Research Of The Operation For Grid-Connecting And Islanding Of Distributed Generation Contained Energy Storage

With the rapid growth of economy,the demand on electric power is rising increasingly.For meeting the requirement of national energy development strategy,green energy has been vigorously developed,such as solar energy and wind power.The research and development of distributed generation may alleviate the pressure of power transmission and distribution,mitigate the problem of regional power shortages,and improve the reliability and stability of grids.The paper studies the distributed resource grid-connection of wind power generation and PV power generation,as well as the strategies of controlled islanding in ways that ensure the microgrid system operate normally and meet the demands of customers on power quality.First,the paper analyzes the PQ,V/f,and droop control of distributed generation,whose limitations in the mode switch of microgrid grid-connection to islanding are also made a comparison.An upgraded V/f droop control strategy is generated to keep a stable frequency and voltage in the process of switching microgrid.At the same time,the voltage and frequency of microgrid are also can be regulated effectively to remain the output voltage constant.Second,the paper studies the configuration method of hybrid energy storage systems.The optimal capacity configuration of a hybrid energy storage system is improved by utilizing discrete wavelet transform,and entropy method is adopted to optimize the wavelet that is how energy storage systems can give a quick response to power surge in the period of microgrid switches,minimizing the charge and discharge times of accumulators and extending life-cycle.Third,by the comparison of master-slave control strategy with peer-to-peer one,the paper studies different microgrid control strategies in accordance with varied micro-source types.In practical terms,an upgraded V/f droop control strategy is used to control the DC regulated micro-source or the micro-source connected to energy storage devices so as to gain stable system voltages and frequencies,while PQ control strategy is utilized for other distributed generation.In addition,Matlab/Simulink Simulation proves the strategy can guarantee the system voltage and frequency stable during microgrids switch,and keep a constant power output of microgrids,reducing the switch times of microgrids effectively.