Nonrecursive True Open-Loop Approach for Robust Estimation of Three-Phase Grid Frequency

This article proposes a nonrecursive true open-loop method for robust and reliable estimation of three-phase grid frequency under harmonics. The proposed method combines Clarke and Park transforms with a constant time delay-based relatively simple finite-impulse-response low-pass filters. The method does not include any kind of feedback path or recursive signal or integrator, thus no accumulation error or stability issue is present. A fixed frequency-tuned orthogonal oscillations approach is used in the Park transform to avoid implementing computationally demanding Taylor infinite series for sine and cosine functions. A detail analysis of the proposed method for discrete implementation, response time, tuning guidelines, and computational burden is presented. The method generates improved results when compared with several techniques reported in the technical literature. Simulated and experimental results are shown for confirming the robustness of the proposed method.