Multi-level Shunt Active Power Filter Using Modular Cascade H-bridge and Delay Firing

A novel design of a multi-level shunt active power filter using a modular cascade H-bridge is presented in this article. The proposed approach enables a modular approach in the design of a multi-level active power filter. As an illustration, a five-level H-bridge active power filter with a novel switching strategy has been implemented. The design is able to reduce the voltage stress across the filter inductor and to reduce the average switching frequency. Proportional plus integral controllers have been implemented for the current control loop, overall voltage control loop, and voltage balancing loop. A feedforward controller has also been added to the current control loop to improve the current tracking. By delaying the firing time of one of the H-bridges, five levels can be realized from a cascade H-bridge active power filter. The proposed switching strategy and the realization of the five-level switching scheme are presented. Experimental results are included to demonstrate the effectiveness of the proposed filter scheme.