In order to study the performance of inverters under unbalanced voltage in photovoltaic systems, a new reaching law sliding mode control phase-locked loop is introduced on the basis of virtual synchronous generator control. Firstly, the new sliding mode phase-locked loop is used in the virtual synchronous generator to regulate the positive sequence components of the voltage separated from the decoupled dual synchronous reference coordinate system; then, the positive and negative sequence components of the voltage and the current are separated using the decoupled dual synchronous reference coordinate system and the symmetric component method respectively; and then they are individually controlled and generated as voltage modulated signals. Simulation results show that the phase-locking error of the new sliding mode phase-locked loop are only 0.0197 and 2.4015×10-10, which are much smaller than 1.4853 and 1.6405 of the decoupled double synchronous phase-locked loop, when the grid voltage drops and the phase jumps occur.The introduction of a new sliding mode phase-locked loop can enhance the stability and robustness of the system and improve the operational performance of PV inverters under voltage imbalance conditions, which provides a certain reference for the design and optimization of PV system inverters.