Load frequency control of a two area hybrid system consisting of a grid conne...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Flux Based Sensorless Speed Sensing and Real and Reactive Power Flow Control ...ijeei-iaes
This aim of this paper is to design controller for Doubly Fed Induction Generator (DFIG) converters and MPPT for turbine and a sensor-less rotor speed estimation to maintain equilibrium in rotor speed, generator torque, and stator and rotor voltages. It is also aimed to meet desired reference real and reactive power during the turbulences like sudden change in reactive power or voltage with concurrently changing wind speed. The turbine blade angle changes with variations in wind speed and direction of wind flow and improves the coefficient of power extracted from turbine using MPPT. Rotor side converter (RSC) helps to achieve optimal real and reactive power from generator, which keeps rotor to rotate at optimal speed and to vary current flow from rotor and stator terminals. Rotor speed is estimated using stator and rotor flux estimation algorithm. Parameters like tip speed ratio; coefficient of power, stator and rotor voltage, current, real, reactive power; rotor speed and electromagnetic torque are studied using MATLAB simulation. The performance of DFIG is compared when there is in wind speed change only; alter in reactive power and variation in grid voltage individually along with variation in wind speed.
Load frequency control of a two area hybrid system consisting of a grid conne...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Flux Based Sensorless Speed Sensing and Real and Reactive Power Flow Control ...ijeei-iaes
This aim of this paper is to design controller for Doubly Fed Induction Generator (DFIG) converters and MPPT for turbine and a sensor-less rotor speed estimation to maintain equilibrium in rotor speed, generator torque, and stator and rotor voltages. It is also aimed to meet desired reference real and reactive power during the turbulences like sudden change in reactive power or voltage with concurrently changing wind speed. The turbine blade angle changes with variations in wind speed and direction of wind flow and improves the coefficient of power extracted from turbine using MPPT. Rotor side converter (RSC) helps to achieve optimal real and reactive power from generator, which keeps rotor to rotate at optimal speed and to vary current flow from rotor and stator terminals. Rotor speed is estimated using stator and rotor flux estimation algorithm. Parameters like tip speed ratio; coefficient of power, stator and rotor voltage, current, real, reactive power; rotor speed and electromagnetic torque are studied using MATLAB simulation. The performance of DFIG is compared when there is in wind speed change only; alter in reactive power and variation in grid voltage individually along with variation in wind speed.
Design of Hybrid Solar Wind Energy System in a Microgrid with MPPT Techniques IJECEIAES
DC Microgrid is one feasible and effective solution to integrate renewable energy sources as well as to supply electricity. This paper proposes a DC microgrid with enhanced Maximum Power Point Tracking (MPPT) techniques for wind and solar energy systems. In this paper, the PV system power generation is enhanced by introducing a two-model MPPT technique that combines incremental conductance and constant voltage MPPT algorithms. Also, for the Wind Energy Conversion System (WECS) with pitch angle controlling technique, an Optimal Power Control MPPT technique is added. The Space Vector Pulse Width Modulation technique is introduced on grid side converter to improve the supply to the grid. The performance of proposed system is analyzed and the efficiency obtained with these methods is enhanced as compared with the previous methods.
Stand-alone applications of Photovoltaic (PV) can be found in water pumping systems for rural area. The proper electric motor must be chosen for optimal considerations. One of the modern electric motor called brushless motor (BLDC) can be an alternative for this application although it has complexity in control. Powering such a motor by using electric energy generating by PV modules will be an interesting problem. In this paper, a PV powered BLDC motor system is proposed. The PV modules must produce maximum power at any instant time and then this power must be able to rotate the motor. By combining sequential stator energizing due to a rotor detection and a PWM concept, the speed of BLDC can be controlled. Meanwhile, to get maximum power of PV modules, detection of voltage and current of the modules are required to be calculated. Digital Signal Control (DSC) is implemented to handle this control strategy and locks the width of the PWM signal to maintain the PV modules under maximum power operation. The effectiveness of the proposed system has been verified by simulation works. Finally the experimental works were done to validate.
Fuzzy Sliding Mode Control for Photovoltaic SystemIJPEDS-IAES
In this study, a fuzzy sliding mode control (FSMC) based maximum power point tracking strategy has been applied for photovoltaic (PV) system. The key idea of the proposed technique is to combine the performances of the fuzzy logic and the sliding mode control in order to improve the generated power for a given set of climatic conditions. Different from traditional sliding mode control, the developed FSMC integrates two parts. The first part uses a fuzzy logic controller with two inputs and 25 rules as an equivalent controller while the second part is designed for an online adjusting of the switching controller’s gain using a fuzzy tuner with one input and one output. Simulation results showed the effectiveness of the proposed approach achieving maximum power point. The fuzzy sliding mode (FSM) controller takes less time to track the maximum power point, reduced the oscillation around the operating point and also removed the chattering phenomena that could lead to decrease the efficiency of the photovoltaic system.
Stabilization and Frequency Regulation in Microgrid by Controlling Pitch Angleijtsrd
PID controller based pitch angle controller for the frequency regulation and active power control in a wind turbine and diesel engine powered hybrid power system, is presented in this paper. For testing the prosed controller, variable wind speed pattern is used for realization of real time wind behavior. Furthermore, the variable load is also connected to the hybrid power system to test the efficacy of the prosed controller. The system is modelled and simulated in MATLAB environment and results obtained are compared with and without pitch angle controller. The frequency deviations in PID based pitch angle controller is less than the without controller. Aman Malik | Kavita Sharma "Stabilization and Frequency Regulation in Microgrid by Controlling Pitch Angle" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33303.pdf Paper Url: https://www.ijtsrd.com/engineering/electrical-engineering/33303/stabilization-and-frequency-regulation-in-microgrid-by-controlling-pitch-angle/aman-malik
Defining Control Strategies for Micro Grids Islanded Operation with Maximum P...IAES-IJPEDS
This paper explains about an intelligent control method for the maximum
power point tracking (MPPT) of a photo voltaic system with different
temperature and insolation conditions. This method uses a fuzzy logic
controller applied to a DC-DC converter. The different steps of the design of
this controller are presented together with its simulation and the feasibility of
control methods to be adopted for the operation of a micro grid when it
becomes isolated. Normally, the micro grid operates in interconnected mode
with the medium voltage network; however, scheduled or forced isolation
can take place. In such conditions, the micro grid must have the ability to
operate stably and autonomously. An evaluation of the need of storage
devices and load to take off strategies is included in this paper. The MPPT of
a photovoltaic system for Micro Grid operaion using a Fuzzy logic control
scheme is successfully designed and simulated by using MATLAB/Simulink
Software.
Coordinated Control of Interconnected Microgrid and Energy Storage System IJECEIAES
Several microgrids can be interconnected together to enhance the grid reliability and reduce the cost of supplying power to an island area where conventional power grid cannot be connected. Source and load demand do not properly balance always. Besides that, sometimes power and frequency fluctuation has occurred in MG at island mode. Need to design a special control for maintaining the state of charge (SoC) of energy storage system. This paper proposes a new power supply system for an island area that interconnects two microgrids with a single energy storage system (ESS). An algorithm has been proposed that control the microgrids energy storage system for spinning reserve and load power/frequency regulation purpose. The minimum loading constraints of diesel engine generator (DEG) is considered and the SOC of the ESS is properly maintained.
Performance analysis of various parameters by comparison of conventional pitc...eSAT Journals
Abstract This paper deals with a variable speed wind turbine coupled with a permanent magnet synchronous generator connected through a two mass drive train. This drive train is connected to synchronous generator and after the conversion process finally connected to grid and the idea of transmission over a long distance makes the use of converter necessary and at the receiving end. The inverter is used to convert it back and the inverter is designed with a proper gate signal to get the best output three phase voltages. The fuzzy logic controller is used to track generator speed with varying wind speed to optimize turbine aerodynamic efficiency in the outer speed loop. Pitch angle control of wind turbine has been used widely to reduce torque and output power variation in high rated wind speed areas .The machine side converter is designed to extract maximum power from the wind. In this work a WECS connected with grid is designed in Matlab and a Fuzzy controller is designed to improve the output and we can see the major difference in DC link voltage and reactive power in transmission line. From the outputs we can also go through the reactive power issue which system is best for inductive load or capacitive load. The simple PI system is good for capacitive load and the fuzzy system is better option for the inductive load. The results of both the system of normal controller and fuzzy controller is compared and analyzed. Key Words: Fuzzy logic controller (FLC), permanent magnet synchronous generator (PMSG), insulated gate bipolar transistor (IGBT) , Pulse width modulation (PWM), Wind energy conversion system, DC link capacitor. FACTS Flexible A.C Transmission system, PI proportional integral
Performance analysis of various parameters by comparison of conventional pitc...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
In this paper, an optimization of PV grid connected system is investigated. This is achieved by considering the application of artificial intelligence in the DC side to realize maximal power extraction, and using a sine-band hysteresis control in the AC side of the system, to generate a sine current/voltage suitable for grid connection IEEE929-2000 standards. The overall system has been simulated taking into account environmental effects and standards constraints in order to achieve best performance. The choice of sine band hysteresis control was selected considering its implementation simplicity. The algorithm runs fast on a low-cost microcontroller allowing to avoid any delay that can cause a phase shift in the system. An experimental setup has been realized for tests and validation purposes. Both simulation and experimental results lead to satisfactory results which are conform to the IEEE929-2000 standards.
The energy sector is moving into the era of distributed generation (DG) and microgrids
(MGs). The stability and operation aspects of converter-dominated DG MGs, however, are faced by
many challenges. To overcome these difficulties, this paper presents a new large-signal-based control
topology for DG power converters that is suitable for both grid connected and islanding modes of
operation without any need to reconfigure the control system and without islanding detection. To
improve MG stability and to guarantee stability and high performance of the MG system during sudden
harsh transients such as islanding, grid reconnection, and large load power changes, a nonlinear MG
stabilizer is proposed. We propose a novel control topology for microgrids which can work in both grid
connected and islanding modes without reconfiguration so it does not require islanding detection
technique, the controller is based on the concept of synchronverter In this paper, a radical step is taken
to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated
synchronization unit
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Control for Grid Connected and Intentional Islanding of Distributed Power Gen...ijtsrd
As the demand for more reliable and secure power system with greater power quality increases, the concept of distributed generation DG have become more popular. This popularity of DG concept has developed simultaneously with the decrease in manufacturing costs associated with clean and alternative technologies like fuel cells, biomass, micro turbine and solar cell systems. Intentional islanding is the purposeful sectionalisation of the utility system during widespread disturbances to create power “islandâ€. This island can be designed to maintain a continuous supply of power during disturbances of the main distribution system. Ruchali Borkute | Nikita Malwar ""Control for Grid Connected and Intentional Islanding of Distributed Power Generation"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23679.pdf
Paper URL: https://www.ijtsrd.com/engineering/electrical-engineering/23679/control-for-grid-connected-and-intentional-islanding-of-distributed-power-generation/ruchali-borkute
Enhanced MPPT Technique For DC-DC Luo Converter Using Model Predictive Contro...IJERD Editor
The present study explored an enhanced maximum power point tracking technique which ensures fast tracking in PV systems. This system represents a Model Predictive Control (MPC) MPPT technique. Extracting the maximum power from PV systems has been widely investigated. The main benefaction of this article is an improvement of the Perturb and Observe (P&O) method through a fixed step predictive control under measured fast solar radiation. The preferred predictive control to achieve Maximum Power Point (MPP) speeds up the control loop since it predicts error before the switching signal is applied to the DC-DC Luo converter. Comparing the improved technique to the conventional P&O method indicates significant improvement in PV system performance. The proposed MPC-MPPT technique for a Luo converter is implemented using the MAT LAB SIMULINK
This paper presents the analysis, modeling and control of a grid connected photovoltaic generation system. The model contains a detailed representation of the solar array, grid side multilevel neutral point clamped voltage source inverter. Fuzzy logic controller for the maximum power point tracking of a photovoltaic system under variable temperature and insulation conditions is discussed. The PQ control approach has been presented for the multilevel inverter. One of the most common control strategies structures applied to decentralized power generator is based on power direct control employing a controller for the dc link voltage and a controller to regulate the injected current to the utility network. The proposed models were implemented in Matlab/Simulink.
Design of Hybrid Solar Wind Energy System in a Microgrid with MPPT Techniques IJECEIAES
DC Microgrid is one feasible and effective solution to integrate renewable energy sources as well as to supply electricity. This paper proposes a DC microgrid with enhanced Maximum Power Point Tracking (MPPT) techniques for wind and solar energy systems. In this paper, the PV system power generation is enhanced by introducing a two-model MPPT technique that combines incremental conductance and constant voltage MPPT algorithms. Also, for the Wind Energy Conversion System (WECS) with pitch angle controlling technique, an Optimal Power Control MPPT technique is added. The Space Vector Pulse Width Modulation technique is introduced on grid side converter to improve the supply to the grid. The performance of proposed system is analyzed and the efficiency obtained with these methods is enhanced as compared with the previous methods.
Stand-alone applications of Photovoltaic (PV) can be found in water pumping systems for rural area. The proper electric motor must be chosen for optimal considerations. One of the modern electric motor called brushless motor (BLDC) can be an alternative for this application although it has complexity in control. Powering such a motor by using electric energy generating by PV modules will be an interesting problem. In this paper, a PV powered BLDC motor system is proposed. The PV modules must produce maximum power at any instant time and then this power must be able to rotate the motor. By combining sequential stator energizing due to a rotor detection and a PWM concept, the speed of BLDC can be controlled. Meanwhile, to get maximum power of PV modules, detection of voltage and current of the modules are required to be calculated. Digital Signal Control (DSC) is implemented to handle this control strategy and locks the width of the PWM signal to maintain the PV modules under maximum power operation. The effectiveness of the proposed system has been verified by simulation works. Finally the experimental works were done to validate.
Fuzzy Sliding Mode Control for Photovoltaic SystemIJPEDS-IAES
In this study, a fuzzy sliding mode control (FSMC) based maximum power point tracking strategy has been applied for photovoltaic (PV) system. The key idea of the proposed technique is to combine the performances of the fuzzy logic and the sliding mode control in order to improve the generated power for a given set of climatic conditions. Different from traditional sliding mode control, the developed FSMC integrates two parts. The first part uses a fuzzy logic controller with two inputs and 25 rules as an equivalent controller while the second part is designed for an online adjusting of the switching controller’s gain using a fuzzy tuner with one input and one output. Simulation results showed the effectiveness of the proposed approach achieving maximum power point. The fuzzy sliding mode (FSM) controller takes less time to track the maximum power point, reduced the oscillation around the operating point and also removed the chattering phenomena that could lead to decrease the efficiency of the photovoltaic system.
Stabilization and Frequency Regulation in Microgrid by Controlling Pitch Angleijtsrd
PID controller based pitch angle controller for the frequency regulation and active power control in a wind turbine and diesel engine powered hybrid power system, is presented in this paper. For testing the prosed controller, variable wind speed pattern is used for realization of real time wind behavior. Furthermore, the variable load is also connected to the hybrid power system to test the efficacy of the prosed controller. The system is modelled and simulated in MATLAB environment and results obtained are compared with and without pitch angle controller. The frequency deviations in PID based pitch angle controller is less than the without controller. Aman Malik | Kavita Sharma "Stabilization and Frequency Regulation in Microgrid by Controlling Pitch Angle" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33303.pdf Paper Url: https://www.ijtsrd.com/engineering/electrical-engineering/33303/stabilization-and-frequency-regulation-in-microgrid-by-controlling-pitch-angle/aman-malik
Defining Control Strategies for Micro Grids Islanded Operation with Maximum P...IAES-IJPEDS
This paper explains about an intelligent control method for the maximum
power point tracking (MPPT) of a photo voltaic system with different
temperature and insolation conditions. This method uses a fuzzy logic
controller applied to a DC-DC converter. The different steps of the design of
this controller are presented together with its simulation and the feasibility of
control methods to be adopted for the operation of a micro grid when it
becomes isolated. Normally, the micro grid operates in interconnected mode
with the medium voltage network; however, scheduled or forced isolation
can take place. In such conditions, the micro grid must have the ability to
operate stably and autonomously. An evaluation of the need of storage
devices and load to take off strategies is included in this paper. The MPPT of
a photovoltaic system for Micro Grid operaion using a Fuzzy logic control
scheme is successfully designed and simulated by using MATLAB/Simulink
Software.
Coordinated Control of Interconnected Microgrid and Energy Storage System IJECEIAES
Several microgrids can be interconnected together to enhance the grid reliability and reduce the cost of supplying power to an island area where conventional power grid cannot be connected. Source and load demand do not properly balance always. Besides that, sometimes power and frequency fluctuation has occurred in MG at island mode. Need to design a special control for maintaining the state of charge (SoC) of energy storage system. This paper proposes a new power supply system for an island area that interconnects two microgrids with a single energy storage system (ESS). An algorithm has been proposed that control the microgrids energy storage system for spinning reserve and load power/frequency regulation purpose. The minimum loading constraints of diesel engine generator (DEG) is considered and the SOC of the ESS is properly maintained.
Performance analysis of various parameters by comparison of conventional pitc...eSAT Journals
Abstract This paper deals with a variable speed wind turbine coupled with a permanent magnet synchronous generator connected through a two mass drive train. This drive train is connected to synchronous generator and after the conversion process finally connected to grid and the idea of transmission over a long distance makes the use of converter necessary and at the receiving end. The inverter is used to convert it back and the inverter is designed with a proper gate signal to get the best output three phase voltages. The fuzzy logic controller is used to track generator speed with varying wind speed to optimize turbine aerodynamic efficiency in the outer speed loop. Pitch angle control of wind turbine has been used widely to reduce torque and output power variation in high rated wind speed areas .The machine side converter is designed to extract maximum power from the wind. In this work a WECS connected with grid is designed in Matlab and a Fuzzy controller is designed to improve the output and we can see the major difference in DC link voltage and reactive power in transmission line. From the outputs we can also go through the reactive power issue which system is best for inductive load or capacitive load. The simple PI system is good for capacitive load and the fuzzy system is better option for the inductive load. The results of both the system of normal controller and fuzzy controller is compared and analyzed. Key Words: Fuzzy logic controller (FLC), permanent magnet synchronous generator (PMSG), insulated gate bipolar transistor (IGBT) , Pulse width modulation (PWM), Wind energy conversion system, DC link capacitor. FACTS Flexible A.C Transmission system, PI proportional integral
Performance analysis of various parameters by comparison of conventional pitc...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
In this paper, an optimization of PV grid connected system is investigated. This is achieved by considering the application of artificial intelligence in the DC side to realize maximal power extraction, and using a sine-band hysteresis control in the AC side of the system, to generate a sine current/voltage suitable for grid connection IEEE929-2000 standards. The overall system has been simulated taking into account environmental effects and standards constraints in order to achieve best performance. The choice of sine band hysteresis control was selected considering its implementation simplicity. The algorithm runs fast on a low-cost microcontroller allowing to avoid any delay that can cause a phase shift in the system. An experimental setup has been realized for tests and validation purposes. Both simulation and experimental results lead to satisfactory results which are conform to the IEEE929-2000 standards.
The energy sector is moving into the era of distributed generation (DG) and microgrids
(MGs). The stability and operation aspects of converter-dominated DG MGs, however, are faced by
many challenges. To overcome these difficulties, this paper presents a new large-signal-based control
topology for DG power converters that is suitable for both grid connected and islanding modes of
operation without any need to reconfigure the control system and without islanding detection. To
improve MG stability and to guarantee stability and high performance of the MG system during sudden
harsh transients such as islanding, grid reconnection, and large load power changes, a nonlinear MG
stabilizer is proposed. We propose a novel control topology for microgrids which can work in both grid
connected and islanding modes without reconfiguration so it does not require islanding detection
technique, the controller is based on the concept of synchronverter In this paper, a radical step is taken
to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated
synchronization unit
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Control for Grid Connected and Intentional Islanding of Distributed Power Gen...ijtsrd
As the demand for more reliable and secure power system with greater power quality increases, the concept of distributed generation DG have become more popular. This popularity of DG concept has developed simultaneously with the decrease in manufacturing costs associated with clean and alternative technologies like fuel cells, biomass, micro turbine and solar cell systems. Intentional islanding is the purposeful sectionalisation of the utility system during widespread disturbances to create power “islandâ€. This island can be designed to maintain a continuous supply of power during disturbances of the main distribution system. Ruchali Borkute | Nikita Malwar ""Control for Grid Connected and Intentional Islanding of Distributed Power Generation"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23679.pdf
Paper URL: https://www.ijtsrd.com/engineering/electrical-engineering/23679/control-for-grid-connected-and-intentional-islanding-of-distributed-power-generation/ruchali-borkute
Enhanced MPPT Technique For DC-DC Luo Converter Using Model Predictive Contro...IJERD Editor
The present study explored an enhanced maximum power point tracking technique which ensures fast tracking in PV systems. This system represents a Model Predictive Control (MPC) MPPT technique. Extracting the maximum power from PV systems has been widely investigated. The main benefaction of this article is an improvement of the Perturb and Observe (P&O) method through a fixed step predictive control under measured fast solar radiation. The preferred predictive control to achieve Maximum Power Point (MPP) speeds up the control loop since it predicts error before the switching signal is applied to the DC-DC Luo converter. Comparing the improved technique to the conventional P&O method indicates significant improvement in PV system performance. The proposed MPC-MPPT technique for a Luo converter is implemented using the MAT LAB SIMULINK
This paper presents the analysis, modeling and control of a grid connected photovoltaic generation system. The model contains a detailed representation of the solar array, grid side multilevel neutral point clamped voltage source inverter. Fuzzy logic controller for the maximum power point tracking of a photovoltaic system under variable temperature and insulation conditions is discussed. The PQ control approach has been presented for the multilevel inverter. One of the most common control strategies structures applied to decentralized power generator is based on power direct control employing a controller for the dc link voltage and a controller to regulate the injected current to the utility network. The proposed models were implemented in Matlab/Simulink.
Adaptive Neuro-Fuzzy Inference System based Fractal Image CompressionIDES Editor
This paper presents an Adaptive Neuro-Fuzzy
Inference System (ANFIS) model for fractal image
compression. One of the image compression techniques in
the spatial domain is Fractal Image Compression (FIC)
but the main drawback of FIC using traditional
exhaustive search is that it involves more computational
time due to global search. In order to improve the
computational time and compression ratio, artificial
intelligence technique like ANFIS has been used. Feature
extraction reduces the dimensionality of the problem and
enables the ANFIS network to be trained on an image
separate from the test image thus reducing the
computational time. Lowering the dimensionality of the
problem reduces the computations required during the
search. The main advantage of ANFIS network is that it
can adapt itself from the training data and produce a
fuzzy inference system. The network adapts itself
according to the distribution of feature space observed
during training. Computer simulations reveal that the
network has been properly trained and the fuzzy system
thus evolved, classifies the domains correctly with
minimum deviation which helps in encoding the image
using FIC.
Development of Adaptive Neuro Fuzzy Inference System for Estimation of Evapot...ijsrd.com
The accuracy of an adaptive neurofuzzy computing technique in estimation of reference evapotranspiration (ETo) is investigated in this paper. The model is based on Adaptive Neurofuzzy Inference System (ANFIS) and uses commonly available weather information such as the daily climatic data, Maximum and Minimum Air Temperature, Relative Humidity, Wind Speed and Sunshine hours from station, Karjan (Latitude - 22°03'10.95"N, Longitude - 73°07'24.65"E), in Vadodara (Gujarat), are used as inputs to the neurofuzzy model to estimate ETo obtained using the FAO-56 Penman.Monteith equation. The daily meteorological data of two years from 2009 and 2010 at Karjan Takuka, Vadodara, are used to train the model, and the data in 2011 is used to predict the ETo in that year and to validate the model. The ETo in training period (Train- ETo) and the predicted results (Test-ETo) are compared with the ETo computed by Penman-Monteith method (PM-ETo) using "gDailyET" Software. The results indicate that the PM-ETo values are closely and linearly correlated with Train- ETo and Test- ETo with Root Mean Squared Error (RMSE) and showed the higher significances of the Train- ETo and Test- ETo. The results indict the feasibility of using the convenient model to resolve the problems of agriculture irrigation with intelligent algorithm, and more accurate weather forecast, appropriate membership function and suitable fuzzy rules.
This Paper mainly deals with the implementation of Adaptive Neuro Fuzzy Inference System (ANFIS) in Pulse Width Modulation control of Single Ended Primary Inductor Converter (SEPIC). Generally PID, Fuzzy techniques are being used to control DC – DC converter. This paper presents a ANFIS controller based SEPIC converter for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system. The ANFIS controller for the SEPIC MPPT scheme shows a high precision in current transition and keeps the voltage without any changes represented in small steady state error and small overshoot. The proposed scheme ensures optimal use of photovoltaic (PV) array, wind turbine and proves its efficacy in variable load conditions, unity and lagging power factor at the inverter output (load) side. The performance of the proposed ANFIS based MPPT operation of SEPIC converter is compared to those of the conventional PID and Fuzzy based SEPIC converter. The results show that the proposed ANFIS based MPPT scheme for SEPIC can transfer power to about 20 percent (approx) more than conventional system.
The electric power supplied by a photovoltaic power generation system depends on the solar radiation and temperature. Designing efficient PV systems heavily emphasizes to track the maximum power operating point.
This work develops a three-point weight comparison method that avoids the oscillation problem of the perturbation and observation algorithm which is often employed to track the maximum power point. Furthermore, a low cost control unit is developed, based on a single chip to adjust the output voltage of the solar cell array.
COORDINATED CONTROL AND ENERGY MANAGEMENT OF DISTRIBUTED GENERATION INVERTERS...ijiert bestjournal
In modern world,our entire life moves around Computers. Most of our tasks are dependent on the Computers,like Communication,Ticket Reservations,Researches,Printing,and Education etc. When we communicate with each other by using Computers through E Mails,a number of Computers are used for this purpose and the collection of these computers forms a network,which is called a Computer Network. As more and more peoples are going to be connected through the general network (INTERNET),the problem of security arises. Now a day,a number of security issues occur in networks which include Sniffing,Spoofing,Security Attacks,Malwares,Unauthorized Access,etc. This will create havoc for the users,who wants to communicate with each other through these networks. So,to make the communication between two users via the Computer Networks,we have to follow some security measures,which include using the Firewalls,Anti Malicious Software,Intrusion Detection Systems,Cryptography Techniques,et c. This paper is basically focused on how the communication between two users has been performed by using Computer Networks and how to make such a communication
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 parameters of inverter-based microgrid to improve transient response IJECEIAES
The inertia issues in a microgrid can be improved by modifying the inverter control strategies to represent a virtual inertia simulation. This method employs the droop control strategy commonly used to share the power of a load among different power sources in the microgrid. This paper utilizes a modified droop control that represents this virtual inertia and applies an optimization algorithm to determine the optimal parameters and improve transient response. The results show better control when different variations are presented in the loads, leading the microgrid to have a better control of the operation. The optimization method applied in this research allows improvement to the transient response, thus avoiding unnecessary blackouts in the microgrid.
Adıgüzel Hydroelectric Power Plant’s Modelling and LoadFrequency Control by F...IJERA Editor
In this study, to realize the load-frequency control according to different loading statuses, modelling of dynamic
behaviour of the Adıgüzel Hydroelectric Power Plant (HEPP) was made by using the Matlab/Simulink program.
By establishing the dynamic model of 36MVA synchronous generator and other components in the system in a
manner reflecting its behaviour in the real system, performance of classical controller and self-adjusting fuzzy
logic controller in electro-hydraulic governor circuit was examined according to different load statuses. During
the simulation works carried out when both control systems closely watched in the fuzzy logic control system
according to different loads the frequency of load and the number of frequency have been observed to be stable
in short period of time and allowed tolerance limits.
Reactive Power Sharing Droop Control Strategy for DG Units in an Islanded Mic...IJMTST Journal
The proposed method mainly includes two important operations: error reduction operation and voltage
recovery operation. The sharing accuracy is improved by the sharing error reduction operation, which is
activated by the low-bandwidth synchronization signals. However, the error reduction operation will result in
a decrease in output voltage amplitude. Therefore, the voltage recovery operation is proposed to compensate
the decrease., due to increasing the demand of electricity as well as rapid depletion of fossil fuels, and the
government policies on reduction of greenhouse gas emissions , renewable energy technologies are more
attractive and various types of distributed generation sources, such as wind turbine generators and solar
photo voltaic panels are being connected to low-voltage distribution networks. Micro grid is an integrated
system that contain in s distributed generation sources, control systems, load management, energy storage
and communication infrastructure capability to work in both grid connected and island mode to optimize
energy usage. The paper presents a advanced control technique for a micro grid system which works
efficiently under a decentralized control system.
A review of optimal operation of microgrids IJECEIAES
The term microgrid refers to small-scale power grid that can operate autonomously or in concurrence with the area’s main electrical grid. The intermittent characteristic of DGs which defies the power quality and voltage manifests the requirement for new planning and operation approaches for microgrids. Consequently, conventional optimization methods in new power systems have been critically biased all through the previous decade. One of the main technological and inexpensive tools in this regard is the optimal generation scheduling of microgrid. As a primary optimization tool in the planning and operation fields, optimal operation has an undeniable part in the power system. This paper reviews and evaluates the optimal operation approaches mostly related to microgrids. In this work, the foremost optimal generation scheduling approaches are compared in terms of their objective functions, techniques and constraints. To conclude, a few fundamental challenges occurring from the latest optimal generation scheduling techniques in microgrids are addressed.
Fixed-time observer-based distributed secondary voltage and frequency control...IJECEIAES
This paper deals with the problem of voltage and frequency control of distributed generators (DGs) in AC islanded microgrids. The main motivation of this work is to obviate the shortcomings of conventional centralized and distributed control of microgrids by providing a better alternative control strategy with better control performance than state-of-the art approaches. A distributed secondary control protocol based on a novel fixed-time observer-based feedback control method is designed for fixed-time frequency and voltage reference tracking and disturbance rejection. Compared to the existing secondary microgrid controllers, the proposed control strategy ensures frequency and voltage reference tracking and disturbance rejection before the desired fixed-time despite the microgrid initial conditions, parameters uncertainties and the unknown disturbances. Also, the controllers design and tuning is simple, straightforward and model-free.i.e, the knowledge of the microgrid parameters, topology, loads or transmission lines impedance are not needed in the design procedure. The use of distributed control approach enhances the reliability of the system by making the control system geographically distributed along with the power sources, by using the neighboring DGs informations instead of the DG’s local informations only and by cooperatively rejecting external disturbances and maintaining the frequency and the voltage at their reference values at any point of the microgrid. The efficiency of the proposed approach is verified by comparing its performance in reference tracking and its robustness to load power variations to some of the works in literature that addressed distributed secondary voltage and frequency control.
Stochastic control for optimal power flow in islanded microgridIJECEIAES
The problem of optimal power flow (OPF) in an islanded mircrogrid (MG) for hybrid power system is described. Clearly, it deals with a formulation of an analytical control model for OPF. The MG consists of wind turbine generator, photovoltaic generator, and diesel engine generator (DEG), and is in stochastic environment such as load change, wind power fluctuation, and sun irradiation power disturbance. In fact, the DEG fails and is repaired at random times so that the MG can significantly influence the power flow, and the power flow control faces the main difficulty that how to maintain the balance of power flow? The solution is that a DEG needs to be scheduled. The objective of the control problem is to find the DEG output power by minimizing the total cost of energy. Adopting the Rishel’s famework and using the Bellman principle, the optimality conditions obtained satisfy the Hamilton-Jacobi-Bellman equation. Finally, numerical examples and sensitivity analyses are included to illustrate the importance and effectiveness of the proposed model.
Fuzzy logic-based controller of the bidirectional direct current to direct cu...IJECEIAES
Microgrids are small-scale power networks that include renewable energy sources, load, energy storage systems, and energy management systems (EMS). Lithium-ion batteries are the most used battery for energy storage in microgrids due to their advantages over other types of batteries. However, to protect the battery from the explosion and to manage to charge and discharge based on state-of-charge (SoC) value, this type of battery requires the use of an energy management system. The main objective of this paper is to propose an intelligent control strategy for energy management in the microgrid to control the charge and discharge of Li-ion batteries to stabilize the system and reduce the cost of electricity due to the high cost of grid electricity. The proposed technique is based on a fuzzy logic controller (FLC) for voltage control. The FLC is based on the measured voltage of the direct current (DC) bus and the fixed reference voltage to generate buck/boost converter signal control. The proposed technique has been simulated and tested using MATLAB/Simulink software which illustrates the tracking of desired power and DC bus voltage regulation. The simulation results confirm that the proposed systems can diminish the deviations of the system's voltage.
This article addresses the problem of controlling an overall wind energy conversion system (WECS) formed by a wind turbine connected to the grid via a doubly fed introduction generator (DFIG) and an AC/DC/AC converter. The main control objectives are fourfold: (i) designing an output feedback speed controller that makes the DFIG rotate at the optimal value delivered by the MPPT strategy, (ii) controlling the stator reactive power so as to be null, (iii) guaranteeing the DC-link voltage in the grid side converter to be at a given constant value, (iv) ensuring a unitary power factor. A high gain observer is synthesized, in order to provide estimated values of the mechanical variables. To achieve the control objectives, a sliding mode controller involving the mechanical observer is designed. The performance of the system configuration based on the 2MW-DFIG with the proposed controller is evaluated by a numerical simulation under a realistic wind profile using MATLAB/SIMULINK/SimPowerSystems environment.
Voltage Compensation in Wind Power System using STATCOM Controlled by Soft Co...IJECEIAES
When severe voltage sags occur in weak power systemsassociated with gridconnected wind farms employing doubly fed induction generators, voltageinstability occurs, which may lead to forced disconnection of wind turbine.Shunt flexible AC transmission system devices like static synchronous compensator (STATCOM) may be harnessed to provide voltage support bydynamic injection of reactive power.In this work, the STATCOM providedvoltage compensation at the point of common coupling in five test cases,namely, simultaneous occurrence of step change (drop) in wind speed and dip in grid voltage, single line to ground, line to line, double line to groundfaults and sudden increment in load by more than a thousand times. Threetechniques were employed to control the STATCOM, namely, fuzzy logic,particle swarm optimization and a combination of both. A performancecomparison was made among the three soft computing techniques used tocontrol the STATCOM on the basis of the amount of voltage compensationoffered at the point of common coupling. The simulations were done with thehelp of SimPowerSystems available with MATLAB / SIMULINK and theresults validated that the STATCOM controlled by all the three techniques offered voltage compensation in all the cases considered.
1. ARCHIVES OF ELECTRICAL ENGINEERING VOL. 63(4), pp. 551-578 (2014)
DOI 10.2478/aee-2014-0038
Improvement of microgrid dynamic performance
under fault circumstances using ANFIS
for fast varying solar radiation
and fuzzy logic controller for wind system
MAZIAR IZADBAKHSH, ALIREZA REZVANI, MAJID GANDOMKAR
Department of Electrical Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran
e-mail: m.izadbakhsh@iau-saveh.ac.ir
(Received: 20.05.2014, revised: 11.08.2014)
Abstract: The microgrid (MG) technology integrates distributed generations, energy
storage elements and loads. In this paper, dynamic performance enhancement of an MG
consisting of wind turbine was investigated using permanent magnet synchronous
generation (PMSG), photovoltaic (PV), microturbine generation (MTG) systems and
flywheel under different circumstances. In order to maximize the output of solar arrays,
maximum power point tracking (MPPT) technique was used by an adaptive neuro-fuzzy
inference system (ANFIS); also, control of turbine output power in high speed winds was
achieved using pitch angle control technic by fuzzy logic. For tracking the maximum
point, the proposed ANFIS was trained by the optimum values. The simulation results
showed that the ANFIS controller of grid-connected mode could easily meet the load
demand with less fluctuation around the maximum power point. Moreover, pitch angle
controller, which was based on fuzzy logic with wind speed and active power as the
inputs, could have faster responses, thereby leading to flatter power curves, enhancement
of the dynamic performance of wind turbine and prevention of both frazzle and
mechanical damages to PMSG. The thorough wind power generation system, PV system,
MTG, flywheel and power electronic converter interface were proposed by using
Mat-lab/Simulink.
Key words: MG, dynamic performance, photovoltaic, PMSG, ANFIS, droop control
1. Introduction
Nowadays, the world is looking for energy alternative sources as the energy demand
continues to grow. Wind, PV, MTG are three of the most promising renewable power gene-
ration technologies due to their advantages. However, each of the aforementioned technologies
has its own drawbacks. Interconnection networks of distributed energy resources, energy
storage systems and loads define an MG that can operate in stand-alone or in grid-connected
mode [1, 2]. An MG is disconnected automatically from the main distribution system and
changed to islanded operation when a fault occurs in the main grid or the power quality of the
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2. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.552
grid falls below a required standard. In the grid connected mode, the grid dominates most of
the system dynamics and no significant problem needs to be addressed except the power flow
control, whereas in the islanding mode, once the isolating switch disconnected the utility from
the MG [3, 4].
Developing PV energy sources can reduce fossil fuel dependency [5]. In recent years,
many different technics have been applied in order to reach the maximum power. The most
prevalent technics are perturbation and observation (P&O) algorithm [6, 7], Incremental
conductance (IC) [8, 9], fuzzy logic [10, 11] and artificial networks (ANN) [12-14]. According
to the above mentioned researches, the benefits of perturbation and observation algorithm and
incremental conductance are: 1 – low cost implementation, and 2 – simple algorithm. The
depletion of these methods is vast fluctuation of output power around the MPP even under
steady state, resulting in the loss of available energy [15].
Using fuzzy logic can solve the two mentioned problems dramatically. In fact, with fuzzy
logic controller, proper switching can reduce oscillations of output power around the MPP and
losses. Furthermore, in this way, convergence speed is higher than the other two ways men-
tioned. A weakness of fuzzy logic, compared to neural network, refers to oscillations of output
power around the MPP [16]. Nowadays, artificial intelligence (AI) techniques have numerous
applications in determining the size of PV systems, MPPT control and the optimal structure of
photovoltaic systems [17].
Neural networks can be considered as a powerful technique for mapping inputs-outputs of
non-linear functions, but it lacks subjective sensations and acts as a black box. On the other
hand, through fuzzy rules and membership functions, fuzzy logic has the ability to transform
linguistic and mental data into numerical values. However, the determination of membership
functions and fuzzy rules depends on the previous knowledge of the system. Neural networks
can be integrated with fuzzy logic and through the combination of these two smart tools,
a robust AI technique called ANFIS can be obtained [18]. In [19, 20], the structure of ANFIS
have been used, but one of the major drawbacks in these articles is that they were not con-
nected to the grid in order to ensure the analysis of system performance, which was not con-
sidered.
In terms of wind power generation system (WPGS), it is proposed as one of the out-
standing renewable energy sources [21, 22]. One of the approaches used to reach the MPP is
pitch angle control, in which small turbines with low power delivery are not possible due to
mechanical difficulties in production [23].
In the past, PIDs were used mostly in controllers design, but by the introduction of fuzzy
logic instead of PID created a better performance such that it was the best preventative way to
eliminate the profound mathematical understanding of system. Comparing PIDs and fuzzy
logic systems shows that fuzzy logic has more stability, faster and smoother response, and
smaller overshoot. It does not need a fast processor, and is more powerful than other non-
linear controllers too [24]. In [25-27], a pitch angle controller based on fuzzy logic was pre-
sented. In [27], active power and in [25, 27], both reactive power and rotational rotor speed
were used as input signals. As in the mentioned items wind speed was ignored, the controller
did not show as fast response and could cause mechanical damages to the synchronous
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3. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 553
generator. Also, another problem with these studies was that they were not practically con-
nected to grid to analyze the system performance [26-28].
In this paper, the simulation and structure of MTG and flywheel have been presented, as
investigated in [29-31].
The system modeling for grid, load and inverter in MG has been discussed in [32]. The
authors in [33] studied the MG during both connected and islanding modes. In [34], the
researchers described the feasibility of a control strategy adopted in the operation of the MG
during the islanding mode.
The MG’s grid connected operation during and subsequent to the islanding mode were pre-
sented in [35], but the DGs dynamic model was not included, which could have a great effect
on the dynamic performances of the MG subsequent to islanding. Furthermore, DGs (wind,
PV, MTG and etc.) were not considered in their model. Virtually, in the former references, the
grid connected process has not discussed to show the effect of wind speed fluctuations in
dynamic performances of the MG, especially after the islanding occurrence. In [36], a very
simple structure of an MG with three DGs has been studied; however; there is no mention or
analysis of the DGs structure, controllers of each micro source, fault occurrence in the grid
and response of MG against the sudden circumstances, and the exchanged power between
DGs. In [37, 38], authors utilized perturbation and observation algorithm in a PV and wind
system in which the mentioned algorithm had vast fluctuation of output power around the
MPP even under the steady state. Furthermore, in mentioned paper, there was not any
controller (pitch angle control) to control the output power of wind turbine in high speed as it
could cause the damages to generator; also, the P-Q control method for wind system was not
used in the grid side inverter.
In this paper, three issues were addressed in order to overcome the disadvantages of the
aforementioned references: 1) the use of complete model that described in detail all the MG
elements (DGs, converter control schemes, control strategies (P-Q and droop control) and etc),
2) the application of fuzzy controller (for pitch angle) instead of PI controller to smooth the
output power of wind turbines caused by wind speed fluctuations and a comparison of the
performances of the fuzzy controller with the conventional PI controller, and 3) the applica-
tion of ANFIS controller to capture the MPPT of photovoltaic panels mounted in the MG.
Temperature and irradiance as inputs data were given to genetic algorithm and optimal voltage
(Vmpp) corresponding to the MPP delivery from the PV system; then the optimum values were
utilized for training the ANFIS.
2. Photovoltaic cell model
Figure 1 shows the equivalent circuit of one PV cell [5]. Characteristics of one solar array
are explained in following equations:
,IIII RPdPV ++= (1)
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4. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.554
Fig. 1. Equivalent circuit of one PV array
,1exp
P
S
th
S
dpv
R
IRV
nV
IRV
III
+
−⎥
⎦
⎤
⎢
⎣
⎡
−⎟
⎠
⎞
⎜
⎝
⎛ +
−= (2)
Where I is the output current, V is the output voltage, Ipv is the generated current under
a given insolation, IRP is diode current, I0 is the diode reverse saturation current, n is the
ideality factor for a p-n junction, Rs is the series loss resistance, and Rp is the shunt loss resis-
tance. Vth is known as the thermal voltage. Red sun 90w is taken as the reference module for
simulation and the name-plate details are given in Table 1. The array is the combination of 4
cells in series and 3 cells in the parallel of the 90w module; hence an array generates 1.1 kW.
Table 1. Red sun 90w
IMP (current at maximum power) 4.94 A
VMP (voltage at maximum power) 18.65 V
PMAX (maximum power) 90 W
VOC (open circuit voltage) 22.32
ISC (short circuit current) 5.24
NP (total number of parallel cells) 1
NS (total number of series cells) 36
3. Maximum power tracking – ANFIS and genetic algorithm technic
3.1. The Steps in implementing genetic algorithm
In order to pursue the optimum point for maximum power in any environmental condition,
ANFIS and genetic algorithm technic are used. Besides, genetic algorithm is used for optimum
values and then optimum values are used for training ANFIS [39, 40]. The procedure emp-
loyed for implementing genetic algorithm is as follows [41]: 1) defining the objective function
and recognizing the design parameters, 2) defining the initial production population, 3) eva-
luating the population using the objective function, and 4. conducting convergence test stop if
convergence is provided.
The objective function of genetic algorithm is used for its optimization (using Matlab
software) by the following: finding the optimum X = (X1, X2, X3,..., Xn) to put the F(X) in the
maximum value, where the number of design variables are considered as 1. X is the design
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5. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 555
variable equal to array current and also, F(X) is the array output power which should be maxi-
mized [39]. To determine the objective function, the power should be arranged based on the
current of array (IX). The genetic algorithm parameters are given in Table 2.
( ) ,* XXX IVF = (3)
.0 CSX II << (4)
Table 2. The genetic algorithm parameters
Number of design variable 1
Population size 20
Crossover constant 80%
Mutation rate 10%
Maximum generations 20
The current constraint should be considered too. With maximizing this function, the opti-
mum values for Vmpp and MPP will result in any particular temperature and irradiance in-
tensity.
3.2. Adaptive neuro-fuzzy inference systems
ANFIS refers to adaptive neuro-fuzzy inference system. An adaptive neural network has
the advantages of learning ability, optimization and balancing. However, a fuzzy logic is
a method based on rules constructed by the knowledge of experts [42]. The good performance
and effectiveness of fuzzy logic have been approved in nonlinear and complicated systems.
ANFIS combines the advantages of using adaptive neural network and fuzzy logic. ANFIS
makes use of Sugeno type [19, 20]. For a fuzzy inference system, with 2 inputs and 1 output,
a common rule set is obtained with 2 fuzzy if-then rules by the following Equations. The fuzzy
rules can typically be as follows:
Rule 1. If x is A1 and y is B1; then
.1111 ryqxpf ++= (5)
Rule 2. If x is A2 and y is B2; then
.2222 ryqxpf ++= (6)
Where x and y are the inputs and f is the output. [A1, A2, B1, B2] are called the premise
parameters. [pi, qi, ri] are called the consequent parameters, i = 1, 2. The consequent para-
meters (p, q, and r) of the nth rule contribute through a first order polynomial .These para-
meters are called result parameters. The ANFIS structure of the above statements is shown in
Figure 2.
This structure has five layers. It can be seen that the nodes of the same layer have the same
functions. i output node in layer 1 is named as Q1i.
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6. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.556
Fig. 2. ANFIS architecture of a 2-input first-order Sugeno fuzzy model with 2 rules
Layer 1. Every node in this layer consists of an adaptive node with a node function. We
have:
( ) 2,1for,,1 == ixAQ ii μ , (7)
( ) 4,3for,2,1 == − iyBQ ii μ . (8)
Where x (or y) is the input of node i and Ai (or Bi – 2) is a fuzzy set related to that node. In
other words, the output of this layer is its membership value. Membership functions for A can
be any appropriate parameterized membership function. Each parameter in this layer is re-
garded as a default parameter.
Layer 2. Each node in this layer has been labeled with an “n” and the output of each node
is the product of multiplying all incoming signals for that node. These nodes perform the fuzzy
AND operation, and we have:
( ) ( ) 2,1,,2 === iforyxAwQ Biiii μμ , (9)
where the output of each node indicates firing strength of each rule.
Layer 3. Each node in this layer has been labeled with an “N”. Nodes in this layer calculate
the normalized output of each rule. Then we have:
,2,1
21
,3 =
+
== i
WW
W
wQ i
ii (10)
where Wi is the firing strength of that rule. The output of this layer is called the normalized fir-
ing strength.
Layer 4. Each node in this layer is associated with a node function. Then we have:
( ),,4 iiiiiii ryqxpwfwQ ++== (11)
where Wi is the normalized firing strength of the third layer and {pi, qi, ri} are parameters sets
of the node i. Parameters of this layer are called “consequent parameters”.
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7. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 557
Layer 5. The single existing node in this layer is labeled as Σ. It computes the sum of all its
input signals and sends them to the output section.
,
Σ
Σ
,5
ii
iii
iii
w
fw
fwQ == ∑ (12)
where Q5i is the output of node (i) in the fifth layer. For this reason, first, all existing rules will
be established in the layer 1.
In this paper, a hybrid learning algorithm was used. The hybrid learning algorithm is
a combination of gradient descent and least squares methods. In this simulation, irradiance and
temperature were regarded as the input and output was an optimal voltage (Vmpp) corres-
ponding to the MPP delivery from the PV system. Then, the output voltage of PV module with
ANFIS output voltage was deducted to obtain the error signal. Then, through a PI controller,
this error signal was given to a pulse width modulation (PWM) block. The block diagram of
the proposed MPPT scheme is shown in Figure 3.
Fig. 3. Proposed MPPT Scheme
Fig. 4. The output data Vmpp corresponding to (MPP)
The PV system was designed in order to obtain data by genetic algorithm. A set of 360 data
was put to temperature and irradiance as inputs. Also, the output was Vmpp corresponding to the
MPP delivery from the PV panels as depicted in Figure 4. Then these optimum values were
utilized for training the ANFIS. All input were 360 data in which a set of 330 data was used
for training the developed ANFIS model and also, a set of 30 data samples not included in the
PV
ANFIS
Boots
converter
Grid
PI
controller
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8. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.558
training was used for the testing. Input temperature ranged from 5 to 55°C in the steps of 5° C
and irradiance varied from 50 to 1000 (W/m2
) in the steps of 32 (W/m2
).
ANFIS input structure is shown in Figure 5. It includes five layers. The two inputs re-
present irradiance and temperature, both of which have 3 membership functions. The structure
shows two inputs of the solar irradiance and cell temperature, which are translated into ap-
propriate membership functions. Three functions for the solar irradiance are shown in Figure
6(a) and three functions for temperature are illustrated in Figure 6(b). The network is trained
for 30,000 epochs. After the training process, the output of the trained network should be very
close to the target outputs as shown in Figure 7(a). According to Figures 7(b) and 7(c), Vmpp
was compared with the target value and in Figures 8(a), 8(b) and 8(c) the output of ANFIS test
was compared with the target value, showing a negligible training error percentage of about
1.4%.
Fig. 5. ANFIS controller structure
Fig. 6. ANFIS membership function: (a) solar irradiance membership function, (b) temperature
membership functions
4. Wind system configuration
The diagram of a wind generation system in the presence of PMSG integrated with the grid
is illustrated in Figure 9. Turbine output was rectified by using the uncontrolled rectifier. Then
dc link voltage was adjusted by PI controller until it reached a constant value and then this
constant voltage was inverted to AC voltage using sinusoidal PWM inverter. Inverter adjusted
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9. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 559
a)
b)
c)
Fig. 7. The output of the ANFIS: (a) The output of the ANFIS with the amount of target data; (b) The output
of ANFIS (Vmpp)with the amount of target data; (c) Percentage error of the (Vmpp) after training data
the dc link voltage and injected active power by d-axis and injected reactive power by q-axis
using P-Q control method. Furthermore, turbine output was regulated through pitch angle
controller based on fuzzy logic in extra high wind speeds.
4.1. Wind turbine and PMSG modeling
The amount of electricity a turbine is able to produce depends on the speed of the rotor and
the speed of the wind that propels the rotor. Aerodynamic wind power is calculated in Equa-
tion (13):
( ) ,,5.0 3
Wp VACP βλρ= (13)
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10. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.560
(a)
(b)
(c)
Fig. 8. The output of the ANFIS test: (a) The output of the ANFIS test with the amount of target data; (b)
The output of the ANFIS test (Vmpp) with the amount of target data; (c) Percentage error of test data
(Vmpp) after training data
,
w
m
V
RW
=λ (14)
where P, D, A, Vw, Wm and R are power, air density, rotor swept area of the wind turbine, wind
speed in m/sec, rotor speed in rad/sec and the radius of the turbine, respectively. Also, CP is
the aerodynamic efficiency of the rotor. PMSG voltage equations and other equations of wind
turbine are presented in [28, 43].
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11. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 561
Fig. 9. The block diagram of wind power generation system
4.2. Pitch angle based on fuzzy controller
The presented fuzzy controller consists of two input signals and one output signal. The first
input signal is based on the deviation between active power and the rated value in P.U, which
was mentioned as error signal. Thus, its positive value indicates turbine’s normal operation
and its negative value shows the extra power generation during the above rated wind speed. In
this case, controller should modify pitch angle degree by increasing the nominal value. The
pitch angle degree is regulated on zero in a normal condition. The whole wind energy can be
converted to mechanical energy and when the pitch angle starts to increase from the zero
value, the wind attach angle to the blades will be increased, thereby leading to aerodynamic
power reduction and consequently, drawing down the output power. Besides, the second signal
is taken from anemometer nacelle [44].
Controller’s response is so faster when wind speed is used as an input signal compared to
the time when inputs are rotor rotational speed or active power in large turbines with a high
moment of inertia [25-27]. However, mechanical erosion in large and high speed turbines will
be diminished by adjusting this fuzzy controller. Designing a pitch angle controller based on
fuzzy logic for wind turbine power adjustment in high wind speeds is being proposed in this
paper. Three Gaussian membership functions are considered in this paper. Also, Min-Max
method is used as a defuzzification reference mechanism for Centroid. The membership
functions are shown in Figure 10.
Moreover, The rules implemented to obtain the required pitch angle (β) are shown in
Table 3.The linguistic variables are represented by VG(very great), SG (small great),OP (opti-
mum), SL (small low),and VL (very low) for error signal and VL (very low), SL (small low),
OP (optimum), SH (small high) and VH (very high) for wind speed signal and NL (negative
large), NS (negative small), Z (zero), PS (positive small) and PL (positive large) for output
signal, respectively.
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12. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.562
Table 3. Fuzzy rules
Pitch command Active power (error)
VG SG OP SL VL
VL PL PS Z Z Z
SL PL PS Z Z Z
OP PL PS Z Z Z
SH PL PS PS PS PS
Wind speed
VH PL PL PL PL PL
(a)
(b)
(c)
Fig. 10. The membership function of fuzzy logic: (a) Membership functions of active power (error sig-
nal); (b) Membership functions of wind speed; (c) Membership functions of output (β)
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13. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 563
5. MTG system configuration
The modeling and simulation of a single-shift MTG is presented in Figure 11. This model
includes the speed governor, acceleration control block, temperature control and fuel system
control. MTG details are presented in [29]. The power producer is a synchronous generator
with a permanent magnet, which has two poles and a salient pole rotor. The generator
produces a high frequency three-phase signal of about 1500 to 4000 Hz. This high frequency
voltage is rectified by rectifiers, and then converted to a voltage of 60 Hz by the inverter. The
rated output power generated by MTG is 25 kW. The nominal design speed of the generator is
66000 rpm.
Fig. 11. Simulink implementation of microturbine model
6. Flywheel energy storage system (FESS)
As one type of storage device, flywheel has a comparatively fast response. Therefore,
flywheel is generally useful when there is an imbalance between supply and demand. In MG,
the flywheel can handle the power demands of the peak load and store the energy at the low
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14. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.564
load period. The flywheel can contribute to the stability of MG voltage amplitude and
frequency. Flywheel is connected at the DC bus to provide instantaneous power required by
droop controller. In this paper, the storage device used is a flywheel connected to the voltage
sources inverter (VSI). The detailed model of flywheel has been presented in [31].
7. Control strategies
7.1. P-Q control strategy
Inverter control model has been illustrated in Figure 12. The goal of controlling the grid
side is keeping the dc link voltage in a constant value regardless of production power magni-
tude. Internal control-loop controls the grid current and external control loop controls the
voltage. Also, internal control-loop is responsible for power quality such as low Total harmo-
nic distortion (THD) and the improvement of power quality and external control-loop is res-
ponsible for balancing the power. For reactive power control, reference voltage will be set the
same as dc link voltage. In grid-connected mode MG must supply local needs to decrease
power from the main grid.
Fig. 12. The P-Q control model
One of the main aspects of P-Q control loop is operating in grid connected and stand-alone
mode. The advantages of this operation mode are higher power reliability and higher power
quality [45]. Active and reactive components of the injected current are id and iq, respectively.
iq current reference is set to zero in order to obtain only a transfer of active power. For the
independent control of both id and iq, the decoupling terms are used. To synchronize the con-
verter with grid, a three Phase lock loop (PLL) is used.
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15. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 565
7.2. Droop control strategy
The VSI is to be coupled with a storage device (Flywheel) to balance load and generation
during islanded operation. Its control is performed using droop concepts [34]. The output
power of the VSI is defined from the droop characteristics as shown in Figure 13. During
islanded operation, when the unbalance of active power and reactive power occur, the
frequency and voltage will fluctuate. As a result, the MG will experience a blackout without
any effective controller. If the system is transferred to the islanded mode when importing
power from the grid, then the generation needs to increase power to balance power in the
islanded mode. The new operating point (B) will be set at a frequency (f1) lower than the
nominal value (f0). If the system is transferred to the islanded mode when exporting power to
the grid, then the new frequency (f2) will be higher [2, 38]. Also, the reactive power is injected
when voltage (V1) falls from the nominal value (V0) and absorbs the reactive power if the
voltage (v2) rises above its nominal value.
(a)
(b)
Fig. 13. Droop-characteristics: (a) frequency droop control; (b) voltage droop control
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16. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.566
7.3. Backup controller
Storage devices such as a flywheel have high capabilities for injecting power during
islanding operation; however one of the drawbacks is a limited storage capacity. Therefore, it
needs the supplementary source to support the frequency deviation. In this case, MTG is
utilized for compensating the drifted frequency. The structure of PI controller is illustrated in
Figure 14. Restoration of the frequency/voltage of the MG to their normal values requires a
supplementary action to adjust the output of the DG [38].
Fig. 14. Back up controller
Fig. 15. Case study system
8. Simulation results
In this section, simulation results under different terms of operation in MG are presented
using Matlab/Simulink. System block diagram is shown in Figure 15. The grid voltage and
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17. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 567
frequency were 220 V and 60 Hz, respectively. Detailed model descriptions have been given
in Appendix A. In Figures 16, 17 and 18, PV, wind system and MTG connected to grid by ap-
plying P-Q controller can be seen. Also, Figure 19 shows the FESS connected to grid by ap-
plying droop controller.
Fig. 16. PV system connected to grid by applying P-Q controller
8.1. Case study 1
In this case, the aim was load fault analysis of MG connected to the grid. It was assumed
that the sensitive loads (SL) were not connected in MG, and distributed generation sources fed
only the non-sensitive load (NSL). The amount of NSL was 75 kW.
The MG included 1.1 kW PV system, 88 kW wind turbine system, 25 kW MTG and
25 kW FESS. The system was controlled by P-Q and droop technic. In the grid connected
mode, because storage device (Flywheel) based on droop controller was installed in MG, there
was no power exchange between MG and the flywheel. The simulation results for PV are
shown in Figure 20. Different irradiance levels, according to Figure 20(a) evaluate the PV's
performance. The output current of PV is depicted in Figures 20(b). When irradiance was
increased at t = 2.5 and t = 4.5, it led to the increase in the output current of PV as shown in
Figure 20(b). The performance of the proposed controller was compared and analyzed with the
conventional techniques of fuzzy logic, P&O and IC. The proposed MPPT algorithm could be
converged to MPP’s target very fast to track it without any oscillation as shown in Fig. 20(c).
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18. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.568
Fig. 17. Wind system connected to grid by applying P-Q controller
Fig. 18. MTG system connected to grid by applying P-Q and backup controller
Also, in this case, during 0 < t < 1 sec, the load power was 75 kW and at t = 1, it had 40%
step increase in load. Wind speed during 0< t <1 was 11 m/s and at t = 2.3 s, it was reduced to
9 m/s. Then, during 1 < t < 2.3, wind speed was 9 m/s and after that, at t = 3.8 s, it was
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19. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 569
extremely increased to 16m/s. Through designing fuzzy controllers, when wind speed was
more than nominal (12 m/s), turbine output power was increased by extremely increasing
wind speed; however, without controller, the power was constant at a high level and in the
presence of fuzzy controller, it was reduced to the nominal power and made smoother, thereby
leading to the prevention of mechanical fatigue to generator.
Fig. 19. Flywheel system connected to grid by applying droop controller
Fig. 20. Simulated results for PV in case 1: a) irradiance ; b) output current of PV (after filter) ; c) PV power
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20. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.570
Fig. 21. Simulated results for wind system in case 1: (a) wind speed; (b) variation of pitch angle with
presence of fuzzy controller; (c) turbine output power with absence of controller; (d) turbine output
power with presence of fuzzy controller; (e) inverter output current with absence of controller; (f) in-
verter output current with presence of controller; (g) THD(%); (h) Inverter output voltage
Figure 21(a) shows the wind speed used. Figure 21(b) also displays the variation of pitch
angle in the presence of controller. As can be seen, in normal situations, the pitch angle was
set as zero. At wind speeds above the rated wind, the extracted wind power had to be limited
by increasing the pitch angle (β). Figures 21(c) and 21(d) show the active power of wind
turbine in the absence and presence of fuzzy logic controller according to wind speed. It was
obvious that fuzzy controller made a smoother power curve. By increasing the pitch angle via
fuzzy controller, the exceeding power of wind turbine was limited, reaching to the nominal
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21. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 571
value. Figures 21(e) and 21(f) show inverter output current in the absence of controller and in
the presence of controller, respectively. It shows the effectiveness of fuzzy controller by
increasing pitch angle. The exceeding power of wind turbine was limited and also, the inverter
output current was reduced in comparison to that without controller.
One of the most important aspects of using DG sources and connecting them to grid is
keeping the THD at the minimum of its value. According to IEEE Std.1547.2003, it should be
around 5%. In THD curve, it was around 1.5% to 2.5%. THD is shown Figure 21(g). Inverter
output voltage, as shown in Figures 21(h), was constant. Figures 22(a) and 22(b) show the grid
current in the absence and presence of controller, respectively. It can be observed from Figures
22(c) and 22(d) that pitch angle based on fuzzy controller can limit the exceeding output
power of turbine. Therefore, by the reduction of injected output power of wind turbine, the
injection of extra total active power of MG to grid was decreased. It is clear that the grid, with
the cooperation of wind, PV, MTG systems and FESS, can easily meet the load demand.
Fig. 22. Simulated results for grid in case 1: (a) Grid current with absence of fuzzy controller; (b) Grid
current with presence of fuzzy controller; (c) Active powers with absence of fuzzy controller; (d) Active
powers with presence of fuzzy controller
8.2. Case study 2
This section aimed to examine the MG from grid connected state to the islanding mode.
The MG, after applying a three-phase fault, was separated from the grid. It was assumed that
NSL was not connected in MG and the distributed generation sources fed only SL. The MG
imported around 15 kW and 11 kvar from the upstream MV network, with a local generation
of 93 kW and 5 kvar and an MG load of 108 kW and 16 kvar. Active and reactive power
demands in MG are illustrated in Figure 23. Flywheel provided a primary voltage and
frequency regulation in the islanded MG. Depending on the load, the (VSI) real and reactive
power was defined. The VSI was used to interface the flywheel (storage device) to the MG
during and subsequent to the islanding occurrence.
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22. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.572
Fig. 23. Active and reactive power demands in MG
At t = 5 sec, the fault was applied to the system and MG became the islanding mode. Also
wind power had high fluctuation, leading to high fluctuations in frequency, active and reactive
power injected by the VSI, and the voltages of the MG buses. In other words, fuzzy controller
acted when wind speed became more than the nominal value. The variation of pitch angle,
based on the fuzzy logic in wind turbine, led to smooth turbine output power as shown in Fi-
gure 24(a) and 24(b), respectively. Smoothing the output power of wind system led to smooth
active power, reactive power, frequency and voltages at all buses of the MG, especially the
wind generation bus. During the islanding mode, the reactive power imported from the main
grid was lost, and the voltage was dropped to 96% at the bus of wind generation as depicted in
Figure 24(c). Then the VSI injected the reactive power to balance the reactive power in the
MG as illustrated in Figure 25(a). Frequency deviation forced the VSI to inject the active
power according to frequency droop and to balance the generations and loads in the MG, as
shown in Figure 25(b). The proposed fuzzy pitch angle controller led to smooth the output
power of wind turbine and reduce frequency fluctuations as shown in Figure 26.
The output power of flywheel and MTG in the fuzzy controller had a larger value and less
oscillation than PI controller because the fuzzy controller increased the pitch angles of wind
turbine, which, in turn, smoothed the output power as shown in Figures 25(b) and 27(a).
The performance of the ANFIS controller in PV was compared and analyzed with the
conventional techniques such as fuzzy logic, P&O and IC when operating during a cloudy day
with rapid irradiance changes. According to Figure 27(b), it had a good performance and low
oscillation in comparison with the mentioned technique. The output power of PV was the
same in both cases because PV panel power depended only on irradiance and temperature.
9. Conclusion
The presented study was a kind of modeling and analysis of an MG consisting of PMSG
wind turbine, PV, MTG systems and FESS under fault circumstances. Variation of wind speed
and irradiance and also, the enhancement of dynamic performance of MG were considered.
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23. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 573
a)
b)
c)
Fig. 24. Wind system: (a) pitch angle (deg); (b) active power; (c) voltage at terminal (bus 3)
The simulation results in the grid connected mode showed that using ANFIS controller could
dramatically reduce the disadvantages of the previous approaches. In fact, this research sug-
gested that using ANFIS controller could decrease oscillations of power output around the
MPP and increase the convergence speed to achieve the MPP. Also, the presented controller in
the wind system, by adding wind speed as an input signal of fuzzy logic, could have a faster
and smoother response. The benefit of fuzzy controller is that it keeps the turbine output in an
X: 13.47
Y: 25.04
X: 11.51
Y: 12.05
X: 3.472
Y: 102.5
X: 21.48
Y: 94.44
X: 8.438
Y: 0.9642
X: 20.43
Y: 0.9568
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24. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.574
admissible value and can prevent more mechanical erosion and fatigue and also, the dynamic
performance of PMSG can be improved. On the other hand, by increasing pitch angle via
fuzzy controller, the exceeding power of wind turbine is limited, reaching to the nominal value
and reducing inverter output current. Therefore, by the reduction of injected output power of
wind turbine, the injection of extra total active power of MG to grid is decreased.
a)
b)
Fig. 25. Flywheel: (a) reactive power; (b) active power
During islanding mode, the performance of the ANFIS controller in PV was compared and
analyzed with conventional techniques operating during a cloudy day with rapid irradiance
changes, showing that this controller could increase convergence speed to achieve the MPP.
Due to the proposed fuzzy controller, it was possible to smooth wind power fluctuations well.
Smoothing wind power inside the MG improved the dynamic response of the MG subsequent
to the islanding occurrence. The output power of the MTG in the fuzzy controller had a larger
value with less oscillation than PI controller because the fuzzy controller increased the pitch
angles of wind turbines, which smoothed the output power. Flywheel provided a primary
X: 16.98
Y: 13.11
X: 19.56
Y: 18.09
X: 7.562
Y: 16.82
X: 14.9
Y: 7.693
X: 23.07
Y: 3.904
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25. Vol. 63(2014) Improvement of microgrid dynamic performance under fault circumstances 575
voltage and frequency regulation in the islanded MG. By applying the appropriate controller,
the MG in grid-connected mode and islanding mode could meet the load demand assuredly.
Fig. 26. Frequency variation
a)
b)
Fig. 27. Generated active power: (a) MTG; (b) PV system
X: 29.08
Y: 60.31
X: 6.422
Y: 59.46
X: 19.1
Y: 17.36
X: 19.16
Y: 15.13X: 9.473
Y: 10.09
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26. M. Izadbakhsh, A. Rezvani, M. Gandomkar Arch. Elect. Eng.576
Appendix A. Description of the detailed model
PV parameters: output power = 1.1 kW, Carrier frequency in VMPPT PWM generator = 4 kHz
and in grid-Sid controller = 5.5 kHz, boost converter parameters: L = 5mH, C = 800µF, PI co-
efficients in grid-side controller: KpVdc = 2, KiVdc = 9, KpId = 10, KiId = 400, KpIq = 10, KiIq = 400.
PMSG parameters: output power = 88 kW, Stator resistance per phase = 2.7 Ω, inertia:
0.9e-3
kg-m2, torque constant 12N-M/A, Pole pairs = 8, Nominal speed = 12 m/s, Ld = La = 8.9 mH.
Grid parameters: X/R = 7, and other parameters, DC link Capacitor = 5300 µF, DC link vol-
tage = 1050. PI coefficients in grid-side controller: KpVdc = 8, KiVdc = 400, KpId = 0.83, KiId = 5,
KpIq = 0.83, KiIq = 5.
MTG parameters: MTG ratings = 25 kW, Rotor speed = 66000 rpm, T1 = 0.4, T2 = 1,
K = 25. FESS parameters: output power = 25 kW, J = 0.07 Kg.m2
, L = 8 mH.
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