Compensating the Harmonic Distortion Introduced by Instrument Transformers: An Improved Method Based on Frequency-Domain Polynomials

Monitoring harmonic components has paramount importance in modern distribution grids characterized by a strong penetration of nonlinear, power electronics-based devices. In this respect, the accuracy of harmonic assessment is heavily affected by the performance of instrument transformers, which depends also on their nonlinear behavior. This paper proposes an improved technique that enables an accurate reconstruction of primary harmonics from the secondary side. The method is based on polynomial modeling and compensation of harmonic distortion, which is the strongest nonlinear effect at low-order harmonics. The structure is extremely flexible, so that it can be tailored to reach the best tradeoff between performance and complexity, while avoiding overparametrization.