多采样率信号处理在数字化变电站差动保护中的应用

Application of Multi-rate Signal Processing in Differential Protections of Digital Substations

数字化变电站中,差动保护各分支电子式电流互感器(ECT)的采样频率不完全相同时,需要将原各分支ECT的输出数据转换为同一采样频率。文中研究了多采样率信号处理算法和采样数据频率转换对差动保护差电流的影响,通过将信号的抽取和插值环节级联,可以实现任意分数倍采样频率转换。采用基于切比雪夫逼近原理的等波纹设计方法进行低通滤波器设计,与多采样率信号处理算法配合使用,减小了频率混叠造成的误差,从而在ECT应用环境下,将任意不同采样频率的分支电流统一到相同的采样基准下,实现了测量环节与智能电子设备的无缝连接。仿真试验验证了所提出方法的可行性和有效性。

In digital substations, it is necessary to convert different sampling rates to the same rate when the differential protection relay is connected to electronic current transducers （ECTs） with different sampling rates. This paper studies the impact of the multi-rate signal processing technique and rate conversion of sampling data on the differential current of the differential protection and proposes an effective sampling rate conversion mechanism with cascade connection of decimation and interpolation, by which sampling rate conversion in a rational factor can be realize. An optimum equiripple low-pass filter based on the Chebyshev approximation principle for multi-rate signal processing is designed and combined with multi-rate signal processing technique to reduce the frequency aliasing error. Based on the above design, the branch current in differential relays with ：different sampling rates can be converted to the same one, so an accurate differential protection can be realized under the ECT circumstances. Simulation results show the feasibility and effectiveness of the method proposed.