This paper first studies the electromagnetic force and vibration characteristics of the permanent magnet assisted synchronous reluctance machines (PM-SynRMs). Firstly, an analytical method to calculate the radial force is proposed based on the Maxwell stress tensor method. The temporal and spatial orders of radial force are obtained by two-dimensional fast Fourier transform, then the combinations of stator slots and rotor virtual slots of PM-SynRMs is proposed to give a guideline for initial design of PM-SynRM to achieve low noise and vibration. A PM-SynRM is designed and a multi-physics model for electromagnetic vibration is established. The radial and tangential force under no-load and load conditions are calculated by finite element method (FEM), and then compared with the analysis results. Modal analysis is implemented to capture the structural parameters of the stator. Based on the proposed multi-physics model, the vibration responses under both no-load and load conditions are calculated through modal superposition method (MSM). Finally, a PM-SynRM is built and vibration test is performed to investigate its vibration characteristics.

This paper proposes a novel fault-tolerant control strategy of the open winding inverter for DC-biased vernier reluctance machines (DC-biased-VRMs), aiming to maintain the output capability after the open-circuit fault occurs in the inverter switches. DC-biased-VRMs are with integrated winding current for both DC component for field excitation and AC component for torque generation. The torque generation is not associate with the current direction, making the full-bridge inverter can be divided into two groups of devices. The proposed fault-tolerant control strategy is based on the regular full-bridge inverter for each open-winding, and can control the motor in the fault tolerant mode with one group of devices. When device open circuit fault appears in the normal mode, the controller will switch to the fault tolerant mode. After a short transient period, the motor will be able to work. Moreover, in the fault tolerant mode, a PMW driving method is proposed to reduce the current ripple. The proposed method does not require any additional components, and the reliability of the drive control system is improved considerably. Experimental results verify the validity and feasibility of the proposed fault-tolerant control strategy.

The rotor topologies have a great influence on the vibration characteristics of permanent magnet assisted synchronous reluctance machines (PM-SynRMs). In this article, the vibrations of PM-SynRMs with different rotor topologies are studied and compared. First, the electromagnetic force harmonics of PM-SynRMs have been studied and the design rule about the combination of stator slots and “rotor virtual slots” is given to achieve low vibration. Then, a multiphysics model is established to calculate the vibration of the PM-SynRMs with different rotor topologies. The modal analysis is conducted through finite element method considering the orthotropic of materials and validated by the modal test. Besides, the prototype has been built and the vibration test is performed to confirm the accuracy of the vibration simulation. Based on the multiphysics model, the influence of the shapes of flux barriers and the number of “rotor virtual slots” is investigated. It proves that the design rule about the combination of stator slots and “rotor virtual slots” can achieve low vibration for PM-SynRMs.

This paper investigates the optimal design method of switched reluctance machines (SRMs) for mitigating torque ripple and improving average torque under the low speed operation. In order to produce high torque for hill climbing or overload start-up of micro electric vehicles (EVs) and reduce the converter capacity, an SRM with four times torque overload capability and two times speed range with constant power is needed. To improve the SRM performance, first, a new method called multiphase excitation (MPE) method for calculating resultant static torque is adopted, which takes the cross-coupling and magnetic saturation into consideration to reduce the calculation error bought by the traditional method called single-phase excitation (SPE) method; second, optimal methods, including parameters sensitivity analysis, multi-objective optimization function, and winding connection types, have been taken to release the magnetic saturation, to improve average torque, and to depress torque ripple. Compared with the initial scheme, the torque ripple is minimized from 55.33% to 14.84% and the average torque is improved by 8.36%. The experimental results validate the effectiveness of the proposed methods.

An optimal three-dimensional current computation flux weakening control strategy for DC-Biased Vernier Reluctance Machines is proposed in this paper. Compared with permanent magnet synchronous machines (PMSMs), DC-Biased Vernier Reluctance Machines have an additional degree of freedom to regulate the rotor flux through variable DC-biased armature current. The conventional flux weakening control strategy does not utilize the adjustable DC field current, and the output ability in flux weakening region are limited. In this paper, the optimal three-dimensional current distribution is calculated at the intersection of current and voltage constraint. Meanwhile, in order to maintain the armature voltage within the voltage constraint, the inductance nonlinearity is reflected by constructing the inductance table. The algorithm provides maximum output capability and high efficiency for DC-biased-VRMs despite the changes in inductance parameters in the whole flux weakening region. Finally, the effectiveness of the proposed control strategy is validated by experimental results for a prototype machine.

In a hybrid-inverter open-winding permanent magnet synchronous motor (OW-PMSM) drive, the motor and the floating capacitor are controlled simultaneously. Besides, since the compensatory inverter barely provides active power under steady-state operation, the unity power factor control (UPFC) of the main inverter (MI) is also required. However, the conventional model-based predictive control of the hybrid-inverter OW-PMSM is highly sensitive to the accuracy of parameters, including the floating capacitance and stator inductance. Serious current distortions and system oscillations appear when the model parameters are mismatched with the actual ones. In addition, unmodeled parts such as power switch voltage drops and disturbances also degrade the system performance. Hence, a linear disturbance observer (LDO) based model-free predictive control (MFPC) is put forward. By using ultralocal models to substitute the mathematical models of the floating capacitor and OW-PMSM, the proposed scheme maintains satisfactory performance when system parameters are mismatched. Moreover, because system disturbances are obtained by LDO, the tracking errors can be eliminated even when parameters of ultralocal model are less appropriate. Thus, high precision of UPFC for the MI is guaranteed. Finally, experiments are carried out on a 500 W hybrid-inverter OW-PMSM drive, proving the superiority and effectiveness of the proposed MFPC strategy.