Wenxiang Zhao

Remedial Injected-Harmonic-Current Operation of Redundant Flux-Switching Permanent-Magnet Motor Drives

Redundant flux-switching permanent-magnet (R-FSPM) motors are a new class of brushless machines having magnets in the stator, offering high power density, simple and robust rotor structure, and good thermal dissipation conditions. This paper proposes a new control strategy for fault-tolerant operation of the R-FSPM motor drive considering the capability limitation of the power converter. The key is to operate the R-FSPM motor in the remedial mode by injecting harmonic currents, the so-called remedial injected-harmonic-current (RIHC) operation mode. Moreover, the motor losses at the existing and the proposed remedial operations are compared for evaluation. Both cosimulation and experimental results are presented, confirming that the proposed RIHC operation can offer good steady-state and dynamic performances while reducing the motor losses and the capability requirements of the power converter during fault.

Design and Analysis of a Linear Permanent- Magnet Vernier Machine With Improved Force Density

This paper proposes a novel linear permanent-magnet (PM) vernier machine, which offers high force density, high efficiency, simple structure, and low cost. The novelty of the proposed machine is substantiated by integrating appropriate magnetization directions of PMs in the armature core. First, the structure and the operation principle of the proposed machine are descried. The machine is subsequently designed for a given set of specifications and its electromagnetic performances are analyzed by time-stepped transient finite-element method. An analytical equation is derived for evaluation of the thrust force ripple. Finally, experiments on a prototype of the proposed machine are carried out for validation.

Design and Comparison of Two Fault-Tolerant Interior-Permanent-Magnet Motors

The aim of this paper is to design and investigate two fault-tolerant interior-permanent-magnet motors for high reliability operation. The first one is the spoke type, while the second one has V-shape magnets embedded in the rotor. The structures and features of both motors are presented and the optimal designs are performed. The electromagnetic performances, such as dq-axis inductances, torque, flux weakening, and partial demagnetization, are investigated and compared. In order to calculate the dq-axis inductances accurately and segregate the torque components, the frozen-permeability method is adopted. Additionally, a method to obtain the maximum flux-weakening speed is introduced. Moreover, the partial demagnetization performances of both motors are evaluated under no-load, on-load, overload, and short-circuit conditions. Also, the fault-tolerant capacities of both motors are compared. Finally, both motors are built for exemplification. The analysis is confirmed by experimental results.

Integrated Magnetic-Geared Machine With Sandwiched Armature Stator for Low-Speed Large-Torque Applications

This paper proposes a novel integrated magnetic-geared machine for low-speed large-torque applications. By embedding the armature windings into the air slots adjacent to the modulating segments, a complex component which can serve as the armature stator and the modulating stator simultaneously is achieved. Therefore, the proposed integrated machine is with simpler mechanical structure than the existing integrated machine. Since the permanent magnets on the two rotors are all effectively involved in the energy conversion process, high torque density can be achieved. Moreover, the proposed machine exhibits high power factor due to the week armature-excited field.

Comparison of Linear Primary Permanent Magnet Vernier Machine and Linear Vernier Hybrid Machine

This paper presents the comparison of linear primary permanent magnet vernier (LPPMV) machine and linear vernier hybrid (LVH) machine. The LPPMV machine and the LVH machine both operate based on the magnetic gear principle, hence possessing the advantages of low speed and high thrust force density. In addition, both machines employ similar configurations between which the key difference is that a one-piece primary iron core is employed in the LPPMV machine instead of the modular cores in the LVH machine. Using the finite element method (FEM), the characteristics and performances of two machines are analyzed and compared. The results show that the LPPMV machine exhibits higher thrust force and lower cogging force. Finally, the FEM results are validated by experiments based on a prototype of the LPPMV machine.

Quantitative Comparison of Flux-Modulated Interior Permanent Magnet Machines with Distributed Windings and Concentrated Windings

Low speed flux-modulated permanent magnet machines (FMPMs) which are based on `magnetic-gearing effect have attracted increasing attention due to their high torque capability and simple structure. In order to assess the potentials of FMPMs in the application of low-speed direct-drive, two flux-modulated interior PM machines with distributed windings and concentrated windings are quantitatively compared by using finite element method. The results demonstrate that the machine with distributed windings can offer higher peak electromagnetic torques and lower torque ripples. Moreover, the machine with distributed windings also present stronger flux-weakening capability and lower power losses. The results also indicates that the magnetic saturation problem should be paid full attention when design flux-modulated interior PM machine with concentrated windings. If this problem can be well solved, the performance of machine with concentrated windings may be improved.

Novel hybrid excitation permanent magnet vernier machines

Two novel hybrid excitation permanent magnet (PM) vernier machines with surface and V shape PMs (termed as the hybrid excitation surface PM vernier) and hybrid excitation V shape interior PM vernier machines are proposed in this paper. These configurations aim to solve the problems of mechanical integrity and thermal instability since the PMs in the machines are located on the rotor.

Electrification and Renewable Energy Generation

With increasing worldwide concerns on energy crisis and global warming, the topics on both electrification and renewable energy generation have become very attractive most recently. In our opinion, electrification means higher energy efficiency and thereby effective energy saving, while renewable energy generation means independence of fossil energy and thereby zero emission. Consequently, electrification plus renewable energy generation points a promising way to environmental and sustainable development of human beings. Nevertheless, we are still facing critical challenges in many aspects, such as how to harvest and utilize renewable energy in a high-efficient and low-costly way and how to process and convert electrical energy so as to better fulfill the demands in practical applications. n nThe main objective of this special issue is to bring together researchers pursuing these fields and present their most recent working progress. After critical peer review, several papers are selected for publication in this issue, which cover many significant aspects related to the topic of electrification and renewable energy generation. L. Xu et al. proposed a novel linear fault-tolerant permanent-magnet machine, which can be applied to high-efficient urban rail transit systems. Y. Fan et al. investigated a new flux-modulated brushless drive motor for electric vehicles. Q. Zhang et al. proposed a novel pulse-wide modulation method to reduce current ripples of Z-source inverters. H. Li et al. presented an effective multisource energy harvesting system for wireless sensor nodes. In order to solve problems arising from wide-area backup protection, Z. Zhang et al. proposed a novel protection algorithm. J. Si et al. reported a tubular linear generator for harvesting wave energy. G. S. B. Ganandran et al. reported the result of an investigation on the potential energy saving of the lighting systems at selected buildings of the Universiti Tenaga Nasional. X. Yu et al. built up a mathematic model to estimate hydraulic transients in long diversion type hydropower station. Z. Chen et al. proposed an optimal control method for maximizing the efficiency of direct drive ocean wave energy extraction system. Y. Xu et al. investigated the iron losses in deep-sea motors when taking into account the seawater compressive stress. N. Dai et al. proposed a multifunctional voltage source inverter for renewable energy integration and power quality conditioning. A. Tomczewski presented the issues of a wind turbine flywheel energy storage system operation under real conditions. H. Yuan et al. investigated biochars derived from banana at different thermotreatment temperatures and with or without chemical activation. A. Hubackova et al. reported a solar drying technique for fish processing in Cambodia. Q. Wang et al. proposed an optimal coefficients selection method for improving power quality of photovoltaic generation. M. A. Islam et al. comprehensively reviewed various sources of renewable energy and their efficient utilization all over the world. C. Peng and K. Qian developed a ZigBee-based building energy monitoring and control system. S. Apelfrojd and S. Eriksson presented a novel electrical system configuration for variable speed wind turbines. H. Geng and G. Yang discussed the structure, performance, implementation cost, advantages, and disadvantages of different linear and nonlinear schemes applied to the pitch control of wind power generation systems. n nIn summary, how to tap renewable energy sources efficiently and economically remains a huge challenge for all of us. With no doubt, development of technologies in electrical and electronic engineering, control engineering, and material sciences will bring our human being to a clean and sustainable future. We look forward to further new progress on the basis of and beyond the work reported in this issue. n n nLinni Jian n nHua Bai n nWenxiang Zhao n nJianing Liang

A novel double-sided flux-switching permanent magnet linear motor

This paper proposes a novel double-sided flux-switching permanent magnet (PM) linear (DS-FSPML) motor which is suitable for low speed and high thrust force applications. In order to balance the normal force, the motor adopts double-sided arrangement in which the mover is sandwiched between two stators. The mover teeth alternately located on both sides of the mover are composed of laminated iron core segments between which the axially magnetized PMs of alternate polarity are inserted. Similar to conventional flux-switching PM (FSPM) motor, the 3-phase concentrated windings are employed. And the stator is designed as a double-sided simple iron core with salient teeth so that it is very robust to transmit high thrust force. By using the finite element method, the characteristics and performances of the proposed motor are analyzed and compared with the conventional single-sided FSPM linear motor.

Design Optimization and Test of a Radially Magnetized Magnetic Screw With Discretized PMs

A magnetic screw is a new type of high force density linear actuator. One of the key challenges for realization of the magnetic screw concept is the manufacturing process of its helical permanent-magnet (PM) poles. Structure simplification and simple assembly process are essential in promoting the development of the magnetic screw. This paper studies several PM configurations employed to realize the magnetic screw and proposes a new structure, which can well approximate the helical magnetic poles in a very simple way. The electromagnetic performances are assessed analytically and by time-stepping finite-element analysis (FEA). Finally, both the analytical model and the FE results are validated by experiments based on a prototype machine.