It is necessary to capture the phase of positive-sequence fundamental component of voltage accurately for series compensation devices, under voltage disortion.The software phase locked loop(SPLL) method based on the instantaneous reactive power theory is commonly used,which has some errors.A low pass filter is added based on the analysis and it can improve the SPLL precision under the condition that the sags, harmonics and DC component occur in power system.So a better compensation effect can be achieved by series compensation devices.Simulation and experimental results verify the accuracy and feasibility of the method.%串联补偿设备要求在电网电压畸变的条件下,能够准确地锁住电压基波正序相位.基于瞬时无功理论的软件锁相环(SPLL)技术是目前常用的锁相方法,但该方法有一定的误差.这里设计了一个低通滤波器(LPF),能够在电网电压存在谐波、跌落、直流分量等情况下高精度地锁相,从而使串联补偿设备获得较好的补偿效果.仿真和实验证明了该方法的精确性和可行性.
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