New mathematical model for analysing three-phase controlled rectifier using switching functions

This paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library.The aim of this study is to present a set of closed-form analytical equations in order to enable the computation of the three-phase bridge rectifier steady-state performance estimation. The proposed method presented in this study is a fast, accurate and effective mathematical model for analysing three-phase full-wave controlled rectifiers. The steady-state mathematical model is based on the derivation of an appropriate set of switching functions using the general switching matrix circuit (GSMC) techniques. Once the switching functions are derived, the output current, input current and output dc voltage can all be easily derived and generated from the application of this technique. The effect of overlap is accurately modelled and the distortion (notches), frequency content on the input (voltage and current) and output voltage distortion are derived. The proposed mathematical model, unlike conventional analytical methods, can be integrated in the design of active filters. Furthermore, the output voltage reduction, the rms, average and peak values of voltages and currents for the thyristors and any other semiconductor devices used are readily available for the designer by direct substitution into closed-form equations without any need for the waste of time for worst-case scenario simulations. This method can also be applied to other types of converters, specifically to all voltage fed power converters

Modular OrCAD simulation approach in teaching power electronics

In this paper the authors present a new technique which can be used in simulating multi power electronic circuits at the same time in a very accurate way without the worries of the circuit analysis being diverted during the simulation. In this technique each circuits is simulated alone and the output current/voltage waveform(s) of this circuit is presented as a 'wave-form' generator. Then the final multi circuit design will be a collection of these 'wave-form' generators. This technique can be used in teaching power electronics system design for undergraduate as well as postgraduate levels and can also be used in the industry. A UPS system is used as an example in demonstrating this technique but this approach could equally be applicable to other multi circuit design configurations

Variable var compensator circuits

A family of two reactive-power compensator circuit is presented. A general model of some basic linear elements and switching function blocks is developed first. Then the two proposed compensator circuits are derived from the generalised model. The proposed circuits are capable of supplying leading as well as lagging reactive currents in stepless variation without using an inverter configuration. The switching frequency is in the range of 2.5 kHz and the largest capacitor utilised does not exceed 60 muF. The generated reactive current, in either the leading or lagging modes, contains less than 2% total harmonic distortio

Fast functional modelling of diode-bridge rectifier using dynamic phasors

In this paper, a functional model for diode-bridge rectifiers is developed based on the dynamic phasor concept. The developed model is suitable for accelerated simulation studies of the electric power systems under normal, unbalanced and line faulty conditions. The high accuracy and efficiency of the developed model have been demonstrated by comparison against three-phase time-domain model and against the model employing synchronous space-vector representations. The experimental verification of the developed model is also reported. In addition, an error analysis shows that the error of the developed model is less than 10% at the most severe unbalanced conditions. The prime purpose of the model is for the simulation studies of more-electric aircraft power architectures at a system level; however it can be directly applied for simulation study of any other electrical power system interfacing with uncontrolled diode bridge rectifiers

Representational similarity analysis reveals commonalities and differences in the semantic processing of words and objects.

Understanding the meanings of words and objects requires the activation of underlying conceptual representations. Semantic representations are often assumed to be coded such that meaning is evoked regardless of the input modality. However, the extent to which meaning is coded in modality-independent or amodal systems remains controversial. We address this issue in a human fMRI study investigating the neural processing of concepts, presented separately as written words and pictures. Activation maps for each individual word and picture were used as input for searchlight-based multivoxel pattern analyses. Representational similarity analysis was used to identify regions correlating with low-level visual models of the words and objects and the semantic category structure common to both. Common semantic category effects for both modalities were found in a left-lateralized network, including left posterior middle temporal gyrus (LpMTG), left angular gyrus, and left intraparietal sulcus (LIPS), in addition to object- and word-specific semantic processing in ventral temporal cortex and more anterior MTG, respectively. To explore differences in representational content across regions and modalities, we developed novel data-driven analyses, based on k-means clustering of searchlight dissimilarity matrices and seeded correlation analysis. These revealed subtle differences in the representations in semantic-sensitive regions, with representations in LIPS being relatively invariant to stimulus modality and representations in LpMTG being uncorrelated across modality. These results suggest that, although both LpMTG and LIPS are involved in semantic processing, only the functional role of LIPS is the same regardless of the visual input, whereas the functional role of LpMTG differs for words and objects.This work was supported by the European Research CouncilThis is the final version of an article originally published in the Journal of Neuroscience and available online at http://www.jneurosci.org/content/33/48/18906.abstract

Review of Wireless Charging of EV

Electrified transportation will minimise greenhouse gas emissions while also lowering gasoline prices. To encourage the adoption of electrified transportation, a variety of charging networks must be established in a user-friendly environment. WEVCS (wireless electric vehicle charging systems) could be a viable alternative technology for charging electric vehicles (EVs) without the need for a plug. The work done in the area of wireless power transfer technology for electric vehicles is described in this paper

Power Switching Device Losses - Simulation and Non-Simulation Methods of Calculations

In the design and manufacture of power supplies and converters, commercial factors demand high efficiency figures in the operation and performance of these products. Potential loss areas in the circuits are identified to achieve minimum losses [1] [2]. One of the main component contributing to losses in converters is the switching device.The methods to calculate switching loss [3] are complex and involves several related parameters [4] [5]. Conduction loss, radiation interference [6] and temperature rise, impacts on design efficiency. Depending on the design limitations, a balance between the related parameters is necessary, which can be achieved by optimization processes. The method of linear approximation has useful deductions in the control of turn-on switch loss, choosing switches devices with short switching times, which offers high operating frequencies

Optimisation and Simulation of RC Time Constants in Snubber Circuits

Semiconductor devices are subjected to elevated levels of stresses when used at high voltage high current and temperature applications. This stress is mainly due to hard switching which is proportional to the switching frequency. This paper presents methods used to remove this energy to prevent expensive switch damage due to overheating and high dv/dt oscillations. In confirmation of the research title, the process in the determination of 'RC' in snubber circuits has been proven by OrCAD optimisation and presented