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The modelling and analysis of Brushless Doubly Fed Reluctance Machines (BDFRMs), taking into account magnetic saturation and rotor movement, by conventional modelling techniques are very difficult, if not impossible, because the two stator windings have different number of poles leading to a complex flux pattern. To overcome this drawback, Finite Element Analysis (FEA) is generally used for modelling and analysing BDFRMs. But it requires a considerable computational time compared with semi-analytical methods. This article, therefore, steps forward by proposing a new approach to dynamical modelling of BDFRM based on the Reluctance Network Method (RNM), which can enable accurate calculation of the electromagnetic parameters and performances of BDFRMs. Indeed, the reluctance network method offers an interesting compromise between precision and computation time compared to finite element analysis. To validate the proposed model, simulations are carried out and comparison are made with FEA. It is observed that the greatest error between the values of the proposed model and those from FEA is close to 1%. The accuracy in the calculation of electromagnetic parameters, as well as the computational time leads us to the conclusion that the proposed model could be suitable for optimisation and control purposes.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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PurposeThe purpose of this paper is to present a coupled finite element (FE) – reluctance network model for a hybrid step motor.Design/methodology/approachThe equivalent permeances of the air‐gap are determined by 2D nonlinear FE computations. The results of the 2D model are used in a 3D analytical model. A spectral decomposition and a nonlinear fitting of the amplitudes of the permeance harmonics are performed to account for both saturation and high order harmonic effects. The nonlinear resolution of the circuit equations is performed with an iterative process. The performances are determined by using the principle of virtual works.FindingsThe method is validated with a 2D FE computation and then applied to a 3D hybrid step motor.Originality/valueThe proposed method enables fast and efficient computations of the performances of hybrid stepping motor.

Multilevel inverter has appeared as one of the important topologies in the area of high power and medium voltage because it can efficiently realize lower harmonics with reduced switching frequency. These Multilevel inverters (MLI) improve the energy quality shaped by producing many voltage levels. However, improving the quality of the output voltage of a multilevel inverter requires many switches, which tend to weigh down the structure and make it complex to control. This work deals with a comparison in terms of the spectral content of two configurations of thirty-one-level inverters for injection into the electrical grid. The first configuration is a classical cascaded H-bridge and the second one is a reconfigured Packed U-Cell (PUC) multilevel inverter. The classical configuration requires sixteen switches while the second uses only ten ones. The control technique based on the half-height modulation was performed and the Total Harmonic Distortion (THD) is calculated for each topology. For the PUC, we got a THD equal to 2.61% while we got 2.72% for the cascaded H-bridge. These results obtained in the MATLAB/Simulink environment, show that the reconfigured structure of the PUC inverter is a good candidate for injection into the electrical network.