Frequency control of islanded microgrid using fuzzy-PI and autotuned controllers (original) (raw)
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Frequency regulation by fuzzy and binary control in a hybrid islanded microgrid
Journal of Modern Power Systems and Clean Energy, 2014
Islanded microgrids must be self-sufficient in terms of frequency and voltage control due to their islanded operation. A control strategy for frequency regulation by combining the operation of a wind generator, a diesel generator, a battery energy storage system and a dump load in a microgrid is proposed in this paper. In the proposed strategy, the control task is partitioned into two subtasks: 1) choosing the appropriate element to be used for regulation, and 2) providing frequency regulation. A global controller chooses the element to operate. Then, the frequency regulation is provided by separate individual controllers. The proposed control strategy is tested on a microgrid with mixed types of generation and modeled on Simulink. By monitoring the power of individual elements and system frequency, it is shown that the proposed control strategy operates efficiently. The proposed strategy facilitates the integration of renewable energy sources and enhances frequency regulation.
Application of Neuro-Fuzzy Controller on Voltage and Frequency Stability in Islanded Microgrids
2012
This paper presents a new droop control strategy based on neuro-fuzzy technique to minimize voltage and frequency deviations in islanded microgrids (MGs) under severe changes in load. In islanded MGs, due to lack of the backup power, the imbalance between consumption and generation usually leads to violent voltage/frequency fluctuations. Therefore, designing a reliable control structure to prevent the MG instability is needed. The proposed control strategy is designed to maintain the system stability and minimize the voltage/frequency fluctuations regardless of the MG structure. The most important advantage of the proposed controller is independency from the MG structure and operating conditions. The simulation results show the appropriate operation and efficacy of the proposed controller in the presence of severe changes in load.
Recently, microgrid has become popular in the electric power industry and the important performance parameters considered, particularly when it is operating in islanded mode or under the load change condition, are voltage-frequency regulation, dynamic and steady-state response. In this paper, an intelligent optimal power control strategy, based on fuzzy gain scheduling of the conventional proportional-integral controller, is proposed for voltage-frequency control in an inverter based distributed generation unit. Simulations results, of the proposed control strategy, are compared against that of the conventional PI controller under islanded mode and under load change condition. It is evident that the proposed control strategy provides improved response.
Fuzzy Based Intelligent Frequency Control Strategy in Standalone Hybrid AC MicroGrid
Due to environmental concerns, there is lot of emphasis on the use of renewable energy sources as distribution generation sources for electric power generation. These distributed sources have resulted in the concept of AC/DC micro-grids. But the intermittent nature of these sources cause many control problems and thereby affect the quality of the power within a micro-grid operating in a standalone or grid connected mode. In this paper an AC micro-grid operating in standalone mode and consisting of wind turbine generators (WTGs), solar photovoltaic (PV), diesel engine generators (DEGs), fuel cells (FCs) and battery energy storage system (BESS) has been considered for simulation studies. An intelligent control technique based on fuzzy gain scheduling of the conventional proportional-integral-derivative (PID) controller is proposed for frequency regulation for sudden changes in load or generation power or both. The performance of the fuzzy gain scheduled PID (FGSPID) controller is compared with that of the conventional PID controller for comparative analysis. The simulation results demonstrate the effectiveness of the FGSPID controller in terms of less oscillations and reduced settling time and overshoot.
Fuzzy-PI-based supervisory frequency control design in a stand-alone AC microgrid
2014
Frequency stability in microgrids under islanded operation mode is one of the most important control problems in new power system design. Due to increasing number of microgrids (MGs) in power systems, and variable inherent of renewable energy sources, this issue gets more attention recently. In industrial environments, PI controllers due to low-cost, reliability and simplicity in design are more popular; but in new power systems these controllers may not provide desirable performance. For sake of this challenge, in this paper after a brief review on the frequency control in MGs, a new intelligent secondary control method using a supervisory fuzzy logic controller is proposed with two main goals: holding of structure simplicity that is desirable in industrial environment and implementable capability without opening the existing conventional PI control loops. In this method which is applied on an AC MG, if system dynamics change, the PI controller parameters do not need to be retuning, and the supervisory fuzzy logic controller minimizes the MG frequency deviation.
International Transactions on Electrical Energy Systems, 2017
The increasing penetration of renewable energy resources in power systems has improved microgrid's implementation. A microgrid is a localized grouping of electricity sources and loads that normally operates connected to and synchronous with the traditional centralized grid but can disconnect and function autonomously as physical and economic conditions dictate. Main factors to control in a microgrid are mainly frequency and voltage regulation, energy management, operation, and control scheme. This high penetration of renewable generation systems with their intermittent nature and unpredictable output power fluctuations might cause many control problems and large frequency/voltage deviation in microgrid stand-alone operation. Thus, to maintain the microgrid stability, an efficient and highly reliable control scheme is required. In this paper, a newly proposed fuzzy logic-based robust control mechanism is used to stabilize the frequency and direct current bus voltages in large fluctuations caused by sudden changes in power generation or load side. Also, supercapacitor and battery energy storage system are used to stabilize direct current bus voltages. This proposed method ensures the system efficiency and stability by reducing the system complexity and transient time, minimizing the frequency deviations, and preventing synchronous generator units from surpassing their power ratings in response to these disruptions. Simulation results also validate the effectiveness of the proposed controller in comparison with previous techniques.
Frequency control of PV-connected micro grid system using fuzzy logic controller
Frequency is a variable parameter in a power system, and it denotes the balance among the generation and the requirement. The operator of the system has to maintain the frequency within certain acceptable limits. The tediousness of integrating Distributed Generators (DGs), like solar photovoltaic (PV) system or wind turbines is the intermittency in power system that balances the power and regulates the frequency and voltage. If a number of electric motors are connected along with PV, the frequency of rotor speed will be varied. Hence, this paper intends to propose a Fuzzy Logic Controller (FLC) for controlling the frequency of rotor speed to enhance the power system performance. Hence, the major objective of the proposed model is to provide control over the output signal by reducing the error between the reference signal and control signal. The performance evaluation of the proposed model is done and proved over other controllers with respect to switching time, and the performance metrics, namely settling time, rise time, and percentage overshoot.
Fuzzy-PI Controllers for Grid-Connected and Islanded Operation of DG in a Microgrid
2013
Islanding describes the condition in which a microgrid or a portion of the power grid, which consists of a load and a distributed generation (DG) system, is isolated from the remainder of the utility system. In this situation, it is important for the microgrid to continue to provide adequate power to the load. To demonstrate the operation of microgrid in grid connected mode and islanded mode, a simulink model has been designed with necessary parameters by connecting with the main grid allowing the sharing of different loads with reference to grid connection and disconnection. An islanding detection algorithm has been used to act as a switch between the two controllers so that the system operates under intentional islanded mode. This paper also proposes an algorithm of synchronization for grid reconnection. In addition, fuzzy logic controller and SVPWM have been used to reduce the THD of the inverter output.
In this paper, a new efficient Fuzzy-PID controller with Derivative Filter (Fuzzy-PIDN) optimized via Grasshopper Optimization Algorithm (GOA) was proposed for Load Frequency Control (LFC) of an interconnected microgrid. The GOA was employed to fine tune the scaling factors of fuzzy logic and PIDN controllers gains by generating their optimal settings. The investigated microgrid system includes two interconnected areas incorporating Diesel engine, Wind turbine, Solar Photovoltaic (PV), and Energy storage systems including Redox Flow Batteries (RFBs), Superconducting Magnetic Energy Storage (SMES), Fuel Cells (FCs) and Aqua Electrolyzers (AEs). The frequency control of the addressed autonomous microgrid was studied using a dynamic modeling of each unit. The power demand variation was considered as disturbance, where, the conventional controllers PID, Fuzzy-PID and Fuzzy-PIDN were implemented for comparative analysis of the LFC performance. The superiority of the proposed GOA strategy was demonstrated under various scenarios using four performance criteria functions, which are : Integral Square Error (ISE), Integral Absolute Error (IAE), Integral Time multiply Absolute Error (ITAE) and Integral Time multiply Square Error (ITSE). The behavior of the microgrid was analyzed in several case studies, and some control actions were suggested to improve the frequency control in presence of renewable energy. The obtained results were compared in view of peak undershoot / overshoot and settling time. The performed simulations prove the validity of the used GOA optimization tool, and shows that GOA optimized Fuzzy-PIDN controller was robust and can cope with system disturbance to solve frequency regulation problem.
Fuzzy-IP Controller for Voltage Regulation in a Stand-Alone Microgrid System
International Review of Automatic Control (IREACO), 2018
This paper presents a method that combines fuzzy inference system and Integral-Proportional named Fuzzy-IP controller to regulate an independent microgrid voltage with a distributed energy resource unit. The unit employed photovoltaic (PV) array with DC voltage converted to three-phase AC voltage. The control design was carried out through modeling and simulation using Matlab software environment. Transfer function with the 2×2 structure using system identification has estimated the non-linear plant model. Two controllers transformed the ab-c to the d-q axis coordinates of voltage to simplify linear control design. An oscillator is applied to set frequency according to the recommendation. The results show that the compensated casestudy system using Fuzzy-IP with disturbance tracked the setpoint excellently and it regulated the voltage properly including frequency control using internal oscillator. The paper presents performance superiority of the proposed method over PI control by comparing the transient response, the mean squared error, and the root mean squared error.