Analysis of DC-Link Voltage Controls in Three-Phase Four-Wire Hybrid Active Power Filters

This paper investigates different dc-link voltage control strategies in a three-phase four-wire LC coupling hybrid active power filter (LC -HAPF) for reactive power compensation. By using direct current (current reference) pulsewidth modulation (PWM) control method, to achieve dc-link voltage self-charging function during LC -HAPF start-up process, the dc-link voltage control signal feedback as reactive current component is more effective than the traditional method as an active current component. However, when the LC-HAPF is performing dynamic reactive power compensation, this dc-link voltage control scheme will influence the reactive power compensation, and thus, makes the LC-HAPF lack of success to carry out dynamic reactive power compensation. In this paper, a novel dc-link voltage control scheme for LC-HAPF is proposed so that the dc-link voltage control with start-up self-charging process can be obtained as well as providing dynamic reactive power compensation. Representative simulation and experimental results of the three-phase four-wire center-spilt LC-HAPF are presented to verify all deductions, and also show the effectiveness of the proposed dc-link voltage control scheme in dynamic reactive power compensation.