Iet Electric Power Applications最新文献

Electrical machines play the role of energy conversion for wind power generation, rail transit systems, electric vehicle traction, and ship propulsion applications. While there has been a steady growth in the use of electrical machine systems, their performance and reliability can become degraded due to the effects of complex operating conditions, which imposes a significant challenge for the applications of electrical machine systems in modern industry. Considering this, new machine topology, optimisation design, condition monitoring methods, and diagnostic techniques as well as control technologies must be developed. In line with the trend of reliable operation of electrical machine system, this Special Issue aims to present state-of-the-art research works on reliability-oriented study of electrical machine systems, including diagnostic techniques, topology, monitoring, and control. Through careful peer reviews and revisions, there are 17 papers accepted for publication in this Special Issue, which have been categorised into four topics, that is, advanced fault diagnosis techniques vibration and noise suppression method, emerging condition monitoring approach, and high-performance sensorless control strategy. The summary of every topic is given below. However, it is strongly encouraged to read the full paper if interested.

Rare earth elements (REEs) are central to the current solutions used for traction applications. However, REEs have fragile supply chains, which exposes them to supply interruptions and price spikes. Research has been focusing on REE-free solutions, either exploring REE-free topologies, such as induction and electromagnetised machines, or investigating the use of alternative hard magnetic materials, such as ferrite permanent magnets (PMs). This paper presents a novel methodology for designing and optimising spoke type permanent magnets synchronous machines (spoke machines) with ferrite PMs. The novelty of the methodology is the unique strategy used to integrate mechanical and demagnetisation constraints. Using this methodology, a novel rotor is optimised using FEM simulations to directly substitute a previous REE-based motor. The optimised design represents a unique rotor, mainly due to its large magnet size, which enables a demagnetisation-safe high-torque motor. A prototype is built and tested to verify the FEM results experimentally. The experimental results show a prototype magnetically resilient to permanent demagnetisation and with higher efficiencies at field weakening when compared with an equivalent REE machine.

This paper investigates the thermal performance of modular flux-switching permanent magnet (FSPM) machines under forced air cooling. Unlike conventional designs with continuous stator iron core, the modular configuration with segmented stator core introduces flux gaps between stator segments that can be used as extra cooling channels to increase the internal heat exchange surface area. To assess the impact of this innovative cooling design, models with varying flux gap widths (0–8 mm) were analysed using 3D computational fluid dynamics (CFD) modelling. Results indicate that at constant inlet air speed, the lowest machine temperature is achieved at 1 mm flux gap. Under constant pressure loss, the optimal cooling is achieved at a 4 mm flux gap. Although extreme flux gap widths hinder the cooling efficiency, the modular FSPM machines still outperform their nonmodular counterparts thermally. The study also examines the effect of rotor speed, revealing that higher speeds induce greater turbulence and reduce machine temperature, particularly beyond 2800 rpm, albeit with increased system pressure loss. The CFD simulation results were validated through a series of thermal experiments, confirming the accuracy of the CFD models and demonstrating the feasibility of using flux gaps as cooling channels in modular FSPM machines.

Non-singular fast terminal sliding mode control (NFTSMC) is a promising control method for permanent magnet synchronous motor (PMSM) control due to its fast convergence speed. However, the presence of unknown disturbances poses a significant challenge to its performance. This article focuses on the fast position tracking and improved anti-disturbance performance for PMSM control system. The main contribution is a composite logarithmic sliding mode control (CLnSMC) scheme incorporating a disturbance observer (DOB) based on a novel sliding mode reaching law. This approach effectively mitigates the impact of unknown disturbances on the control system. The proposed scheme stands out by effectively integrating a disturbance observer (DOB) into the traditional LnSMC framework. This integration not only enhances the control performance but also enables the direct estimation and suppression of complex disturbances, thereby improving the robustness and reliability of the control system. Extensive simulation and semi-physical experimental studies have been carried out to verify the effectiveness of the proposed control strategy. The results show that the proposed CLnSMC outperforms NFTSMC in both transient response and steady-state performance.

Low-frequency vibration is a key performance indicator for underwater vehicles, especially in applications with strict acoustic compliance requirements. The main source of vibration in integer slot permanent magnet synchronous motors (PMSM) is various orders of electromagnetic force waves acting on the stator tooth tips. Research has shown that for surface mounted permanent magnet synchronous motors, the surface vibration of the motor casing is closely related to the tangential force acting on the stator teeth. Reducing the number of stator teeth appropriately can effectively alleviate this type of vibration. Firstly, based on the Maxwell stress tensor method, the electromagnetic force model acting on the stator teeth was derived, and the mechanism of vibration caused by tangential force was analysed. Secondly, establish a mathematical model to describe the radial vibration transmitted from the tangential force on the stator teeth to the shell through the lever effect. Then, perform finite element simulation to compare the radial and tangential vibration characteristics of motors with different numbers of teeth. The simulation results show that reducing the number of teeth can effectively reduce the surface vibration of the casing caused by tangential forces on the stator teeth while maintaining the same volume of the motor. Finally, vibration and underwater noise tests were conducted on two prototype motors of underwater vehicles with the same volume but different numbers of teeth to verify the effectiveness of this method.

Conventional permanent magnet synchronous machine (PMSM) control methods often struggle to maintain satisfactory performance due to their dependency on parametric machine models. Parameter-free control methods have garnered significant attention in addressing machine uncertainties; however, their continuous online optimisation increases computational demands and can degrade performance. Recently, machine learning (ML) approaches have emerged as a promising alternative, enabling control methods independent of machine models and parameters. These ML methods are trained offline to create computationally efficient control models without the need for continuous online optimisation. This article reviews and thoroughly investigates various ML-based control approaches for PMSM drives, including reinforcement learning (RL) and supervised ML. The fundamentals and design principles of these methods are discussed with a focus on PMSM current control. Conventional RL, robust RL and classification-type and regression-type supervised ML are implemented and compared with traditional PMSM control methods. Simulation results, quantitative evaluations, and robustness analyses reveal that supervised ML-based control methods outperform other approaches in the presence of uncertainties for electrical machines.

Bearingless motors can realise the rotor active suspension by the radial electromagnetic force, whereas the suspension force and torque ripple will increase the difficulty of motor control, which may lead to the stator and rotor collision and irreversible damage to the motor. In order to obtain the principle and variation of the suspension force ripple and torque ripple of bearingless induction motors under the condition of multi-harmonic magnetic field, the complex coupling relationship between harmonic magnetomotive force (MMF), magnetic permeance and harmonic magnetic field is clarified firstly. Based on the traditional mathematical model of the suspension force, the calculation formula of the radial suspension force is derived and the mechanism of the radial suspension force ripple is revealed. Secondly, the radial suspension force and the electromagnetic torque are calculated by the finite element method, and the torque magnetic field and the suspension magnetic field are decoupling analysed. The dynamic changes of the radial suspension force and the torque with the time are given, and the relationship among multi-harmonic magnetic field coupling, radial suspension force ripple and torque ripple is clarified. Finally, the accuracy of analytical calculation and finite element calculation is proved by experiments.

Aiming at the problems of large normal force, large electromagnetic force pulsation and high cost of permanent magnet track of permanent magnet linear motor (PMLM), this paper proposes a novel double-sided flux-concentrating and stacked-winding permanent magnet linear motor (DFS-PMLM). To seek a PMLM with high thrust density and low electromagnetic force pulsation, this paper analyses and compares various motor structures and then optimises the parameters of the proposed motor structure. During optimisation, the objective function is first determined and then a Kriging model is established. Global optimisation is then performed within the agent model using the genetic algorithm-particle swarm optimisation (GA-PSO) and nondominated sorting genetic algorithm II (NSGA-II) sequentially. Finally, the structural parameters optimised by NSGA-II are more capable of improving the performance of the motor as verified by finite element simulation. Compared to conventional motors, the DFS-PMLM achieves a thrust of 506 N, a 30.3% increase in volumetric thrust density; a thrust fluctuation of 11.8%, a 62.5% reduction and a normal force of 21 N, a 2124 N reduction. Overall, the DFS-PMLM has higher thrust density, lower normal force and lower thrust fluctuation than conventional motors.

The rapid development of DC power systems in applications such as electric aircraft and microgrids has highlighted the need for high-performance DC short-circuit protection. Solid-state circuit breakers (SSCBs), utilising power semiconductor devices, offer superior performance compared to traditional mechanical circuit breakers by providing fast arc-free interruption and improved reliability. Whereas silicon carbide (SiC) MOSFETs and silicon (Si) insulated-gate bipolar transistors (IGBTs) are widely used in these applications, their overcurrent capabilities and long-term reliability under repetitive operation remain critical research topics. This paper investigates the overcurrent capability of SiC MOSFETs and Si IGBTs and analyzes their degradation mechanisms under repetitive overcurrent cycling. Experimental results show that although the SiC MOSFET has a longer overcurrent withstand time due to its saturation characteristics, it suffers from more severe ageing behaviours. Its gate-source voltage (V_GS) was found to drop by 3.3 V, its saturation current (I_sat) dropped by 45.2 A, and its on-state voltage drop significantly increased as the number of cycles reached 250. In contrast, the Si IGBT exhibited minimal degradation in its dynamic performance under the same conditions. To understand the underlying physics of these behaviours, detailed TCAD simulation models were developed based on the real device structures. Simulations revealed a single, concentrated hotspot in the SiC MOSFET near the gate, reaching a peak temperature of ∼1000 K. The Si IGBT, however, presented two distinct hotspots: one near the gate and another near the interface between the buffer and drift regions. We propose that this distributed thermal profile in the IGBT mitigates localised stress, which explains its superior long-term reliability. Conversely, the high concentration of thermal stress in the SiC MOSFET's gate region leads to its severe ageing.

Permanent magnet linear synchronous motors (PMLSMs) are widely used in high-precision servo systems. However, the detent force negatively affects servo performance. To address this issue, a novel double-sided PMLSM with closed-secondary structure is proposed in this paper. The magnetic bridges with auxiliary windings are installed at both secondary core ends. The magnetic flux paths through bridges and primary end teeth influence end leakage flux. Therefore, the detent force is suppressed utilising this magnetic path. First, the compensation current in the auxiliary windings is designed based on detent force and back EMF in auxiliary windings. Affected by nonlinear factors, such as core saturation, significant detent force remains after applying compensation current. Thus, the compensation current is iteratively adjusted according to the residual detent force. When a staggered-tooth design is applied to the primary core, the compensation current amplitude decreases, but the detent force can still be effectively suppressed. When the secondary core is extended to 30 pole pitches, the required compensation current increases due to diminished flux bridge influence. Nevertheless, FEM verification confirms that the suppression strategy maintains effectiveness. The prototype shows detent force reduction from 3.7 to 0.8 N with optimised compensation current. Experimental results verify the method's feasibility.