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Single-phase grid-connected integrated on-board charger (IOBC) can significantly reduce the cost and the bulk of electric vehicles and has been used in real products. However, there are still two problems that have not been discussed and solved. First, when permanent magnet synchronous motor drives are used for single-phase IOBC, there are second-order current harmonic and the possibility of instability in the system. Second, when multiphase motor (MPM) drives are used for single-phase IOBC, the currents’ assignment strategy and the dc voltage utilization of inverter need to be dissected. This article does detailed research works about these two problems. The origin of the second-order harmonic and the instability are exposed. Furthermore, proportional-double-resonant regulator and adaptive proportional (P) parameter control schemes are proposed to solve these problems. The operation principle of single-phase IOBC with MPM drive is analyzed. Two different operating modes are recommended, and an optimal zero-sequence voltage is designed to increase the dc voltage utilization capability of the inverter. At last, the feasibility of the proposed operation and control schemes are verified by experiments. [ABSTRACT FROM AUTHOR]

A doubly-fed induction machine (DFIM) is a promising choice for the shipboard propulsion system (SPS) of a more-electric ship (MES) to increase the system safety level by employing less power electronics. In this paper, the detailed impedance model of DFIM-SPS is established, with a salient-pole synchronous generator (SPSG) acting as the power source and a DFIM functioning as the propulsion load. The impedance modelling of DFIM is carried out from the aspect of ac coupling between the stator and rotor circuits, which is easy for physical understanding. In addition, the back-to-back power converter (BTBPC) is regarded as controlled voltage sources with impedances in the equivalent circuit. The phase-locked loop (PLL) is a key element in influencing the system stability, and it is integrated to upgrade the system dq impedance model. Moreover, the impedance shaping effect caused by dc-bus voltage control is investigated. Nyquist stability criterion is employed for system small-signal stability analysis, which is implemented with respect to the DFIM operation mode and PLL controller effect, and the time-domain simulations are carried out to verify the stable operation of a 5 MW DFIM-SPS in Matlab/Simulink. Furthermore, the experimental verification is done on a 1.5 kW DFIM electric drivetrain platform. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article proposes a direct torque control (DTC) strategy for dc-biased vernier reluctance machines (dc-biased-VRMs) capable of zero-sequence current regulation. The phase current waveform of the dc-biased-VRM is sinusoidal with dc bias. To regulate the dc bias current, the proposed method reserves the adjustment time in each switching period. Then, to achieve the maximum torque per ampere condition, the unique dc bias current needs to be distributed closely with respect to the reference torque and reference flux. In addition, a reference voltage distribution method is associated with the proposed DTC strategy to further reduce the procedure of rotating coordinate transformation. The proposed DTC strategy simplifies the control algorithm, and the torque reference can be directly responded. Finally, the effectiveness of the proposed method is verified experimentally. [ABSTRACT FROM AUTHOR]

A novel brushless dual-mechanical-port dual-electrical-port (BLDD) machine and its modeling and drive method are introduced in this article. The two-set-of-winding structure of the conventional BLDD machine is replaced by an integrated winding. Thus, the manufacturing of the stator and winding is simplified. Correspondingly, two kinds of current have to be injected into the winding simultaneously. By using the integrated drive method, the copper loss will be reduced by 50% under the ideal condition. In order to achieve the control of two kinds of current in the same winding, the mathematical model of the integrated winding concerning the coupling effect is first developed. Then, the dual-frequency current drive or integrated drive strategy is proposed, in which the transformation matrix of the current and the controller structure are modified to generate the two-frequency current. Furthermore, the harmonics in the currents have been analyzed and its compensation strategy is investigated. Finally, the proposed scheme is implemented on a prototype. The experimental results of the machine have verified the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In recent years, high-precision servo systems have attracted much attention due to the development of aerospace and electronic industries. Given the requirement of the servo systems, the machine torque ripple, including the no-load cogging torque and the load torque ripple, must be limited under a low level to achieve the high precision. The ironless permanent magnet-machine (ironless PMM) is usually adopted in high-precision servo systems due to its characteristics of zero cogging torque and low torque ripple. However, ironless PMM has a lot of drawbacks such as low torque density and large PM consumption, making the system size large and expensive. The permanent-magnet vernier machine (PMVM) is also studied for servo applications for its low torque ripple and large torque density due to the adoption of the so-called magnetic gearing effect. However, its torque ripple is still apparently larger than that of the ironless PMM. In order to achieve low torque ripple and large torque density at the same time, a novel modular stator fractional pole-pair PMVM (MFP-PMVM) is proposed and analyzed in this article. The cogging torque and torque ripple of the proposed MFP-PMVM is 93% and 70% lower than that of the conventional PMVM without an obvious decrease on the rated torque. The proposed MFP-PMVM exhibits a low torque ripple close to the ironless PMM while the torque density and PM utilization of the proposed MFP-PMVM is 163% and 14 times higher than that of the ironless PMM. Based on the finite-element method (FEM) results, the superiorities of the proposed MFP-PMVM are verified. [ABSTRACT FROM AUTHOR]

The thrust force ripple of a linear motor includes positioning force and electromagnetic thrust ripple. Compared to the conventional rotary motor, linear vernier permanent magnet machines (LVPMM) break at both ends, leading to three-phase asymmetry. This article focuses on the elimination of the electromagnetic thrust ripple caused by the special structure of the LVPMM, and an asymmetrical current control strategy using in power grids is introduced to the drive system. However, unlike power grids working at a fixed frequency, the drive system of the LVPMM needs variable speed operations, and some improvements are made to the original method. High bandwidth of current loop is guaranteed, and the stability of the control system is achieved with the proposed method. Experimental results obtained are presented. It verifies that the asymmetrical current control strategy reduces electromagnetic thrust ripple by more than 67%. [ABSTRACT FROM AUTHOR]