A harmonic excitation brushless synchronous machine has higher power density compared with the traditional aerial three-stage generator due to removing the axial exciter and is suitable for use as an integrated starting-generator (ISG). However, the field current cannot always be generated in the field windings at different rotor positions in the starting mode. A new excitation scheme employing double three-phase phase orthogonal zero-sequence armature currents is proposed in this article. Harmonic electromotive forces and field current can be produced by the zero-sequence rotating excitation magnetic field and almost has no relationship with the rotor positions. In addition, in order to obtain a constant field current during the starting process, a control method of the generated field current is also presented. The rotating speed and field intensity of the zero-sequence excitation magnetomotive forces are both feedback controlled by the zero-sequence current in the whole starting process. Comparing with the original harmonic excitation machine, a higher and more stable field current can be generated in the proposed ISG whenever the rotor is at any position or at a low speed. The prototype machine is manufactured and experiments are carried out together with the excitation control method to verify the effectiveness of the theoretical and finite element analysis results.

This article proposes a new brushless hybrid harmonic excitation scheme for wind generators, in which the excitation power is provided by the armature current and the stator harmonic control winding current together. In the generation of the field current, besides the main component produced by the excitation control winding equivalent magnetomotive force (MMF), one additional field current component is also produced by on-load armature high-order harmonic and tooth harmonic MMFs, which lead to a self-excitation loop existing in the excitation process. The additional field current component can compensate the flux weakening effect of the load current, which helps to maintain the output voltage characteristic stable in the case of load fluctuation. Besides, the power level of the excitation converter can be greatly reduced. Experimental results on prototype machines validate the effectiveness of the theoretical analyses and finite element analysis (FEA) results.

Modular multilevel converters (MMCs) will be widely applied in onboard integrated power systems due to their high levels of electric power output and good-quality sine waveform outputs. However, the capacitor voltage of MMCs fluctuates greatly because the charge–discharge process of the capacitor is continuous when the system is working. In order to reduce voltage ripples efficiently, a capacitor voltage ripple-suppression strategy employing a reversed PWM switching channel is proposed in this paper. For one pair of the upper and lower arm submodules, a switching channel is built. Then, the highest ripple voltage possible can be offset since the voltage fluctuation direction of the upper and the lower arm capacitors would be reversed. In addition, a clamping capacitor is added to the switching channel to further suppress the fluctuation voltage by 78%. Compared to traditional large capacitance suppression methods, only 12% capacitance is used in the proposed method. The reliability and power density of the proposed MMC both increased, and there are no additional losses compared with previous voltage ripple suppression methods. The effectiveness of the proposed voltage ripple suppression strategy is verified by simulation results.

The development of traditional vehicles which consume fossil carbon-based fuels is constrained by environmental pollution and the energy crisis, and it has become a social consensus to develop electric vehicles with new energy resources and low emissions. The drive system of electric vehicles should be able to reliably operate over a long period. When a short-circuit fault occurs in the driving motor, the current in the winding will increase sharply and threaten driving safety. This paper proposed a short-circuit fault-tolerant control strategy for a dual three-phase permanent magnet synchronous traction motor (DT-PMSTM) which can resolve the problem of short-circuit faults. The current in non-short-circuit fault windings has been reconstructed to offset the interference of the short-circuit current and output a stable torque. Based on the principle of constant composited magnetic motive force (MMF), the dimension-reduced orthogonal transformation matrix was derived. The compensation currents were designed according to the interference effect of the short-circuit current to the normal MMF of the motor. Consequently, the lost torque component caused by the lack of the short-circuit winding was compensated, and the torque pulsation was also reduced. The performance of the topologies with neutral point-isolated mode and neutral point-connected mode were both investigated and compared. The validity of the proposed short-circuit fault-tolerant control strategy was proved by the simulation results.

Dual three-phase permanent-magnet synchronous motors (PMSM) have wide applications in electric vehicles due to advantages such as excellent control performance and outstanding fault tolerance capability. However, present fault-tolerant control of inverter single-leg open-circuit faults cannot make full use of each phase winding of the motor, which limits the torque-production capability. This paper proposes a torque superposition compensation (TSC) control which can minimize the stator copper losses while increasing the torque-production capability. The phase winding originally connected to the faulty inverter leg is then linked to the DC-link mid-point. Thus, the winding in the faulty phase can be utilized to generate an additional torque. The symmetric dual three-phase windings torque model and the asymmetric five-phase windings compensation torque model for U_d/2 voltage level are constructed according to the torque superposition, respectively. Then, the three-subplane decomposition transformation matrix for the post-fault dual three-phase PMSM is derived, and the decoupling model in the d-q subplane is constructed, which achieves the optimal enhancement of the torque-production capability. The simulation results verify the effectiveness of the proposed TSC fault-tolerant control.

This paper describes a position error compensated ripple torque suppression method (PEC-RTSM) for reducing the vibration of the integrated on-board electric vehicle (EV) charging system caused by the rotor position error in reality. The static electromagnet torque model considering the rotor position error of the multiplexed DTPMSM is established. Under the constraint condition of the stable grid-side currents, the amplitude and phase angle of each phase current in the stator winding can be regulated by the compensated asymmetric current for achieving a minimum instantaneous torque. Compared with the original methods, the proposed static electromagnetic ripple torque suppression method has the capacity of reducing the torque vibration effectively in a wide rotor position error range, rather than the strict specific position. Besides, the copper loss related with the rotor angle error is also analyzed and calculated. Results indicate that the copper loss increment rate is limited while the rotor angle error is in the normal range or the rotor position returning loop is employed. This method would improve the reliability of the charging process and extend the application of the integrated on-board charging system. Experimental and simulation results verified the effectiveness of the theoretical analysis.