A Non-PLL Pre-Synchronization Method for Vsgbased Inverter Considering the Effects of Grid Voltage Imbalance and Harmonics

The widespread application of nonlinear loads has led to increasingly severe issues of power grid voltage imbalance and harmonics. Under these circumstances, research on the presynchronization control of virtual synchronous generator (VSG) is highly necessary. To address this problem, this paper eliminates voltage and frequency deviations through a deviation integral feedback method. Simultaneously, it utilizes a generalized delayed signal superposition operator (GDSS) method to filter the grid voltage and extract the positive sequence component. Subsequently, the processed grid voltage information is used to construct a virtual power signal, which is then introduced into the active power loop to achieve phase synchronization. Through these strategies, the synchronization of the VSG output voltage with the grid voltage is ultimately achieved. Finally, simulation studies conducted on the Matlab/Simulink platform verify that, compared to traditional phase-locked loop (PLL) presynchronization and non-PLL pre-synchronization methods, the pre-synchronization method proposed in this paper exhibits stronger adaptability under conditions of grid voltage imbalance and harmonics. It can further reduce the instantaneous value of frequency deviation during grid connection, thereby enhancing the reliability of grid connection.