针对电网不平衡与谐波的锁相环改进设计

摘要

在新能源并网发电系统中,准确地提取电网电压的频率、相位和幅值等电网同步信号是实施有效控制的基础.针对电网不平衡与谐波条件下电网同步信号的检测需求,提出了一种静止坐标系下的改进型锁相环设计方法.该方法采用谐振器提取并滤除电网电压中的高频谐波,结合自适应陷波器(ANF)与正负序消除环路(PNSC)完成电压正负序分离,进而准确地提取电网正序电压的同步信息.仿真和实验结果表明,在不平衡与谐波电网条件下,所设计的锁相环能够快速准确地锁定电网电压的属性,且具有检测精度高、对频率波动鲁棒性强等优点,可为新能源并网发电控制提供可靠的基准信号.%In grid-connected renewable energy generation systems, the accurate extraction of voltage synchronization signals, such as frequency, phase and amplitude, is the basis of effective control. To meet the detection requirement of such voltage synchronization signals under unbalanced and distorted grid conditions, a modified phase-locked loop (PLL) under stationary reference frame is proposed. This proposed PLL scheme extracts and eliminates the harmonic components existing in the distorted grid through resonators. The positive and negative components of the fundamental grid voltage are separated completely by combining the adaptive notch filter (ANF) and positive/negative-sequence calculator (PNSC). Then, the voltage synchronization signals of positive voltage can be detected accurately. The simulation and experimental results indicate that the modified PLL can track the synchronization signals, and has the advantages of fast dynamic response, high detection accuracy and strong robustness against the frequency fluctuation. Thus, the modified PLL can offer effective control basis for the renewable energy generation systems.