电网谐波和不平衡对锁相环影响及改进策略

A Study of Impacts of Harmonic and Unbalance on Phase-locked Loop and Improvement Strategy

新能源并网发电系统中,准确获取电网同步信息是进行有效并网控制的基础,故提出了一种基于对称分量法的单同步坐标系改进型锁相策略。该策略利用改进的全通滤波器(APF)基于对称分量法完成电网电压正、负序分离,能够快速适应电网频率波动,再通过基于二阶广义积分器(SOGI)的自适应滤波器在采样信号相位不发生偏移时,快速稳定地抑制电网谐波,从而准确地获取电网电压的同步信息。在电网谐波和不平衡的条件下,所提锁相环(PLL)策略能够快速准确地锁定电网信息,且具有检测精度高、对电网波动适应性强等优点。

Grid synchronization information can be accurately obtained as the basis for effective grid-connected control in photovoltaic grid-connected systems.An improved phase-lock strategy of single synchronous coordinate system based on symmetric component method is proposed.This strategy uses an improved all-pass filter(APF) to complete the positive and negative sequence separation of the grid voltage based on the symmetric component method and can quickly adapt to the frequency fluctuations of the grid.Then the adaptive filter based on the second-order generalized integrator(SOGI) can quickly and steadily suppress the harmonic of the grid without the phase offset of the sampling signal,so as to accurately obtain the synchronous information of the grid voltage.The proposed PLL strategy can lock the grid information quickly and accurately under the condition of harmonic and unbalanced power grid.