Real-Time Optimal Control of a 3-Phase PMSM in 2-Phase Degraded Mode

This paper aims to optimize real-time control for the degraded mode of a fault-tolerant power architecture but not the fault detection and isolation procedure itself. Such power architecture is dedicated to electric vehicles in which it performs the three following essential functions: traction, battery charging, and electric-grid assistance. For safety reasons, in the degraded mode, power control is limited to the traction mode. Thus, for a given torque, the proposed innovative strategy uses a novel current/voltage transform that leads to efficient real-time control of the torque. The key idea is to drive the current without a priori restrictions on its waveform, while minimizing Joule losses, i.e., the effective value of the current. It has been validated on a laboratory test bench. The studied system is based on a three-phase open-end-winding synchronous machine powered by an inverter with three full H-bridges. The last section of the paper analyzes the comparison between the classic sinusoidal current waveforms and the proposed sinusoidal current waveforms while operating on the two remaining motor phases. It results in a 14% increase of the torque produced by the permanent-magnet machine under test and a 14% decrease of the global system losses in traction mode. As a result, the new control strategy enhances traction performance in degraded mode and increases electric-vehicle autonomy in a postfailure condition.