远方保护信号接收低频化技术的理论分析与应用

THEORETICAL ANALYSIS AND REALIZATION OF FREQUENCYDOWN^CONVERSION METHOD IN RECEIVING PROTECTION SIGNALS

针对电力系统继电保护中接收较高频远方保护信号这一课题 ,通过理论推导 ,证明了在精度有限的实际系统中 ,低频化处理的优越性。根据理论分析结果 ,提出了将信号插入低频段后进行自适应滤波的技术方案 ,并与在较高频直接进行自适应滤波的方案进行性能比较。计算机仿真和实际的硬件实验均说明 ,使用低频化方案 ,可接收更多的单频信号 ,信号的接收范围可扩大 2 5倍 ,允许的发信频率误差也提高约 1倍。

UP to now, adaptive notch filters have been used in receiving protection signals successfully. But there is asituation where protection signals are placed in high frequencies tightly. Adaptive notch filters' performance is not goodenough when used under such conditions directly. To resolve this problem. a frequency down--conversion method is proposedin this paper. Firstly. the adaptive notch filter is analyzed in theory to discover the elements that affects its performance. Theresult has shown that the performance is much better when the signals are processed in low frequency. Then a low--frequencyplan using frequency down--conversion method is presented. and computer simulations and hardware experiments are carriedout to verify the new method. All the results show that the low--frequency plan has a much better performance than the highfrequency plan without frequency down-conversion. The speed requirement is lowered. there is more protection signals to bereceived, the tracking range of signal frequency is larger. the range of input signals is 25 times larger than the high--frequencyplan.