应用于频率宽范围波动电网的自适应采样相位差校正法

指出了定速率采样下,非同步采样造成的频谱泄漏是相位差校正法测量误差的主要来源,尤其在对频率宽范围波动的电网信号进行连续测量时,采用相位差校正法可能造成测量失败。文中提出了一种基于自适应采样的改进方法。根据前次测得的基波频率与前次计算所得的频率变化率来预测电网的实时基波频率,并实时修正采样频率,使之跟踪变化的基波频率。分别在自适应采样与定速率采样下使用相位差校正法对频率动态变化的电网信号进行仿真对比。结果表明,该方法较定速率采样方法对同一变频电网信号的幅值测量精度提高一个数量级,相位测量精度提高3~14倍,采样窗长为IEC标准规定窗长的40%。该方法减小了因基波频率动态变化而产生的频谱泄漏,使相位差校正法在频率宽范围波动的电网中能够满足谐波连续测量的精度与实时性需要。

Phase Difference Correction Method Based on Adaptive Sampling Applied in Power Systems with Wide Frequency Fluctuation Range

The spectral leakage from asynchronous sampling is the main source of the measurement error for the phase difference correction method in the power harmonic analysis undergoing constant sampling. When making continuous measurement of the power signals in the wide frequency fluctuation range, the measurement of phase difference correction method may fail. An improved method based on adaptive sampling is presented. The real-time fundamental frequency is predicted according to the fundamental frequency of the previous measurement and the rate of change of frequency calculated in the previous measurement. The sampling rate is adjusted according to the predicted fundamental frequency in time to make the sampling rate match the real-time fundamental frequency. The variable-frequency power signals are simulated under the conditions of adaptive sampling and constant sampling, respectively. The results show that the accuracy of amplitudes is improved by one order of magnitude, that of phases 3 to 14 times and the time length of the window is 40% of that prescribed by IEC standard. This method reduces the spectral leakage from dynamic fundamental frequency offset and makes the phase difference correction method accurate and quick in the continuous harmonic measurement of the power systems in the wide frequency fluctuation range.