Research On Optimal Control Strategy Of Active Dynamic Response For Microgrid Based On Energy Storage VSG

In recent years,in response to the call for the national "dual carbon" policy,the installed capacity of renewable energy is increasing,and the microgrid used to regulate distributed power sources and improve the local consumption of new energy is increasingly concerned.Virtual synchronous generator(VSG)technology provides rotational inertia and damping characteristics for power electronic interface micro sources and provides stable voltage and frequency support for microgrid systems.However,active power dynamic oscillation and overshoot are prone to occur when the microgrid system is subjected to external disturbances under islanding and gridconnected operation conditions,which seriously endangers the reliability of microgrid system operation.Given that,the paper takes the micro-grid system with diesel generator set(DGS)and VSG as the research object and explores the dynamic response characteristics of the output active power and its optimal control strategy after the system is disturbed by external disturbances.The main research work is as follows:(1)The topology structure of the microgrid system is briefly introduced,and the control structure and mathematical model of DGS and energy storage VSG are described,including the speed regulation and excitation system of DGS,the active power-frequency,reactive power-voltage and voltage-current double-loop control of energy storage VSG,which lays a foundation for the study of the active power response optimization strategies of the microgrid system in the two operation modes of islanding and grid-connected.(2)The phase difference between the grid-connected current of the current-source energy storage converter and the voltage of the power grid under the modes of the grid-connected is studied.Based on the analysis of the phase difference between the grid voltage and the grid-connected current of the current source energy storage converter,three phase compensation strategies are proposed,which are based on phase detection compensation,output power detection compensation,and filter inductance regulation compensation.The design methods of the three strategies are given.The simulation results show that the three compensation strategies can effectively eliminate the phase difference between the grid-connected output current of the energy storage converter and the voltage of the grid.(3)The active power dynamic oscillation of DGS and energy storage VSG parallel system systems under the modes of islanding is studied.Based on the analysis of active power dynamic oscillation in DGS and energy storage VSG parallel system under load disturbance,two VSG control strategies based on active-power proportional differential feedforward compensation and improved active-power proportional differential feedforward compensation are presented,and the parameter design processes are given.The simulation results verify that the two strategies can effectively suppress the oscillation and overshoot of the output active power of the DGS and VSG parallel system.(4)The dynamic overshoot and steady-state deviation of the stored energy VSG grid-connected active power under the modes of the grid-connected under the two disturbances of active power reference and power grid frequency are studied.Based on analyzing the dynamic overshoot and steady-state deviation of active power in the energy storage VSG grid-connected system under two disturbances,two transient damping strategies of active power differential feedback compensation and active power differential feed-forward compensation are proposed,and parameter tuning methods are given.The simulation and experimental comparison results verify that the two transient damping strategies effectively suppress the dynamic overshoot of energy storage VSG grid-connected active power without steady-state deviation.