A General Graphical Method for Filter-Based Active Damping: Evaluation, Exploration, and Design

Abstract

Filter-based active damping is a promising solution to tackle the resonance hazard of LCL-filtered inverters. Although various methods have been developed it still lacks guidelines to evaluate and select them In this paper, a general graphical method is proposed to fill this void, and the desired phase regions of the damping filters for stabilization are identified. As a benchmark, the proposed method is used to evaluate the existing damping filters and further explore the proper ones on the robustness against the drift of LCL resonance frequency. It reveals that the low pass filter, the all-pass filter the delay filter, and the resonant-notch filter are less robust, and finds that the phase-lag filter, the notch filter with its notch frequency equaling one third of the sampling frequency, the quasi-notch filter and the bi-quad filter are highly robust. Taking the phase-lag filter as an example, the design guideline of the filter parameters is presented according to the proposed method Experiments tested on a 6-kW prototype validate the theoretical analysis.