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Switched reluctance machines (SRMs) are witnessing increased interests and applications in the industry and scientific communities thanks to the advantages of rigid structures, high reliability and robustness, the absence of permanent magnets, fast dynamic response, and low manufacturing cost. SRMs have become a feasible and popular alternative to conventional electric machines, such as induction machines and permanent magnet machines, with variable speed drives in many applications. Since improving the electromagnetic and thermal performances of an SRM at the design stage is of significant value, this paper presents an in-depth literature review on the status and potential trends of the technology pertinent to the design and optimization of SRMs in the following aspects: the mathematical modeling of the electromagnetic and thermal fields in SRMs, the enhancement of the performances in terms of the torque ripple, acoustic noise, efficiency, and torque density, and the multiobjective design optimization incorporating all the above factors. Finally, the presence of SRMs and their design considerations for specific applications in electric vehicles, aircraft and aerospace systems, wind generators, high speed, and energy storage systems are extensively discussed in this paper. The existing approaches advancing the SRM technologies are systematically and comprehensively summarized and compared for each category. [ABSTRACT FROM AUTHOR]

Dual stator-winding induction generator (DWIG) is one kind of emerging multiport electrical machine. It has become a promising direction in the last two decades, especially for stand-alone power systems and renewable energy power systems. This paper mainly focuses on the DWIG with similar-poles stator windings and cage-type rotor. An overview of DWIG and its system is given. Recent advances of this generator in system topologies, mathematical model, optimal design, control strategies, and performance analysis are presented. The developments and potential applications of the DWIG-based system are also discussed. [ABSTRACT FROM AUTHOR]

Flux-switching permanent magnet machine typically suffers from relatively high cogging torque due to its special doubly salient structure and high air-gap flux density, causing undesired torque ripples, as well as acoustic noise and vibration, especially at low speeds. In this paper, an analytical expression of cogging torque is derived based on a magnetomotive force-permeance model, through which the optimal design parameters and dimensions, such as combinations of stator slots and rotor poles, skewing angle, stator tooth width, rotor tooth width, and magnet thickness, can be determined. Based on the derived analytical model, two novel approaches for cogging torque reduction are proposed, i.e., asymmetric magnetomotive force and asymmetric permeance, respectively, and consequently, the optimal designs are also acquired analytically. However, it is also found that the optimal choice of the proposed techniques depends on the combinations of stator slots and rotor poles of the machines. Finally, the effectiveness of the proposed approaches is verified by both finite element analytical predictions and experimental results. [ABSTRACT FROM PUBLISHER]

Six-phase electrical machines have received significant attention in the literature due to their use in special purpose applications (e.g., aircraft, naval, and vehicular systems). Recently, such machines have also been considered for renewable energy systems including wind generators. Modeling of such machines in commonly available transient simulation programs is not straightforward, especially when the machine model is interfaced with external inductive network and/or power electronic converters. The available modeling approaches include the classical qd 0 model, the coupled-circuit-phase-domain and the voltage-behind-reactance (VBR) models (each having its interfacing challenges). This paper extends the prior research in this area and proposes a constant-parameter VBR model that has a very convenient constant RL−branch interfacing circuit (even for salient pole machines), which makes it simple to implement in most state-variable-based simulations programs. The presented computer studies demonstrate significant numerical advantages of the new model over the existing alternative models. [ABSTRACT FROM PUBLISHER]

A new method of hierarchically partitioning the numerical calculations associated with the finite-element analysis of rotating electrical machinery is set forth. In this method, the device is partitioned geometrically and hierarchically into its constituent subsystems. Each Newton–Raphson iteration in a magnetically nonlinear device involves the hierarchical solution of relatively compact linear algebraic equations. This is contrasted with conventional approaches involving the formation or updating and solution of a single but large-dimensional sparse equation. In addition to an improvement in the computational efficiency, this approach facilitates efficient management of rotation. The proposed approach is demonstrated to require less than one-fourth the computation time, while producing identical results to those of a conventional formulation when solving for cogging torque and back electromotive force (back-EMF) of a permanent-magnet synchronous machine. The numerical results are also shown to be in agreement with the measured data. [ABSTRACT FROM AUTHOR]

In speed sensorless induction machine control, the reduced-order observer, i.e., the combined voltage and current (UI) mode flux observer, obtains good flux estimation results in the full-speed range but has some drawbacks in the stability characteristics. This paper constructs the small-signal model of the UI mode flux observer and derives the characteristic matrix to realize the stability analysis, based on which the stable range with corresponding conditions has been calculated explicitly. Furthermore, a cross-coupling feedback mechanism is proposed to solve the instability problem when the machine runs in the low-speed regenerating or plugging-in mode. The cross-coupling feedback coefficient is adjusted by the estimated speed or the speed command (conditional) for further simplification and is easy to be implemented. The improvement strategy is well verified by both the simulation in MATLAB and corresponding experimental results. [ABSTRACT FROM AUTHOR]