Dynamically corrected fast estimators of current and voltage magnitude

Fast digital estimation of current and voltage magnitude for power system protection purposes is considered. The magnitude estimators applied nowadays very frequently employ sine/cosine nonrecursive filters, and their response time is determined by the filter data window, which is usually not shorter than one period of the fundamental frequency. The response time of such estimators can be significantly reduced (in the fastest variant up to two sampling periods) by use of a new dynamic correction method which is presented in the paper. It is shown that application of the method to the estimator design simplifies the estimator structure, since the orthogonal filters are not necessary for magnitude calculations. Thus the computational burden in real-time implementations can be reduced remarkably and the optimisation of the filtration process can be carried out. Results of simulation tests of the proposed method are also included