Robust Sensorless Strategy Based on Dual Extended State Observer Without Fault Localization for Open-Phase Faults in Dual Three-Phase SPMSM Drives

Dual three-phase surface-mounted permanent magnet synchronous motor (SPMSM) are widely used in various high-reliability applications owing to their high power conversion capability and excellent fault tolerance. With an appropriate fault-tolerant control (FTC) strategy, dual three-phase SPMSM can achieve derated operation without the need for additional hardware support. However, in sensorless control mode, open-phase fault degrades the accuracy of rotor position estimation, thereby affecting the overall system performance. In response to this issue, this article proposes a robust sensorless control strategy that operates without the need for fault localization. The strategy demonstrates a capability for high-precision operation following a single open-phase fault ensuring that the steady-state performance of the drives is largely unaffected. First, the mechanism by which open-phase faults interfere with traditional back electromotive force (EMF) estimation methods is analyzed. Then, a robust sensorless strategy based on a dual extended state observer is proposed to enhance back-EMF estimation performance by adjusting the reference voltage in harmonic subspace. Without altering the motor model or the control structure, a novel harmonic subspace control framework is proposed. The proposed sensorless strategy eliminates the need for fault localization modules, not only mitigating the risk of misdiagnosis but also preventing performance degradation caused by diagnostic delays. Experimental results verify that the proposed sensorless strategy can achieve effective postfault operation without the need for fault localization or control reconfiguration.