Postfault Strategy for Dual Three-Phase PMSM With Reduced Current Loops Considering Leakage Inductance

One of the main advantages of dual three-phase permanent magnet synchronous machines (DTP-PMSMs) is their fault-tolerant capability. However, the complex fault-tolerant controller structure, high copper loss and unneglectable torque ripple under postfault operation limit their further development. The inaccurate transmission of control signals under the open-phase fault (OPF) is considered in this article. Undesirable second-order torque ripple and 3rd order current harmonics are induced by the transmission error between the controller output voltage and the actual stator voltage according to theoretical analysis. To cope with this issue, a fault tolerant control strategy based on voltage compensation is developed for DTP-PMSMs under OPF without introducing extra complex control schemes. The current references are derived in sinusoidal forms with minimum copper loss. Only three current loops are utilized in the proposed fault-tolerant strategy, compared to four current loops under normal operation, without changing the control strategy and controller parameters. In terms of compensation performance, since the leakage inductance affects the voltage compensation, a parameter acquisition method based on sine wave current injection is proposed. The proposed strategy does not induce heavy computation burden and has a good steady-state and dynamic response. Simulation and experiment results prove the theoretical analysis and the superiority of the proposed strategy.