Control Strategy Of Distributed Resource With Improved Virtual Synchronous Generator Algorithm

With the increasing application of renewable energy such as wind turbine and solar energie etc,the proportion of distributed generation in the power grid has gradually increased.However,the current control based grid-connected inverter control strategy lacks inertia and has an adverse influence on the stability of the distribution network frequency.The virtual synchronous generator(VSG)strategy is a new type of distributed generation control scheme that allows the inverter to have virtual inertia and damping with better grid compatibility,and thereby improving the grid’s ability to accept distributed power generation.The paper focuses on the damping realization method of virtual synchronous generator,studies the influence of phase-locked loop on damping characteristics,proposes a new damping design scheme of virtual synchronous generator,and optimizes the controller parameters for different impedance environments.The main research contents of this paper are as follows:(1)The paper explains the background and significance of the generation of VSG,introduces the mathematical model of synchronous generator and the principle of voltage regulation and frequency regulation,sorts out the form of VSG,summarizes and summarizes the electronic voltage equation,power control loop and the implementation of the reactive control loop of voltage source type VSG.(2)A VSG small-signal model with two damping forms is established.The effects of different damping forms on the dynamic and steady-state performance of the system are analyzed in detail.The influence of the phase-locked loop on the stability of the system is revealed.The phase-locked loop is eliminated by equivalent transformation method.And a dynamic damping scheme based on power lead feedback and a damping link parameter design method based on phase margin correction are proposed,which improves the dynamic performance of VSG power output.(3)The VSG small-signal model with dynamic damping under low-voltage distribution network is established,and the parameter sensitivity equation is established.The influence level of system parameters on coupling is quantitatively analyzed.It is pointed out that the reactive-active coupling loop will reduce the stability of the system.The controller parameters of the reactive loop are optimized constrained by reducing the coupling effect.(4)A 5kW VSG experimental platform was built based on NI-PXIe-7868 R FPGA semi-physical simulation platform.The effectiveness of the proposed dynamic damping and the feasibility of the parameter optimization design under different impedance conditions have been verified by experiments.