Study of multi-sample-rate signal conversion in digital substation and wide area measurement of power system

Digital substations based on IEC61850 standard have been equipped with digital equipments, have owned uniform data model and communication platform, and have realized the intelligent devices' inter-operation. Meanwhile, Wide Area Measurement System (WAMS) with real-time monitoring the power system dynamic process forms a platform for on-line security and stability analysis of the whole power grid. Because current (voltage) transformers in power grid are different in type and sampling rates, it is necessary to convert them to the same rate. In this paper, sampling rate conversion in a rational factor is realized through cascade connection of extraction, interpolation and low-pass filter. A digital narrow band-pass filter algorithm based on full cycle Fourier algorithm is proposed. This algorithm can not only obtain the useful frequency component fast and effectively, but also realize the normalization of signals' sampling rate without distortion.