Open-Switch Fault Tolerance Control of Two Parallel Interleaved Three-Phase Power Converters

This article introduces a novel open-switch tolerance control strategy for two parallel converters with an open-switch fault. Our detailed postfault modeling highlights the challenges: the open-switch fault inhibits vital commutations, and the centralized controller compensates for the absent commutations by injecting two distinct voltages into the original modulation signals, ensuring a consistent line current as in normal states. This process, however, results in severe current imbalance and overloads the operational switches. To address those challenges, we assess and optimize current paths in the postfault condition, introducing eight vector sequences and a carrier-based modulation method. In addition, we propose two current zero-crossing estimation techniques: a direct detection and an indirect method using reference voltage polarity. These methods lead to two postfault control strategies, each with trade-offs between current balance and line current quality. Experimental results confirm the effectiveness of the proposed postfault control strategies, ensuring dependable postfault operations.