the control system loop gain should be achieved as follows:
Gol;sysðsÞ ¼ Gi1ðsÞ Á GsysðsÞ ð10Þ
where Gsys is the control system loop gain when Gi1 = 1.
GsysðsÞ ¼
GdðsÞ Á KPWM1 Á G11ðsÞ
1 þ s2L21C31 þ GdðsÞ Á KPWM1 Á G11ðsÞ Á s2L21C31
ð11Þ
With defining outer loop cut-off frequency as xouter and regard-
ing to this fact that if xouter x0 [24], the PR controller can be sim-
plified as
Gi1ðsÞjjxouter
¼ GPRðsÞjjxouter
% kp ð12Þ
Therefore, kp can be yield as
jGi1ðsÞ Á GsysðsÞjs¼jxouter
¼ 1 ) kp ¼
1
jGsysðsÞjs¼jxouter
ð13Þ
Then, with defining a specific phase margin (PM) such as PMdef,
next equation at cut-off frequency yields.
With a bit mathematical simplification, kr can be achieved as
kr ¼ kp Á
x2
outer À x2
0
xouter
Á tan ]GsysðsÞjs¼jxouter
þ 180 À PMdef
ð15Þ
Obviously, xinner should be greater than xouter in order to
decouple inner loop from outer loop.
5. Simulation results
In this section, a single phase microgrid with three-paralleled
grid-connected inverters with LCL filter is simulated using
MATLAB/SIMULINK software. The simulation results are analyzed
so as to validate the theoretical study of previous sections. The
key parameters of the inverters are shown in Table 1. To show
necessity of considering coupling effect in multi-paralleled grid-
connected inverters, two different simulations are performed. At
]Gol;sysðsÞjs¼jxouter
¼ À180 þ PMdef ) ]Gi1ðsÞjs¼jxouter
þ ]GsysðsÞjs¼jxouter
¼ À180 þ PMdef ð14Þ
1( )iG s ( )dG s 1PWMK 11( )G s
31
1
.s C 21
1
.s L
1( )refi s 21( )i s
( )pccv s
31( )i s11( )i s
Fig. 7. Block diagram of the control systems of Inverter 1.
358 A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362
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6. first, Set I control parameters listed in Table 2 is used for
simulation. These parameters are designed using bode diagram
and without considering the coupling effect of three inverters.
In other words, block diagram which shown in Fig. 3(b) is used
for design of controllers of each inverter, individually. The magni-
tudes of reference injected currents (iref) of these inverters are 20,
30 and 40 A, respectively and the corresponding phase angles are
0°. In Fig. 8(a)–(c), simulation results for single grid-connected
inverter are shown for each inverter. As shown in these figures,
all three inverters are stable when they are connected to the grid,
individually. Total harmonic distortion (THD) of each inverter
injected current are 3.50%, 1.22% and 1.05%, respectively. The sim-
ulation results for parallel connection of all three inverters to the
grid, with previous control parameters, are shown in Fig. 9(a)–
(c). As shown in these figures, although the individual connection
of each inverter to the grid is stable, parallel connection of invert-
ers to the grid will be unstable. This simulation results show that
considering of coupling effect in multi-paralleled grid-connected
inverters is necessary.
In the next step, Set II control parameters listed in Table 2 is used
for simulation. The controller parameters are designed with consid-
ering of coupling effect as shown in Fig. 7 for each inverter. In this
paper, the inner loop cut-off frequencies of the inverter systems are
designed 650 Hz, 700 Hz and 800 Hz, respectively. Also, the outer
loop cut-off frequencies of the inverter systems are designed
500 Hz, 250 Hz and 500 Hz, respectively, with the PM of 80°.
The open-loop bode diagrams of the control system in Fig. 7 for
each inverter are plotted in Fig. 10(a)–(c), respectively. It can be
observed that with active damping, the resonance of the LCL filter
is effectively damped and also, the loop gain at fundamental fre-
quency (50 Hz) is higher than 150 dB for all three systems, which
ensures the tracking error of the injected grid current is less than
1% thanks to PR controllers. According to Fig. 10(a)–(c), the three
systems have cut-off frequency about 500 Hz, 250 Hz and 500 Hz,
respectively with PM of about 80°.
The injected current of three inverters are shown in Fig. 11(a)–
(c). It can be seen that, despite of differences in inverters and their
control parameters, injected currents track the reference values.
Also, THD of each inverter injected current and total injected cur-
rent are 3.33%, 0.78%, 1.51% and 1.17%, respectively. Fig. 11(d)
shows the total grid-injected current which is exactly in phase with
the PCC voltage and tracks the sum of reference currents thanks to
PR controllers. The grid inductance (Lg) is selected a high value
intentionally to simulate a weak grid. However, due to adequate
control system design, this inductance reduces the harmonic dis-
tortion of the total grid-injected current as shown in Fig. 11(d).
To analyze the coupling effect of grid impedance and in order to
validate control system performance, a step change occurs in the
reference current of each inverter in different times. The reference
current of inverter 1 is reduced by 50% at t = 0.105(s). The reference
current of inverter 2 is increased by 50% at t = 0.205(s). The refer-
ence current of inverter 3 is reduced by 50% at t = 0.305(s). The sim-
ulation results using Set I control parameters in Table 2 are shown
in Fig. 12(a)–(d). As shown in this figures, the grid-injected current
of each inverter and also, the total grid-injected current are
distorted and thier quality are not acceptable at all. Also, PCC volt-
age is distorted seriously, which affects connected loads at the PCC.
The simulation is repeated using Set II control parameters in
Table 2 and its results are shown in Fig. 13(a)–(d). It can be seen
that despite of step change in the reference current of each
inverter, other inverters track their own reference currents with
negligible disturbances in specified time. Also, total injected cur-
Table 2
Parameters of the controllers.
Set I
Parameters of the controllers of
inverter 1
Parameters of the controllers of
inverter 2
Parameters of the controllers of
inverter 3
Kpwm1 7.35 Kpwm1 37.2 Kpwm1 15.2
Kp 0.72 Kp 1.29 Kp 0.65
Kr 350 Kr 233 Kr 281
Set II
Parameters of the controllers of
inverter 1
Parameters of the controllers of
inverter 2
Parameters of the controllers of
inverter 3
Kpwm1 5.37 Kpwm1 10.6 Kpwm1 6.24
Kp 0.66 Kp 0.34 Kp 0.60
Kr 318 Kr 66.7 Kr 267
(a) (b)
(c)
0.04 0.12 0.2 0.28
-40
-20
0
20
40
Time(s)
i21(A)
0.04 0.12 0.2 0.28
-40
-20
0
20
40
Time(s)
i22(A)
0.04 0.12 0.2 0.28
-40
-20
0
20
40
Time(s)
i23(A)
Fig. 8. Simulated waveforms for single grid-connected inverter without considering the coupling effect of the inverters in design of controller parameters. (a) Inverter 1, (b)
Inverter 2 and (c) Inverter 3.
A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362 359
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7. (a) (b)
(c)
0.04 0.12 0.2 0.28
-40
-20
0
20
40
Time(s)
i21(A)
0.04 0.12 0.2 0.28
-40
-20
0
20
40
Time(s)
i22(A)
0.04 0.12 0.2 0.28
-40
-20
0
20
40
Time(s)
i23(A)
Fig. 9. Simulated waveforms for multi-paralleled grid-connected inverters without considering the coupling effect of the inverters in design of controller parameters. (a)
Inverter 1, (b) Inverter 2 and (c) Inverter 3.
)c()b()a(
-150
-100
-50
0
50
100
150
200
Magnitude(dB)
10
0
10
1
10
2
10
3
10
4
10
5
-180
-90
0
90
180
Phase(deg)
Bode Diagram
Frequency (Hz)
-150
-100
-50
0
50
100
150
200
Magnitude(dB)
10
0
10
1
10
2
10
3
10
4
10
5
-180
-90
0
90
180
Phase(deg)
Bode Diagram
Frequency (Hz)
-150
-100
-50
0
50
100
150
200
Magnitude(dB)
10
0
10
1
10
2
10
3
10
4
10
5
-180
-90
0
90
180
Phase(deg)
Bode Diagram
Frequency (Hz)
Fig. 10. Open loop bode diagram of the control systems (a) Inverter 1, (b) Inverter 2 and (c) Inverter 3.
(a) (b)
(c) (d)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i21(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i22(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i23(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-300
-200
-100
0
100
200
300
Time(s)
ig Vpcc
Fig. 11. Simulated waveforms for multi-paralleled grid-connected inverters with considering the coupling effect of the inverters in design of controller parameters. (a)
Inverter 1, (b) Inverter 2, (c) Inverter 3, (d) Total injected current (ig) and PCC voltage (Vpcc).
360 A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362
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8. rent tracks the sum of reference currents exactly without any
instability which validates the proposed control system despite
of inverters with different characteristics.
6. Conclusion
This paper analyses the modeling and design of a multivariable
control system for multi-paralleled grid-connected inverters with
LCL filter in a microgrid. The coupling effect due to grid impedance
is described and dual-loop active damping control with capacitor
current feedback is used to damp the LCL filter resonances. The
inverters are modeled as a multivariable system considering the
different characteristics for inverters such as LCL filters and rated
powers. Three paralleled single-phase grid-connected inverters
are considered as a case study. Then, the control system design
guidelines are suggested based on multivariable control theory.
By using the PR controllers, the performance of the control system
is improved. Simulation results of three-paralleled grid-connected
inverters with LCL filter, in different conditions, confirm the validity
of the modeling and effectiveness of the proposed control system.
Appendix A
G11 ¼
i11
vinv1
¼
1
Z11 þ Zgk½Z23 þ ðZ13kZ33ÞŠk Z22 þ ðZ12kZ32Þ½ Š þ Z21
À Á
kZ31
G12 ¼
i11
vinv2
¼
1
1 þ Z12
Z32
þ Z12
Z22
À 1 þ Z22
Z21
þ Z22
Zg k½Z23þðZ13kZ33ÞŠ
Z11 þ Z21 þ Z11Z21
Z31
þ Z11Z22
Z21
h i
þ Z12
Z22
Z11 þ Z21 þ Z11Z21
Z31
(a) (b)
(c) (d)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i21(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i22(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i23(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-300
-200
-100
0
100
200
300
Time(s)
ig
Vpcc
Fig. 12. Simulated waveforms with a step change in the reference current without considering the coupling effect of the inverters in design of controller parameters. (a)
Inverter 1, (b) Inverter 2, (c) Inverter 3, (d) Total injected current (ig) and PCC voltage (Vpcc).
(a) (b)
(c) (d)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i21(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i22(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-40
-20
0
20
40
Time(s)
i23(A)
0.02 0.06 0.1 0.14 0.18 0.22 0.26 0.3 0.34 0.38
-300
-200
-100
0
100
200
300
Time(s)
ig
Vpcc
Fig. 13. Simulated waveforms with a step change in the reference current with considering the coupling effect of the inverters in design of controller parameters. (a) Inverter
1, (b) Inverter 2, (c) Inverter 3, (d) Total injected current (ig) and PCC voltage (Vpcc).
A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362 361
: کن ترجمه خودتhttps://freepaper.me/t/250851
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G13 ¼
i11
vinv 3
¼
1
1 þ Z13
Z33
þ Z13
Z23
À 1 þ Z23
Z21
þ Z23
Zg k½Z22þ Z12kZ32ð ÞŠ
Z11 þ Z21 þ Z11Z21
Z31
þ Z11Z23
Z21
h i
þ Z13
Z23
Z11 þ Z21 þ Z11Z21
Z31
G21 ¼
i12
vinv 1
¼
1
1 þ Z11
Z31
þ Z11
Z21
À 1 þ Z21
Z22
þ Z21
Zg k Z23þðZ13kZ33Þ½ Š
Z12 þ Z22 þ Z12Z22
Z32
þ Z12Z21
Z22
h i
þ Z11
Z21
Z12 þ Z22 þ Z11Z22
Z32
G22 ¼
i12
vinv 2
¼
1
Z12 þ ðZgk Z23 þ Z13kZ33ð Þ½ Šk½Z21 þ ðZ11kZ31ÞŠ þ Z22ÞkZ32
G23 ¼
i12
vinv 3
¼
1
1 þ Z13
Z33
þ Z13
Z23
Àð1 þ Z23
Z22
þ Z23
Zg k Z21þðZ11kZ31Þ½ Š
ÞðZ12 þ Z22 þ Z12Z22
Z32
Þ þ Z12Z23
Z22
h i
þ Z13
Z23
Z12 þ Z22 þ Z12Z22
Z32
G31 ¼
i13
vinv 1
¼
1
1 þ Z11
Z31
þ Z11
Z21
À 1 þ Z21
Z23
þ Z21
Zg k Z22þ Z12kZ32ð Þ½ Š
Z13 þ Z23 þ Z13Z23
Z33
þ Z13Z21
Z23
h i
þ Z11
Z21
Z13 þ Z23 þ Z13Z23
Z33
G32 ¼
i13
vinv 2
¼
1
1 þ Z12
Z32
þ Z12
Z22
À 1 þ Z22
Z23
þ Z22
Zg k Z21þðZ11kZ31Þ½ Š
Z13 þ Z23 þ Z13Z23
Z33
þ Z13Z22
Z23
h i
þ Z12
Z22
Z13 þ Z23 þ Z13Z23
Z33
G33 ¼
i13
vinv 3
¼
1
Z13 þ Zgk Z21 þ ðZ11kZ31Þ½ Šk Z22 þ Z12kZ32ð Þ½ Š þ Z23
À Á
kZ33
362 A. Akhavan et al. / Electrical Power and Energy Systems 94 (2018) 354–362
: کن ترجمه خودتhttps://freepaper.me/t/250851