基于滑动离散傅里叶变换的锁相环设计

摘要

In order to ensure the photovoltaic (PV) grid inverter to operate in normal condition under voltage unbalance,frequency distortion and harmonic pollution,it is necessary to track the phase and frequency of the voltage quickly and accurately.For the large overshoot and long response time of double second-order generalized integrator frequency-locked loop(DSOGI-FLL),a PLL method based on sliding discrete Fourier transform (SDFT) was proposed.With the filtering characteristic of DFT and the moving average,the system frequency can be obtained accurately.The errors of the phase and frequency are corrected under the distortion,which achieves the rapid tracking of grid voltage.The simulation model was established in the Matlab/Simulink environment,and compared with DSOGI-FLL,it verifies that the SDFT-PLL can be quickly and accurately phase-locked in the context of grid voltage harmonics,amplitude and frequency mutation.%为保证光伏并网逆变器在电网电压三相不平衡、谐波污染及频率畸变情况下能正常运行,必须快速、准确地检测电网电压的相位信息,锁相环(PLL)的性能起着至关重要的作用.针对基于双二阶广义积分器的锁频环(DSOGI-FLL)动态响应速度差,且对谐波敏感等问题,提出基于滑动离散傅里叶变换(SDFT)的锁相环实现方法,利用离散傅里叶变换的滤波特性及滑动平均得到系统频率,校正电网畸变时电压相角和系统频率误差,实现电网电压的快速跟踪.在MATLAB/Simulink环境下建立仿真模型,与DSOGI-FLL进行对比分析,验证了SDFT-PLL在电网电压出现谐波、幅值和频率突变等情况下能快速准确地锁相.