Robust fault-tolerant design for LC-coupling hybrid active power filter

In this paper, an open-circuit fault-tolerant topology of LC-coupling hybrid active power filter (LC-HAPF) and its control strategy are proposed at the switch level, which can greatly improve the reliability of the system. The proposed structure has a contactor between the midpoint of each bridge arm and the negative bus of the dc-link capacitor. When a single-phase fault occurs, the proposed LC-HAPF can be reconstructed into a three-phase four-switch system to compensate for the harmonic and reactive power, while the power quality compensation effect is hardly affected. When a two-phase fault occurs, the operation of the normal bridge arm is not affected, and the two faulty bridge arms can suppress harmonic current and compensate for a fixed reactive power through the passive filters. When the bridge arms all fail, the whole device acts as a passive filter to suppress the harmonic current of the load and to compensate for reactive power as well. Finally, the effectiveness of the proposed topology and its control strategy is verified by simulation and experiment results.