Effective Controller Design for the Cascaded H-Bridge Multilevel Active Power Filter (APF) for Power Quality Compensation in Distribution Utilities

The cascaded H-bridge (CHB) multilevel inverters are recognized as the most suitable topology for high-power medium-voltage power quality conditioning applications. This paper presents the effective controller design methodology for the CHB-based active power filters, which achieves dynamic reactive power compensation and harmonic mitigation. To achieve dc-link voltage stabilization, a novel voltage balancing algorithm is proposed by splitting the dc-link voltage control task into two parts, namely, the average voltage controller and the voltage balancing controller. The resonant controller is adopted for current tracking and reference compensation signal is derived using the instantaneous reactive power theory (IRPT). The experimental result from a three-cell prototype system is presented, which verifies the effectiveness of the devised control scheme.