Research on fault-tolerant control and topology reconstruction for offshore PV inverters

The operation and maintenance of offshore photovoltaic (PV) inverters presents a significant challenge, thereby highlighting the importance of their reliability and fault-tolerant control. This paper introduces a novel fault-tolerant design that is realised through the reconstruction of PV inverter topology. This inverter is secondary reconfigurable, This design effectively addresses power switch faults located in various positions, with a particular emphasis on multiple open-circuit faults. Faults are classified into two levels: primary and secondary. By incorporating one redundant bridge arm, one relay and five additional bidirectional thyristors, the system can achieve fault-tolerant operation. For primary faults, the redundant bridge arm is activated to sustain the normal six-switch operation mode. In the case of secondary faults, the system leverages the faulty phase and adjusts the control strategy accordingly, secondary faults trigger a transition to a three-phase four-switch operation mode of the inverter, resulting in a 50% reduction in power output. Simulation results validate the effectiveness of this approach.