应用复系数滤波器的不平衡电网电压锁相方法

Synchronous Reference Frame PLL with Complex Coefficient Filter Under Unbalanced Three-Phase System

并网型电力电子变流设备需要精确、实时检测电网电压的相位以实现同步控制。若三相电压不平衡,同步旋转变换锁相方法经Clark变换后存在负序分量,引起相位偏差的信息不准确,导致相位检测偏差。复系数滤波器具有极性频率选择带通特性,保留正序分量,衰减同频率的负序分量,同时抑制其他高次谐波分量。本文分析了复系数滤波器的特性,将其应用至锁相环外,使馈入后级鉴相器的信号无污染,Matlab/Simulink数字仿真结果表明了该滤波器针对不平衡电压的有效性,最后采用TMS320F28335控制器实现了算法控制软件,实验波形验证了该方法的正确性。

Grid connected power electronic device requires precise detection of the grid voltage phase angle for synchronization in real time. If three-phase grid voltages are unbalanced, the α-axis and β -axis voltage contains negative sequence components. It gives rise to ripple in phase detector of synchronous reference frame phase-locked loop （SRF-PLL） and causes detected phase angle inaccurate. Complex coefficient filter （CCF） has the characteristics of band-pass at the positive frequency sequence meanwhile attenuates the negative sequence as well as other high order harmonics. In the paper, the feature of CCF is analyzed and its application in pre-loop of SRF-PLL to make the signal fed SRF-PLL clean is analyzed. The simulation is carried out by Matlab/Simulink to verify the correctness and effectiveness. In the end, the algorithm has been implemented and tested in a float-point DSP TMS320LF28335.