Application of Multi-Resonator Notch Frequency Control for Tracking the Frequency in Low Inertia Microgrids Under Distorted Grid Conditions

Frequency variations are much faster and more significant in microgrids with low-inertia inverters and other control devices for distributed generation. Accordingly, it is imperative to utilize a concise frequency estimation method for analyzing the transient behavior of microgrids. This paper proposes a robust algorithm which is based on multi-resonator and adaptive notch filter and is referred to as the multi-resonant notch frequency control for improving the frequency estimation of perturbed power system. In general, power system distortions such as harmonics, inter-harmonics, and faults may affect the accuracy of frequency estimation. In contrast to conventional methods for frequency estimator, the proposed method is less sensitive to distortions and unbalanced power system conditions. The proposed method uses the information in all three-phase signals which is proved to be more robust against signal variations than single-phase methods. Simulation results demonstrate the accuracy and the speed of the proposed method for frequency estimation in both grid-connected and islanded mode of low inertia microgrids under grid faults.