This study presents a comprehensive analytical analysis of line start permanent magnet (LSPM) synchronous motors in both steady-state and transient domains. The PM flux, the back-EMF and the winding inductances are first calculated in the steady-state based on the hybrid solution of magnetic circuit and the magnetic islands. Next, the motor voltage relations are mapped into an arbitrary d-q reference frame to dynamically assess the transient speed response as well as the individual motor torque components. Based on the presented analytical modelling, the parameters of the motor are optimised via genetic algorithm to maximise the back-EMF voltage and the overall steady-state performance. Given the parabolic relation between the back-EMF and the braking torque, the starting capability of the motor is defined as the optimisation constraint. Finally, the analytical results are verified by using a finite element analysis software package.

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An analytical model is proposed for the prediction of the no-load air gap magnetic flux density and the armature reaction in the slotless surface-inset PM machines. For this purpose, the exact 2D solution of the Poisson equation is derived. In the modelling process, the rotor salient poles are taken away and some surface magnetisation currents are considered at the borders of the removed salient poles. The contribution of this work is finding the value of the surface magnetisation currents such that the rotor saliency is accurately considered. The field solution in the provided surfacemounted PM machine is simply obtained by the separation of variables method. The machine back-EMF and its inductances is obtained by the predicted flux density due to the PMs and the stator currents, respectively. In addition, using the resultant air gap flux density in the Maxwell stress tensor, the developed electromagnetic torque is computed. Finally, the ability of the proposed model is evaluated by finite element analysis as well as experimental tests.

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In this study, the equivalent boundary method is applied for modelling of the air gap flux density in the eccentric surface-mounted permanent magnet (PM) machines. In the presented model, neither conformal transformations nor perturbation analysis methods are applied. In this approach, a two-dimensional Poisson solution for the eccentric PM machines is developed. Therefore, the proposed model is simple, precise and efficient. To make the solution of the Poisson equation in the eccentric air gap easy, the concept of the equivalent boundary method is exploited to find an equivalent concentric geometry for the eccentric problem. All the claimed theorems are mathematically approved. The model is valid for static and dynamic eccentricities at no-load and on-load conditions. Using the analytically predicted air gap flux density, electromagnetic torque, back-EMF and the resulted radial force are computed. The correctness of the predicted results is validated by means of finite-element analysis.

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This paper presents a new method for control of the grid-side converter (GSC) of a doubly fed induction generator (DFIG) system under unbalanced and harmonic grid voltage conditions. The proposed controller is designed based on the sliding-mode control (SMC) method, and operates better than the current ones as the power quality of the DFIG is improved. The fluctuations in electromagnetic torque and stator reactive power are removed by control of the rotor-side converter (RSC). In addition, the GSC keeps the DC-link voltage at a reference value and mitigates not only fluctuations but also oscillations in steady injected active power to the network. Therefore, the output power of the system is free from any fluctuation and distortion. The control algorithm is implemented in the stationary reference frame and it is not necessary to extract voltage or current sequences in either of the converters. The proposed control algorithms are also robust against parameter variations and the resulting dynamic response is fast. The simulation results confirm the validity of the mentioned advantages and the effectiveness of the proposed method.

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