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This paper proposes, a novel soft‐switching bidirectional direct current to direct current (DC–DC) converter based on switched‐capacitor and coupled‐inductor. The proposed converter has a simple structure and utilizes four switches and a three‐winding coupled inductor and can achieve a high voltage conversion ratio in both step‐up/step‐down operations. By employing the switched‐capacitor technique, voltage stress across the power switches is low and therefore low voltage rating switches can be adopted to reduce the losses of their conduction. Soft‐switching characteristic of the proposed converter reduces the switching loss of active power switches and raises the conversion efficiency. This paper presents theoretical analysis for all operating modes of the converter, voltage conversion ratio, voltage and current stresses of all power switches. Finally, to test the validity of theoretical results and demonstrate the performance of the converter, experimental results are provided. [ABSTRACT FROM AUTHOR]

The paper presents the use of the finite element technique for determining the parameters of a three-phase squirrel-cage induction motor. The common parameters in addition to the core losses and ratio of number of turns are obtained from the finite-element field solutions. The magnetizing characteristic and core losses curve are used to determine the flux distribution within the motor structure. The linear time harmonic vector potential field solution is used for the inductances computation. The accuracy of the finite-element application is verified using the available precise results. Index Terms--Equivalent circuit, finite-elements method, induction motor.

Power transformers are one of the key components of power systems. Therefore, they must be operated efficiently to obtain satisfactory system performance, since any distortion or failure in power transformer structures may cause drastic damages. In order to detect deficiencies in power transformers, various methods are utilised. Frequency response analysis (FRA) is one of the most well-known methods used for fault detection in power transformers. However, the interpretation of FRA results is subjective, and depends primarily on the opinion of a human expert. In other words, there is no comprehensive, accepted and standardised method to interpret FRA results. Subsequently, fault detection based on FRA is prone to error. In this study, a new mathematical approach is used to interpret the frequency response of power transformers based on evidence theory method. This method is more accurate and less computationally burdensome compared to conventional methods. Simulations are implemented on an operating 125 MVA, 230/132/20 kV autotransformer using finite-element method and the results are compared to the corresponding FRA results of the same autotransformer in order to evaluate the proposed method. The obtained results indicate the efficiency of the proposed method in detecting probable faults of transformer windings through analysing the FRA results. [ABSTRACT FROM AUTHOR]

The electric vehicles (EVs), depending on the charging or discharging modes, can act as flexible loads or as flexible energy sources. Therefore, this paper proposes a method for achieving the following objectives: improvement the voltage profile of the point of common coupling (PCC), control the charging and discharging of EVs in an appropriate scheduling so that at the end of the charging and discharging process all EVs are fully charged, improvement the profiles of active and reactive loads based on the peak shaving and the valley filling, charging rate control and energy management for the economic justification of vehicle to grid (V2G) technology based on the proposed method. Considering that the penetration of EVs and state of charge (SOC) of battery at any time is random, this paper extracts and analyzes the data that is available through national household travel surveys (NHTS). In order to determine the desired parameters, two stochastic algorithms are integrated with Monte Carlo simulations. To prove the performance superiority of the proposed method over conventional methods under high EVs-penetration, an IEEE 14-bus system is used for real-time simulation. [ABSTRACT FROM AUTHOR]

Transient surges cause ruinous overvoltages along the transformer windings. The overvoltages can damage the insulation of the transformer windings. As a result, it is necessary to protect the transformers against the surges. In order to study the behavior of the transformers against the surge overvoltages, the transient model of them should be considered. Various transient models are available for the transformers. However, a complete comparison of the models has not been considered in the literature. In this paper, different transient models of the distribution transformers are mathematically analyzed by full details and compared together for electromagnetic transient studies. The models can be divided into two main types: the transformer models based on equivalent lumped circuits and the transmission line model of transformer or detail model. Moreover, the transmission line model includes single transmission line (STL) model, original multiconductor transmission line (MTL) model and the modified MTL model. Each of the transformer models are described in details. [ABSTRACT FROM AUTHOR]