Gaohong Xu

Asymmetrical SVPWM Fault-Tolerant Control of Five-Phase PM Brushless Motors

In this paper, an asymmetrical space vector pulse-width modulation (SVPWM) fault-tolerant control is proposed for the five-phase permanent-magnet motor under the open-circuit condition of a single phase. The key of this method comes from two parts. First, the voltage vector diagram is rebuilt in the event of an open-circuit fault. Second, the switching signals constructing an asymmetry waveform are selected in one sector. Then, this asymmetrical SVPWM control can reduce the amplitude and total harmonic distribution of currents in healthy phases, though it has limitation for the open-circuit condition of two phases. Additionally, both simulated and experimental results are provided to validate the good performances of the proposed fault-tolerant drive, maintaining average torque, and low torque ripple during fault. Finally, the dynamic responses of open-loop and close-loop condition are measured. The results show that the proposed method can offer comparable dynamic performance of normal SVPWM control that is widely used in healthy five-phase motor drive.

Improvement of Torque Capability of Permanent-Magnet Motor by Using Hybrid Rotor Configuration

This paper proposes a novel hybrid rotor permanent-magnet (HRPM) motor to improve torque capability, including average torque and torque ripple. The key of the proposed motor is that it can utilize high PM torque of surface-inserted PM (SPM) rotor module and high reluctance torque of interior PM (IPM) rotor module at the same time. Meanwhile, the shifting angle of SPMs and open angle of air barriers are introduced to improve the average torque and reduce the torque ripple, respectively. The two variables are employed to create circumferential asymmetry of the rotor for generating an angular difference of the electromagnetic torque between adjacent N-pole and S-pole, thus minimizing torque ripple. In order to evaluate the proposed motor, an IPM motor and a SPM motor with the same dimension and volume of PM are used as benchmarks. Through theoretical analysis and experimental test, it is verified that the proposed HRPM motor can offer higher torque density and lower torque ripple simultaneously.

Third Harmonic Current Injection in Fault-Tolerant Five-Phase Permanent-Magnet Motor Drive

This paper presents a third harmonic current injection method for a five-phase permanent-magnet (PM) motor with trapezoidal back electromotive force (EMF) under postfault field oriented control (FOC). The key of the proposed method is the third harmonic current online calculation and injection under postfault FOC. The postfault FOC lies in the fundamental decoupled model based on the concept of maintaining spatial circular rotation of fundamental PM flux linkage vector and magnetic motive force under open-circuit fault. Based on the mathematical model of torque pulsations caused by third harmonics of air-gap flux, the injected third harmonic current can be calculated by the radio of the amplitude of third harmonic EMF and fundamental EMF easily. The presented fault-tolerant control strategy can achieve the real time optimal current reference generation and third harmonic current injection under postfault FOC while reducing the torque pulsations. The effectiveness of the proposed method is verified by experimental results under various operation conditions.

Decoupling control of a five-phase fault-tolerant permanent magnet motor by radial basis function neural network inverse

Permanent magnet (PM) motors are employed into electric vehicles extensively because of high efficiency, high power density, and high torque density.

A new fault-tolerance motor with decoupled reluctance channel and PM channel

Permanent magnet (PM) motor can offer high fault tolerant by introducing fractional slot concentrated winding. However, this winding configuration produces high back-EMF under flux weakening capacity because of low reluctance torque. Then, other protection techniques will likely be required to prevent dangerous overvoltage conditions if the inverter shuts down unexpectedly at high speeds. Additionally, the traditional PM fault tolerant motor suffers from demagnetization fault. By considering the advantages of switch reluctance motor (SRM), this paper presents a new dual-channel motor to improve the reluctance torque of PM motor by introducing SRM channel. The key of this paper is to find a suitable magnetic path which can combine the SRM channel and PM channel. Then, the proposed motor can provide high PM torque and high reluctance torque. Although the torque ripple of proposed motor is large, the improvement of reluctance torque in motor with fractional slot concentrated winding is realized, which gives some guidance and reference for other designers to overcome demagnetization fault in PM motor.

Optimal Design of an Inset PM Motor With Assisted Barriers and Magnet Shifting for Improvement of Torque Characteristics

This paper presents an optimal design of an inset permanent magnet (PM) motor for improved torque characteristics. The key of the design is to introduce a bidirectional way of magnet shifting, along with assisted air barriers, into an inset PM motor, where magnets are shifted clockwise or anti-clockwise as needed. The introduced bidirectional shifting way lowers the requirement for shifting space between poles and also can reduce undesirable radial force to decrease vibration and noise. Moreover, the proposed inset PM motor can guarantee the torque density with great reduction of on-load torque ripple because the assisted air barriers can not only enhance the utilization of reluctance torque but also will not introduce any other torque harmonic and even can reduce torque ripple further. Also, the analytical expressions of torques are established and the appropriate angles of magnets shifting and assisted air barriers are, respectively, chosen to obtain low torque ripple and optimal torque density. Finally, these theoretical analyses are verified by the finite-element method.

Decoupling control of five-phase fault-tolerant permanent magnet motor by radial basis function neural network inverse

Permanent magnet (PM) motors are employed into electric vehicles extensively because of high efficiency, high power density, and high torque density.

Cost-Effective Vernier Permanent-Magnet Machine With High Torque Performance

As a promising candidate applied in direct-drive applications due to high torque characteristics at low speed, vernier permanent-magnet (VPM) machines have been paid increasingly attention in many direct-drive fields, such as electric vehicle propulsion and wind power generation [1–2].

A novel PM motor with hybrid PM excitation and asymmetric rotor structure for high torque performance

This paper proposes a novel permanent magnet (PM) motor for high torque performance, in which hybrid PM material and asymmetric rotor design are applied. The hybrid PM material is adopted to reduce the consumption of rare-earth PM because ferrite PM is assisted to enhance the torque production. Meanwhile, the rotor structure is designed to be asymmetric by shifting the surface-insert PM (SPM), which is used to improve the torque performance, including average torque and torque ripple. Moreover, the reasons for improvement of the torque performance are explained by evaluation and analysis of the performances of the proposed motor. Compared with SPM motor and V-type motor, the merit of high utilization ratio of rare-earth PM is also confirmed, showing that the proposed motor can offer higher torque density and lower torque ripple simultaneously with less consumption of rare-earth PM.

Design and analysis of novel permanent- magnet motors with hybrid rotor configurations

This paper deals with a novel hybrid rotor permanent magnet motor which incorporates the merits of interior permanent magnet motor and surface-inset permanent magnet motor. An appropriate asymmetric rotor structure is adopted in the design to reduce torque ripple and improve torque density. It can be observed that the reluctance torque of the motor has approximately 50% contribution to the total torque.