An Efficient Analytical Solution to Speed Extended Fault Tolerant Control of Dual Three-phase PMSMs Under Open-phase Fault

For dual three-phase PMSM (DT-PMSM) operating under open-phase fault, the harmonics in the post-fault currents could substantially elevate the peak phase voltages (PPVs) as compared with healthy operating conditions. This voltage amplification phenomenon can critically limit the maximum achievable operating speed due to the fixed inverter voltage. To address this issue, this paper presents a novel speed extended FTC to optimize the PPV and improve the maximum attainable speed under open-phase fault. To achieve improved performance and speed extension, the proposed FTC aims to minimize the fault-induced ripple, maximize torque generation and minimize PPV. In the proposed design, the currents in torque frame are designed as DC values to achieve zero torque ripple and the current angle as well as the currents in the harmonic frame are optimized to maximize torque and minimize PPV. The conditions to achieve minimal PPV are analyzed and the optimal solutions to FTC are analytically designed with high computation efficiency. Compared with existing FTCs, the proposed analytical FTC can achieve a lower PPV and higher maximum attainable speed without degrading torque production. The effectiveness of the proposed FTC is verified with extensive experiments and comparisons on a laboratory DT-PMSM.