Wavelet-Based Frequency Tracking Monitor Applied for Low-Inertia AC Microgrids

Abstract

This article proposes a wavelet-based frequency tracking monitor (WB-FTM) applied for low-voltage ac microgrids. It is based on a modified continuous wavelet transform (CWT) algorithm that makes it feasible for real-time applications (RT-CWT). The WB-FTM provides the frequency estimation through the point of common coupling voltage measurements and can be employed in single-phase or three-phase microgrids. Also, this estimation approach overcomes the main drawbacks of the standard techniques presented in the literature. The effectiveness of the WB-FTM was evaluated in comparison with the discrete Fourier transform, augmented complex least mean square, and second-order generalized integrator based on a frequency-locked loop based standard frequency estimation methods. Experimental results obtained from an ac microgrid laboratory setup, under different operational scenarios, demonstrated that WB-FTM overcomes conventional estimators' limitations, with faster convergence time, which is essential for frequency restoration systems applied for low-inertia ac microgrids.