A Cascaded Multilevel Inverter System with Hot-Swapping and Fault Isolation Capability for Improved Resiliency

The cascaded multilevel inverter (CMI) system is a promising solution for reliable inverter-based resource (IBR) applications due to its inherent modular redundancy. In the event of a fault, bypassing and isolating faulty sub-modules (SMs) within the CMI mitigates total system failure and enhances fault resiliency. However, hot-swapping a SM without interrupting the CMI presents implementation challenges. In this paper, a three phase CMI system is proposed for improved resiliency by hot-swapping the faulty SM without interrupting the system operation. Controllers were developed that permit hot-swapping of both grid forming and grid following CMIs. A power electronic module called AC smart port, is proposed and can successfully isolate the faulty SM from the system. A small-scale hardware prototype of a single-phase CMI with three H-bridge sub-modules has been successfully implemented for experimental validation.