Adaptive Channel Equalization for Frequency Response Correction of Instrument Transformers

Power quality (PQ) assessment has proven to be important in recent years for the power grid. The influence of the instrumentation transformer frequency response on some PQ metrics can be critical. For example, the measurement of harmonics can exhibit great inaccuracy if the measurement transformers have a frequency response that is not constant in the frequency range of interest. This problem is very similar to that found in communication systems where a non-ideal communication channel distorts the transmitted information. Thus the channel equalization approach can be used to adaptively compensate for the distortions caused by the current and voltage transducers. In the equalization approach, adaptive filtering algorithms such as RLS (Recursive Least Square) and LMS (Least Mean Squares) are commonly used to find the equalization filter coefficients. In this work, the novelty is adaptive channel equalization methodology applied to compensate for the frequency response of instrumentation transformers. Simulated results show that the methodology can reduce significantly the TVE (Total Vector Error) caused by voltage and current transformers.