This paper proposes a zero-sequence model-based sensorless control strategy for open-winding permanent-magnet synchronous machine (OW-PMSM) with common dc bus. The third harmonic back electromotive force (EMF) in zero-sequence is utilized to estimate the rotor position information. The novelty is that the third harmonic back EMF is reconstructed based on the zero-sequence model together with zero-sequence current, instead of using voltage transducer and three phase resistance network which can be eliminated from the control system. Due to the essence of back EMF, the developed method is appropriate for the applications including wind power generation and motor drives operating above certain speed. Meanwhile, the phase shift-based space vector pulse width modulation method for OW-PMSM is also presented for easier implementation to form zero voltage disturbance in zero-sequence from the inverter side and hence the corresponding influence can be consequently minimized. The torque ripple, loss, and parameter sensitivity analysis are also carried out, as confirmed by predictions of two-dimensional finite element analysis. Due to the essence of decouple, the estimation can be more robust than the conventional fundamental model-based sensorless methods. Finally, the effectiveness of the proposed method is validated experimentally on a 3-kW OW-PMSM drive system with 2.5 kg·m ² total inertia.

With the merits of high torque density, unintentional demagnetization (UD) withstand capability and satisfactory flux regulation range, series magnetic circuit variable flux memory machines (VFMMs) have been recently utilized in the new-generation household appliance, e.g., washing machine. However, the conventional series structure leads to the increase of cost and magnetization current amplitude due to a larger volume of permanent magnet (PM) material, which are unfavorable for the industrialization of this kind of machines in domestic appliance applications. In order to address the foregoing issues, a novel consequent-pole hybrid magnet VFMM (CPHM-VFMM) with dual-layer delta-type PMs is proposed and optimized for belt-drive washing machine application in this paper. The machine is geometrically characterized by a novel rotor-PM consequent-pole (CP) design, which replaces half of the magnetic poles with iron parts, thus increasing d -axis magnetic permeance to decrease the corresponding required magneto-motive-force (MMF) for flux regulation while maintaining satisfactory electromagnetic performance. The topology and operating principles of the proposed CPHM-VFMM are firstly introduced and analyzed. The air-gap flux density and flux regulation range of the machine are analytically identified with equivalent magnetic circuit method. Then the machine is optimized with multimode field-current coupled (MMFCC) solution considering the operation situation in the washing machine. Afterwards, the electromagnetic characteristics of the machine are evaluated and compared with those of a conventional VFMM by finite element (FE) method. It shows that the proposed CPHM-VFMM has the merits of smaller PM usage, higher torque density, lower flux regulation current, wider flux regulation range, as well as higher global efficiency compared with the conventional counterpart. A 36-slot/6-pole CPHM-VFMM prototype is manufactured and tested to validate the FE analyses.

This paper focuses on the electromagnetic-thermal coupled design optimization of a yokeless and segmented armature (YASA) Halbach-array axial flux permanent magnet (AFPM) machine for direct-drive automated guided vehicles (AGVs). According to the application condition, extra high torque density is required with the constraints of natural-cooling and compact size. The machine topology with Halbach-array permanent magnets (PMs) and segmented stator is firstly introduced, and different slot/pole combinations are compared. Then, comprehensive sensitivity analysis is carried out, and the electromagnetic-thermal coupled design optimization consisting of rough and refined processes is carried out based on a newly established thermal network model. Subsequently, the electromagnetic performance of the optimized machine is evaluated and compared with that of an optimized surface-mounted PM YASA (SPM-YASA) benchmark with the same envelop dimension by three-dimensional (3D) finite-element (FE) method. The mechanical structure of the investigated machine with specially-designed heat-transmission mechanism is introduced, and the mechanical strength analysis is carried out. Finally, a machine prototype is manufactured and tested to validate the FE analyses.

The concept of asymmetric magnetic pole (AMP) has been developed to further improve the torque density of interior permanent magnet (IPM) machines. Compared with the conventional IPM machine, the AMP-IPM machine exhibits different operating characteristics in different rotating directions due to its unique magnetic-field-shifting (MFS) effect. Therefore, this article investigates the operating characteristics of AMP-IPM machine with aligned magnet and reluctance torques. To obtain the torque–speed relations, the maximum torque per ampere (MTPA) control method is studied. It shows that the MTPA trajectory obtained from AMP-IPM machine mathematical model is straight, which significantly simplifies the control efforts. On this basis, the torque–speed curves over the entire operating region are then analytically derived and compared, which indicate that AMP-IPM machine in low-speed region exhibits large peak torque in forward direction, while the machine in reverse direction is suitable for wide-speed range operation. Besides, the electromagnetic performances of the AMP-IPM machine are compared with those of the conventional IPM machine to further highlight the particular impact of MFS effect. The experimental results on an AMP-IPM prototype are obtained to verify all the theoretical analyses.

Zero-sequence current excited memory machine (ZSCE-MM) employs transient zero-sequence current (ZSC) to change the magnetization state of low-coercive-force (LCF) magnet. Hence, the torque density improvement and flexible flux regulation can be realized simultaneously without requiring additional magnetizing winding as well as associate current controller. However, this advantage of ZSCE-MM cannot be fully utilized through the traditional virtual voltage vector based-space vector modulation (V³-SVM) strategy, which constrains the ZSC generation ability. Consequently, a novel V³-SVM based on virtual voltage vector reconstitution technology with high dc-link voltage utilization is proposed for ZSCE-MM drive, while the simple identification progress is also preserved. Since the virtual voltage vector is expanded from the 0-axis to 3-D space, the linear modulation region in 3-D space can be enlarged. The proposed novel V³-SVM strategy can generate a higher amplitude of ZSC under the on-load situation, which means a wider flux regulation region can be achieved which is beneficial for global efficiency improvement of ZSCE-MM. The effectiveness of proposed novel V³-SVM strategy is validated by both simulation and experimental results.

In this article, the phenomenon of the additional average torque produced from high frequency (HF) current injection is first revealed and a novel high efficiency and robust variable-axis HF injection based sensorless method for interior permanent magnet synchronous motor (IPMSM) utilizing the discovered phenomenon is proposed. First, the production mechanism and characteristics for the additional average torque are introduced and analyzed. Besides, the stability margin and the rate of convergence for variable-axis HF injection based sensorless method are analyzed, and a robust position tracking performance is achieved with the proposed sensorless method by synthesizing signals from both d- and q-axis. In addition, to maintain the signal-to-noise ratio (SNR) for position observer under variable-axis injection condition, a compensation-based HF SNR controller is proposed. The validity of the HF SNR controller and the performance of the proposed variable-axis HF injection based sensorless method are verified with experiments. The experimental results also prove the ability of efficiency improvement in a wide range of operation conditions with the proposed method.