Virtual Power Plant Supported Frequency Control Of Hybrid Microgrid Both In Isolated And Interconnected Mode
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Date
2019
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Department of Electrical Engineering, NITS
Abstract
The population growth and rapid industrialization rises power demand with depleting fossil fuels for conventional power generation day-by-day. It is also very tough to meet the varying electricity demand of consumers by conventional energy sources in current scenario, which leads to an increase in green house gases and CO2 emission. To address the above problem scientists and researchers looked into renewal energy resources like wind power, solar power, hydro power, tidal power, etc. which have sufficient potential to get better of these issues. One of the biggest reasons for the popularity of renewal energy resources is that it is cleanest form of energy available on earth. However, the main drawback with renewal sources is the dependency on the environment, so referred to as an intermittent generation. Therefore, we need some kind of enhanced concept in this field. So, for the better consistency and better facility of power supply, the small scale power generating technology such as wind, mini/micro- hydro, solar power etc. are gradually replacing conventional/traditional technology in various applications. These technologies are referred to as distributed energy recourses (DER) which represent a modular electric generation. However, there are various challenges associated with designing such power systems. In this regard, voltage and frequency are the most important aspects to be controlled. In addition, power quality is also taken into consideration for effective power dispatch to the consumers. Microgrid and virtual power plant (VPP), among many innovative paradigms in facilitating the integration of the DER, are two of the attractive conceptual solutions which provide coordination and aggregation for the DER. Coordinated control of VPP comprising of solar photovoltaic (SPV), wind turbine generator (WTG) and controllable load such as plugged-in hybrid electric vehicle (PHEV) and heat pump (HP) have been explored. The control concept includes the flexible adjustment of the aggregated power output of the VPP so as to address the frequency regulation. Investigation under simulation environment has been carried out to assess the effectiveness of the VPP to offer frequency support to both an isolated and interconnected microgrid mode. The parameters of the proportional–integral-differential (PID) controllers, employed with SPV, WTG, DIESEL, PHEV, and HP are optimized simultaneously using integral square error (ISE) criterion. The analyzed performance of ISE optimized PID controllers on the hybrid system model has been presented considering step change and random variations of SPV and critical load. Simulation results revealed that ISE optimized controllers for SPV, WTG, DIESEL, PHEV, and HP can provide the dynamic performance of the hybrid energy system. Present work considers VPP supported frequency control of hybrid microgrid in the isolated mode of operation. Since SPV generation is intermittent in nature, causing a variation power generation and also the load is variable. This results in a mismatch in generation and consumption of power. And this is the main reason system frequency deviates, which are never desirable. Therefore to minimize the effect and mismatch in power generation and consumption in the system tuned PID controllers are used. In conservative idea, the gain values of the PID controllers are chosen by trial and error method or by the traditional method as described in Ziegler and Nichols. The controller gains once tuned for a given operating point are only suitable for limited operating point changes. Therefore, the use of the conventionally tuned PID controller does not meet the requirements of healthy performance. Computational intelligence has opened paths to a new generation of advance process control. Present work considers PSO (Particle Swarm Optimization) algorithm and SSA (Salp Swarm Algorithm) optimization technique to optimize the gains of the controller employed with SPV, WTG, DIESEL, PHEV, and HP for automatic power control of the proposed hybrid system. Scope of the work includes the following major performance studies in time-domain simulation under different operating conditions of the proposed hybrid system in isolated and interconnected modes respectively. Isolated mode: (a) Performance of the system consisting of a PID controller for the step disturbance in critical load and SPV generation. (b) Performance of the system consisting of PID for the variable load. (c) Performance of the system consisting of PID for variable generation in SPV. (d) Performance of the system consisting of PID for variable generation in SPV as well as variable critical. In each of the above-mentioned cases controller parameters are tuned using SSA and PSO. Interconnected mode: (a) Performance of the interconnected system consisting of a PID controller for the step disturbance in critical load. (b) Performance of the interconnected system consisting of a PID controller for the variable power generation in SPV. (c) Performance of the interconnected system consisting of a PID controller for the variable power generation in SPV as well as variable critical load. In each of the above-mentioned cases controller parameters are tuned with SSA and PSO.