The Research on Pre-Synchronization Control for Virtual Synchronous Generator Inverter

VSG inverters simulate the characteristics of synchronous generators, which can provide inertia support capability for the grid. Since the inverter with virtual synchronous control will reduce the frequency and voltage magnitude of the system, there is a deviation between the operating state of the VSG inverter and the power grid, and the output impedance of the VSG inverter is small compared to that of the synchronous generator, so that the output voltage magnitude, frequency, and phase of the inverter are out of sync with that of the power grid when it is connected to the grid. And when the power command of VSG inverter is changed suddenly, it will cause large current impact, so in order to realize safe and effective grid connection, it is necessary to carry out the pre-synchronization control of grid connection. In order to realize the smooth grid connection of VSG inverter and reduce the grid current impact caused by frequency, amplitude, phase unsynchronization and sudden change of power command, a control strategy of regulator graded startup and power command slow startup control strategy are proposed. Finally, experimental verification is carried out through MATLAB simulation, and the experimental results verify the effectiveness of the proposed method.