Cascaded Open-Circuit Fault Ride-Through of Modular Multilevel Converters with Model Predictive Control

Abstract

This paper proposes a model predictive control (MPC) of modular multilevel converters (MMCs) with cascaded open-circuit fault ride-through to improve the reliability of MMCs. Taking advantage of the known switching state in MPC, the open-circuit fault in a submodule (SM) can be detected and isolated within milliseconds by the proposed fault detection and isolation (FDI) scheme. Incorporated with a health state set into MPC, the proposed fault-tolerant control scheme can be integrated into the MPC, and the control of output current, circulating current, and capacitor voltage can be automatically adapted for fault-tolerant operation. Furthermore, the FDI can be reset after one open-circuit fault is isolated, which makes the cascaded multiple open-circuit fault ride-through possible. Experimental results show that fault isolation and system reconfiguration can be completed within several milliseconds and it is possible to seamlessly ride-through cascaded multiple open-circuit faults using the proposed scheme.