抢先看 | CES TEMS 2024年第3期目次及摘要

Abstract—The performance characteristics, particularly the starting performance of direct line-fed induction motors, which are mainly influenced by the design of the rotor, are crucial considerations for end-users. It is quite a challenging issue for motor manufacturers to enhance the starting performance of existing mass-produced motors with minimal modifications and expenses. In this paper, a simple and cost-effective method to improve the starting performance of a commercial squirrel-cage induction motor (SCIM) is proposed. The influence of geometric parameters of the end-ring on the performance characteristics, including starting (locked rotor) torque, pull-up and break down torque, starting current, rotor electric parameters, current density, power losses, and efficiency have been comprehensively investigated. It has been revealed that among the other end-ring design parameters, the ring thickness has a significant effect on the performance characteristics. An optimal end-ring thickness is determined, and its performance characteristics have been compared to those of its initial counterpart. Numeric and parametric analyses have been conducted using a 2D time-stepping finite element method (FEM). The FEM results were validated using experimental measurements obtained from an 11 kW SCIM prototype.

Abstract—This paper proposes and implements a model-free open-loop iterative learning control (ILC) strategy to realize the speed control of the single-phase flux switching motor (FSM) with an asymmetrical rotor. Base on the proposed winding control method, the asymmetrical rotor enables the motor to generate continuous positive torque for positive rotation, and relatively small resistance torque for negative rotation. An initial iteration coefficient and variable iteration coefficient optimized scheme was proposed based on the characteristics of the hardware circuit, thereby forming the model-free strategy. A series of prototype experiments was carried out. Experimental results verify the effectiveness and practicability of the proposed ILC strategy.

Abstract—Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability. Meanwhile, fractional slot concentrated windings (FSCW) are well known because of short end winding length, simple structure, field weakening sufficiency, fault tolerant capability and higher slot fill factor. The five-phase machines equipped with FSCW, are very good candidates for the purpose of designing motors for high reliable applications, like electric cars, major transporting buses, high speed trains and massive trucks. But, in comparison to the general distributed windings, the FSCWs contain high magnetomotive force (MMF) space harmonic contents, which cause unwanted effects on the machine ability, such as localized iron saturation and core losses. This manuscript introduces several new five-phase fractional slot winding layouts, by the means of slot shifting concept in order to design the new types of synchronous reluctance motors (SynRels). In order to examine the proposed winding's performances, three sample machines are designed as case studies, and analytical study and finite element analysis (FEA) is used for validation.

Abstract—The mechanical strength of the synchronous reluctance motor (SynRM) has always been a great challenge. This paper presents an analysis method for assessing stress equivalence and magnetic bridge stress interaction, along with a multiobjective optimization approach. Considering the complex flux barrier structure and inevitable stress concentration at the bridge, the finite element model suitable for SynRM is established. Initially, a neural network structure with two inputs, one output, and three layers is established. Continuous functions are constructed to enhance accuracy. Additionally, the equivalent stress can be converted into a contour distribution of a three-dimensional stress graph. The contour line distribution illustrates the matching scheme for magnetic bridge lengths under equivalent stress. Moreover, the paper explores the analysis of magnetic bridge interaction stress. The optimization levels corresponding to the length of each magnetic bridge are defined, and each level is analyzed by the finite element method. The Taguchi method is used to determine the specific gravity of the stress source on each magnetic bridge. Based on this, a multiobjective optimization employing the Multiobjective Particle Swarm Optimization (MOPSO) technique is introduced. By taking the rotor magnetic bridge as the design parameter, ten optimization objectives including air-gap flux density, sinusoidal property, average torque, torque ripple, and mechanical stress are optimized. The relationship between the optimization objectives and the design parameters can be obtained based on the response surface method (RSM) to avoid too many experimental samples. The optimized model is compared with the initial model, and the optimized effect is verified. Finally, the temperature distribution of under rated working conditions is analyzed, providing support for addressing thermal stress as mentioned earlier.

Abstract—A novel topology of modular ferrite magnet flux-switching linear motor (FMFSLM) use for track transport is presented in this paper, which enables more ferrite magnets to be inserted into the primary iron core. The motor has a significant low-cost advantage in long-distance linear drive. The proposed FMFSLM's structure and working principle were introduced. Further, the thrust force expression of the motor was established. The thrust force components triggering thrust force ripple were investigated, and their expressions can be obtained according to the inductances' Fourier series expressions. Resultantly, the relationship between the harmonics of thrust force and that of self- and mutual inductances was revealed clearly. Based on the relationship, a skewed secondary should be practical to reduce the thrust force ripple. Thus, the effect of employing a skewed secondary to the proposed FMFSLM was investigated, and an optimized skewing span distance was determined. Finite element analysis (FEA) was conducted to validate the exactness of the theoretical analysis. The simulation results indicate that the strategy of suppressing thrust force ripple has a significant effect. Meanwhile, the motor maintains a good efficiency characteristic. The results of the prototype experiment are in good agreement with FEAs, which further verifies the proposed modular interior FMFSLM's practicability.

Abstract—In traditional electricity generation plants, large powerful synchronous, induction, and direct current generators were used. With the proliferation of microgrids focused on electricity generation from renewable energy sources in today's power grids, studies have been conducted on different types of generators. Instead of the traditional generator architecture, generators with brushless structures, particularly those utilizing magnets for excitation, have found broad applications. Flux-switching generators (FSGs) are innovative types owing to their robust structure, active stator design, and high power density capabilities. However, designs have typically relied on rare-earth element magnets. Rare-earth magnets possess negative characteristics such as price uncertainty, the potential risk of scarcity in the future, and limited geographical production, leading to research on FSGs that do not depend on rare-earth magnets. This study comprehensively examines FSGs that do not use rare-earth element magnets. The study delves into the usage areas, operational mechanisms, structural diversities, and counterparts in the literature of these generators.

Abstract—The induction motor, which converts electrical energy into mechanical energy, has been recognized as the cornerstone of industrialization. The rotor of an induction motor can be either a squirrel cage rotor or a wound-type rotor, both existing as magnetless topologies. Three-phase squirrel cage induction motors are frequently utilized in industrial drives because they are dependable, have high starting torque, are self-starting and affordable. Single-phase induction motors, on the other hand, are commonly used for small loads such as domestic appliances in form of modest fans, pumps and electric power tools. In South Africa, there have been reports of fires and explosions resulting in live and property loss because of induction motors that have not been thoroughly tested or are incorrectly labelled in terms of ratings, electrical safety and performance. The goal of this study is targeted at preventing end-user injuries and failures caused by non-compliant induction motors, by evaluating locally manufactured/imported induction motors based on tests and evaluation from standards (IEC and SANS). The study is conducted using experimental procedures at the Explosion Prevention Technology and Rotating Machines (EPT and RM) laboratory, South African Bureau of Standards (SABS), South Africa. The main finding from the study shows differences in the nameplate characteristics of various induction motors which could have detrimental effects such as production and operational downtime in their end-use industries, at later stages.

Abstract—Due to high power density, high efficiency, and accurate control performance, permanent magnet synchronous motors (PMSMs) have been widely adopted in equipment manufacturing and energy transformation fields. To expand the speed range under finite DC-bus voltage, extensive research on field weakening (FW) control strategies has been conducted. This paper summarizes the major FW control strategies of PMSMs, which are categorized into calculation-based methods, voltage closed-loop control methods, and model predictive control related methods. The existing strategies are analyzed and compared according to performance, robustness, and execution difficulty, which can facilitate the implementation of FW control.

Abstract—In the current vehicle electric propulsion systems, the thermal design of power modules heavily relies on empirical knowledge, making it challenging to effectively optimize irregularly arranged Pinfin structures, thereby limiting their performance. This paper aims to review the underlying mechanisms of how irregularly arranged Pinfins influence the thermal characteristics of power modules and introduce collaborative thermal design with DC bus capacitor and motor. Literature considers chip size, placement, coolant flow direction with the goal of reducing thermal resistance of power modules, minimizing chip junction temperature differentials, and optimizing Pinfin layouts. In the first step, algorithms should efficiently generating numerous unique irregular Pinfin layouts to enhance optimization quality. The second step is to efficiently evaluate Pinfin layouts. Simulation accuracy and speed should be ensured to improve computational efficiency. Finally, to improve overall heat dissipation effectiveness, papers establish models for capacitors, motors, to aid collaborative Pinfin optimization. These research outcomes will provide essential support for future developments in high power density motor drive for vehicles.

Abstract—This article proposes a dual-negative-objective coordinated control strategy for brushless doubly fed induction generator (BDFIG) based wind power generation system under unbalanced grid voltage. To alleviate the mechanical stress and impaction on rotating shaft, the negative control objective (NCO) of machine side converter (MSC) is set to suppress the ripple of electromagnetic torque. While the NCO of grid side converter (GSC) is selected to suppress the oscillation of total output active power or the unbalanced degree of total output current for BDFIG generation system. In comparison with traditional single converter control scheme of the MSC or GSC, dual NCOs can be satisfied at the same time due to the enlarged freedom degree in the proposed improved coordinated control system for back-to-back converters. The effectiveness of proposed control strategy is validated by simulation and experimental results on a dual-cage-rotor BDFIG (DCR-BDFIG) prototype.

Abstract—High-efficient isolated DC/DC converters with a high-efficiency synchronous reluctance generator (SRG) are the ultimate solutions in DC microgrid systems. The design and modeling of isolated DC/DC converters with the performance of SRG are carried out. On the generator side, reactive and active powers are used as pulse width modulation (PWM) control variables. Further, the flux estimator is used. Three-phase PWM rectifier is used by applying space vector modulation (SVM) with a constant switching frequency for direct power control. Further, the paper also includes the experimental validation of the results. The paper also proposes that highly efficient power converters and synchronous reluctance generators are required to achieve high performance for hybrid renewable energy systems applications.

Abstract—Converters rely on passive filtering as a crucial element due to the high-frequency operational characteristics of power electronics. Traditional filtering methods involve a dual inductor-capacitor (LC) cell or an inductor-capacitor-inductor (LCL) T-circuit. However, capacitors are susceptible to wear-out mechanisms and failure modes. Nevertheless, the necessity for monitoring and regular replacement adds to an elevated cost of ownership for such systems. The utilization of an active output power filter can be used to diminish the dimensions of the LC filter and the electrolytic dc-link capacitor, even though the inclusion of capacitors remains an indispensable part of the system. This paper introduces capacitorless solid-state power filter (SSPF) for single-phase dc-ac converters. The proposed configuration is capable of generating a sinusoidal ac voltage without relying on capacitors. The proposed filter, composed of a planar transformer and an H-bridge converter operating at high frequency, injects voltage harmonics to attain a sinusoidal output voltage. The design parameters of the planar transformer are incorporated, and the impact of magnetizing and leakage inductances on the operation of the SSPF is illustrated. Theoretical analysis, supported by simulation and experimental results, are provided for a design example for a single-phase system. The total harmonic distortion observed in the output voltage is well below the IEEE 519 standard. The system operation is experimentally tested under both steady-state and dynamic conditions. A comparison with existing technology is presented, demonstrating that the proposed topology reduces the passive components used for filtering.