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A novel analysis for a new type of variable reluctance resolvers (VR-Resolvers) with toroidal windings based on the magnetic equivalent circuit (MEC) method is presented in this work. Different cases including various windings configurations as well as different rotor structures are considered in order to investigate the performance of the resolver precisely. The position error of both healthy and eccentric resolvers are studied by a flexible MEC model. The effect of the eccentricity fault on the resolvers with different specifications is also evaluated to analyze the manufacturing tolerance due to the eccentric rotor for several cases. It is notable that the presented MEC provides the opportunity to adjust accuracy and model several structures in both healthy and faulty conditions by just a single model. Finally, the MEC results are confirmed by finite element method and experimental results to show the effectiveness of the proposed model. In general, development of a new VR-Resolver and analyzing its performance under different windings configurations and rotor structures by proposing a modified MEC approach are the paper novelties. [ABSTRACT FROM AUTHOR]

This paper presents a new Magnetic Equivalent Circuit (MEC) to model the Variable Reluctance Resolver (VR-Resolver) and study the effect of different windings configurations on its performance. Therefore, VR-Resolver with non-overlapping (constant turn) and overlapping (variable turn) windings are modeled to investigate their effect on the accuracy of obtained results. The proposed method gives the possibility to model both healthy and faulty conditions by a unique model to analyze faults effects on the position error. For this purpose, the inter-turn fault is considered on the excitation winding, and both dynamic and static eccentric rotors (DE and SE) are studied. It is shown that the variable turn VR-Resolver has more accuracy and lower sensitivity to eccentricity fault, while the constant turn type is less sensitive to inter-turn fault. However, the latter may be preferred in some applications thanks to its simpler windings and lower manufacturing costs. Finally, the MEC results are proved by Finite Element Method (FEM) and experimental results. Generally, the model flexibility and shorter processing time can be considered as the proposed MEC advantages over FEM. [ABSTRACT FROM AUTHOR]

Solid-state transformers (SSTs) have a great ability to improve power quality problems. In this article, an effective strategy is proposed to improve voltage unbalance conditions by these transformers. A searching optimization algorithm is presented to estimate the optimal required negative-sequence current vector. Injection of this current vector into a medium-voltage network provides maximum compensation in the voltage unbalance factor. In this method, the amplitude of the negative-sequence current vector is determined based on the current limitation of the SST and its phase angle is optimized to maximum improve the voltage unbalance conditions. Parametric analysis proves that the proposed injection current vector is unique. This negative-sequence current vector is obtained based on a simple process that is presented in the form of a flowchart. Independence from the extraction of positive and negative sequences of the measured currents is one of the main advantages of the proposed control method. Simulation and experimental results by using a laboratory three-stage SST approve the proposed optimization method. These results show that SSTs can acceptably decrease grid unbalanced voltage by an optimal injection current. [ABSTRACT FROM AUTHOR]

This article presents a new parametric magnetic equivalent circuit (MEC) for modeling a new permanent magnet resolver (PM-Resolver) with adjustable accuracy. Pole saliency of the rotor is considered based on a function and air-gap permeances are computed in such a way that different types of eccentric rotor can be modeled for the first time. Moreover, this comprehensive method makes it possible to evaluate PM-Resolver performance with different geometry in both healthy and faulty conditions by a unique model. Hence, both healthy and eccentric PM-Resolver with various rotor structures are modeled, where the position accuracy and its sensitivity to the eccentricity fault are studied. It is shown that the analyzed resolver has acceptable accuracy in position estimation, but the error increases due to the mentioned fault. Finally, the MEC results are validated by 2D-EM and experimental results to show the effectiveness of the proposed modeling technique. In general, the model flexibility and shorter processing time can be considered as the proposed MEC advantages over finite element method (FEM). [ABSTRACT FROM AUTHOR]

This paper analyzes the voltage notches in ac/dc converters and the problems that they create. Voltage notch disturbs the voltage's waveform and excites the natural frequencies of the system. In some systems, these excisions create considerable high- frequency oscillations in the voltages of the converter and the adjacent buses; this can damage capacitor banks, create parallel resonance, and generate radio disturbances. This paper analyzes the effect of snubber circuits on the voltage oscillations that arise from commutation. It also presents the theoretical foundation and analytical derivation that are used to calculate notch depth and the frequency of oscillations. To achieve accurate and applicable results, various loads of the converter, the dc current ripple, and the characteristic impedance of the system are considered. Several experimental results are shown in order to illustrate the effects of changes in the system and converter parameters on the voltage waveform of the converter. Computer simulations and experimental results indicate the accuracy of the theoretical relations. The proposed equations make it possible to effectively study the harmonic and power quality in networks that include high-power converters. [ABSTRACT FROM AUTHOR]