Traditional perspective considers that there is a trade-off between the postfault operational performance and the implementation complexity of the control scheme. To approach this problem, this paper proposes a natural full range minimum-loss strategy by analyzing the current relation between torque subspace and harmonic subspace. The harmonic subspace current references satisfying full range minimum-loss are generated by a simple expression according to the real-time subspace current vector features. Compared with existing fault-tolerant control methods, the proposed strategy does not need complicate fault diagnosis, as well as offline or online optimization process. The experimental results demonstrate that the proposed fault-tolerant control strategy can achieve smooth prefault to postfault transition and FRML simultaneously.

Finite control-set model predictive control (FCS-MPC) has received extensive attention because of its excellent dynamic performance, however, it is still need to be studied in terms of torque ripples reduction and parameter robustness. To reduce the steady-state torque ripples and maintain the appropriate anti-parameter perturbation ability, this paper proposes a model predictive direct duty-cycle control (MPD2C) strategy based on “variable control-set (VCS)”. In the proposed strategy, the direct mapping relations between the electromagnetic torque, flux and three-phase duty-cycles has been established, by exploring the dual relationship of vector synthesis and duty-cycles. On this basis, the novel predictive model and VCS that using the three-phase duty-cycles as the key variable are constructed. Finally, the proposed strategy determines the three-phase duty-cycles from VCS by employing a two-stage optimization mechanism, which means the proposed strategy can generate virtual vectors with multiple IGBT switching patterns. Then, the high-precision torque and flux adjustment would be achieved. The experimental results show that VCS-MPD2C has excellent static and dynamic control performance, acceptable execution efficiency and relatively good parameter robustness.

The five-leg voltage source inverter (FL-VSI) is a fault-tolerant control scheme, which has the advantages of small size and low cost. Sensorless control has the advantages of increasing the reliability of permanent magnet synchronous motor (PMSM), reducing system cost and saving system space. Combining characteristics of the traditional modulation strategy of FL-VSI, a sensorless control method for the dual-PMSM system is proposed. The contributions of the proposed method are as follows. First, based on the traditional modulation strategy of the FL-VSI, the high-frequency (HF) square-wave voltages are injected in the half period of zero vectors action, which realizes the separation of the vector control period and the HF signals’ injection period and eliminates the filters for position information demodulation. Besides, a novel duty cycle modification strategy of FL-VSI is adopted to meet the switching constraints of the common leg. The proposed method can independently control two motors and is easy to implement in engineering with no additional external circuit. The experimental results show that the proposed method can accurately estimate the positions of the two motors and has good dynamic and steady-state performance.

The dual-motor system driven by five-leg voltage source inverter (FL-VSI) has been widely studied as a better fault-tolerant scheme. In this paper, a phase current reconstruction strategy based on a single current sensor is proposed to realize the phase currents reconstruction of the dual permanent magnet synchronous motors (PMSM). Firstly, the FL-VSI adopts a centralization modulation strategy to realize independent control of the two motors while expanding the speed range of the motors. Then, a pulse shift strategy applied for the dual-PMSMs system driven by FL-VSI is proposed. The phase currents can be reconstructed when two motors are running in the low modulation region, sector boundary region, or the new phase current reconstruction dead zone by the proposed method. The experimental results show that the reconstructed phase currents can always be consistent with the actual phase currents, which proves the feasibility and effectiveness of the proposed method.