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Three-Phase Adaptive Frequency Estimator with a Delayed Signal Cancellation Pre-Filter Under Heavily Distorted Grid Conditions

A reliable and precise frequency detection algorithm is useful for different control strategies, especially on microgrid and aerospace applications. The widely-linear adaptive frequency estimator is based on the Augmented Complex Least Mean Square Filter and, thus inherits its fast dynamic response. However, it presents a high susceptibility to input noise, which might present an unexpected behaviour under distorted grid conditions. Therefore, this work proposes a Delayed Signal Cancellation pre-filter stage to eliminate most of the harmonics to achieve fast estimation response and high rejection of harmonic distortions.