Design Optimization of PMU Anti-Aliasing Filters using Taguchi Method

Abstract

A Phasor Measurement Unit (PMU) is a monitoring device, which serves in checking the power system condition by measuring voltage and current phasors along with frequency at a particular node. The basic structure of PMU consists of Synchronization Unit, Measurement Unit and Data Transmission Unit. The Measurement Unit has three components: Anti-aliasing filters, Analog-to-Digital Converter and Phasor measurement Unit/ Processor. An anti-aliasing filter ensures that all the analog signals have the same phase shift and attenuation thus assuring that the phase angle differences and relative magnitudes of the different signals are unchanged. Anti-aliasing filters made up of an analog front end and a digital decimation filter are far more stable as far as aging and temperature variations are concerned. IEEE C37.118 standard stipulates that it is mandatory to use the filter for avoiding any aliasing errors. Out of various analog filters, the Butterworth has been preferred due to its flat response in pass-band as compared to other filters. In this work, it is attempted to design anti-aliasing filters to be used in PMUs. The design problem is formulated as an optimization task that is solved using the Taguchi method. The results show better performance in terms characteristics compared to the conventional filters. The designed filters may be employed as building blocks in modern PMUs.