在系统电压畸变的条件下，并网逆变器通过双二阶广义积分器(dual second-order generalized integrator，DSOGI)锁相环提取基频信号，从而实现电压定向矢量控制。但是系统电压中常含有较高的低次谐波，此时DSOGI的滤波效果将不理想，锁相环提取的同步信号出现波动。通过建立DSOGI的复矢量模型，分析了传统DSOGI锁相环输出电压包含谐波机理。根据二阶广义积分器(second-order generalized integrator，SOGI)的正交特性，推导了正交消谐法消除谐波。该锁相环对DSOGI输出电压进行微分运算，利用谐波电压微分方法逐次消除系统电压中的各次谐波，实现对系统电压中基频电压的准确提取。仿真表明，在系统电压谐波含量较高时，改进后的锁相环能有效提取基波的相位。

Grid inverters can extract fundamental signal with dual second-order generalized integrator(DSOGI) phase-locked loop under harmonic distorted system conditions, so as to ensure voltage oriented vector control. The synchronous signals extracted through DSOGI-PLL fluctuate when there are a large amount of low order harmonics among voltage sequence in system, which reduces the performance of second-order generalized integrator (SOGI). The complex vector model for DSOGI is established, the mechanisms that output voltage of the traditional DSOGI phase-locked loop contains harmonic can be analysized. According to the orthogonal characteristics of SOGI, the principle of eliminating harmonics is derived through the orthogonal harmonic elimination method.The phase-locked loop derivatives the DSOGI output voltage, and successively eliminates harmonics in system with a harmonic voltage differentiation method. And extract fundamental voltage of the system voltage accurately. Simulation shows that the fundamental phase angle can be obtained effectively in the case of multiple harmonics in system.