Research On Parameter Identification And Optimal Control Of Microgrid System

The development of power energy has a positive effect on social development.New energy power generation such as PV power generation and wind power generation is an inevitable trend of social development.The volatility and randomness of new energy generation often lead to the unstable of voltage and frequency of micro-grid,which is easy to cause great impact on large power grid,so micro-grid technology emerges as the times require.With the wide application of microgrid technology,higher requirements are put forward for its safety,stability and reliability.This dissertation studies the parameter design method and optimization control of microgrid system.The main research contents are as follows.(1)This dissertation introduces the background,significance and research status of microgrid development at home and abroad,and discusses the problems faced by the development of microgrid system.(2)Inverter of microgrid system control strategies of their basic principles,implementation methods and applications,such as constant voltage constant frequency control,constant power control,droop control and virtual synchronous generator control are analyzed.Microgrid system modeling includes inverters,networks and load small signal models,which provide a basis for parameter design and control optimization of microgrid system.(3)In this dissertation,carrying out the design of control parameters for VSG controlled inverters,and proposing a VSG parameter identification method based on recursive least squares,which provides a basis for the optimal design of microgrid systems.Firstly,the main parameters of VSG control are designed according to the dynamic performance and steady-state performance requirements of the system.Then,according to the second-order transfer function model of VSG output power to command power,according to the relationship between model parameters and inertia and damping coefficient,the inertia and damping coefficient are obtained by the identification algorithm,and the error caused by the steady-state equilibrium point offset and bilinear are further analyzed.Finally,the MATLAB simulation and experiments verify that the proposed identification method is feasible and effective,and can meet certain accuracy requirements.(4)In view of the steady-state error caused by the traditional VSG control of the microgrid,this chapter gives the centralized control of the micro-grid voltage and frequency secondary regulation control,which can reduce the voltage deviation and frequency deviation at the PCC.The central controller(MGCC)collects system information and distributes the load power according to a certain scale factor.A dual optimization control of voltage and frequency based on particle swarm optimization(PSO)is presented.The algorithm uses voltage deviation and frequency deviation as the objective function,and seeks the VSG control main parameters that minimize the objective function.Then,it is uniformly sent to each VSG control unit by the MGCC,thereby implementing micro-grid optimization control.