基于Hilbert移相滤波的全数字锁相环

AN ALL DIGITAL PHASE-LOCKED LOOP BASED ON HILBERT FILTERING

提出了一种基于Hilbert移相滤波实现的全数字锁相环,用于实现低频交流信号频率和相位的数字化测量。先将被测信号经过模数变换后输入到一对全数字的Hilbert移相滤波器,得到幅值相等相位相差90的两个信号,计算出输入信号相位角,再将输入信号相位角输入到一个基于锁相环结构设计的全数字处理系统,测算出信号的频率和相位。该测量方法充分利用了信号波形本身所包含的相位信息,提高了低频交流信号相位鉴别的准确度及锁相跟踪的速度,减少了测量过程达到稳定所需的时间。该算法可通过数字信号处理器(DSP)等微处理软件方便地实现。适用于测量电力系统工频电压信号的频率和相位,所获得的数据既可用于电力系统的监测,也可为需要同步工作的电力电子设备提供相位基准。

Based on Hilbert filtering an all-digital phase-locked loop (ADPLL) is designed to actualize thedigitalized measurement of the frequency and phase of lowfrequency AC signal. Firstly, after the DA conversion thesignal to be measured is inputted into a pair of all digitalHilbert phase-shifting filters and two orthogonal output signals with same amplitudes are obtained, proceeding to the next step, the phase angle of the input signal can be calculated. Then the calculated phase angle of the input signal is inputted into an all digital processing system based on PLL structure and thefrequency and phase angle of the measured signal can bemeasured and calculated. In this measuring method the phase information contained in the waveform of the input signal itself is fully utilized, so both the accuracy of the phasediscrimination for low frequency signals and the tracing speed of the locked phase are improved, and the consumed time at which the measurement process reaches its steady state can be saved. The proposed algorithm can be easily realized with DSP or other microprocessor programming codes. The presentedmethod is suitable for measuring the frequency and phase offundamental frequency of power system and the obtained data can be used in the monitoring of power system, at the same time, it can provide the phase reference to power electronic devices which should be operated synchronously.