针对双二阶广义积分锁相环(dual second-order generalized integrator phase locked loop，DSOGI-PLL)在不平衡电网下锁相效果不理想的问题，提出了一种改进二阶广义积分正交信号发生器(second-order generalized integrator quadrature signal generator，SOGI-QSG)的频率自适应锁相环，来提高并网电流在不平衡电网下的并网质量。改进SOGI-QSG能够很好地滤除直流分量，同时加入了频率自适应功能，再通过级联谐振滤波器来消除奇次谐波对并网的影响，最后对q轴的正序分量进行锁相。在Simulink中对基于改进SOGI-QSG的频率自适应锁相环进行了仿真，结果表明：在电网电压单相跌落或频率出现微小波动时，基于改进SOGI-QSG的频率自适应锁相环比DSOGI-PLL有更好的锁相效果。

Based on dual second-order generalized integrator phase locked loop (DSOGI-PLL), the effect of phase-locked in unbalanced power system is not ideal. In this paper, an improved frequency adaptive phase-locked loop of SOGI-QSG (second order generalized integral quadrature signal generator) is proposed to improve the quality of grid connected current in unbalanced power grid. The improved SOGI-QSG can filter the DC component well, and add the frequency self-adaptive function, and then through the cascaded resonance filter to eliminate the influence of odd harmonics on the grid connection. Finally, the positive sequence component of q-axis is locked. In Simulink, the frequency adaptive PLL based on the improved SOGI-QSG is simulated. The results show that the frequency adaptive PLL based on the improved SOGI-QSG is better than DSOGI-PLL in the case of single-phase voltage drop or small frequency fluctuation.