Adaptive Sensorless Strategy for Dual Three-Phase PMSM by the Enhanced Sliding Mode Observer under Open-phase Faults

Sensorless control of dual three-phase permanent magnet synchronous motors (DTP-PMSMs) has been extensively investigated to enhance operational reliability. However, when open-phase faults (OPFs) occur, conventional sensorless methods fail to achieve accurate rotor position estimation due to distortions in the back electromotive force (EMF) waveform. These distortions arise from the interruption of voltage signal transmission in the faulted phase, leading to erroneous observer outputs. To overcome this limitation, this paper proposes an enhanced sliding mode observer (SMO) incorporating voltage constraints, designed to suppress the back EMF distortion under OPFs. The proposed method ensures robust position estimation by explicitly accounting for the voltage limitations imposed by the faulted phase. Combined with adaptive control strategies, it can also be extended to OPFs of any phase. Experimental results validate that the enhanced SMO maintains high estimation accuracy under OPFs, demonstrating its superiority over conventional methods.