Research On Coordination Control Strategy Of Wind/PV/Battery Microgrid During Islanded Operation

Micro grid,which can make full use of distributed energy and improve the reliability of power system supply as well as meet the electricity demand of power users,is an effective means of distributed power accessing to power grid,and has become the key point of domestic and oversea research.The coordination control strategy under islanded operation is studied in the Wind-PV-Battery micro grid to achieve the optimal and reliable operation of micro grid,and the feasibility of the coordination control strategy is verified by simulation study.Firstly,this thesis introduces the background and significance of the subject research,expounds the microgrid research and application status of domestic and overseas,and summarizes the development status of micro grid control technology.Secondly,the thesis outlines the composition principle of Wind/PV/Battery micro grid,and designs the capacity of Wind,PV and Battery in the system based on the resource and users' load.The working principle and characteristics of the wind power generation subsystem,photovoltaic power generation subsystem and energy storage subsystem are described,the transformation technology of AC/DC,DC/DC as well as DC/AC in the system topology are discussed,and the main parameters of inductance and capacitance are designed.Thirdly,by analyzing the energy flow relationship based on the basic idea of control under islanded operation among wind turbine,PV array,battery and load,according to the variation of wind speed,light intensities,battery working status and random load,the coordination control strategy is proposed under islanded operation with the operation modes in micro grid.Different control strategies for different subsystems under different working states in the Wind-PV-Battery micro grid are employed,where the MPPT and PQ control strategy are adopted in the wind power generation subsystem;the MPPT,LPTC and PQ control strategy are applied to the photovoltaic power generation subsystem;the control strategy of battery charge and discharge and V/f control strategy based on droop control are designed for the energy storage subsystem;load switching control strategy is designed for some non-critical loads.Finally,a simulation model of the Wind/PV/Battery micro grid system is established in Simulink,and simulation study is carried out under the different SOC.The results show that energy storage subsystem can keep the power balance of micro grid and maintain the voltage and frequency stability of the AC bus,both the wind power subsystem and photovoltaic power subsystem are able to work respectively in their reasonable operation modes,and load can switch to the system automatically,which achieve the safe and stable operation of micro grid,thus the correctness and feasibility of the coordination control strategy proposed in the paper is verified.