The most important components of the distributed generation frameworks is the GTIs which is an interface amidst the utility and the source of energy. The recent years have seen an increased interest in the design and usage of GTIs due to its smaller weight and size, low cost and higher efficiency. But the problem of leakage currents in the transformerless inverter that is dependant on its topology and control scheme needs to be looked into carefully. Also, the high performance of the GTI requires a stringent control and various control systems are being developed and applied to the GTIs. This paper reviews the various topologies that are classified based on the attributes of the leakage current and the method of decoupling. Further it reviews and compares the different control techniques applied to the GTIs with respect to the frame of reference, controller, modulation technique and the control parameters considered.
Optimal Placement of Distributed Generation on Radial Distribution System for...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Optimal Siting And Sizing Of Distributed Generation For Radial Distribution S...inventy
Research Inventy provides an outlet for research findings and reviews in areas of Engineering, Computer Science found to be relevant for national and international development, Research Inventy is an open access, peer reviewed international journal with a primary objective to provide research and applications related to Engineering. In its publications, to stimulate new research ideas and foster practical application from the research findings. The journal publishes original research of such high quality as to attract contributions from the relevant local and international communities.
Distributed energy units cannot be directly integrated into the power grid due to their inherently varying output. An interfacing technology is required. The power electronic interface is used for connecting distributed energy resources to the smart grid. It can also be used in any type of electric vehicles. It does not store energy in its circuitry. It receives power from the distributed energy source and converts it to power at the required voltage and frequency. This paper provides a brief introduction on power electronic interface. Matthew N. O. Sadiku | Adedamola A. Omotoso | Sarhan M. Musa "Power Electronic Interface" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-1 , December 2019, URL: https://www.ijtsrd.com/papers/ijtsrd29394.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/29394/power-electronic-interface/matthew-n-o-sadiku
Single core configurations of saturated core fault current limiter performanc...IJECEIAES
Economic growth with industrialization and urbanization lead to an extensive increase in power demand. It forced the utilities to add power generating facilities to cause the necessary demand-generation balance. The bulk power generating stations, mostly interconnected, with the penetration of distributed generation result in an enormous rise in the fault level of power networks. It necessitates for electrical utilities to control the fault current so that the existing switchgear can continue its services without upgradation or replacement for reliable supply. The deployment of fault current limiter (FCL) at the distribution and transmission networks has been under investigation as a potential solution to the problem. A saturated core fault current limiter (SCFCL) technology is a smart, scalable, efficient, reliable, and commercially viable option to manage fault levels in existing and future MV/HV supply systems. This paper presents the comparative performance analysis of two single-core SCFCL topologies impressed with different core saturations. It has demonstrated that the single AC winding configuration needs more bias power for affecting the same current limiting performance with an acceptable steady-state voltage drop contribution. The fault state impedance has a transient nature, and the optimum bias selection is a critical design parameter in realizing the SCFCL applications.
Various demand side management techniques and its role in smart grid–the stat...IJECEIAES
The current lifestyle of humanity relies heavily on energy consumption, thusrendering it an inevitable need. An ever-increasing demand for energy hasresulted from the increasing population. Most of this demand is met by thetraditional sources that continuously deplete and raise significantenvironmental issues. The existing power structure of developing nations isaging, unstable, and unfeasible, further prolonging the problem. The existingelectricity grid is unstable, vulnerable to blackouts and disruption, has hightransmission losses, low quality of power, insufficient electricity supply, anddiscourages distributed energy sources from being incorporated. Mitigatingthese problems requires a complete redesign of the system of powerdistribution. The modernization of the electric grid, i.e., the smart grid, is anemerging combination of different technologies designed to bring about theelectrical power grid that is changing dramatically. Demand sidemanagement (DSM) allow customers to be more involved in contributors tothe power systems to achieve system goals by scheduling their shiftableload. Effective DSM systems require the participation of customers in thesystem that can be done in a fair system. This paper focuses primarily ontechniques of DSM and demand responses (DR), including schedulingapproaches and strategies for optimal savings.
Improved Power Quality by using STATCOM Under Various Loading ConditionsIJMTST Journal
A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that
results in a failure or a mis-operation of end user equipment’s. Utility distribution networks, sensitive
industrial loads and critical commercial operations suffer from various types of outages and service
interruptions which can cost significant financial losses. With the restructuring of power systems and with
shifting trend towards distributed and dispersed generation, the issue of power quality is going to take
newer dimensions. Injection of the wind power into an electric grid affects the power quality. The
performance of the wind turbine and thereby power quality are determined on the basis of measurements
and the norms followed according to the guideline specified in International Electro-technical Commission
standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality
measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical
behavior of switching operation and these are measured according to national/international guidelines.
Static Compensator (STATCOM) is connected at a point of common coupling with a battery energy storage
system (BESS) to mitigate the power quality issues. The battery energy storage is integrated to sustain the
real power source under fluctuating wind power. Here two control schemes for STATCOM are Fuzzy logic
controller and hybrid Fuzzy logic controller. We can better response for hybrid fuzzy compare to fuzzy logic
controller. The STATCOM control scheme for the grid connected wind energy generation system for power
quality improvement is simulated using MATLAB/SIMULINK in power system block set. Finally the proposed
scheme is applied for both balanced and unbalanced linear nonlinear loads.
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.
Optimal Placement of Distributed Generation on Radial Distribution System for...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Optimal Siting And Sizing Of Distributed Generation For Radial Distribution S...inventy
Research Inventy provides an outlet for research findings and reviews in areas of Engineering, Computer Science found to be relevant for national and international development, Research Inventy is an open access, peer reviewed international journal with a primary objective to provide research and applications related to Engineering. In its publications, to stimulate new research ideas and foster practical application from the research findings. The journal publishes original research of such high quality as to attract contributions from the relevant local and international communities.
Distributed energy units cannot be directly integrated into the power grid due to their inherently varying output. An interfacing technology is required. The power electronic interface is used for connecting distributed energy resources to the smart grid. It can also be used in any type of electric vehicles. It does not store energy in its circuitry. It receives power from the distributed energy source and converts it to power at the required voltage and frequency. This paper provides a brief introduction on power electronic interface. Matthew N. O. Sadiku | Adedamola A. Omotoso | Sarhan M. Musa "Power Electronic Interface" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-1 , December 2019, URL: https://www.ijtsrd.com/papers/ijtsrd29394.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/29394/power-electronic-interface/matthew-n-o-sadiku
Single core configurations of saturated core fault current limiter performanc...IJECEIAES
Economic growth with industrialization and urbanization lead to an extensive increase in power demand. It forced the utilities to add power generating facilities to cause the necessary demand-generation balance. The bulk power generating stations, mostly interconnected, with the penetration of distributed generation result in an enormous rise in the fault level of power networks. It necessitates for electrical utilities to control the fault current so that the existing switchgear can continue its services without upgradation or replacement for reliable supply. The deployment of fault current limiter (FCL) at the distribution and transmission networks has been under investigation as a potential solution to the problem. A saturated core fault current limiter (SCFCL) technology is a smart, scalable, efficient, reliable, and commercially viable option to manage fault levels in existing and future MV/HV supply systems. This paper presents the comparative performance analysis of two single-core SCFCL topologies impressed with different core saturations. It has demonstrated that the single AC winding configuration needs more bias power for affecting the same current limiting performance with an acceptable steady-state voltage drop contribution. The fault state impedance has a transient nature, and the optimum bias selection is a critical design parameter in realizing the SCFCL applications.
Various demand side management techniques and its role in smart grid–the stat...IJECEIAES
The current lifestyle of humanity relies heavily on energy consumption, thusrendering it an inevitable need. An ever-increasing demand for energy hasresulted from the increasing population. Most of this demand is met by thetraditional sources that continuously deplete and raise significantenvironmental issues. The existing power structure of developing nations isaging, unstable, and unfeasible, further prolonging the problem. The existingelectricity grid is unstable, vulnerable to blackouts and disruption, has hightransmission losses, low quality of power, insufficient electricity supply, anddiscourages distributed energy sources from being incorporated. Mitigatingthese problems requires a complete redesign of the system of powerdistribution. The modernization of the electric grid, i.e., the smart grid, is anemerging combination of different technologies designed to bring about theelectrical power grid that is changing dramatically. Demand sidemanagement (DSM) allow customers to be more involved in contributors tothe power systems to achieve system goals by scheduling their shiftableload. Effective DSM systems require the participation of customers in thesystem that can be done in a fair system. This paper focuses primarily ontechniques of DSM and demand responses (DR), including schedulingapproaches and strategies for optimal savings.
Improved Power Quality by using STATCOM Under Various Loading ConditionsIJMTST Journal
A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that
results in a failure or a mis-operation of end user equipment’s. Utility distribution networks, sensitive
industrial loads and critical commercial operations suffer from various types of outages and service
interruptions which can cost significant financial losses. With the restructuring of power systems and with
shifting trend towards distributed and dispersed generation, the issue of power quality is going to take
newer dimensions. Injection of the wind power into an electric grid affects the power quality. The
performance of the wind turbine and thereby power quality are determined on the basis of measurements
and the norms followed according to the guideline specified in International Electro-technical Commission
standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality
measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical
behavior of switching operation and these are measured according to national/international guidelines.
Static Compensator (STATCOM) is connected at a point of common coupling with a battery energy storage
system (BESS) to mitigate the power quality issues. The battery energy storage is integrated to sustain the
real power source under fluctuating wind power. Here two control schemes for STATCOM are Fuzzy logic
controller and hybrid Fuzzy logic controller. We can better response for hybrid fuzzy compare to fuzzy logic
controller. The STATCOM control scheme for the grid connected wind energy generation system for power
quality improvement is simulated using MATLAB/SIMULINK in power system block set. Finally the proposed
scheme is applied for both balanced and unbalanced linear nonlinear loads.
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.
A non-isolated tri-port converter is a fully compact and functional system by the integration of basic converters. This can be used for renewable energy applications. This converter is capable of achieving different switching patterns of power flow between the source and load, interfaced sources of various voltage and current levels with the dc grid. This tri-port converter has to be used for continuous power distribution of rechargeable battery, photovoltaic panels and load. Due to the implementation of this dc-dc converter some operations like buck, boost and buck-boost operations became easy. Use of this converter helps in easy implementation of the system. The solar PV panel implementation boosts the system to a high level and bidirectional flow became easy from source to load and vice versa.
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.
As the rapid development of photovoltaic (PV) technology in recent years with the growth of electricity demand, integration of photovoltaic distributed generation (PVDG) to the distribution system is emerging to fulfil the demand. There are benefits and drawbacks to the distribution system due to the penetration of PVDG. This paper discussed and investigated the impacts of PVDG location and size on distribution power systems. The medium voltage distribution network is connected to the grid with the load being supplied by PVDG. Load flow and short circuit calculation are analyzed by using DigSILENT Power Factory Software. Comparisons have been made between the typical distribution system and the distribution system with the penetration of PVDG. Impacts in which PVDG location and size integrates with distribution system are investigated with the results given from the load flow and short circuit analysis. The results indicate positive impacts on the system interconnected with PVDG such as improving voltage profile, reducing power losses, releasing transmission and distribution grid capacity. It also shows that optimal locations and sizes of DGs are needed to minimize the system’s power losses. On the other hand, it shows that PVDG interconnection to the system can cause reverse power flow at improper DG size and location and increases short circuit level.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
The negative impacts or side effects of a damper circuit insertion in an LCL passive filter utilized to filter DC/AC inverters output voltage is presented in this paper. For comparative study, this paper discusses two damping configurations, namely series and parallel damping, as well as the LCL filter without damping element. Four criteria are used to explore the impacts of the damper circuits, i.e. their total harmonic distortions (THDs), the output voltage amplitude, the output power and the power efficiency. Theoretically and emphirically shown by previous studies, the damper can indeed reduce the peak resonance frequency of the filter in its frequency response curve. However, in any circumstance, it can potentially reduce the inverters power and efficiency, voltage output amplitude, and cannot improve its THD reduction. The analysis results have shown that the side effects depends also on the load conditions, which are different for each damping circuit configuration.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
In microgrid, if fault occurs or any other contingency happens, then the problems would be created which are related to power flow, also there are various protection schemes are used for minimize or eliminate these problems.
Voltage control is used for reactive power balance and P-f control is used for active power control.
Various protection schemes such as, over current protection, differential protection scheme, zoning of network in adaptive protection scheme are used in microgrid system .
Operation and Control of Grid Connected Hybrid AC/DC Microgrid using Various RESIAES-IJPEDS
This paper proposes a Hybrid AC/DC Microgrid in alliance with Photo Voltaic (PV) energy, Wind Energy and Proton Exchange Membrane (PEM) Fuel cells. Microgrids are becoming increasingly attractive to the researchers because of the less greenhouse gases, low running cost, and flexibility to operate in connection with utility grid. The Hybrid AC/DC Microgrid constitutes independent AC and DC subgrids, where all the corresponding sources and loads are connected to their respective buses and these buses are interfaced using an interfacing converter. The Hybrid AC/DC Microgrid increases system efficiency by reducing the multiple reverse conversions involved in conventional RES integration to grid. A Small Hybrid AC/DC Microgrid in grid connected mode was modeled and simulated in MATLAB- SIMULINK environment. The simulation results prove the stable operation considering the uncertainty of generations and loads.
Fuzzy logic control of hybrid systems including renewable energy in microgrids IJECEIAES
With a growing demand for more energy from subscribers, a traditional electric grid is unable to meet new challenges, in the remote areas remains the extension of the conventional electric network very hard to do make prohibitively expensive. Therefore, a new advanced generation of traditional electrical is inevitable and indispensable to move toward an effective, economical, green, clean and self-correcting power system. The most well-known term used to define this next generation power system is micro grid (MG) based on renewable energy sources (RES). Since, the energy produced by RES are not constant at all times, a wide range of energy control techniques must be involved to provide a reliable power to consumers. To solve this problem in this paper we present a fuzzy logic control of isolated hybrid systems (HRES) including renewable energy in micro-grids to maintain a stability in voltage and frequency output especially in the standalone application. The considered HRES combine a wind turbine (WT) and photovoltaic (PV) panels as primary energy sources and an energy storage system (ESS) based on battery as a backup solution. Simulation results obtained from MATLAB/Simulink environment demonstrate the effectiveness of the proposed algorithm in decreasing the electricity bill of customer.
This work highlights a modular power conditioning system (PCS) in photovoltaic (PV) applications which consists with a DC-DC converter. The converter is able to regulate and amplify the input DC voltage produced by the PV panal. The implementation of Mosfet as bidirectional switch on the converter yields greater conversion ratio and better voltage regulation than a conventional DC-DC step up converter and PWM resonant converter. It also reduces the switching losses on the output DC voltage of the converter, as the MOSFET switches on primary winding of converter switch on under ZVS conditions. The proposed resonant converter has been designed, with the modification of series resonant converter and PWM boost converter that utilizes the high frequency of AC bidirectional switch to eliminate the weaknesses of used converters. The topology of the proposed converter includes the mode of operations, designing procedure and components selection of the new converter elements. This topology provides a DC output voltage to the inverter at range of about 120Vac-208 Vac.
Grid Interconnection of Renewable Energy Sources at the Distribution Level Wi...Pradeep Avanigadda
Renewable energy resources (RES) are being increasingly
connected in distribution systems utilizing power electronic
converters. This paper presents a novel control strategy for
achieving maximum benefits from these grid-interfacing inverters
when installed in 3-phase 4-wire distribution systems. The inverter
is controlled to perform as a multi-function device by incorporating
active power filter functionality. The inverter can thus be
utilized as: 1) power converter to inject power generated from
RES to the grid, and 2) shunt APF to compensate current unbalance,
load current harmonics, load reactive power demand and
load neutral current. All of these functions may be accomplished
either individually or simultaneously. 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 and validated through digital signal processor-based
laboratory experimental results.
Index Terms—Active power filter
Droop control method for parallel dc converters used in standalone pv wind po...eSAT Journals
Abstract The rising rate of consumption and price of fossil fuel along with environmental pollution by conventional power generation draw global attention to renewable energy sources and technology. Paper gives analysis study on current sharing issues of parallel DC converters in standalone photovoltaic (PV) WIND system. Solar wind power generating system with maximum power point tracking (MPPT) technique – incremental conductance method is used for the simulation analysis. The main drawbacks of parallel converters used in system are poor power sharing and voltage drop. The paper describes about instantaneous droop calculation considering effect of cable resistance using droop index to improve the power sharing performance. The control technique is simulated using MATLAB/SIMULINK in PV- wind power generating system with MPPT and case study has been done on the control strategy and verifies the effectiveness of adaptive droop control on output converter voltage. Key Words: Microgrid; droop method; incremental conductance (Incond); maximum power point tracking (MPPT).
Hybrid bypass technique to mitigate leakage current in the grid-tied inverterIJECEIAES
The extensive use of fossil fuel is destroying the balance of nature that could lead to many problems in the forthcoming era. Renewable energy resources are a ray of hope to avoid possible destruction. Smart grid and distributed power generation systems are now mainly built with the help of renewable energy resources. The integration of renewable energy production system with the smart grid and distributed power generation is facing many challenges that include addressing the issue of isolation and power quality. This paper presents a new approach to address the aforementioned issues by proposing a hybrid bypass technique concept to improve the overall performance of the grid-tied inverter in solar power generation. The topology with the proposed technique is presented using traditional H5, oH5 and H6 inverter. Comparison of topologies with literature is carried out to check the feasibility of the method proposed. It is found that the leakage current of all the proposed inverters is 9 mA and total harmonic distortion is almost about 2%. The proposed topology has good efficiency, common mode and differential mode characteristics.
A non-isolated tri-port converter is a fully compact and functional system by the integration of basic converters. This can be used for renewable energy applications. This converter is capable of achieving different switching patterns of power flow between the source and load, interfaced sources of various voltage and current levels with the dc grid. This tri-port converter has to be used for continuous power distribution of rechargeable battery, photovoltaic panels and load. Due to the implementation of this dc-dc converter some operations like buck, boost and buck-boost operations became easy. Use of this converter helps in easy implementation of the system. The solar PV panel implementation boosts the system to a high level and bidirectional flow became easy from source to load and vice versa.
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.
As the rapid development of photovoltaic (PV) technology in recent years with the growth of electricity demand, integration of photovoltaic distributed generation (PVDG) to the distribution system is emerging to fulfil the demand. There are benefits and drawbacks to the distribution system due to the penetration of PVDG. This paper discussed and investigated the impacts of PVDG location and size on distribution power systems. The medium voltage distribution network is connected to the grid with the load being supplied by PVDG. Load flow and short circuit calculation are analyzed by using DigSILENT Power Factory Software. Comparisons have been made between the typical distribution system and the distribution system with the penetration of PVDG. Impacts in which PVDG location and size integrates with distribution system are investigated with the results given from the load flow and short circuit analysis. The results indicate positive impacts on the system interconnected with PVDG such as improving voltage profile, reducing power losses, releasing transmission and distribution grid capacity. It also shows that optimal locations and sizes of DGs are needed to minimize the system’s power losses. On the other hand, it shows that PVDG interconnection to the system can cause reverse power flow at improper DG size and location and increases short circuit level.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
The negative impacts or side effects of a damper circuit insertion in an LCL passive filter utilized to filter DC/AC inverters output voltage is presented in this paper. For comparative study, this paper discusses two damping configurations, namely series and parallel damping, as well as the LCL filter without damping element. Four criteria are used to explore the impacts of the damper circuits, i.e. their total harmonic distortions (THDs), the output voltage amplitude, the output power and the power efficiency. Theoretically and emphirically shown by previous studies, the damper can indeed reduce the peak resonance frequency of the filter in its frequency response curve. However, in any circumstance, it can potentially reduce the inverters power and efficiency, voltage output amplitude, and cannot improve its THD reduction. The analysis results have shown that the side effects depends also on the load conditions, which are different for each damping circuit configuration.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
In microgrid, if fault occurs or any other contingency happens, then the problems would be created which are related to power flow, also there are various protection schemes are used for minimize or eliminate these problems.
Voltage control is used for reactive power balance and P-f control is used for active power control.
Various protection schemes such as, over current protection, differential protection scheme, zoning of network in adaptive protection scheme are used in microgrid system .
Operation and Control of Grid Connected Hybrid AC/DC Microgrid using Various RESIAES-IJPEDS
This paper proposes a Hybrid AC/DC Microgrid in alliance with Photo Voltaic (PV) energy, Wind Energy and Proton Exchange Membrane (PEM) Fuel cells. Microgrids are becoming increasingly attractive to the researchers because of the less greenhouse gases, low running cost, and flexibility to operate in connection with utility grid. The Hybrid AC/DC Microgrid constitutes independent AC and DC subgrids, where all the corresponding sources and loads are connected to their respective buses and these buses are interfaced using an interfacing converter. The Hybrid AC/DC Microgrid increases system efficiency by reducing the multiple reverse conversions involved in conventional RES integration to grid. A Small Hybrid AC/DC Microgrid in grid connected mode was modeled and simulated in MATLAB- SIMULINK environment. The simulation results prove the stable operation considering the uncertainty of generations and loads.
Fuzzy logic control of hybrid systems including renewable energy in microgrids IJECEIAES
With a growing demand for more energy from subscribers, a traditional electric grid is unable to meet new challenges, in the remote areas remains the extension of the conventional electric network very hard to do make prohibitively expensive. Therefore, a new advanced generation of traditional electrical is inevitable and indispensable to move toward an effective, economical, green, clean and self-correcting power system. The most well-known term used to define this next generation power system is micro grid (MG) based on renewable energy sources (RES). Since, the energy produced by RES are not constant at all times, a wide range of energy control techniques must be involved to provide a reliable power to consumers. To solve this problem in this paper we present a fuzzy logic control of isolated hybrid systems (HRES) including renewable energy in micro-grids to maintain a stability in voltage and frequency output especially in the standalone application. The considered HRES combine a wind turbine (WT) and photovoltaic (PV) panels as primary energy sources and an energy storage system (ESS) based on battery as a backup solution. Simulation results obtained from MATLAB/Simulink environment demonstrate the effectiveness of the proposed algorithm in decreasing the electricity bill of customer.
This work highlights a modular power conditioning system (PCS) in photovoltaic (PV) applications which consists with a DC-DC converter. The converter is able to regulate and amplify the input DC voltage produced by the PV panal. The implementation of Mosfet as bidirectional switch on the converter yields greater conversion ratio and better voltage regulation than a conventional DC-DC step up converter and PWM resonant converter. It also reduces the switching losses on the output DC voltage of the converter, as the MOSFET switches on primary winding of converter switch on under ZVS conditions. The proposed resonant converter has been designed, with the modification of series resonant converter and PWM boost converter that utilizes the high frequency of AC bidirectional switch to eliminate the weaknesses of used converters. The topology of the proposed converter includes the mode of operations, designing procedure and components selection of the new converter elements. This topology provides a DC output voltage to the inverter at range of about 120Vac-208 Vac.
Grid Interconnection of Renewable Energy Sources at the Distribution Level Wi...Pradeep Avanigadda
Renewable energy resources (RES) are being increasingly
connected in distribution systems utilizing power electronic
converters. This paper presents a novel control strategy for
achieving maximum benefits from these grid-interfacing inverters
when installed in 3-phase 4-wire distribution systems. The inverter
is controlled to perform as a multi-function device by incorporating
active power filter functionality. The inverter can thus be
utilized as: 1) power converter to inject power generated from
RES to the grid, and 2) shunt APF to compensate current unbalance,
load current harmonics, load reactive power demand and
load neutral current. All of these functions may be accomplished
either individually or simultaneously. 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 and validated through digital signal processor-based
laboratory experimental results.
Index Terms—Active power filter
Droop control method for parallel dc converters used in standalone pv wind po...eSAT Journals
Abstract The rising rate of consumption and price of fossil fuel along with environmental pollution by conventional power generation draw global attention to renewable energy sources and technology. Paper gives analysis study on current sharing issues of parallel DC converters in standalone photovoltaic (PV) WIND system. Solar wind power generating system with maximum power point tracking (MPPT) technique – incremental conductance method is used for the simulation analysis. The main drawbacks of parallel converters used in system are poor power sharing and voltage drop. The paper describes about instantaneous droop calculation considering effect of cable resistance using droop index to improve the power sharing performance. The control technique is simulated using MATLAB/SIMULINK in PV- wind power generating system with MPPT and case study has been done on the control strategy and verifies the effectiveness of adaptive droop control on output converter voltage. Key Words: Microgrid; droop method; incremental conductance (Incond); maximum power point tracking (MPPT).
Hybrid bypass technique to mitigate leakage current in the grid-tied inverterIJECEIAES
The extensive use of fossil fuel is destroying the balance of nature that could lead to many problems in the forthcoming era. Renewable energy resources are a ray of hope to avoid possible destruction. Smart grid and distributed power generation systems are now mainly built with the help of renewable energy resources. The integration of renewable energy production system with the smart grid and distributed power generation is facing many challenges that include addressing the issue of isolation and power quality. This paper presents a new approach to address the aforementioned issues by proposing a hybrid bypass technique concept to improve the overall performance of the grid-tied inverter in solar power generation. The topology with the proposed technique is presented using traditional H5, oH5 and H6 inverter. Comparison of topologies with literature is carried out to check the feasibility of the method proposed. It is found that the leakage current of all the proposed inverters is 9 mA and total harmonic distortion is almost about 2%. The proposed topology has good efficiency, common mode and differential mode characteristics.
Power Quality Improvement with Multilevel Inverter Based IPQC for MicrogridIJMTST Journal
A micro grid is a hybrid power system consists of several distributed resources and local loads .Now a
days with increasing on a day to day life micro grid plays a vital role in power generation using Renewable
Energy Sources. Usage of power electronic devices in a micro grid results in harmonic generation and leads to
various power quality issues. Inorder to overcome voltage fluctuations and over current a magnetic flux
control based variable reactor is proposed. The performance of IPQC can be verified by using
MATLAB/SIMULINK`
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.
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.
Solid-State Transformer (S2T) also known as Power Electronic Transformer (PET) is applied in various industrial fields compared to the conventional transformer due to it flexible voltage transfer ratio, high power density, and low harmonic distortion. This paper presents the S2T of Single Phase Matrix Converter (SPMC) that acts as cyclo-converter. A 1kHz frequency was synthesized on the primary side of the transformer using Pulse Width Modulation (PWM) technique, whilst, the output converted by the SPMC that produces the 50Hz frequency. A part of AC to AC operation, the switching algorithm for safe-commutation technique is also presented to solve the commutation problem caused by the usage of inductive load. Minimization of size, losses and optimal efficiency are the advantages of this approach. The proposed model was simulated by using MATLAB/Simulink (MLS).
In the microgrid systems, three-phase inverter becomes the main power electronic interface for renewable distributed energy resources (DERs), especially for the islanded microgrids in which the power quality is easily affected by unbalanced and nonlinear loads, this is due to the fact that the voltage and frequency of the microgrid are not supported by the main power grid but determined only by the inverters. Therefore, the compensation of the load unbalances and harmonics in autonomous microgrid inverters are getting more attention in power quality research areas. The main purpose of this paper is to represent an overview of the control strategies of various inverters for unbalanced load compensation.
Analysis and Design of Solar Photo voltaic Grid Connected Inverterijeei-iaes
This paper presents common mode voltage analysis of single phase grid connected photovoltaic inverter. Many researchers proposed different grid tie inverters for applications like domestic powering, street lighting, water pumping, cooling and heating applications, however traditional grid tie PV inverter uses either a line frequency or a high frequency transformer between the inverter and grid but losses will increase in the network leading to reduced efficiency of the system. In order to increase the efficiency, with reduced size and cost of the system, the effective solution is to remove the isolation transformer. But common mode (CM) ground leakage current due to parasitic capacitance between the PV panels and the ground making the system unreliable. The common mode current reduces the efficiency of power conversion stage, affects the quality of grid current, deteriorate the electric magnetic compatibility and give rise to the safety threats. In order to eliminate the common mode leakage current in Transformerless PV systm two control algorithms of multi-carrier pwm are implemented and compared for performance analysis.The shoot-through issue that is encountered by traditional voltage source inverter is analyzed for enhanced system reliability. These control algorithms are compared for common mode voltage and THD comparisons. The proposed system is designed using MATLAB/SIMULINK software for analysis.
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.
OPTIMAL PLACEMENT OF DISTRIBUTED GENERATION FOR LOSS REDUCTION IN DISTRIBUTIO...ijiert bestjournal
Due to the increasing interest on renewable sources in recent times,the studies on integration of distributed generation to the power grid have rapid ly increased. Distributed generations (DGs) play an important role in distribution networks. Am ong many of their merits,loss reduction and voltage profile improvement can be the salient spec ifications of Distributed generations (DG). Non-optimal locations and non-optimal sizes of Dist ributed generations (DG) units may lead to increase losses,together with bad effect on voltag e profile. Proper location of Distributed generations (DGs) in power systems is important for obtaining their maximum potential benefits. Distributed generation (DG) units reduce electric p ower losses and hence improve reliability and voltage profile. Determination of appropriate size and location of Distributed generation (DG) is important to maximize overall system efficiency. In this project,Newton raphson method optimization technique has been presented to determ ine the appropriate size and proper allocation of Distributed generation (DG) in a dist ribution network.So,this project focus towards,at determining optimal DG allocation and s izing as well as analyzing the impact of Distributed generation (DG) in an electric power sy stem in terms of voltage profile improvement and line loss reduction
The aim of this research is the speed tracking of the permanent magnet synchronous motor (PMSM) using an intelligent Neural-Network based adapative backstepping control. First, the model of PMSM in the Park synchronous frame is derived. Then, the PMSM speed regulation is investigated using the classical method utilizing the field oriented control theory. Thereafter, a robust nonlinear controller employing an adaptive backstepping strategy is investigated in order to achieve a good performance tracking objective under motor parameters changing and external load torque application. In the final step, a neural network estimator is integrated with the adaptive controller to estimate the motor parameters values and the load disturbance value for enhancing the effectiveness of the adaptive backstepping controller. The robsutness of the presented control algorithm is demonstrated using simulation tests. The obtained results clearly demonstrate that the presented NN-adaptive control algorithm can provide good trackingperformances for the speed trackingin the presence of motor parameter variation and load application.
This paper presents a fast and accurate fault detection, classification and direction discrimination algorithm of transmission lines using one-dimensional convolutional neural networks (1D-CNNs) that have ingrained adaptive model to avoid the feature extraction difficulties and fault classification into one learning algorithm. A proposed algorithm is directly usable with raw data and this deletes the need of a discrete feature extraction method resulting in more effective protective system. The proposed approach based on the three-phase voltages and currents signals of one end at the relay location in the transmission line system are taken as input to the proposed 1D-CNN algorithm. A 132kV power transmission line is simulated by Matlab simulink to prepare the training and testing data for the proposed 1D- CNN algorithm. The testing accuracy of the proposed algorithm is compared with other two conventional methods which are neural network and fuzzy neural network. The results of test explain that the new proposed detection system is efficient and fast for classifying and direction discrimination of fault in transmission line with high accuracy as compared with other conventional methods under various conditions of faults.
Among the most widespread renewable energy sources is solar energy; Solar panels offer a green, clean, and environmentally friendly source of energy. In the presence of several advantages of the use of photovoltaic systems, the random operation of the photovoltaic generator presents a great challenge, in the presence of a critical load. Among the most used solutions to overcome this problem is the combination of solar panels with generators or with the public grid or both. In this paper, an energy management strategy is proposed with a safety aspect by using artificial neural networks (ANNs), in order to ensure a continuous supply of electricity to consumers with a maximum solicitation of renewable energy.
In this paper, the artificial neural network (ANN) has been utilized for rotating machinery faults detection and classification. First, experiments were performed to measure the lateral vibration signals of laboratory test rigs for rotor-disk-blade when the blades are defective. A rotor-disk-blade system with 6 regular blades and 5 blades with various defects was constructed. Second, the ANN was applied to classify the different x- and y-axis lateral vibrations due to different blade faults. The results based on training and testing with different data samples of the fault types indicate that the ANN is robust and can effectively identify and distinguish different blade faults caused by lateral vibrations in a rotor. As compared to the literature, the present paper presents a novel work of identifying and classifying various rotating blade faults commonly encountered in rotating machines using ANN. Experimental data of lateral vibrations of the rotor-disk-blade system in both x- and y-directions are used for the training and testing of the network.
This paper focuses on the artificial bee colony (ABC) algorithm, which is a nonlinear optimization problem. is proposed to find the optimal power flow (OPF). To solve this problem, we will apply the ABC algorithm to a power system incorporating wind power. The proposed approach is applied on a standard IEEE-30 system with wind farms located on different buses and with different penetration levels to show the impact of wind farms on the system in order to obtain the optimal settings of control variables of the OPF problem. Based on technical results obtained, the ABC algorithm is shown to achieve a lower cost and losses than the other methods applied, while incorporating wind power into the system, high performance would be gained.
The significance of the solar energy is to intensify the effectiveness of the Solar Panel with the use of a primordial solar tracking system. Here we propounded a solar positioning system with the use of the global positioning system (GPS) , artificial neural network (ANN) and image processing (IP) . The azimuth angle of the sun is evaluated using GPS which provide latitude, date, longitude and time. The image processing used to find sun image through which centroid of sun is calculated and finally by comparing the centroid of sun with GPS quadrate to achieve optimum tracking point. Weather conditions and situation observed through AI decision making with the help of IP algorithms. The presented advance adaptation is analyzed and established via experimental effects which might be made available on the memory of the cloud carrier for systematization. The proposed system improve power gain by 59.21% and 10.32% compare to stable system (SS) and two-axis solar following system (TASF) respectively. The reduced tracking error of IoT based Two-axis solar following system (IoT-TASF) reduces their azimuth angle error by 0.20 degree.
Kosovo has limited renewable energy resources and its power generation sector is based on fossil fuels. Such a situation emphasizes the importance of active research and efficient use of renewable energy potential. According to the analysis of meteorological data for Kosovo, it can be concluded that among the most attractive potential wind power sites are the locations known as Kitka (42° 29' 41" N and 21° 36' 45" E) and Koznica (42° 39′ 32″ N, 21° 22′30″E). The two terrains in which the analysis was carried out are mountain areas, with altitudes of 1142 m (Kitka) and 1230 m (Koznica). the same measuring height, about 84 m above the ground, is obtained for these average wind speeds: Kitka 6,667 m/s and Koznica 6,16 m/s. Since the difference in wind speed is quite large versus a difference in altitude that is not being very large, analyses are made regarding the terrain characteristics including the terrain relief features. In this paper it will be studied how much the roughness of the terrain influences the output energy. Also, that the assumption to be taken the same as to how much they will affect the annual energy produced.
Large-scale grid-tied photovoltaic (PV) station are increasing rapidly. However, this large penetration of PV system creates frequency fluctuation in the grid due to the intermittency of solar irradiance. Therefore, in this paper, a robust droop control mechanism of the battery energy storage system (BESS) is developed in order to damp the frequency fluctuation of the multi-machine grid system due to variable active power injected from the PV panel. The proposed droop control strategy incorporates frequency error signal and dead-band for effective minimization of frequency fluctuation. The BESS system is used to consume/inject an effective amount of active power based upon the frequency oscillation of the grid system. The simulation analysis is carried out using PSCAD/EMTDC software to prove the effectiveness of the proposed droop control-based BESS system. The simulation result implies that the proposed scheme can efficiently curtail the frequency oscillation.
This study investigates experimentally the performance of two-dimensional solar tracking systems with reflector using commercial silicon based photovoltaic module, with open and closed loop control systems. Different reflector materials were also investigated. The experiments were performed at the Hashemite University campus in Zarqa at a latitude of 32⁰, in February and March. Photovoltaic output power and performance were analyzed. It was found that the modified photovoltaic module with mirror reflector generated the highest value of power, while the temperature reached a maximum value of 53 ̊ C. The modified module suggested in this study produced 5% more PV power than the two-dimensional solar tracking systems without reflector and produced 12.5% more PV power than the fixed PV module with 26⁰ tilt angle.
This paper focuses on the modeling and control of a wind energy conversion chain using a permanent magnet synchronous machine. This system behaves a turbine, a generator, DC/DC and DC/AC power converters. These are connected on both sides to the DC bus, where the inverter is followed by a filter which is connected to the grid. In this paper, we have been used two types of controllers. For the stator side converter, we consider the Takagi-Sugeno approach where the parameters of controller have been computed by the theory of linear matrix inequalities. The stability synthesis has been checked using the Lyapunov theory. According to the grid side converter, the proportional integral controller is exploited to keep a constant voltage on the DC bus and control both types of powers. The simulation results demonstrate the robustness of the approach used.
The development of modeling wind speed plays a very important in helping to obtain the actual wind speed data for the benefit of the power plant planning in the future. The wind speed in this paper is obtained from a PCE-FWS 20 type measuring instrument with a duration of 30 minutes which is accumulated into monthly data for one year (2019). Despite the many wind speed modeling that has been done by researchers. Modeling wind speeds proposed in this study were obtained from the modified Rayleigh distribution. In this study, the Rayleigh scale factor (Cr) and modified Rayleigh scale factor (Cm) were calculated. The observed wind speed is compared with the predicted wind characteristics. The data fit test used correlation coefficient (R2), root means square error (RMSE), and mean absolute percentage error (MAPE). The results of the proposed modified Rayleigh model provide very good results for users.
This paper deals with an advanced design for a pump powered by solar energyto supply agricultural lands with water and also the maximum power point is used to extract the maximum value of the energy available inside the solar panels and comparing between techniques MPPT such as Incremental conductance, perturb & observe, fractional short current circuit, and fractional open voltage circuit to find the best technique among these. The solar system is designed with main parts: photovoltaic (PV) panel, direct current/direct current (DC/DC) converter, inverter, filter, and in addition, the battery is used to save energy in the event that there is an increased demand for energy and not to provide solar radiation, as well as saving energy in the case of generation more than demand. This work was done using the matrix laboratory (MATLAB) simulink program.
The objective of this paper is to provide an overview of the current state of renewable energy resources in Bangladesh, as well as to examine various forms of renewable energies in order to gain a comprehensive understanding of how to address Bangladesh's power crisis issues in a sustainable manner. Electricity is currently the most useful kind of energy in Bangladesh. It has a substantial influence on a country's socioeconomic standing and living standards. Maintaining a stable source of energy at a cost that is affordable to everyone has been a constant battle for decades. Bangladesh is blessed with a wealth of natural resources. Bangladesh has a huge opportunity to accelerate its economic development while increasing energy access, livelihoods, and health for millions of people in a sustainable way due to the renewable energy system.
When the irradiance distribution over the photovoltaic panels is uniform, the pursuit of the maximum power point is not reached, which has allowed several researchers to use traditional MPPT techniques to solve this problem Among these techniques a PSO algorithm is used to have the maximum global power point (GMPPT) under partial shading. On the other hand, this one is not reliable vis-à-vis the pursuit of the MPPT. Therefore, in this paper we have treated another technique based on a new modified PSO algorithm so that the power can reach its maximum point. The PSO algorithm is based on the heuristic method which guarantees not only the obtaining of MPPT but also the simplicity of control and less expensive of the system. The results are obtained using MATLAB show that the proposed modified PSO algorithm performs better than conventional PSO and is robust to different partial shading models.
A stable operation of wind turbines connected to the grid is an essential requirement to ensure the reliability and stability of the power system. To achieve such operational objective, installing static synchronous compensator static synchronous compensator (STATCOM) as a main compensation device guarantees the voltage stability enhancement of the wind farm connected to distribution network at different operating scenarios. STATCOM either supplies or absorbs reactive power in order to ensure the voltage profile within the standard-margins and to avoid turbine tripping, accordingly. This paper present new study that investigates the most suitable-location to install STATCOM in a distribution system connected wind farm to maintain the voltage-levels within the stability margins. For a large-scale squirrel cage induction generator squirrel-cage induction generator (SCIG-based) wind turbine system, the impact of STATCOM installation was tested in different places and voltage-levels in the distribution system. The proposed method effectiveness in enhancing the voltage profile and balancing the reactive power is validated, the results were repeated for different scenarios of expected contingencies. The voltage profile, power flow, and reactive power balance of the distribution system are observed using MATLAB/Simulink software.
The electrical and environmental parameters of polymer solar cells (PSC) provide important information on their performance. In the present article we study the influence of temperature on the voltage-current (I-V) characteristic at different temperatures from 10 °C to 90 °C, and important parameters like bandgap energy Eg, and the energy conversion efficiency η. The one-diode electrical model, normally used for semiconductor cells, has been tested and validated for the polemeral junction. The PSC used in our study are formed by the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Our technique is based on the combination of two steps; the first use the Least Mean Squares (LMS) method while the second use the Newton-Raphson algorithm. The found results are compared to other recently published works, they show that the developed approach is very accurate. This precision is proved by the minimal values of statistical errors (RMSE) and the good agreement between both the experimental data and the I-V simulated curves. The obtained results show a clear and a monotonic dependence of the cell efficiency on the studied parameters.
The inverter is the principal part of the photovoltaic (PV) systems that assures the direct current/alternating current (DC/AC) conversion (PV array is connected directly to an inverter that converts the DC energy produced by the PV array into AC energy that is directly connected to the electric utility). In this paper, we present a simple method for detecting faults that occurred during the operation of the inverter. These types of faults or faults affect the efficiency and cost-effectiveness of the photovoltaic system, especially the inverter, which is the main component responsible for the conversion. Hence, we have shown first the faults obtained in the case of the short circuit. Second, the open circuit failure is studied. The results demonstrate the efficacy of the proposed method. Good monitoring and detection of faults in the inverter can increase the system's reliability and decrease the undesirable faults that appeared in the PV system. The system behavior is tested under variable parameters and conditions using MATLAB/Simulink.
The electrical distribution network is undergoing tremendous modifications with the introduction of distributed generation technologies which have led to an increase in fault current levels in the distribution network. Fault current limiters have been developed as a promising technology to limit fault current levels in power systems. Though, quite a number of fault current limiters have been developed; the most common are the superconducting fault current limiters, solid-state fault current limiters, and saturated core fault current limiters. These fault current limiters present potential fault current limiting solutions in power systems. Nevertheless, they encounter various challenges hindering their deployment and commercialization. This research aimed at designing a bridge-type nonsuperconducting fault current limiter with a novel topology for distribution network applications. The proposed bridge-type nonsuperconducting fault current limiter was designed and simulated using PSCAD/EMTDC. Simulation results showed the effectiveness of the proposed design in fault current limiting, voltage sag compensation during fault conditions, and its ability not to affect the load voltage and current during normal conditions as well as in suppressing the source powers during fault conditions. Simulation results also showed very minimal power loss by the fault current limiter during normal conditions.
This paper provides a new approach to reducing high-order harmonics in 400 Hz inverter using a three-level neutral-point clamped (NPC) converter. A voltage control loop using the harmonic compensation combined with NPC clamping diode control technology. The capacitor voltage imbalance also causes harmonics in the output voltage. For 400 Hz inverter, maintain a balanced voltage between the two input (direct current) (DC) capacitors is difficult because the pulse width modulation (PWM) modulation frequency ratio is low compared to the frequency of the output voltage. A method of determining the current flowing into the capacitor to control the voltage on the two balanced capacitors to ensure fast response reversal is also given in this paper. The combination of a high-harmonic resonator controller and a neutral-point voltage controller working together on the 400 Hz NPC inverter structure is given in this paper.
Direct current (DC) electronic load is a useful equipment for testing the electrical system. It can emulate various load at a high rating. The electronic load requires a power converter to operate and a linear regulator is a common option. Nonetheless, it is hard to control due to the temperature variation. This paper proposed a DC electronic load using the boost converter. The proposed electronic load operates in the continuous current mode and control using the integral controller. The electronic load using the boost converter is compared with the electronic load using the linear regulator. The results show that the boost converter able to operate as an electronic load with an error lower than 0.5% and response time lower than 13 ms.
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Nonlinear control of GTI for stabilizing future smart grids
1. International Journal of Power Electronics and Drive System (IJPEDS)
Vol. 11, No. 3, September 2020, pp. 1268~1277
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v11.i3.pp1268-1277 1268
Journal homepage: http://ijpeds.iaescore.com
Nonlinear control of GTI for stabilizing future smart grids
Salam Ibrahim Khather
Department of Systems and Control Engineering, Ninevah University, Iraq
Article Info ABSTRACT
Article history:
Received Aug 8, 2019
Revised Dec 30, 2019
Accepted Feb 20, 2020
The most important components of the distributed generation frameworks is
the GTIs which is an interface amidst the utility and the source of energy.
The recent years have seen an increased interest in the design and usage of
GTIs due to its smaller weight and size, low cost and higher efficiency.
But the problem of leakage currents in the transformerless inverter that is
dependant on its topology and control scheme needs to be looked into
carefully. Also, the high performance of the GTI requires a stringent control
and various control systems are being developed and applied to the GTIs.
This paper reviews the various topologies that are classified based on the
attributes of the leakage current and the method of decoupling. Further it
reviews and compares the different control techniques applied to the GTIs
with respect to the frame of reference, controller, modulation technique and
the control parameters considered.
Keywords:
Controller
Distributed generation
Grid-tied
Inverters
Topology
This is an open access article under the CC BY-SA license.
Corresponding Author:
Salam Ibrahim Khather,
Systems and Control Engineering Department,
Ninevah University, Ninevah, Mosul, Iraq.
Email: salam.khather@uoninevah.edu.iq
1. INTRODUCTION
The traditional systems that use coal, nuclear and hydro energy for generating electricity are
centralized and need the transmission of electricity over large distances. The stability and security of these
systems are under threat due to the blackouts which is a result of grid rupture due to extreme weather
conditions, chain failure. In comparison, the distributed sources of energy like biogas, biomass, wind and
solar are decentralized, flexible and modular. These sources of energy have an added advantage that they can
be produced close to the place of consumption [1]. Also, the environmental concerns like the climatic
changes and global warming are driving the requirement for penetrating the distributed renewable sources of
energy into the future generations of electricity grids. The attributes of electricity generation and supply are
being changed with the aid of generating and storing electricity in an environment-friendly manner.
Hence the microgrids are a unique solution for integration of the renewable sources of energy into the
distribution systems [2]. The microgrids, specifically the ones using wind and solar energy have
accomplished immense response over the recent years for meeting the energy demands of the world and have
become a significant alternative to the conventional sources of power [3].
Implementing the microgrids is advantageous to both the consumer as well as the electricity
provider. From the consumer’s point of view, the microgrid enhances the quality of the network, decreases
the emissions, and cost they incur. From the perspective of the electricity provider the microgrids aid in the
reduction of the power that flows on the transmitting and the distributing lines which results in the reduced
costs and losses for extra power [4]. Additionally, the microgrid also helps in reducing the load on the
network by the elimination of impasse to meet the requirements of electricity and repairing the network in the
case of any errors. The microgrids are the smaller versions of the actual electricity distribution systems.
2. Int J Pow Elec & Dri Syst ISSN: 2088-8694
Nonlinear control of grid-tied inverters (GTI) for stabilizing future smart grids (Salam Ibrahim Khather)
1269
They along with reducing the impacts on the environment by increasing the use of renewable resources have
the ability to enhance the economics, network reliability and quality of the power. From the perspective of
operation, the microgrid consists of power electronic control and interface circuit for meeting the
requirements of quality of the power, flexibility factor, and the energy output [5].
Conversion of the power among DC and AC is a primary issue in the microgrids since the
renewable sources of energy generate DC power whereas the traditional electricity grid is dependant of
generating, transmitting and distributing AC power. Hence there is a need for converting the DC power to
AC power so that the grids can be connected to the standard AC system. The circuits of power electronics are
utilised as an inverter for the DC to AC power conversion. There are numerous types of such inverters and
they are referred to as grid-tied inverters (GTI). The grid tie inverter is the same as that of a DC-AC
converter but with a slight difference in the characteristics. The GTI needs to obey certain conditions without
which it cannot be connected to the grid. The magnitude of the phase and voltage of the GTI must be equal to
that of the grid, the inverter output frequency and the frequency of the grid must be equal [6].
2. TOPOLOGIES OF GRID-TIED INVERTERS
In spite of the development of various GTI topologies, most of them can be classified into three
groups of zero-state decouple, zero-state mid-point clamped, and solidity clamped topologies. These classes
are decided based on the characteristics of leakage current and the decoupling approach of the
transformerless topologies. Each of these classes is discussed below.
2.1. Zero state decoupled transformerless topologies
The traditional full bridge topology has various features for operating in single phase connected to a
simple PV module like the structure of the circuit, low DC bus voltage, high efficiency, low cost in
comparison to the half-bridge topology. Various full bridge topologies have been developed by decoupling
the PV module from the grid during the period of freewheeling. The studies related to zero state coupling are
further discussed.
Yang et al., [7] developed an enhanced single-phase inverter for eliminating the common mode
leakage current in the transformerless PV grid system. Both the control techniques of double-frequency
SPWM and unipolar SPWM were implemented to obtain a three level output for the inverter that assures that
the common-mode leakage current is not generated. In the commutating switches, their switching voltages
are 50% of the input voltage and the losses due to switching were reduced significantly. Addition decoupling
of two switches in the inverter helped in accomplishing high effectivity and feasible thermal design.
Lower ripples in the current and higher frequency were achieved due to double-frequency SPWM.
The authors in [8] developed a high reliability and efficiency (HRE) topology utilising the MOSFETs to be
the main switches. The proposed converter used two split ac-coupled inductors which operated solitarily for
the negative and positive half cycles of the grid. The circuit did not require dead time for commutating at
PWM switching hence achieved a lower distortion for the output current. This topology is an attractive
option for the applications that require transformerless PV inverters.
Yu et al., [9] developed a high-efficiency H6 configuration inverter utilizing MOSFETs.
The developed topology featured high-efficiency over a broad range of the load, low leakage current in the
ground and no requirement for split capacitors. The output inductance was reduced by 50% in comparison to
the full bridge inverter that uses bipolar PWM switching. In [10] the study summarized the derivation rules
from the present inverters having high performance using H6 configuration so that novel topologies are
achievable. As an example, the authors developed a high efficiency 1ϕ transformerless PV inverter with a
hybrid modulation technique. the absence input split capacitors eliminated the issues of leakage current and
common-mode voltage in the nonisolated model with H6-type configuration. They additionally proved that
the H5 topology is a variant of H6 topology. The main demerit of these topologies was the activation of the
anti-parallel diodes of MOSFETs due to the occurrence of a phase shift between the output current and
voltage of the inverter. As a result, the issue of low reverse recovery in the anti-parallel diodes of the
MOSFETs reduces the dependability of the system. The authors in [11] presented a detailed review, analysis
and classification of the single-phase FB inverter topologies that did not face the problem of leakage current.
Based on the elimination of the CM mode voltage these topologies H4, H5, and H6 were bifurcated as
inverters with decoupling and inverters with clamping. Among the clamped inverters they analysed one
topology to validate its efficiency by developing the prototype. The developed inverter prototype gave an
efficiency of 98.5%. The study in [12] presented an improved form of H5 topology for reducing the CM
leakage current. Effective differential mode attributes were obtained for the three-level output voltage since
they employed the unipolar SPWM control technique. The grid-connected current had low THD and high
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current. This inverter obtained a maximum efficiency of 98.2% making suitable for grid-connected
applications.
2.1. Zero-state mid-point clamped transformerless topologies
This topology is similar to the previous one with the only difference that the output voltage which is
short-circuited is during the period of freewheeling will be clamped to DC bus mid-point. As a result, the CM
voltage is maintained at a constant value during the complete period of operation. Most of the mid-point
topologies can be obtained from the decoupled topologies. The authors of [13] developed an optimised H5
topology (oH5) in which the CM voltage is clamped at a constant level so the ground current voltage is
suppressed. The H5 circuit is modified by adding the clamping branch that comprises of the capacitor divider
and a switch. But this circuit requires the addition of a dead time amid the gate signals for avoiding the short-
circuiting at the input split capacitor. Also, the losses due to conduction are high since the inductor current
flows through all the switches when they are in active mode. The study [14] developed a new topology based
on the H-bridge with an AC bypass circuit that comprised of a switch that was clamped to the midpoint of
DC and diode rectifier. The use of unipolar PWM for modulating the switches gives a three level output to
the converter hence, the generated CM voltage had high-frequency components resulting in high leakage
currents at the ground. The authors in [15] introduced two types of switching negative and positive neutral
point clamping to develop an NPC topology referred to as PN-NPC topology. Its principle of working is
similar to H6 topology. At the time of freewheeling the short circuit output voltage is clamped directly to
50% of the input DC voltage due to which the CM voltage remains constant. But the main demerit of this
topology is the higher number of switches which increases the complexity of the circuit. Also, the losses due
to conduction are higher.
2.3. Solidity clamped transformerless topologies
In these topologies, one can observe a solid connection among the grid and the PV module in the
freewheeling mode with an aim to maintain the CM voltages at high frequencies. Although the common
characteristic of the topologies is the solid connection, the principle of operation, boosting, DC bus and the
characteristics of the output voltage can be different. The research work in [16] developed a solidity clamped
transformerless topology referred to as a dual parallel buck converter. For this topology there exists a direct
connection amidst the PV module and the neutral inverter during both the positive as well as the negative half
cycle thus reducing the oscillations of the high frequency CM voltages. The losses due to conduction are also
reduced since the inductor current flows through only two switches. The study in [17] developed the concept
of virtual DC bus for eliminating the CM leakage current in the transformerless PV models. There exists a
direct connection between the grid neutral and the Dc bus negative pole thus bypassing the stray capacitance
that is present between the ground and the PV panels. Hence the CM leakage current is suppressed
completely. In the meantime, a virtual DC bus gets created for providing the negative voltage level for the
negative AC grid for generating the current. Thus the DC bus voltage required is the same as that of the FB
inverter. But it is difficult to control the charging of the virtual capacitor at each of the cycles and the
additional current stresses affect the switches, resulting in reduced reliability and efficiency. The researchers
in [18] developed a positive-negative NPC (PN-NPC) topology for effectively eliminating the leakage
current. The two basic switching cells, the P-NPCC, and the N-NPCC are developed for generating the GTI
topology to build NPC topologies. The main advantages of this approach are that the CM voltage is clamped
at a particular level for effectively suppressing the leakage current, excellent DM mode attributes are
achieved. The requirement of a deadtime is the main demerit of this topology without which there will be a
short circuit in the grid [19].
3. CONTROL OF GRID TIE INVERTERS
There is a requirement of a control system for guaranteeing the high quality of power.
The harmonics for the nonlinear load which is drawn from the grid, the difference in phase between the
current and voltage need to be compensated with the aid of inductor and capacitor as the loads.
To accomplish the current at the output of the inverter, load current, grid current, or the current at any of the
nodes can be controlled. Below discussed are some of the controllers based on their applications.
3.1. Linear controllers
These controllers are a part of the class that features the attributes of the linear systems. The linear
controllers are designed and evaluated using the traditional theory of feedback control. A linear classic
controller for distributed generation (DG) inverters under the influence of voltage sags was developed in
[20]. The control depends on reactive current injection wherein there is a variable ratio amidst the negative
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and positive sequences. This controller aids in restoring the dropped voltages during the limits of continuous
operation determined by the grid. A unified control technique enabling the operation of the DG inverters in
both grid-tied as well as islanded modes without the requirement of switching among the corresponding
controllers was developed in [21]. The inverter is controlled as a current source using the inner current loop
of the inductor in the case of grid-tied operation and when the islanding occurs the voltage controller is
automatically gets activated in order to control the load. This technique was successful in improving the
quality of waveform of the grid current in grid-tied mode and the islanded mode load voltage.
A current controller without PLL that is applicable for PV systems. The developed controller is a
combination of the linear-quadratic regulator (LQR) and the Kalman filter referred to as LQG controller was
developed [22]. This controller made sure that the balanced and sinusoidal currents are injected with high
immunity for both harmonics as well as the imbalances which are existing in the supply voltage. This is
accomplished without a PLL for synchronisation of the grid voltages and the currents. A novel approach for
controlling the reactive and active power of the 1Φ rooftop PV module was presented in [23]. Estimation
dependant improved PLL was employed for locking the grid and the inverter with each other. The stability of
the controller was analysed utilizing the Direct Method of Lyapunov’s Stability Criterion. It was observed
that the controller performed well even though the harmonic compensator was absent. The authors in [24]
introduced an active damping (AD) technique depending on the injected feedback grid current for the GTI
that employs LCL filters. The resonance at the LCL filter is rejected by the phase shifting and high pass
feedback for the injected current at the grid. Contrasted with the conventional control techniques, besides
avoiding additional high-accuracy sensors and perceptions, the proposed control is alluring for both the high
closed-loop transfer speed and the great robustness.
3.2. Robust controllers
The main theory behind these is to design the controllers with respect to uncertainties. The objective
of these strategies is to accomplish robust execution and stability within the sight of constrained modelling
errors. In robust control, great criteria, clear portrayals, and limits must be characterized. Indeed, even in the
multivariable frameworks, this controller can assure robust steadiness and execution of closed loop
frameworks. Figure 1 illustrates the structure of a basic controller.
Figure 1. Robust controller [25]
A current controller based on the H∞ control theory was designed in [26]. The controller has a
stabilizing compensator which can be just an inductor. This results in enhanced tracking performance and a
low value of THD even when the unbalanced or nonlinear loads and distortions in the grid voltages are
present. To achieve this slight compromise was made with respect to slower dynamics with more
complicated calculations. The study in [27] also developed a H∞ controller for dealing with the issue of
stability. The controller exhibited high gains near the high frequency lines just like the conventional
proportional resonant controller. It also has optimum attenuation at high-frequency to maintain the stability
of the control loop. The results of both the experiment and simulations of the proposed H∞ controller and the
ordinary PI controller were compared for validating the performance of the controller. It ought to be noted
that the proposed H∞ controller can be effectively connected to single-stage GTI since it is created in the
stationary frame of reference. The study in [25] developed a robust current controller for a 3Φ GTI that
offered better performance for tracking and higher ability to reject the harmonics when compared to the
conventional PI controller. The authors used the Mu-synthesis technique for considering the effects of
unstructured as well as structured uncertainties on the system performance. Here the nonlinear expressions
were included by modifying the disturbance scaling parameter and the uncertainty model for better
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simulation in the realistic. The low pass filter was modified to a higher order system which helped in
attaining a higher rate of rejecting the harmonics.
3.3. Adaptive controller
Versatile control techniques as shown in Figure 2 can naturally modify the control activity relying
upon the working states of the framework. There is no compelling reason to know the exact framework
parameters with high performance. But the complexity of computations in this approach is very high.
Figure 2. Generalised structure of an adaptive controller [28]
The study in [29] assessed the conduct of an adaptive current controller that is based on a
generalized integrator of reduced order when the frequency of the grid is subjected to the variations.
The proposed plan for frequency adaptation permits to keep the good performance of the present controller
even within the sight of variations in the frequency. The subsequent frequency adaptive controller has
extremely low computational weight, and it is hence feasible for low cost DSP execution. An adaptive
controller for 3Φ stand-alone DGs was developed [30]. For preventing the direct calculation of the
derivatives of time for state variables by developing the adaptive compensating control and the error
dynamics in the model is asymptotically stabilized using the stabilizing control. An optimal observer of the
fourth order estimated the data about load current. The stability of the developed observer and controller was
scientifically demonstrated by applying Lyapunov stability hypothesis. This versatile control technique
accomplished more stable yield voltage and lower THD than the FL-MIMO control plot under abrupt change
in load, uneven and nonlinear load. The viability and possibility of the proposed control system were
confirmed through different simulation and trial results.
An adaptive controller for a 3Φ inverter that can be applied to a UPS was described in [31].
The control law, that employed the integration of state feedback and tracking error is portrayed in a
synchronous dq outline and is actualized utilizing a space vector modulation system. The controller is
structured by a linear matrix inequality (LMI) based streamlining with the goal that the rate of convergence
for the steady state is expanded within the sight of the LC filter vulnerabilities. In the absence of
uncertainties, the designed controller will become a deadbeat controller, whereas, in the presence of
uncertainty, it provides the shortest possible settling time. Thus, the proposed design method provides a
systematic tool to combine the robustness to model uncertainties with deadbeat control. Along these lines, the
proposed technique gives a methodical apparatus to join the strength to display uncertainties with the
deadbeat control. A droop control method that estimated the impedance and controlled the adaptive virtual
power was developed in [32]. The online estimation is acknowledged by delivering a perturbation on the
magnitude of the voltage and estimating the power output variations and afterwards, the impedance highlight
can be determined to update the conversion matrix of the virtual power. This technique is appropriate for
various conditions of working and different line X/R proportions. By considering both the impacts of the
loads as well as the transmission line, the decoupling framework is progressively functional and improves the
power control precision. An adaptive voltage control approach by combining the adoption and a state
feedback control terms was developed in [33]. The former helps in compensating the uncertainties of the
system and the later forces the convergence of error dynamics to zero. Additionally, the developed algorithm
can be implemented easily. The simulation and exploratory outcomes were exhibited under the uncertainties
of the parameter and are contrasted with the exhibitions of the non adaptive voltage controller to approve the
adequacy of the proposed control technique. Without uncertainties, an adaptive controller will turn into a
deadbeat controller, but when the uncertainties are present, it gives the briefest conceivable settling time.
3.4. Predictive controllers
Predictive controllers as shown in Figure 3 utilize a framework model to foresee what's to come in
the conduct of controlled parameters. The controller utilizes this data to get the ideal activation, contingent
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upon a predefined optimization measure. With its quick unique reaction, nonlinearities, and limitations which
can be effectively included and it can be applied to various systems while considering a multivariable case,
moreover, the execution of this controller is simple. The authors in [34] modelled and designed the discrete-
time hybrid current controller which was a combination of PI and repetitive parts. Additional passive filters
were connected between the transformer and the converter terminals to ensure that the converter synthesised
the sinusoidal currents. But these filters have the ability to cause issues pertaining to harmonic resonances.
The authors in [35] digitally implemented a control system considering the imbalance in grid voltage,
imbalance as well as the harmonics of the inductors on the line side. The direct technique of Lyapunov
ensured its stability. Contrasted with a work of classic controller, this controller requires an incredible
number of calculations.
Figure 3. The predictive controller [36]
3.5. Intelligent controllers
Intelligent control gets computerization by imitating biological intelligence. Likewise, it investigates
to obtain thought from the way biological frameworks make sense of issues and uses them for solving the
control issue [37]. The design of a repetitive controller (RC) applied to an LCL filter based GTI was
presented in [38] with a particular emphasis on the bandwidth of the plant. The results indicated that correct
selection of the capacitor value in the filter would provide the appropriate bandwidth for the effective
operation of the RC. It was also observed that the RC effectively handled the higher resonance for the chosen
value of the capacitor. The parallel structure for fractional RC technique for enhancing the performance of
the inverter was developed in [39]. A correction factor is incorporated to increase the gains of all the
harmonics precisely at the harmonic frequencies which have been targeted. This technique accomplished
better rejection and tracking in comparison to the conventional RC. In [40] the authors developed a frequency
adaptive repetitive control scheme (FARC) wherein the rate of sampling was already defined for dealing with
the various kinds of variable frequency periodic signals. This FARC controller offers the quick modification
of the process of fractional delay, and quick reexamine of channel parameters, and after that gives GTI a
basic yet very exact continuous recurrence versatile control answer for the infusion of high calibre
sinusoidal current. The general form of a repetitive controller as shown in Figure 4.
Figure 4. The general form of a repetitive controller [41]
3.6. Nonlinear controllers
The non-linear controllers [42] operate extraordinarily when compared to the basic controllers but
are complex with respect to the aspects of designing and implementing. The nonlinear controllers can be
grouped into three types the Sliding mode controllers [43], PFL controllers and Hysteresis controllers [44].
These controllers are discussed in detail in the next section.
4. TYPES OF NONLINEAR CONTROLLERS
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4.1. Sliding mode controllers (SMC)
This method has been applied to the PWM inverters for regulating the output voltage. The main
merits of this technique are its insensitivity to the disturbances in the load and variations of the parameters.
Hence for the ideal case, an invariant steady-state response is obtained. But finding an easy sliding surface is
a difficult task and the limited sampling rate degrades the performance of the SMC. The phenomenon of
chattering is another demerit of the SMC when a variable reference is tracked. The authors of [45] presented
an SMC through a multi-resonant sliding surface for a 1Φ GTI for eliminating the error in tracking the grid
current and suppressing the THD. To accomplish this completely many terms for error of current tracking are
added with the sliding function. This technique can be employed in arbitrary tracking in an AC system.
A novel SMC for a DG system when there exists a condition of distorted grid was developed [46].
This controller has a SMC current controller and one harmonic detector. The SMC is based on the control of
the integral sliding mode. Effective extraction, without any phase delay, of the harmonic components is
achieved by using a band pass filter of the fourth order. The SMC suppresses these harmonics with a fast
dynamic response. This is a harmonic compensation scheme that is non-selective, hence reducing the burden
due to the computations.
4.2. PFL controllers
A clear route for structuring the nonlinear controllers is feedback linearization since it changes a
nonlinear framework to a halfway linear or a completely linear framework. This can be accomplished by
eliminating the nonlinearities inside the framework. Along these lines, linear controller structure techniques
can be utilized to structure the controller for these frameworks. At the point when the nonlinear framework is
changed into a completely linear framework, the technique is referred to as exact feedback linearization and
if the nonlinear framework is changed into an in a partial linear framework, the strategy is called partial
feedback linearization (PFL) [47].
An effective nonlinear controller for a 3Φ GTI for controlling the injected current and voltage at the
DC link so that maximum power could be extracted from the PV units was designed in [48]. The technique
was based on the PFL and effectiveness was ensured by the consideration of the uncertainties in the PV
system. The results indicated the excellent performance of the controller under different conditions of
operation. The study in [49] presented a controller for controlling the 1Φ GTI having non-linear loads by the
addition of the load current to the current loop of the inductor filter. The GTI is stable in both modes of
standalone and grid-connected. The results from the simulations indicate that the in the grid connected mode
the current is eliminated and quality of the output voltage waveform is high in the stand-alone situation.
4.3. Hysteresis controllers
It is worth referencing that for executing the hysteresis controller, a versatile band of the controller
needs to be designed to accomplish a constant switching frequency. Contemplations in regards to the
disengaged neutral are significant once more, in light of the fact that the yield of this controller is the state of
the switches. The authors in [50] developed a multiple-resonant SMC (MRSMC) along with a variable-band
hysteretic modulator (VHM) for a 3Φ GTI. The VHM eliminates the chattering issue of the SMC. In
comparison to the SMC the designed controller is superior with respect to the higher order harmonic injection
to the grid. The hysteresis current controller for a 3Φ GTI with reduced losses was designed in [51].
Table 1. A comparison of the controllers in the existing literature
Reference Reference frame Controller Control parameter Modulation technique
[26] 3Φ, d-q Robust (H∞) Current PWM
[30] 3Φ, d-q Adaptive Voltage SVPWM
[52] 1Φ Non-linear (Hysteresis) Current PWM
[53] 1Φ Non-linear (Hysteresis) Current PWM
[32] 3Φ, d-q Adaptive Power PWM
[20] 3Φ, αβ Linear (Classic) Voltage, Power PWM
[23] 3Φ, αβ Linear (PR) Current SVM
[54] 3Φ, d-q Non-linear (SMC) Current PWM
[33] 3Φ, d-q Adaptive Voltage SVPWM
[55] 1Φ Non-linear (SMC) Current PWM
[48] 3Φ, d-q Non-linear (PFL) Voltage, Power PWM
[34] 3Φ, d-q Predictive Current SVM
[56] 3Φ, abc Intelligent (fuzzy) Power PWM
[39] 1Φ Intelligent (repetitive) Voltage PWM
[57] 1Φ Intelligent (repetitive) Current PWM
[58] 3Φ, αβ Non-linear (Hysteresis) Current PWM
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The negative or positive buses are clamped to the inverter based on the phase current polarity.
Hence all the phases of the inverter get clamped for ⅓rd of the output period. The clamping process helped in
reducing the average switching losses and frequency. The results indicated that the developed controller has
the ability to decrease the losses of switching without compromising on the waveform of the output current.
A comparison of the controllers in the existing literature as shown in Table 1.
5. CONCLUSION
It can be observed that various studies have been conducted on GTIs based on the inverter topology
and controller for the inverter. The inverter was classified into three basic topologies based on decoupling
and characteristics of the leakage currents. Each of the topologies has its own merits and demerits, hence it
cannot be concluded as to which topology is the best. For selecting a particular topology factors like cost,
efficiency, leakage current and the number of power semiconductor devices need to be considered.
Further the different kinds of control systems that are employed for GTIs along with their features were
reviewed. It can again be observed that none of the controller can be considered the best since each controller
is advantageous in its own way. From the studies it is found that the non-linear controllers performed much
better than the other controller in all aspects but one has to compromise on the complexity factor since the
non-linear controllers are the most complex in comparison to the other controllers. Hence we can conclude
that each feature for a GTI inverter needs to select based on the requirements of the designer.
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BIOGRAPHIES OF AUTHOR
Salam Ibrahim Khather received a B.Sc. degree in Electrical Engineering from Mosul University
in 2005. In 2008, he achieved his M.Sc. in Electrical Engineering from Mosul University. He
started his career working as an Electrical Engineer in the Power Plant and Electrical Substations
(2009-2017). Then, he started his academic journey working as an assistant lecturer at Ninevah
University. His major research areas are Power and Machines, Control Systems and Power
Electronics Applications.