Dynamic behavior of current controllers for selective harmonic compensation in three-phase active power filters

Current regulators are a critical part of active power filters (APF´s). Design of current regulators capable of compensating high frequency harmonics created by non-linear loads is a challenging task. Selective harmonic current compensation using harmonic regulators is a viable method to achieve this goal. However, their design and tuning is not an easy task. The performance -and even the stability- of harmonic current regulators strongly depends on implementation issues, with the tuning of the controller gains being critical. Furthermore, the presence of multiple current regulators working in parallel can create unwanted couplings with the fundamental current regulator, which can result in a deterioration of APF current control, i.e., oscillations and settling times larger than expected. This paper addresses the design and tuning of selective harmonic compensators, with a focus on their stability analysis and transient behavior.