A Highly Efficient and Reliable Inverter Configuration Based Cascaded Multi-Level Inverter for PV Systems
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This document presents a proposed improved cascaded multi-level inverter configuration for photovoltaic systems that aims to minimize leakage current. The proposed topology reduces switch count and has lower switching and conduction losses compared to existing designs. It also aims to reduce high-frequency voltage transitions in the terminal and common-mode voltages to minimize leakage current and reduce the size of EMI filters. Simulation results validating the performance of the proposed five-level inverter configuration are presented along with an analysis and comparison with other topologies.
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Steady state and transient problems in a power system have undesirable consequences on the system. It can limit the amount of power that can be transmitted in the system and consequently leads to voltage instability and at times it may also result into total voltage collapse.The main objective of this paper is a comparative investigate in enhancement of volatge stability via static synchronous series compensator (SSSC) and static var compensator (SVC) externally controlled by a POD controller. The new designed P.O.D controller is very efficient for voltage stability under transient conditions. This paper discusses and demonstrates the comparision between the SVC with P.O.D controller and SSSC with P.O.D controller,applied to power system for effectively regulating system voltage for different types of faulted condition. One of the major reasons for installing a SVC is to improve dynamic voltage control and thus increase system load ability during transient condition. This work is presented to present the transmission line voltage stability & machine oscillation damping stability by using SVC & SSSC with POD controller & compared their performance to enhance the stability of a power system. Simulation results shows that SVC with POD controller is more effective to enhance the voltage stability and increase transmission capacity in a power system.
Three phase unidirectional rectifiers with open-end source and cascaded float...
This paper presents two topologies of three-phase semicontrolled rectifiers suitable for open-end ac power sources. The rectifiers are composed by a combination of two-level three phase bridges (controlled, semicontrolled or uncontrolled), and three single-phase floating capacitor h-bridges (controlled). These topologies generate two powered dc-links, each one belonging to a three-phase bridge. They present a reduced number of controlled power switches if compared to other open-end configurations of similar complexity found in the literature. It is also proposed a space-vector pulse width modulation (SV-PWM) approach and a method of floating capacitor voltage control dedicated to the topologies, with an equivalent approach based on the level-shifted PWM (LS-PWM). The proposed SV-PWM solving method is based on a redundant state selection (RSS) technique, which allows the floating capacitors voltage regulation. On the other hand, the LS-PWM solving method is based on the neutral voltage selection, which is shown to be equivalent to the SVPWM RSS technique seen from the control system. Simulation results are shown to validate proposed topologies, as well as the SV-PWM and LS-PWM techniques, and the control strategy. Experimental results are shown to demonstrate proposed configurations feasibility.
A transformerless grid connected photovoltaic inverter with switched capacitors
In the transformerless photovoltaic (PV) system, the common mode ground leakage current may appear due to the galvanic connection between the PV array and the ground, which causes the safety issues and reduces the efficiency. To solve this problem, a novel inverter topology with switched capacitors is proposed in this paper. By connecting one pole of the PV cell directly to the neutral line of the grid, the common mode current is eliminated. Meanwhile, the switched capacitor technology is applied to increase the DC voltage utilization rate. Furthermore, a modified unipolar sinusoidal pulse width modulation (SPWM) strategy is proposed to reduce the pulsating current caused by the charging and discharging operations of the switched capacitors. Also, several optimization principles are put forward to further reduce the pulsating current to improve the efficiency and reliability. Finally, the proposed topology and modulation strategy are verified with simulation and a 250W experimental prototype.
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A New Family of Step-up Hybrid Switched- Capacitor Integrated Multilevel Inve...
In the low voltage based renewable systems like PV and Fuel cell applications, the step-up of the output voltage to drive the loads is essential. For this, the integration of switched-capacitor (SC) units with the dc-ac converters will have the potential advantages like improved efficiency, optimal switching devices, small size of passive elements (L and C) as compared with traditional two-stage conversion system (dc/dc converter and dc/ac converter). This paper focuses on a new family of step-up multilevel inverter topologies with switched capacitor integration with dual input voltage sources. With the flexibility of 2 dc sources and switching capacitor circuits, four different topologies have been suggested in this paper with features of high voltage gain, reduced component count, reduced voltage stress and self-voltage balancing of the capacitor while achieving a higher number of levels. A detailed analysis of proposed multilevel inverters has been analyzed with the symmetrical and asymmetrical mode of operations and the associated gain, the number of levels, and other performance indices are presented. An in-depth study of all the topologies has been accomplished in this paper with several comparative studies in terms of components count, voltage gain and cost. The effectiveness and practicability of the suggested topology with 13 level output voltage has been explained by the experimental results obtained from a scale down prototype.
Comparison of Modulation Techniques for Matrix Converter
Matrix Converters can directly convert an ac power supply of fixed voltage into an ac voltage of variable amplitude and frequency. Matrix Converter is a single stage converter. The matrix converters can contribute to the realization of low volume, sinusoidal input current, bidirectional power flow and lack of bulky reactive elements. All the reasons lead to the development of matrix converter. Based on the control techniques used in the matrix converter, the performance varies. So this paper analyses the performance of matrix converter with three different modulation techniques such as PWM, SVPWM and SVM. The basic principle and switching sequence of these modulation techniques are presented in this paper. The output voltage, output current waveforms, voltage transfer ratio and THD spectrum of switching waveforms connected to RL load are analyzed by using Matlab/Simulink software. The simulated results are analyzed and show that the THD is better for SVM technique.
Front end buck rectifier with reduced filter size and single-loop control
This paper presents a transformerless solution for front-end rectification, which is particularly suitable for traction applications, requiring high voltages to be stepped down to appropriate dc voltage. The proposed topology is based on pulse widthmodulation buck rectifier (current source inverter topology) and is capable of rectification and stepping down of single-phase ac supply, in a single stage. A new control scheme is proposed to achieve constant dc output voltage and sinusoidal source current, irrespective of large ripples in the dc inductor current. The proposed scheme is configured in single-loop voltage control mode. The relevant small-signal model is derived from the large-signal model using multi order decomposition. An elaborate procedure of dc filter design is discussed, for circuit operation with minimum energy storage. All analytical results are validated by numerical simulation for sinusoidal and distorted source voltage. Experimental verification is achieved through a 1.2-kW grid-connected laboratory prototype.
Adaptive Hysteresis Band Current Control for Transformer-less Single-Phase PV...
Current control based on hysteresis algorithms are widely used in different applications, such as motion control, active filtering or active/reactive power delivery control in distributed generation systems. The hysteresis current control provides to the system a fast and robust dynamic response, and requires a simple implementation in standard digital signal platforms. On the other hand, the main drawback of classical hysteresis current control lies in the fact that the switching
frequency is variable, as the hysteresis band is fixed. In this paper a variable band hysteresis control algorithm will be presented. As it will be shown, this variable band permits overcoming the aforementioned problem giving rise to an almost constant switching frequency. The performance of this algorithm, together with classical hysteresis controls and proportional resonant (PR) controllers, has been evaluated in three different single-phase PV inverter topologies, by means of simulations performed with PSIM. In addition, the behavior of the thermal losses when using each control structure in such converters has been studied as well.
Single- and Two-Stage Inverter-Based Grid-Connected Photovoltaic Power Plants...
Grid-connected distributed generation sources interfaced with voltage source inverters (VSIs) need to be disconnected from the grid under: 1) excessive dc-link voltage; 2) excessive ac currents; and 3) loss of grid-voltage synchronization. In this paper, the control of single- and two-stage grid-connected VSIs in photovoltaic (PV) power plants is developed to address the issue of inverter disconnecting under various grid faults. Inverter control incorporates reactive power support in the case of voltage sags based on the grid codes’ (GCs) requirements to ride-through the faults and support the grid voltages. A case study of a 1-MW system simulated in MATLAB/Simulink software is used to illustrate the proposed control. Problems that may occur during grid faults along with associated remedies are discussed. The results presented illustrate the capability of the system to ride-through different types of grid faults.
An f p q droop control in cascaded-type microgrid
In cascaded-type microgrid, the synchronization and power balance of distributed generators become two new issues that needs to be addressed urgently. To that end, an f-P/Q droop control is proposed in this letter, and its stability is analyzed as well. This proposed droop control is capable to achieve power balance under both resistive-inductive an resistive-capacitive loads autonomously. Compared with the inverse power factor droop control, an obvious advantage consists in extending the scope of application. Finally, the feasibility of the proposed method is verified by simulation results.
Power quality improvement in distribution network using DSTATCOM with battery...
The distribution static compensator (DSTATCOM) provides fast control of active and reactive powers to enable load compensation, harmonics current elimination, voltage flicker mitigation, voltage and frequency regulation. This paper presents power quality improvement technique in the presence of grid disturbances and wind energy penetration using DSTATCOM with battery energy storage system. DSTATCOM control is provided based on synchronous reference frame theory. A modified IEEE 13 bus test feeder with DSTATCOM and wind generator is used for the study. Power quality events during grid disturbances such as feeder tripping and re-closing, voltage sag, swell and load switching have been studied in association with DSTATCOM. The power quality disturbances due to wind generator outage, synchronization and wind speed variations have also been investigated. The study has been carried out using MATLAB/SIMULINK and the simulation results are compared with real time results obtained by the use of real time digital simulator (RTDS) for validating the effectiveness of proposed methodology. The proposed method has been proved to be effective in improvement of power quality with all disturbances stated above.
Novel Zero-Current Switching Current-Fed Half-Bridge Isolated Dc/Dc Converter...
This paper presents a novel zero-current switching (ZCS) current-fed half-bridge isolated dc/dc converter. It is a potential topology for front-end dc/dc power conversion for fuel cell inverters. This proposed converter is unique, not reported in literature and provides a simple solution to switch turn-off problem with ZCS without increase in components count. This will lead to reduced size, lower cost and higher efficiency. Analysis, design and simulation results of the proposed converter are reported in this paper. A comparison with existing active-clamped ZVS current-fed half-bridge converter has been illustrated.
Power Quality Improvement in Solar Fed Cascaded Multilevel Inverter with Outp...
The presence of harmonics in solar Photo Voltaic (PV) energy conversion system results in deterioration of power quality. To address such issue, this paper aims to investigate the elimination of harmonics in a solar fed cascaded fifteen level inverter with aid of Proportional Integral (PI), Artificial Neural Network (ANN) and Fuzzy Logic (FL) based controllers. Unlike other techniques, the proposed FLC based approach helps in obtaining reduced harmonic distortions that intend to an enhancement in power quality. In addition to the power quality improvement, this paper also proposed to provide output voltage regulation in terms of maintaining voltage and frequency at the inverter output end in compatible with the grid connection requirements. The simulations are performed in the MATLAB / Simulink environment for solar fed cascaded 15 level inverter incorporating PI, ANN and FL based controllers. To exhibit the proposed technique, a 3 kWp photovoltaic plant coupled to multilevel inverter is designed and hardware is demonstrated. All the three techniques are experimentally investigated with the measurement of power quality metrics along with establishing output voltage regulation.
Matlab-based Simulation & Analysis of Three level SPWM Inverter
The multilevel began with the three level converters. The elementary concept of a multilevel converter to achieve higher power to use a series of power semiconductor switches with several lower voltage dc source to perform the power conversion by synthesizing a staircase voltage waveform. However, the output voltage is smoother with a three level converter, in which the output voltage has three possible values. This results in smaller harmonics, but on the other hand it has more components and is more complex to control. In this paper, different three level inverter topologies and SPWM technique has been applied to formulate the switching pattern for three level inverter that minimize the harmonic distortion at the inverter output. Simulation result has discussed.
Development of wind and solar based ac microgrid with power quality improveme...
This work proposes a microgrid (μ-grid) integrating wind and solar photovoltaic (PV) resources, along with the battery energy storage (BES) to the three phase grid feeding the nonlinear load. The μ-grid disconcerted by probabilistic nonlinear time dependent parameters and their effects are compensated by cohesive controllers used for utility grid side voltage source converter (GVSC) and machine side VSC (MVSC). The switching controls and the reconfigurability of the μ-grid are addressed on imperative aspects of improving power quality (PQ), power reliability, nonlinear load compensation and economic utilization of resources. The nonlinear load compensation and PQ enhancement are achieved by executing modified version of the adaptive filtering technique including “momentum” based least mean square (MLMS) control technique, utilized for providing the switching control signals to the GVSC. It utilizes two preceding gradient weights for obtaining updated weight thereby improving the convergence rate and overcoming the limitation of conventional control of the same family. The MVSC acquires its switching signals from conventional vector control scheme and the encoderless estimation of speed and rotor position of the synchronous generator (SG) driven by wind turbine through back electromotive force control technique. The external environmental disturbances are overcome by utilizing perturb and observe (P&O) maximum power point (MPP) for wind optimal power extraction and adaptive P&O with variable perturbation step size for solar MPP estimation. Test results are obtained from the laboratory prototype under steady state and dynamic conditions including altering wind speed, intermittent solar insolation and variable load conditions. The PQ issues are addressed and investigated successfully.
Voltage sag enhancement of grid connected hybrid pv wind power system using b...
Renewable energy sources; which are abundant in nature and climate friendly are the only preferable choice of the world to provide green energy. The limitation of most renewable energy sources specifically wind and solar PV is its intermittent nature which are depend on wind speed and solar irradiance respectively and this leads to power fluctuations. To compensate and protect sensitive loads from being affected by the power distribution side fluctuations and faults, dynamic voltage restorer (DVR) is commonly used. This research work attempts to withstand and secure the effect of voltage fluctuation of grid connected hybrid PV-wind power system. To do so battery and super magnetic energy storage (SMES) based DVR is used as a compensating device in case of voltage sag condition. The compensation method used is a pre-sag compensation which locks the instantaneous real time three phase voltage magnitude and angle in normal condition at the point of common coupling (PCC) and stores independently so that during a disturbance it used for compensation. Symmetrical and asymmetrical voltage sags scenario are considered and compensation is carried out using Power System Computer Aided Design or Electro Magnetic Transient Design and Control (PSCAD/EMTDC) software.
Voltage sag enhancement of grid connected hybrid pv wind power system using b...
Renewable energy sources; which are abundant in nature and climate friendly are the only preferable choice of the world to provide green energy. The limitation of most renewable energy sources specifically wind and solar PV is its intermittent nature which are depend on wind speed and solar irradiance respectively and this leads to power fluctuations. To compensate and protect sensitive loads from being affected by the power distribution side fluctuations and faults, dynamic voltage restorer (DVR) is commonly used. This research work attempts to withstand and secure the effect of voltage fluctuation of grid connected hybrid PV-wind power system. To do so battery and super magnetic energy storage (SMES) based DVR is used as a compensating device in case of voltage sag condition. The compensation method used is a pre-sag compensation which locks the instantaneous real time three phase voltage magnitude and angle in normal condition at the point of common coupling (PCC) and stores independently so that during a disturbance it used for compensation. Symmetrical and asymmetrical voltage sags scenario are considered and compensation is carried out using Power System Computer Aided Design or Electro Magnetic Transient Design and Control (PSCAD/EMTDC) software.
New control strategy for three phase grid-connected lcl inverters without a p...
The three-phase synchronous reference frame phase-locked loop (SRF-PLL) is widely used for synchronization applications in power systems. In this paper, a new control strategy for three-phase grid-connected LCL inverters without a PLL is presented. According to the new strategy, a current reference can be generated by using the instantaneous power control scheme and the proposed positive-sequence voltage detector. Through theoretical analysis, it is indicated that a high-quality grid current can be produced by introducing the new control strategy. In addition, a kind of independent control for reactive power can be achieved under unbalanced and distorted grid conditions. Finally, the excellent performance of the proposed control strategy is validated by means of simulation and experimental results.
Statcom for improved dynamic performance of wind farms in power grid
Application of FACTS controller called Static Synchronous Compensator STATCOM to improve the performance of power grid with Wind Farms is investigated .The essential feature of the STATCOM is that it has the ability to absorb or inject fastly the reactive power with power grid . Therefore the voltage regulation of the power grid with STATCOM FACTS device is achieved. Moreover restoring the stability of the power system having wind farm after occurring
severe disturbance such as faults or wind farm mechanical power variation is obtained with STATCOM controller . The dynamic model of the power system having wind farm controlled by
proposed STATCOM is developed . To Validate the powerful of the STATCOM FACTS controller , the studied power system is simulated and subjected to different severe disturbances . The results prove the effectiveness of the proposed STATCOM controller in terms of fast damping the power system oscillations and restoring the power system stability .
Control of a Three-Phase Hybrid Converter for a PV Charging Station
Hybrid boost converter (HBC) has been proposed to replace a dc/dc boost converter and a dc/ac converter to reduce conversion stages and switching loss. In this paper, control of a three-phase HBC in a PV charging station is designed and tested. This HBC interfaces a PV system, a dc system with hybrid plugin electrical vehicles (HPEVs) and a three-phase ac grid. The control of the HBC is designed to realize maximum power point tracking (MPPT) for PV, dc bus voltage regulation, and ac voltage or reactive power regulation. A test bed with power electronics switching details is built in MATLAB/SimPowersystems for validation. Simulation results demonstrate the feasibility of the designed control architecture. Finally, lab experimental testing is conducted to demonstrate HBC’s control performance.
An Efficient Constant Current Controller for PV Solar Power Generator Integra...
This paper presents the detailed design and modeling of grid integrated with the Photovoltaic Solar Power Generator. As the Photovoltaic System uses the solar energy as one of the renewable energies for the electrical energy production has an enormous potential. The PV system is developing very rapidly as compared to its counterparts of the renewable energies. The DC voltage generated by the PV system is boosted by the DC-DC Boost converter. The utility grid is incorporated with the PV Solar Power Generator through the 3-ı PWM DC-AC inverter, whose control is provided by a constant current controller. This controller uses a 3-ı phase locked loop (PLL) for tracking the phase angle of the utility grid and reacts fast enough to the changes in load or grid connection states, as a result, it seems to be efficient in supplying to load the constant voltage without phase jump. The complete mathematical model for the grid connected PV system is developed and simulated. The results verify that the proposed system is proficient to supply the local loads.
An integrated boost resonant converter for photovoltaic applications
Effective photovoltaic power conditioning requires efficient power conversion and accurate maximum power point tracking to counteract the effects of panel mismatch, shading, and general variance in power output during a daily cycle. In this paper, the authors propose an integrated boost resonant converter with low component count, galvanic isolation, simple control, as well as
high efficiency across a wide input and load range. Provided is a discussion of the converter synthesis, key operational features, converter design procedure, and loss analysis, as well as experimental verification by way of a 250-W prototype with a California Energy Commission efficiency of 96.8%.
A generalized multilevel inverter topology with reduction of total standing v...
This paper presents a new multilevel inverter topology with reduced active switches
and total standing voltage. The proposed topology can generate a high number of voltage levels in the symmetric configuration. This topology intuitively generates positive and negative cycles without an additional H-bridge unit, which considerably reduces the total standing voltage of the inverter. A cascaded structure is developed from the proposed topology to create higher voltage levels. To show the novelty of the proposed topology, a thorough comparison between the available and the proposed topologies in terms of the number of switches, standing voltages, and dc-sources is presented. Furthermore, he power loss analysis is carried out for various load values. The feasibility of the proposed nine-level inverter is verified with simulation and experimental results.
Performance comparison of SVC and SSSC with POD controller for Power System S...
Steady state and transient problems in a power system have undesirable consequences on the system. It can limit the amount of power that can be transmitted in the system and consequently leads to voltage instability and at times it may also result into total voltage collapse.The main objective of this paper is a comparative investigate in enhancement of volatge stability via static synchronous series compensator (SSSC) and static var compensator (SVC) externally controlled by a POD controller. The new designed P.O.D controller is very efficient for voltage stability under transient conditions. This paper discusses and demonstrates the comparision between the SVC with P.O.D controller and SSSC with P.O.D controller,applied to power system for effectively regulating system voltage for different types of faulted condition. One of the major reasons for installing a SVC is to improve dynamic voltage control and thus increase system load ability during transient condition. This work is presented to present the transmission line voltage stability & machine oscillation damping stability by using SVC & SSSC with POD controller & compared their performance to enhance the stability of a power system. Simulation results shows that SVC with POD controller is more effective to enhance the voltage stability and increase transmission capacity in a power system.
What's hot (20)
A New Family of Step-up Hybrid Switched- Capacitor Integrated Multilevel Inve...
A New Family of Step-up Hybrid Switched- Capacitor Integrated Multilevel Inve...
Comparison of Modulation Techniques for Matrix Converter
Comparison of Modulation Techniques for Matrix Converter
Front end buck rectifier with reduced filter size and single-loop control
Front end buck rectifier with reduced filter size and single-loop control
Adaptive Hysteresis Band Current Control for Transformer-less Single-Phase PV...
Adaptive Hysteresis Band Current Control for Transformer-less Single-Phase PV...
Single- and Two-Stage Inverter-Based Grid-Connected Photovoltaic Power Plants...
Single- and Two-Stage Inverter-Based Grid-Connected Photovoltaic Power Plants...
Power quality improvement in distribution network using DSTATCOM with battery...
Power quality improvement in distribution network using DSTATCOM with battery...
Novel Zero-Current Switching Current-Fed Half-Bridge Isolated Dc/Dc Converter...
Novel Zero-Current Switching Current-Fed Half-Bridge Isolated Dc/Dc Converter...
Power Quality Improvement in Solar Fed Cascaded Multilevel Inverter with Outp...
Power Quality Improvement in Solar Fed Cascaded Multilevel Inverter with Outp...
Matlab-based Simulation & Analysis of Three level SPWM Inverter
Matlab-based Simulation & Analysis of Three level SPWM Inverter
Development of wind and solar based ac microgrid with power quality improveme...
Development of wind and solar based ac microgrid with power quality improveme...
Voltage sag enhancement of grid connected hybrid pv wind power system using b...
Voltage sag enhancement of grid connected hybrid pv wind power system using b...
Voltage sag enhancement of grid connected hybrid pv wind power system using b...
Voltage sag enhancement of grid connected hybrid pv wind power system using b...
New control strategy for three phase grid-connected lcl inverters without a p...
New control strategy for three phase grid-connected lcl inverters without a p...
Statcom for improved dynamic performance of wind farms in power grid
Statcom for improved dynamic performance of wind farms in power grid
Control of a Three-Phase Hybrid Converter for a PV Charging Station
Control of a Three-Phase Hybrid Converter for a PV Charging Station
An Efficient Constant Current Controller for PV Solar Power Generator Integra...
An Efficient Constant Current Controller for PV Solar Power Generator Integra...
An integrated boost resonant converter for photovoltaic applications
An integrated boost resonant converter for photovoltaic applications
A generalized multilevel inverter topology with reduction of total standing v...
A generalized multilevel inverter topology with reduction of total standing v...
Performance comparison of SVC and SSSC with POD controller for Power System S...
Performance comparison of SVC and SSSC with POD controller for Power System S...
Similar to A Highly Efficient and Reliable Inverter Configuration Based Cascaded Multi-Level Inverter for PV Systems
Three phase unidirectional rectifiers with open-end source and cascaded float...
This paper presents two topologies of three-phase semicontrolled rectifiers suitable for open-end ac power sources. The rectifiers are composed by a combination of two-level three phase bridges (controlled, semicontrolled or uncontrolled), and three single-phase floating capacitor h-bridges (controlled). These topologies generate two powered dc-links, each one belonging to a three-phase bridge. They present a reduced number of controlled power switches if compared to other open-end configurations of similar complexity found in the literature. It is also proposed a space-vector pulse width modulation (SV-PWM) approach and a method of floating capacitor voltage control dedicated to the topologies, with an equivalent approach based on the level-shifted PWM (LS-PWM). The proposed SV-PWM solving method is based on a redundant state selection (RSS) technique, which allows the floating capacitors voltage regulation. On the other hand, the LS-PWM solving method is based on the neutral voltage selection, which is shown to be equivalent to the SVPWM RSS technique seen from the control system. Simulation results are shown to validate proposed topologies, as well as the SV-PWM and LS-PWM techniques, and the control strategy. Experimental results are shown to demonstrate proposed configurations feasibility.
A transformerless grid connected photovoltaic inverter with switched capacitors
In the transformerless photovoltaic (PV) system, the common mode ground leakage current may appear due to the galvanic connection between the PV array and the ground, which causes the safety issues and reduces the efficiency. To solve this problem, a novel inverter topology with switched capacitors is proposed in this paper. By connecting one pole of the PV cell directly to the neutral line of the grid, the common mode current is eliminated. Meanwhile, the switched capacitor technology is applied to increase the DC voltage utilization rate. Furthermore, a modified unipolar sinusoidal pulse width modulation (SPWM) strategy is proposed to reduce the pulsating current caused by the charging and discharging operations of the switched capacitors. Also, several optimization principles are put forward to further reduce the pulsating current to improve the efficiency and reliability. Finally, the proposed topology and modulation strategy are verified with simulation and a 250W experimental prototype.
New ac dc power factor correction architecture suitable for high frequency op...
This paper presents a novel ac-dc power factor correction (PFC) power conversion architecture for single-phase grid interface. The proposed architecture has significant advantages for achieving high efficiency, good power factor, and converter miniaturization, especially in low-to-medium power applications. The architecture enables twice-line-frequency energy to be buffered at high voltage with a large voltage swing, enabling reduction in the energy buffer capacitor size, and elimination of electrolytic capacitors. While this architecture can be beneficial with a variety of converter topologies, it is especially suited for system miniaturization by enabling designs that operate at high frequency (HF, 3 – 30 MHz). Moreover, we introduce circuit implementations that provide efficient operation in this range. The proposed approach is demonstrated for an LED driver converter operating at a (variable) HF switching frequency (3 – 10 MHz) from 120Vac, and supplying a 35Vdc output at up to 30W. The prototype converter achieves high efficiency (92 %) and power factor (0.89), and maintains good performance over a wide load range. Owing to architecture and HF operation, the prototype achieves a high ‘box’ power density of 50W/ in3 (‘displacement’ power density of 130W/ in3), with miniaturized inductors, ceramic energy buffer capacitors, and a small-volume EMI filter.
Mppt with single dc–dc converter and inverter for grid connected hybrid wind-...
A new topology of a hybrid distributed generator based on photovoltaic and wind-driven permanent magnet synchronous generator is proposed. In this generator, the sources are connected together to the grid with the help of only a single boost converter followed by an inverter. Thus, compared to earlier schemes, the proposed scheme has fewer power converters. A model of the proposed scheme in the d − q-axis reference frame is developed. Two low-cost controllers are also proposed for the new hybrid scheme to separately trigger the dc–dc converter and the inverter for tracking the maximum power from both sources. The integrated operations of both proposed controllers for different conditions are demonstrated through simulation and experimentation. The steady-state performance of the system and the transient response of the controllers are also presented to demonstrate the successful operation of the new hybrid system. Comparisons of experimental and simulation results are given to validate the simulation model.
High frequency ac-link pv inverter
In this paper, a high-frequency ac-link photovoltaic (PV) inverter is proposed. The proposed inverter overcomes most of the problems associated with currently available PV inverters. In this inverter, a single-stage power-conversion unit fulfills all the system requirements, i.e., inverting dc voltage to proper ac, stepping up or down the input voltage, maximum power point tracking, generating low-harmonic ac at the output, and input/output isolation. This inverter is, in fact, a partial resonant ac-link converter in which the link is formed by a parallel inductor/capacitor (LC) pair having alternating current and voltage. Among the significant merits of the proposed inverter are the zero-voltage turn-on and soft turn-off of the switches which result in negligible switching losses and minimum voltage stress on the switches. Hence, the frequency of the link can be as high as permitted by the switches and the processor. The high frequency of operation makes the proposed inverter very compact. The other significant advantage of the proposed inverter is that no bulky electrolytic capacitor exists at the link. Electrolytic capacitors are cited as the most unreliable component in PV inverters, and they are responsible for most of the inverters’ failures, particularly at high temperature. Therefore, substituting dc electrolytic capacitors with ac LC pairs will significantly increase the reliability of PV inverters. A 30-kW prototype was fabricated and tested. The principle of operation and detailed design procedure of the proposed inverter along with the simulation and experimental results are included in this paper. To evaluate the long-term performance of the proposed inverter, three of these inverters were installed at three different commercial facilities in Texas, USA, to support the PV systems. These inverters have been working for several months now.
A Unified Control and Power Management Scheme for PV-Battery-Based Hybrid Mic...
Battery storage is usually employed in Photovoltaic (PV) system to mitigate the power fluctuations due to the characteristics of PV panels and solar irradiance. Control schemes for PV-battery systems must be able to stabilize the bus voltages as well as to control the power flows flexibly. This paper proposes a comprehensive control and power management system (CAPMS) for PV-battery-based hybrid microgrids with both AC and DC buses, for both grid-connected and islanded modes. The proposed CAPMS is successful in regulating the DC and AC bus voltages and frequency stably, controlling the voltage and power of each unit flexibly, and balancing the power flows in the systems automatically under different operating circumstances, regardless of disturbances from switching operating modes, fluctuations of irradiance and temperature, and change of loads. Both simulation and experimental case studies are carried out to verify the performance of the proposed method.
A solar power generation system with a seven level inverter
This paper proposes a new solar power generation system, which is composed of a dc/dc power converter and a new seven-level inverter. The dc/dc power converter integrates a dc–dc boost converter and a transformer to convert the output voltage of the solar cell array into two independent voltage sources with multiple relationships. This new seven-level inverter is configured using a capacitor selection circuit and a full-bridge power converter, connected in cascade. The capacitor selection circuit converts the two output voltage sources of dc–dc power converter into a three-level dc voltage, and the full-bridge power converter further converts this three-level dc voltage into a seven-level ac voltage. In this way, the proposed solar power generation system generates a sinusoidal output current that is in phase with the utility voltage and is fed into the utility. The salient features of the proposed seven-level inverter are that only six power electronic switches are used, and only one power electronic switch is switched at high frequency at any time. A prototype is developed and tested to verify the performance of this proposed solar power generation system.
Hybrid topology of asymmetric cascaded multilevel inverter with renewable ene...
This paper presents a binary topology of Multimodule level inverters produce a staircase output voltage from renewable DC voltage sources. The MLI (Multi Level Inverter) Requires many number of semiconductor switches is main drawback of multilevel inverters. The MLI can be classified as two method, one is symmetric and another asymmetric converters. In symmetrical multilevel inverter can apply same voltage level to all cascaded circuit, in asymmetric multilevel inverters can be vary input source voltage at each cascaded H-bridge by using binary algorithm. In this paper, a discrete binary topology for multilevel converters is proposed using cascaded sub-multilevel Cells. This sub-multilevel converter can produce sixty three levels of voltage from five discrete DC source. The Total Harmonic Distortions (THD) is minimized by discrete binary topology. The working operation and performance of the proposed multilevel inverters studies has been verified by simulation of using SIMULINK / MA TLAB results.
Single-phase solar PV system with battery and exchange of power in grid-conne...
A grid tied photovoltaic (PV) power conversion topology is presented in this study with a novel scheme of resynchronization to the grid. This scheme serves the purpose of supplying continuous power to the load along with feeding power to the grid. The control approach helps in mitigation of harmonics and improving the power quality while extracting the optimum power from the PV array. Depending on the availability of grid voltage, the proposed configuration is controlled using three approaches, defined as grid current control, Point of Common Coupling (PCC) voltage control and intentional islanding with re-synchronisation. A simple proportional integral controller manages the grid current, load voltage, battery current and DC Direct Current (DC) link voltage within these modes. Moreover, a control scheme for quick and smooth transitions among the modes is described. The robustness of the system under erratic behaviour of solar insolation, load power and disturbances in grid supply makes it a suitable choice for a residential application. The control, design and simulation results are presented to demonstrate the satisfactory operation of the proposed system.
A New Circuit of Modular Multilevel Inverter for Grid-Connected Photovoltaic ...
This study presents a new circuit topology of the Modular Multilevel Converter (MMC) which is deployed for photovoltaic grid applications. In the conventional MMC, two arm inductors are placed in each phase to limit the circulating current. In the proposed topology, the inductors are replaced by a transformer. The proposed circuit gives a 50% reduction of the voltage rating of the power devices and the capacitors in comparison with the conventional MMC. The required dc-link voltage which is fed directly by PV panels is also reduced by half. The paper presents a PWM method to control the solar inverter output voltage. The proposed concept is confirmed through simulation and experimental results.
Modified phase shifted pwm scheme for reliability improvement in cascaded h-b...
The cascaded H-bridge multilevel inverter (CHMI) is a modular structure that consists of many
power semiconductor switches. With this increase in the number of power semiconductor switches, it is hard to predict and handle the failure of the devices, and hence reliability of CHMI decreases. The major cause of power semiconductor switch failure is junction temperature that is produced by power losses. The study proposes a multi-carrier pulse-width modulation (PWM) scheme for reduction in switching losses of CHMI. In the proposed modulation scheme, the two legs conduct switching operation at different frequencies for switching reduction. One leg conducts switching operation with high frequency, while the other leg conducts switching operation with fundamental frequency. The switching operations with different frequencies cause
unbalanced switching loss to each leg. Therefore, the junction temperature that is based on power losses leads to different life-times for the power semiconductor switch. Additionally, the switching frequency of the two legs is alternated to evenly distribute switching losses and junction temperature. Simulation and experimental results verify the performance of the proposed PWM scheme.
Performance enhancement of actively controlled hybrid dc microgrid incorporat...
In this paper, a new energy control scheme is proposed for actively controlled hybrid dc microgrid to reduce the adverse impact of pulsed power loads. The proposed energy control is an adaptive current-voltage control (ACVC) scheme based on the moving average measurement technique and an adaptive proportional compensator. Unlike conventional energy control methods, the proposed ACVC approach has the advantage of controlling both voltage and current of the system while keeping the output current of the power converter at a relatively constant value. For this study, a laboratory scale hybrid dc microgrid is developed to evaluate the performance of the ACVC strategy and to compare its performance with the other conventional energy control methods. Using experimental test results, it is shown that the proposed strategy highly improves the dynamic performance of the hybrid dc microgrid. Although the ACVC technique causes slightly more bus voltage variation, it effectively eliminates the high current and power pulsation of the power converters. The experimental test results for different pulse duty ratios demonstrated a significant improvement achieved by the developed ACVC scheme in enhancing the system efficiency, reducing the ac grid voltage drop and the frequency fluctuations.
A 5-level High Efficiency Low Cost Hybrid Neutral Point Clamped Transformerle...
With the increase in the level of solar energy integration into the power grid, there arises a need for highly efficient multilevel transformerless grid connected inverter which is able to inject more power into the grid. In this paper, a novel 5-level Hybrid Neutral Point Clamped transformerless inverter topology is proposed which has no inherent ground leakage current. The proposed inverter is analyzed in detail and its switching pattern to generate multilevel output is discussed. The proposed inverter is compared with some popular transformerless inverter topologies. Simulations and experiments results confirm the feasibility and good performance of the proposed inverter.
Combination Analysis and Switching Method of a Cascaded H-Bridge Multilevel I...
This paper analyzes the combination in a cascaded H-bridge multilevel inverter (CHBI) based on transformers with the different turn ratios for increasing the voltage level and proposes the switching method for achieving the output voltage distribution among H-bridge cells (HBCs). The transformers used in this paper are connected to the output of the respective HBCs, and the secondary sides of all the transformers are connected in series for generating the final output voltage. Only one of the transformers, in particular, has a different turn ratio for increasing the output voltage level. In this paper, the possible turn ratio of the special transformer with a different turn ratio is discussed in detail, and a switching method based on the level-shifted switching method for the topology used in this paper is proposed. To verify the effectiveness of the proposed method, a three-phase 21-level CHBI is experimentally tested.
Three Phase Single Stage Isolated Cuk based PFC Converter
In this paper, analysis and design of a three phase isolated Cuk based power factor correction (PFC) converter has been proposed. The proposed converter is operated in discontinuous output inductor current mode (DOICM) to achieve PFC at ac input. This avoids the inner current control loop which further eliminates the sensing of current. This makes the system more reliable and robust. The converter requires only one simple voltage control loop for output voltage regulation and all the power switches are driven by the same gate signal which simplifies the gate driver circuit. The detailed operation of the converter and design calculations are presented. And also a small signal model of the converter by using CIECE approach is presented to aid the controller design. The experimental results from a 2-kW laboratory prototype with 208-V line-to-line input voltage, 400-V output voltage are presented to confirm the operation of the proposed converter. An input power factor of 0.999, an input current total harmonic distortion of as low as 4.06% and a high conversion efficiency of 95.1% are achieved from laboratory prototype.
Novel High Performance Stand Alone Solar PV System with High Gain, High Effic...
This paper proposes a novel 3- stand-alone solar PV system configuration that uses high gain, high efficiency (96%) dc-dc converters both in the forward power stage as well as the bidirectional battery interface. The high voltage gain converters enable the use of low voltage PV and battery sources. This results in minimization of partial shading and parasitic capacitance effects on the PV source. Series connection of a large number of battery modules is obviated, preventing the overcharging and deep discharging issues that reduce the battery life. Also, the proposed configuration facilitates "required power tracking (RPT)" of the PV source as per the load requirements eliminating the use of expensive and 'difficult to manage' dump loads. High performance inverter operation is achieved through abc to dq reference frame transformation, which helps in generating precise information about the load's active power component for RPT, regulation of ac output voltage and minimization of control complexity. Inverter output voltage is regulated by controlling the modulation index of sinusoidal pulse width modulation, resulting in a stable and reliable system operation. The active power demand is controlled by regulating the dc link voltage. All the analytical, simulation and experimental results of this work are presented.
A Fuzzy Logic Based Switching Methodology for a Cascaded H-Bridge Multilevel ...
In this paper, a unusual switching technique is implemented using a fuzzy logic approach. The proposed technique simplifies the conventional method by eliminating the traditional logic gate design. The fuzzy logic pulse generator acts as a look-up table as well as a pulse generator. Based on the modulation index as input, controlled membership functions (MFs) and rules of the fuzzy logic controller (FLC) opens various possibilities in producing pulses directly. The proposed technique is evaluated on the cascaded multilevel inverter with symmetric and asymmetric operations using selective harmonic elimination pulse width modulation (SHE-PWM). MFs are designed based on the pre-calculated firing conditions for different modulation index values. The hardware verification is carried out to support the proposed switching technique.
Power Quality Improvement of Grid-Connected Photovoltaic Systems Using Trans-...
Voltage-source inverter has been used widely in traditional photovoltaic systems which have limitations. To overcome, Z-source inverter has been introduced. In spite of all the features introduced in Z-source inverter, its configuration has been improved over the years, like trans-Z-source inverter which has added advantages compared to traditional inverters, namely buck–boost feature, lesser passive elements, and higher voltage boost gain. In this paper, photovoltaic arrays are connected to the grid via the trans-Z-source inverter with the aim of improving its power quality. Moreover, the shoot through duty ratio is kept constant in the switching control method to add features like lower voltage stress (higher reliability), lower total harmonic distortion (lower maintenance cost), and higher voltage boost ratio. To evaluate the precision of the proposed system, the photovoltaic system is simulated on a standard grid and under partial shading condition which brings about voltage sag, and hence, a dynamic voltage restorer is used to mitigate voltage sag. Simulation results are presented to verify the validation of the proposed photovoltaic system in terms of voltage and current THD reducing 78.2% and 19.7%, respectively.
Permanent Magnet Synchronous Generator-Based Standalone Wind Energy Supply Sy...
In this paper, a novel algorithm, based on dc link voltage, is proposed for effective energy management of a standalone permanent magnet synchronous generator (PMSG)-based variable speed wind energy conversion system consisting of battery, fuel cell, and dump load (i.e., electrolyzer). Moreover, by maintaining the dc link voltage at its reference value, the output ac voltage of the inverter can be kept constant irrespective of variations in the wind speed and load. An effective control technique for the inverter, based on the pulse width modulation (PWM) scheme, has been developed to make the line voltages at the point of common coupling (PCC) balanced when the load is unbalanced. Similarly, a proper control of battery current through dc–dc converter has been carried out to reduce the electrical torque pulsation of the PMSG under an unbalanced load scenario. Based on extensive simulation results using MATLAB/SIMULINK, it has been established that the performance of the controllers both in transient as well as in steady state is quite satisfactory and it can also maintain maximum power point tracking.
Power quality enhancement in residential smart grids through power factor cor...
The proliferation of non-linear loads and the increasing penetration of Distributed Energy Resources (DER) in Medium-Voltage (MV) and Low-Voltage (LV) distribution grids, make it more difficult to maintain the power quality levels in residential electrical grids, especially in the case of weak grids. Most household appliances contain a conventional Power Factor Corrector (PFC) rectifier, which maximizes the load Power Factor (PF) but does not contribute to the regulation of the voltage Total Harmonic Distortion (THDV ) in residential electrical grids. This manuscript proposes a modification for PFC controllers by adapting the operation mode depending on the measured THDV . As a result, the PFCs operate either in a low current Total Harmonic Distortion (THDI ) mode or in the conventional resistor emulator mode and contribute to the regulation of the THDV and the PF at the distribution feeders. To prove the concept, the modification is applied to a current sensorless Non-Linear Controller (NLC) applied to a single-phase Boost rectifier. Experimental results show its performance in a PFC front-end stage operating in Continuous Conduction Mode (CCM) connected to the grid with different THDV .
Similar to A Highly Efficient and Reliable Inverter Configuration Based Cascaded Multi-Level Inverter for PV Systems (20)
Three phase unidirectional rectifiers with open-end source and cascaded float...
Three phase unidirectional rectifiers with open-end source and cascaded float...
A transformerless grid connected photovoltaic inverter with switched capacitors
A transformerless grid connected photovoltaic inverter with switched capacitors
New ac dc power factor correction architecture suitable for high frequency op...
New ac dc power factor correction architecture suitable for high frequency op...
Mppt with single dc–dc converter and inverter for grid connected hybrid wind-...
Mppt with single dc–dc converter and inverter for grid connected hybrid wind-...
A Unified Control and Power Management Scheme for PV-Battery-Based Hybrid Mic...
A Unified Control and Power Management Scheme for PV-Battery-Based Hybrid Mic...
A solar power generation system with a seven level inverter
A solar power generation system with a seven level inverter
Hybrid topology of asymmetric cascaded multilevel inverter with renewable ene...
Hybrid topology of asymmetric cascaded multilevel inverter with renewable ene...
Single-phase solar PV system with battery and exchange of power in grid-conne...
Single-phase solar PV system with battery and exchange of power in grid-conne...
A New Circuit of Modular Multilevel Inverter for Grid-Connected Photovoltaic ...
A New Circuit of Modular Multilevel Inverter for Grid-Connected Photovoltaic ...
Modified phase shifted pwm scheme for reliability improvement in cascaded h-b...
Modified phase shifted pwm scheme for reliability improvement in cascaded h-b...
Performance enhancement of actively controlled hybrid dc microgrid incorporat...
Performance enhancement of actively controlled hybrid dc microgrid incorporat...
A 5-level High Efficiency Low Cost Hybrid Neutral Point Clamped Transformerle...
A 5-level High Efficiency Low Cost Hybrid Neutral Point Clamped Transformerle...
Combination Analysis and Switching Method of a Cascaded H-Bridge Multilevel I...
Combination Analysis and Switching Method of a Cascaded H-Bridge Multilevel I...
Three Phase Single Stage Isolated Cuk based PFC Converter
Three Phase Single Stage Isolated Cuk based PFC Converter
Novel High Performance Stand Alone Solar PV System with High Gain, High Effic...
Novel High Performance Stand Alone Solar PV System with High Gain, High Effic...
A Fuzzy Logic Based Switching Methodology for a Cascaded H-Bridge Multilevel ...
A Fuzzy Logic Based Switching Methodology for a Cascaded H-Bridge Multilevel ...
Power Quality Improvement of Grid-Connected Photovoltaic Systems Using Trans-...
Power Quality Improvement of Grid-Connected Photovoltaic Systems Using Trans-...
Permanent Magnet Synchronous Generator-Based Standalone Wind Energy Supply Sy...
Permanent Magnet Synchronous Generator-Based Standalone Wind Energy Supply Sy...
Power quality enhancement in residential smart grids through power factor cor...
Power quality enhancement in residential smart grids through power factor cor...
More from Asoka Technologies
Solar pv charging station for electric vehicles
Of late, electric vehicles (EVs) have attracted much attention owing to their use of clean energy. Large progress in lithium-ion battery has propelled the development of EVs.However, the challenge is that growing number of EVs leads to huge demand in electric power, which will aggravate the power grid load. This leads to an exploration for alternative and clean sources of energy to charge EVs. This project implements solar energy system to erect a charging station for EV application. The charging station employs multi-port charging by providing a constant voltage DC bus. The charging controllers are operated based on the concept of power balance, and constant current/constant voltage charging. Performance of the charging system is validated with simulation and experimental results.
Generation of Higher Number of Voltage Levels by Stacking Inverters of Lower ...
This paper proposes a new method of generating higher number of levels in the voltage waveform by stacking multilevel converters with lower voltage space vector structures. An important feature of this stacked structure is the use of low voltage devices while attaining higher number of levels. This will find extensive applications in electric vehicles since direct battery drive is possible. The voltages of all the capacitors in the structure can be controlled within a switching cycle using the switching state redundancies (pole voltage redundancies). This helps in reducing the capacitor size. Also, the capacitor voltages can be balanced irrespective of modulation index and load power factor. To verify the concept experimentally, a 9-level inverter is developed by stacking two 5-level inverters and an induction motor is run using V/f control scheme. Both steady state and transient results are presented.
A generalized multilevel inverter topology with reduction of total standing v...
This paper presents a new multilevel inverter topology with reduced active switches and total standing voltage. The proposed topology can generate a high number of voltage levels in the symmetric configuration. This topology intuitively generates positive and negative cycles without an additional H-bridge unit, which considerably reduces the total standing voltage of the inverter. A cascaded structure is developed from the proposed topology to create higher voltage levels. To show the novelty of the proposed topology, a thorough comparison between the available and the proposed topologies in terms of the number of switches, standing voltages, and dc-sources is presented. Furthermore, the power loss analysis is carried out for various load values. The feasibility of the proposed nine-level inverter is verified with simulation and experimental results.
Residential Community Load Management based on Optimal Design of Standalone H...
Microgrids being an important entity in the distribution system, and to get their full advantages
by incorporating maximum distributed generation, standalone hybrid renewable energy systems (HRESs), being environmentally-safe and economically-efficient, are considered as the promising solution to electrify remote areas where the grid power is not available. In this work, a techno-economic investigation with an optimal design of HRES is presented to fulfill the domestic electricity need for a residential area of the Sherani district in the Province of Baluchistan, Pakistan. Nine case studies based on PV/wind/diesel/battery are analyzed based on net present cost (NPC), cost of energy (COE), and emission to decide the feasible solution. HOMER tool is utilized to accomplish modeling and simulation for economic analysis and optimal sizing. Simulation results demonstrated that HRES with PV-wind-battery is the most viable option for the specified area, and the optimal sizing of components are also obtained with $ 28,620 NPC and 0.311 $/kWh COE which shows 81.65% reduction in cost and 100% preserving in toxic emission while fulfilling 100% energy demand with 67.3% of excess energy. Furthermore, MATLAB/Simulink modeling for the optimally designed system is built for technical analysis while its effectiveness is proved by keeping dc and ac buses voltage constant, safe operating range of battery state of charge (SOC) with active power balance between HRES components, as well as efficient ac voltage quality, regardless of generation disturbances and load fluctuations. The output signal has total harmonic distortion (THD) of 0.30% as compared to 5.44% with the conventional control scheme. The novelty lies in the sequential application of both HOMER and MATLAB simulations of the proposed HRES model and validation of the proposition for the studied area; by using and implementing model predictive control (MPC) of a reconfigurable inverter.
Reliability evaluation of MPPT based interleaved boost converter for PV system
The demand for power supply and depletion of the conventional energy sources are increasing drastically. So to overcome this problem, the best alternative power generation for conventional fossil fuel is Photovoltaic solar cell based system because of its advantage of pollution free and its availability in abundance with free of cost. In the MPPT based PV system the converters are the most sensitive part. Therefore to provide uninterrupted power supply without compromising the quality of power, reliability evaluation of interleaved boost converter becomes necessary. MATLAB/Simulink is used for the simulation studies and to determine the power losses of various components of the converter which is used in calculating the failure rates and reliability of the interleaved boost converter. Reliability studies of IBC have not been studied much. However there exists few literature in which reliability expression has been developed using Markov technique which is a more complex method as compare to Reliability Block Diagram (RBD). Therefore this paper proposes reliability modeling and reliability evaluation of Interleaved boost converter in MPPT based photo-voltaic system by using simple RBD method.
Power optimisation scheme of induction motor using FLC for electric vehicle
In electric vehicles (EVs) and hybrid EVs, energy efficiency is essential where the energy storage is limited. Adding to its high stability and low cost, the induction motor efficiency improves with loss minimisation. Also, it can consume more power than the actual need to perform its working when it is operating in less than full load condition. This study proposes a control strategy based on the fuzzy logic control (FLC) for EV applications. FLC controller can improve the starting current amplitude and saves more power. Through the MATLAB/SIMULINK software package, the performance of this control was verified through simulation. As compared with the conventional proportional integral derivative controller, the simulation schemes show good, high-performance results in time-domain response and rapid rejection of system-affected disturbance. Therefore, the core losses of the induction motor are greatly reduced, and in this way improves the efficiency of the driving system. Finally, the suggested control system is validated by the experimental results obtained in the authors’ laboratory, which are in good agreement with the simulation results.
Power Flow Control of Interconnected AC-DC Microgrids in Grid-Connected Hybri...
This paper introduces a new approach for power flow control of interconnected AC-DC microgrids in grid-connected hybrid microgrids based on implementing a modified unified interphase power controller (UIPC). A typical grid-connected hybrid microgrid including one AC microgrid and one DC microgrid is considered as studied system. Instead of using the parallel-connected power converters, these microgrids are interconnected using a modified UIPC. As the first contribution of this paper, the conventional structure of UIPC, which uses three power converters in each phase, is modified so that a reduced number of power converters is implemented for power exchange control between AC-DC microgrids. The modified structure includes one power converter in each phase, named as line power converter (LPC), and a power converter which regulates the DC bus voltage, named as bus power converter (BPC) here. The AC microgrid is connected to the main grid through the LPCs which their DC buses are linked and can operate in capacitance mode (CM) or inductance mode (IM). A fuzzy logic controller is used in the control structure of the LPCs. The fuzzy inference system is optimized based on H∞ filtering method to reduce the errors in membership functions design. Through the BPC, the DC voltage of LPCs is supplied by the DC microgrid. However, since the DC microgrid voltage is provided here by a PV system, the DC link voltage of the LPCs is fluctuating. Thus, as the second contribution, to stabilize the DC link fluctuations, a new nonlinear disturbance observer based robust multiple-surface sliding mode control (NDO-MS-SMC) strategy is presented for DC side control of the BPC. The simulation results confirm the effectiveness of the proposed power flow control strategy of the improved UIPC for hybrid microgrids.
Power flow control of hybrid micro grids using modified uipc
Neuro Fuzzy Inference System (ANFIS) controlled modified Unified Inter-Phase Power Controller (UIPC). For study, a classic hybrid micro-grid connected to grid comprising of a AC micro-grid and a DC micro-grid is taken into account. These micro-grids are interconnected employing a modified UIPC, rather than using the power converters connected in parallel. As the first input of this paper is the standard structure of UIPC, which used three power converters in every phase. It was then modified such as number of power converters is used less and implemented for the control of the exchange of power between AC-DC microgrids. In every phase there is one power electronic converter in the improved structure. It is called as Line Power Converter (LPC). Also there is Bus Power Converter (BPC) to regulate the voltage of the DC bus. The Line Power Converters links the AC micro-grid to the main grid. The DC buses are also linked with them. It can be operated in Inductance Mode (IM) as well as Capacitance Mode (CM). The control structure of LPCs has an Adaptive Fuzzy Logic Controller in it. For hybrid micro-grids, the capability of the suggested power flow control strategy is confirmed by the MATLAB simulation results.
Multifunctional grid tied pv system using modified klms control
This paper deals with the modified kernel least mean square (KLMS) control strategy in double-stage, solar photovoltaic (PV) grid tied system to enhance the power quality at common coupling point (CCP). This proposed control algorithm has less oscillations, fast convergence, fast dynamic response and good steady state performance. A control strategy is used to extract the fundamental active current component of load and generates reference grid current for a DC-AC converter. The proposed modified KLMS control mitigates multiple power quality concerns such as harmonics reduction, unity power factor and load balancing. The dynamic performance of proposed system is confirmed into the MATLAB\Simulink environment. Test results on hardware implementation are presented at varying solar irradiation levels and load unbalancing. Test results are found satisfactory and total harmonic distortion (THD) of the grid currents are observed well within the IEEE-519 standard.
Modelling and voltage control of the solar wind hybrid micro-grid with optimi...
Electricity generation from the wind and solar photovoltaic (PV) systems are highly dependent upon weather conditions. Their intermittent nature leads to fluctuations in their output. Therefore, the need for rapid compensation for energy transmission and distribution systems is increasingly important. Static Synchronous Compensator (STATCOM) can be adopted for reactive power compensation and for decreasing the voltage fluctuation caused by the system and renewable energy sources. This study presents modelling of a Solar PV-Wind Hybrid Micro-grid and the increase of the stable operating limit of the system in case of the incorporation of STATCOM is examined. The major contribution of this paper is the optimization of gain parameters of four PI controllers in STATCOM control circuit based on genetic algorithms (GA) and Bacteria Foraging Algorithm (BFA) and therefore obtaining better responses and voltage stability in terms of nonlinear nature of solar-wind hybrid micro-grid. The Simulink models of the system architecture include a wind turbine model, a solar PV power system model and a STATCOM. It is certified that the voltage fluctuation at the end of the bus bar is reduced by 8% using conventional PI controller, by 10% for GA-based PI controller, and by 15% for BFA based PI controller under variable load. The results obtained by GA and BFA-based optimization of PI controllers are compared with that of the conventional controller and better results attained.
Irradiance-adaptive PV Module Integrated Converter for High Efficiency and Po...
The strive for efficient and cost-effective photovoltaic systems motivated the power electronic design developed here. The work resulted in a DC-DC converter for module integration and distributed maximum power point tracking (MPPT) with a novel adaptive control scheme. The latter is essential for the combined features of high energy efficiency and high power quality over a wide range of operating conditions. The switching frequency is optimally modulated as a function of solar irradiance for power conversion efficiency maximization. With the rise of irradiance, the frequency is reduced to reach the conversion efficiency target. A search algorithm is developed to determine the optimal switching frequency step. Reducing the switching frequency may, however, compromise MPPT efficiency. Furthermore, it leads to increased ripple content. Therefore, to achieve a uniform high power quality at all conditions, interleaved converter cells are adaptively activated. The overall cost is kept low by selecting components that allow for implementing the functions at low cost. Simulation results show the high value of the module integrated converter for DC standalone and microgrid applications. A 400 W prototype was implemented at 0.14 Euro/W. Testing showed efficiencies above 95% taking into account all losses from power conversion, MPPT, and measurement and control circuitry.
Intelligent Power Sharing of DC Isolated Microgrid Based on Fuzzy Sliding Mod...
Linear droop control can realize power sharing among generators in DC microgrid without relying on critical communication links. However, the droop relationship between output power and voltage magnitude of renewable power generate system is nonlinear with uncertainties and disturbances from renewable sources and loads in practical DC microgrid. A novel droop scheme is proposed for an isolated DC microgrid to solve the nonlinear problem. The control strategy is proposed by using the Takagi-Sugeno (T-S) fuzzy model and sliding mode algorithm. The nonlinear droop characteristics can be represented by T-S model through taking advantage of locally measured output variables. The sliding mode droop controller is designed for compensating the uncertainties and disturbances to derive accurate power sharing based on T-S fuzzy model. The proposed scheme is proved to be effective under variable operating conditions through PSIM/Matlab simulation.
Implementation of solar pv battery and diesel generator based electric vehic...
In this paper, a solar PV (Photovoltaic) array, a battery energy storage (BES), a diesel generator (DG) set and grid based EV charging station (CS) is utilized to provide the incessant charging in islanded, grid connected and DG set connected modes. The charging station is primarily designed to use the solar photovoltaic PV array and a BES to charge the electric vehicle (EV) battery. However, in case of exhausted storage battery and unavailable solar PV array generation, the charging station intelligently takes power from the grid or DG (Diesel Generator) set. However, the power from DG set is drawn in a manner that, it always operates at 80-85% loading to achieve maximum fuel efficiency under all loading conditions. Moreover, in coordination with the storage battery, the charging station regulates the generator voltage and frequency without a mechanical speed governor. It also ensures that the power drawn from the grid or the DG set is at unity power factor (UPF) even at nonlinear loading. Moreover, the PCC (Point of Common Coupling) voltage is synchronized to the grid/ generator voltage to obtain the ceaseless charging. The charging station also performs the vehicle to grid active/reactive power transfer, vehicle to home and vehicle to vehicle power transfer for increasing the operational efficiency of the charging station. The operation of the charging station is experimentally validated using the prototype developed in the laboratory.
High step up quasi-z source dc-dc converter
In this paper, a high step-up Quasi-Z Source (QZS) DC-DC converter is proposed. This converter uses a hybrid switched-capacitors switched-inductor method in order to achieve high voltage gains. The proposed converter have resolved the voltage gain limitation of the basic QZS DC-DC converter while keeping its main advantages such as continuous input current and low voltage stress on capacitors. Compared to the basic converter, the duty cycle is not limited, and the voltage stress on the diodes and switch isn’t increased. In addition to these features, the proposed converter has a flexible structure, and extra stages could be added to it in order to achieve even higher voltage gains without increasing the voltage stress on devices or limiting the duty cycle. The operation principle of the converter and related relationships and waveforms are presented in the paper. Also, a comprehensive comparison between the proposed and other QZS based DC-DC converters is provided which confirms the superiority of the proposed converter. Simulations are done in PSCAD/EMTDC in order to investigate the MPPT capability of the converter. In addition, the valid performance and practicality of the converter are studied through the results obtained from the laboratory built prototype.
Fuel cell integrated unified power quality conditioner for voltage and curren...
Electrical and electronic devices when exposed to one or more power quality problems are prone to failure. This paper aims to enhance the quality of power in three-phase four-wire distribution grid using Fuel Cell Integrated Unified Power Quality Conditioner (FCI-UPQC). The proposed FCI-UPQC has four-leg converter on the shunt side and three-leg converter on the series side. A combination of a synchronous reference frame (SRF) and Instantaneous Reactive Power (IRP) theories are utilized to generate reference signals of the FCI-UPQC. Also, this paper proposes Adaptive Neuro-Fuzzy Inference System controller to maintain DC link voltage in the FCI-UPQC. The Adaptive Neuro-Fuzzy Inference System controller is designed like a sugeno fuzzy architecture and trained offline using data from the Proportional Integral (PI) controller. The obtained results proved that the proposed FCI-UPQC compensated power quality problems such as voltage sag, swell, harmonics, neutral current, source current imbalance in three-phase four-wire distribution grid. The presence of fuel cell in this work makes more effectiveness of the proposed system by providing real power support during supply interruption on the grid side.
Distributed incremental adaptive filter controlled grid interactive residenti...
In this paper, a distributed incremental adaptive filter (DIAF) controlled utility interfaced photovoltaic (PV) - battery microgrid system is presented with power quality features. From protection aspects, grid tied solar inverters are required to shut down at loss of the utility. However, the multi-purpose PV-battery system is developed to provide energy to the critical loads, even at loss of distribution network. The bidirectional controlled converter with a battery also mitigates the intermittency of a PV array under rapid variations in the weather. The extracted maximum power is supplied to the voltage source converter (VSC), which is transferred to the nonlinear loads and the utility. The distributed incremental adaptive filter is used to control the VSC with contribution of PV power and the battery. In addition, the DIAF control provides harmonics mitigation, load balancing and power factor improvement functionalities in order to deal with system connected with nonlinear loads. A PV power feed-forward (PVFF) term is incorporated in the current control for injection of active power to the utility as well as to improve the dynamic operation of residential PV-battery microgrid. The battery energy storage (BES) reduces the fuel bills and it is also utilized to provide smoothing attributes to the microgrid. The effectiveness of PV-battery microgrid is validated experimentally developed in the laboratory.
Application of Artificial Neural Networks for Shunt APF Control
Artificial Neural Network (ANN) is becoming an attractive estimation and regression technique in many control applications due to its parallel computing nature and high learning capability. There has been a lot of effort in employing the ANN in shunt active power filter (APF) control applications. Adaptive Linear Neuron (ADALINE) and feed-forward Multilayer Neural Network (MNN) are the most commonly used ANN techniques to extract fundamental and/or harmonic components present in the non-linear currents. This paper aims to provide an in-depth understanding on realizing ADALINE and feed-forward MNN based control algorithms for shunt APF. A step-by-step procedure to implement these ANN based techniques, in Matlab/ Simulink environment, is provided. Furthermore, a detailed analysis on the performance, limitation and advantages of both methods is presented in the paper. The study is supported by conducting both simulation and experimental validations.
Control strategy of pmsg based wind energy conversion system under strong win...
This paper presents a control approach for the Permanent Magnet Synchronous Generator (PMSG) based Wind Energy Conversion Systems (WECS) under a wide range of wind speeds. Generally, most of the wind turbines are turned-off and disconnected from the power grid, in case wind velocity is gone over 25 m/s. It may cause wind power supply shortage from wind farms. This research introduces a pitch angle controller as well as a rotational speed control system so that the PMSG based WECS can generate power if the wind speeds are above 25 m/s. The proposed method reduces the mechanical stress of the wind turbine by preferential reducing of the rotational speed rather than the mechanical torque during strong wind condition. As a result, the chance of turning-off the is reduced compared to the conventional control system because the PMSG based WECS can temporarily tolerate the wind speed up to 35 m/s. A 2 MW WECS with the electrical and mechanical characteristics is modeled in the MATLAB/Sim Power Systems® to verify the proposed research.
Control and energy management of a large scale grid connected pv system
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- 1. ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 For Simulation Results of the project Contact Us Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 A Highly Efficient and Reliable Inverter Configuration Based Cascaded Multi-Level Inverter for PV Systems ABSTRACT: This paper presents an improved Cascaded Multi-Level Inverter (CMLI) based on a highly efficient and reliable configuration for the minimization of the leakage current. Apart from a reduced switch count, the proposed scheme has additional features of low switching and conduction losses. The proposed topology with the given PWM technique reduces the high- frequency voltage transitions in the terminal and common-mode voltages. Avoiding high- frequency voltage transitions achieves the minimization of the leakage current and reduction in the size of EMI filters. Furthermore, the extension of the proposed CMLI along with the PWM technique for 2m+1 levels is also presented, where m represents the number of Photo Voltaic (PV) sources. The proposed PWM technique requires only a single carrier wave for all 2m+1 levels of operation. The Total Harmonic Distortion (THD) of the grid current for the proposed CMLI meets the requirements of IEEE 1547 standard. A comparison of the proposed CMLI with the existing PV Multi-Level Inverter (MLI) topologies is also presented in the paper. Complete details of the analysis of PV terminal and common-mode voltages of the proposed CMLI using switching function concept, simulations, and experimental results are presented in the paper. KEYWORDS: 1. Cascaded multi-level inverter 2. Leakage current 3. Common-mode voltage
- 2. ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 For Simulation Results of the project Contact Us Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 4. Terminal voltage SOFTWARE: MATLAB/SIMULINK CIRCUIT DIAGRAM: Fig. 1. Proposed five-level grid-connected CMLI with PV and parasitic elements.
- 3. ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 For Simulation Results of the project Contact Us Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 EXPECTED SIMULATION RESULTS: Fig. 2. Simulation results of proposed five-level CMLI showing the waveforms of : (a) output voltage vuv; (b) grid current iac; (c) terminal voltage vxg; (d) terminal voltage vyg; (e) terminal voltage vzg; (f) leakage current ileak; (g) common-mode voltage vcm.
- 4. ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 For Simulation Results of the project Contact Us Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 Fig. 3. Proposed five-level CMLI integrated with MPPT. The subplots give waveforms of : (a) voltage VPV1; (b) voltage VPV2; (c) current IPV1; (d) current IPV2; (e) power PPV1; (f) power PPV2; (g) resultant modulation index ma; (h) output power POUT; (i) modified reference wave vref_modified; (j) inverter output voltage vab.
- 5. ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 For Simulation Results of the project Contact Us Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 CONCLUSION: In this paper, an improved five-level CMLI with low switch count for the minimization of leakage current in a transformerless PV system is proposed. The proposed CMLI minimizes the leakage current by eliminating the high-frequency transitions in the terminal and common-mode voltages. The proposed topology also has reduced conduction and switching losses which makes it possible to operate the CMLI at high switching frequency. Furthermore, the solution for generalized 2m+1 levels CMLI is also presented in the paper. The given PWM technique requires only one carrier wave for the generation of 2m+1 levels. The operation, analysis of terminal and common-mode voltages for the CMLI is also presented in the paper. The simulation and experimental results validate the analysis carried out in this paper. The MPPT algorithm is also integrated with the proposed five-level CMLI to extract the maximum power from the PV panels. The proposed CMLI is also compared with the other existing MLI topologies in Table V to show its advantages. REFERENCES: [1] Y. Tang, W. Yao, P.C. Loh and F. Blaabjerg, "Highly Reliable Transformerless Photovoltaic Inverters With Leakage Current and Pulsating Power Elimination," IEEE Trans. Ind. Elect., vol. 63, no. 2, pp. 1016-1026, Feb. 2016. [2] W. Li, Y. Gu, H. Luo, W. Cui, X. He and C. Xia, "Topology Review and Derivation Methodology of Single-Phase Transformerless Photovoltaic Inverters for Leakage Current Suppression," IEEE Trans. Ind. Elect., vol. 62, no. 7, pp. 4537-4551, July 2015.
- 6. ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 For Simulation Results of the project Contact Us Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in 0-9347143789/9949240245 [3] J. Ji, W. Wu, Y. He, Z. Lin, F. Blaabjerg and H. S. H. Chung, "A Simple Differential Mode EMI Suppressor for the LLCL-Filter-Based Single-Phase Grid-Tied Transformerless Inverter," IEEE Trans. Ind. Elect., vol. 62, no. 7, pp. 4141-4147, July 2015. [4] Y. Bae and R.Y.Kim, "Suppression of Common-Mode Voltage Using a Multicentral Photovoltaic Inverter Topology With Synchronized PWM," IEEE Trans. Ind. Elect., vol. 61, no. 9, pp. 4722-4733, Sept. 2014. [5] N. Vazquez, M. Rosas, C. Hernandez, E. Vazquez and F. J. Perez-Pinal, "A New Common- Mode Transformerless Photovoltaic Inverter," IEEE Trans. Ind. Elect., vol. 62, no. 10, pp. 6381- 6391, Oct. 2015.