一种新的过零锁相方法

A new phase locking method with zero crossing

在中频电网中,由于信号频率较高且偏移较大,传统的过零锁相往往难以获得准确的锁相结果。提出了一种新的过零锁相方法,即在电源信号的每个正向过零点通过对正弦表地址指针值与参考值之间的偏差进行PI调节,进而改变系统的采样周期,从而使锁相环的输出信号与电源信号保持同相。该方法能实现在预定采样率下系统采样时间的闭环控制,特别适用于信号频率较高且偏移较大的应用场合。建立了该方法的控制模型,并对其进行了分析。利用DSP实验平台及400HzDVR样机对该方法进行了实验验证。

For the mid-frequency grid, the signal is characterized with a relatively high frequency and a big variation of frequency ,i t’s difficult to obtain an ideal phase locking for the typical phase locking method with zero crossing. To cope with this problem, a new phase locking method with zero crossing is proposed ,which changes the sampling period of system by adjusting the error of the practical and reference address pointer values of sine wave table at each zero crossing point with rising edge of signal through PI loop ,t hus the output signal of PLL will be in phase with source signal.The method realizes a close loop control of sampling time when the sampling rate is constant ,which is suitable especially for signal with a relatively high frequency and a big variation of frequency.The control model of the method is built and analyzed.Finally the method is validated with a DSP experimental platform and a 400 Hz DVR prototype.