Research On Smooth Switching Conreol Method Of Microgrid

With the widespread use of new energy in recent years,small-scale photovoltaic power generation and wind power development,people will have eyes to a more environmentally friendly and efficient micro-grid.It is composed of distributed power generation system(DG),energy storage system,load and protection devices,micro-grid can be divided into two kinds of grid and island operation mode.The smooth switching between these two modes of operation has great influence on the safe and stable operation of the microgrid.Therefore,the smooth switching control of the microgrid is the main part of the control technology.In this paper,the mathematical model And the corresponding control strategy is adopted to study the switching process of two grid operation modes.First,a brief analysis of the working principle of photovoltaic power generation and wind power generation system,the battery and the parts,and set up the mathematical model of photovoltaic power generation system,battery system and wind power system,constant voltage discharge control of photovoltaic power maximum power tracking and battery.Secondly,the two operating modes of microgrid and its working principle are introduced,and different control strategies are given for the different characteristics of micro power supply.In the analysis of microgrid operation control strategy based on PWM inverter control circuit and build mathematical model;put forward the improved PLL technology,mainly by the power grid phase detection module,phase synchronization module,phase generation module,microgrid model is applied to the master-slave control;a brief description of islanding detection technology,and islanding detection circuit of inverter based distributed power supply model is given.Finally,the PSCAD/EMTDC software is used to establish the master slave control system,aiming at the problem of transient voltage and frequency fluctuation in the process of mode switching,the improved state following control strategy is proposed,and the switching mode of the main control unit is described,when the microgrid is connected to the grid,the main controller is controlled by constant power.According to the output of the constant power controller,a negative feedback signal is used as the input signal,the output of the constant voltage constant frequency controller is output with the output of the constant power controller,so as to ensure the smooth switching of the microgrid.Through the selective access to the load,the controllability and the bi-directional flow of the microgrid in different modes are realized,and the simulation results verify the effectiveness of the proposed control strategy.