应用于频率波动电网的改进相位差校正法

An improved phase correction difference method applied to the power systems with frequency fluctuation

针对电网信号基波频率波动时传统相位差校正法测量结果存在较大误差,甚至可能产生测量失败的问题,提出一种改进算法。改进算法相对于传统相位差法有4个改进措施:第一,通过对加窗后的频谱表达式进行多项式变换从而加快旁瓣衰减速度,减小了频谱泄漏和各谱线之间的干扰;第二,通过计算频率变化率(Rate of Change of Frequency,ROCOF)对传统相位差法的校正公式进行了进一步的修正;第三,在计算ROCOF时尽量减小采样窗长,提高了ROCOF的实时性以及计算精度;第四,通过两次相位差法减小基波频率波动导致的非同步采样带来的频谱泄漏。分别在基波频率稳定以及基波频率宽范围波动的两种情况下将改进算法进行仿真验证。仿真结果表明,改进算法的电参量测量精度较传统相位差法有大幅度的提升,分析窗长满足IEC标准规定窗长。

Aiming at the problem that the traditional phase difference correction method has a large error in the fundamental wave frequency fluctuation, it may even produce the problem of measurement failure, and an improved algorithm is proposed. The improved algorithm has four improvement measures compared with the traditional phase difference method. The first is to multiply the sidelobe decay rate by multiplying the spectral expression after windowing, which reduces the spectral leakage and the interference between the spectral lines. Second, the correction formula of the traditional phase difference method is further modified by calculating the frequency change rate （ROCOF）. The third is to reduce the sampling window length and improve the real-time performance and calculation accuracy of ROCOF when calculating ROCOF. The sub-phase difference method reduces the spectral leakage caused by the non-synchronous sampling caused by the fundamental frequency fluctuation. The text is verified by the improved algorithm in two cases where the fundamental frequency is stable and the wide frequency fluctuation of the fundamental frequency is verified. The simulation results show that the accuracy of the improved electrical parameters is much higher than that of the traditional phase difference method, and the window length satisfies the IEC standard.