Research On Quasi-synchronous Grid Control Strategy Of Photovoltaic VSG Inverter

With the energy crisis and increasing environmental problems,distributed power generation systems represented by photovoltaics have developed rapidly in recent years.In distributed power systems,inverters are an indispensable part.Therefore,the advantages and disadvantages of their grid-connected control strategies are the key to determining the distributed power penetration rate.This paper focuses on the virtual synchronous generator technology and the quasi-synchronization control strategy in the distributed power system.The main work contents are as follows:Firstly,the inverter controller interface strategy-Virtual Synchronous Generator(VSG)is introduced.The basic principle and mathematical model of VSG are elaborated.The governor and excitation control of traditional synchronous generator are used for reference.The basic principle of the device is designed with the active frequency controller and reactive voltage controller of the VSG.Secondly,for the current distributed generation system,the quasi-synchronous grid-connected control strategy has too many adjustment links and does not consider the time before the circuit breaker is connected: 1)The method of voltage instantaneous value crossover calculation,the frequency adjustment link and the phase angle The adjustment link has been unified,which effectively reduces the adjustment link and reduces the complexity of control during the quasi-synchronization process.2)The closing controller is designed so that the quasi-synchronous control module can issue the closing signal ahead of the zero phase difference to ensure that the phase difference is zero when the circuit breaker is completely closed,so that the inverter can be smoothly integrated into the grid.Thirdly,the virtual synchronous generator technology and the system model of quasi-synchronous grid-connected control strategy are built on Matlab/simulink simulation software.The system model is simulated and the results are analyzed in detail.The drooping characteristics of the VSG are verified by the off-grid operation simulation.The support of the moment inertia and damping coefficient in the VSG is verified by the characteristic parameter simulation.The consistency of the VSG and the synchronous generator is verified by the grid-connected simulation.Through the quasi-synchronous grid-connected simulation,the correctness and effectiveness of the proposed synchronization control strategy are verified.Finally,the experimental system of this paper is designed,including hardware design and software design.Figure[61] Table[7] Reference[53]...