Iet Electric Power Applications最新文献

Huge regenerative braking (RB) energy is generated in the AC traction power supply system (TPSS) which is related to safe operation and comprehensive energy utilisation. For the RB energy utilisation, the authors propose a railway regenerative braking power conditioner (RBPC) with no energy storage system (ESS) integrated which is located at the end of the power sections between adjacent traction substations (TSSs). First, the RB characteristics are studied based on a large amount of measured data, and the load power states are classified according to the load powers of adjacent power sections. Then, the RB energy utilisation scheme, transferring the RB power to the adjacent power section where traction power exists, has been studied. Moreover, a dual closed-loop control strategy for a back-to-back converter is adopted to achieve RB energy utilisation. Finally, a case study and an engineering application are carried out. The results have verified the feasibility of this method, which can illustrate that more than half of the RB energy can be mutually utilised in adjacent power sections.

This paper introduces a technique aimed at improving the performance of an interior permanent magnet synchronous machine (IPMSM) by reducing torque ripple and radial force harmonics. Unlike conventional IPMSMs, the proposed method employs a variable airgap length that is defined by a mathematical function. Two distinct rotor shapes are investigated to determine the most efficient design. Finite Element Analysis is employed to assess both the electromagnetic and mechanical attributes of the proposed motors. It compares the results for three operating points of the shaped motor with those of a conventional one. The investigation delves into the influence of rotor geometry on key output parameters, including Back Electromotive Force (back-EMF) harmonics, average torque, cogging torque, torque ripple, efficiency, power factor, and radial force harmonics. The findings indicate that optimising rotor shape can significantly enhance IPMSM performance by reducing torque ripples and radial force harmonics, while simultaneously increasing average torque and efficiency at different operating points.

A high speed rigid rotor system supported by active magnetic bearings (AMBs) puts forward higher requirements on the performance of controllers. The fuzzy variable gain H-infinity robust control (FVGRC) method is proposed to simplify controller design while suppressing system uncertainty. First, the T-S fuzzy model of four-degree-of-freedom (4-DOF) AMBs was established based on the 4-DOF AMBs rigid rotor equivalent coupling model optimised by the μ-gap metric. Then, based on the fuzzy models of AMBs systems under different operating conditions, the relative optimal weight function value of H-infinity robust controller was calculated when AMBs system was at value of the speed endpoint, and the fuzzy variable gain H-infinity robust (FVGR) controller was designed on this basis. Finally, the simulation and experimental results showed that the FVGRC can simplify the model of controller and ensure the stable operation of AMBs rigid rotor system in the full speed range under high-speed conditions.

In this paper, counter rotating dual rotor wound field flux switching wind power generator is revisited to study the generating characteristics of the AC output power curves based on finite element analysis (FEA) and experimental study. Analysis are performed under dynamic conditions, such as variable resistance, field excitation and speed. Also, electromagnetic performance is studied under variation of the field and armature currents. Analysis reveals that outer port machines with higher power capability and better electromagnetic performance compared to the inner port counterparts, although with higher fluctuations exhibited on the torque profiles of the former due to higher slotting effects. From the power generation characteristics curves, it is clear that the developed wind generator is able to produce reliable performance over a wide operating range. The accuracy of the FEA predicted results are validated, experimentally.

The cover image is based on the Research Article Generating characteristics and experimentation of counter rotating dual rotor wound field flux switching wind generator by Wasiq Ullah et al., https://doi.org/10.1049/elp2.12374.

To suppress parameter mismatch and improve the output performance of model predictive control (MPC), a new robust virtual-vector MPC strategy is proposed for a five-phase permanent-magnet motor in this study. Firstly, the incremental predictive model is applied to remove the impact of flux mismatch. Then the d-q axis inductance parameter sensitivity of MPC is analysed, which produces the predictive current error between the normal parameter and mismatched parameter. Based on the current error, a new cost function is designed to select the voltage vector more accurately when the d-q axis inductance parameter mismatch occurs. Thus, good robustness to the parameter's variation can be guaranteed. Afterwards, the duty cycle modulation technology is applied to allocate the duration time of two adjacent vector-vectors and zero vector. So the motor current harmonics and torque ripple can be considerably suppressed. Finally, the experimental results are provided to show the effectiveness of this proposed method.

The authors propose a current fluctuation reduction strategy based on optimal three-space-vector pulse-width modulation (TSVPWM), which is used to improve the service-life of the dc-link electrolytic capacitors in two-level three-phase voltage-source inverter (VSI) system. Differing from the typical SVPWM-based method that employs two adjacent active voltage vectors and zero voltage vectors to synthesise the reference voltage, the proposed strategy selects the required voltage vectors based on the minimum dc-link electrolytic capacitor current fluctuation. With the proposed strategy, an objective function for the root-mean-square value of dc-link electrolytic capacitor current is first constructed under the constraint of eight permissible voltage vectors. And then, by solving the minimum of the objective function through the piecewise linear programming, the optimal three voltage vectors under the different modulation ratios and load power factors are obtained accordingly, so as to achieve the minimum dc-link electrolytic capacitor current fluctuations during each switching period. Meanwhile, a PWM implementation scheme based on positive–negative double carrier signals is presented, which not only simplifies the implementation process but also effectively reduces the switching losses of power devices. Finally, the experimental results demonstrate that the proposed strategy can minimise the dc-link electrolytic capacitor current fluctuation under different working conditions.

The authors devote a quantitative assessment on the synchronisation capability of a line-start permanent magnet synchronous motor (LSPMSM) equipped with a hybrid rotor. The quantitative assessment is realised by determining a load criterion consisting of load torques and inertias under which the motor will just synchronise. During the process of load-criterion determination, close attention is paid to parameters governing the motor synchronisation behaviour. Following the principle of stator-current error minimisation, the time-variant magnetising inductances and permanent magnet (PM) flux linkages of the analysed LSPMSM are simplified into slip-dependent constants via the simple and robust genetic algorithm (GA). The load criterion is then obtained after the establishment of a dynamic motor model involving the simplified parameters. Prototyping tests focused on motor speed-time responses under different mechanical loads are carried out to validate the obtained load criterion and the paper analyses.

The vertical stability of permanent magnet (PM) electrodynamic suspension (EDS) system with a passive damping plate is studied because of the well-known under-damped nature of the EDS suspension system. The passive damping plate is installed under the Halbach permanent magnet array. When the vehicle-mounted Halbach array and passive damping plate move to cut the track conductive plate, the 2D eddy current force is derived by establishing equations of magnetic vector potentials and using the Maxwell stress tensor method. And a 2D finite-element model (FEM) is built to validate the accuracy of the derived levitation force equation. Based on the derived levitation force equation, the vertical stability of the PM EDS system with a passive damping plate and the effects of the main parameters on the damping ratio are analysed.

The authors present a new design of a PM-assisted synchronous reluctance motor (PM-SynRM) with uneven air-gap length to improve the power factor and enhance the torque production capability. The rotor structure is modified to properly shift rotor magnetic poles and therefore (i) increases the back-EMF and the electromagnetic torque, (ii) allows electromagnetic torque and reluctance torque components peak near the same current phase angle. The proposed solution is simple, does not require changing the arrangement of magnets and/or flux barriers and is applicable to all types of PM-SynRMs. Sensitivity analysis is carried out to determine the extent of which the proposed magnetic pole shifting may impact the resultant torque profile. To assess the level of success, the electromagnetic characteristics of the proposed design (e.g. torque, power factor, and back-EMF) are compared against the baseline structure under the same operating conditions. For verification purposes, Finite Element simulation results are validated via a series of analytical calculations and experimental measurements, and supported with detailed theoretical discussion.

Due to the existence of the magnetic pole edge effect, the actual cogging torque of the existing segmented step skew motor does not reach the theoretical minimum. Thus, a method for suppressing cogging torque of permanent magnet synchronous motor considering the magnetic pole edge effect is proposed. The magnetic pole edge effect is creatively converted into the amplitude and phase offset of the cogging torque generated by each pole segment. On this basis, an optimization problem is constructed in which the fundamental component of cogging torque is zero and the total harmonics is minimum. The optimal magnetic pole length and skew angle parameters of each segment are obtained by solving the optimization problem quantitatively. The results can provide theoretical guidance for motor design, which can minimize the cogging torque of step skew structures. The effectiveness of the proposed method in weakening the cogging torque of the step skew motor is demonstrated by theoretical calculation, 3D finite element analysis, and experimental results.