Research On Improvement Of Control Algorithm For Grid Connected Inverter Based On Virtual Synchronous Generator

Virtual synchronous generator is a newly proposed concept,and it is aimed to operate inverters to mimic a SG so that the inverter-based DGs can have a large inertia and excellent damping characteristic.Those features usually belong to traditional SGs.In the context of the rapid development of new energy and a large number of distributed power supplies connect to the power grid,virtual synchronous generator technology can make the grid-connected inverter,which is a power electronic equipment,compatible with the traditional power grid in a targeted way,and the electrical power system can smoothly transition from a traditional centralized power supplies dominated system to a distributed power supplies dominated one.However,in the design of the controller of VSG with traditional scheme,there are many parameters and coupling between each loop,which make the design process of parameters complex.In this paper,particle swarm optimization algorithm is proposed as a kind of intelligent algorithm in this paper to simplify the design process and reduce the workload.This paper mainly studies the technology principle and control strategy of three phase grid connected converter that analog synchronous generator.Firstly,the mathematical model of synchronous generator and three-phase grid connected inverter are set up separately,and the principle and realization process of the virtual synchronous generator are expounded,then the whole control block diagram of the virtual synchronizer is derived.On the base of these,the realization scheme of a virtual synchronous generator is designed independently,which includes two parts: the outer virtual synchronization control and the bottom double loop control.According to classical control theory,the control parameters of external and bottom layers are adjusted respectively.Then,with the aid of the software of MATLAB,the rationality of the design of the underlying double loop system and the active and reactive power scheduling function and droop characteristics of the virtual synchronous generator are verified.In order to solve the problem of power oscillation in the simulation of outer control system,the particle swarm optimization(PSO)is introduced to find the optimal control parameters.Through the comparison of simulation between two,the results indicate that this intelligent algorithm gets more ideal simulation results and greatly reduces the power oscillation.It is proved that the particle swarm optimization can be used to find and get the optimal control parameter.