应用于三相并网系统的电网电压快速锁相技术研究

Study on the Fast Phase-locked Technology Applied in Three-phase Grid-connected System

为了提高三相并网系统相位检测环节的快速性及稳定性，提出了一种新型的电网电压快速锁相环技术。通过分析三相电网电压与相位角的内在对应关系，利用查表计算的方法得到电网电压实时相位，再利用数字低通滤波器对相邻两控制周期的相位差进行滤波的方法滤除相位中的波动量和干扰量，进而得到稳定准确的相位信息。对提出的锁相方法在五种电网电压工况下进行实验验证并与传统的SRF-PLL锁相方法进行对比，包括三相电网电压同步跌落、频率变化、相位跳跃、含30％的5次谐波以及单相电压跌落100％至缺相等各种工况。实验结果表明，与传统的SRF-PLL方法相比，提出的锁相方法能够获得更快的相位跟踪速度以及更好的锁相效果，动态响应快，稳定性好。因此，该方法可广泛应用于三相并网系统中对系统动态性能要求高的场合。

For improving the rapidity and stability of the phase detection in a three-phase grid-connected system, we proposed a novel fast phase-locked loop （FPLL） method. Firstly, by analyzing the inherent relationship between the grid voltage and the phase angle, and through calculation and table looking-up, the real-time phase angle can be obtained by the proposed FPLL. Moreover, the harmonic and disturbance contents in phase angle can be eliminated by a digital low-pass filter. Experiments and comparisons between FPLL and SRF-PLL were performed under five conditions of gird voltage, including the conditions of three-phase grid voltages sag synchronously, frequency changes, phase jumps, with harmonics and phase loses, etc. The experimental results show that, compared with SRF-PLL, FPLL has a faster phase tracking speed and a better phase-locking performance. Therefore, the proposed FPLL can be widely applied in the occa- sions where a fast dynamic response performance in three-phase grid-connected systems is required.