Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 5 Articles
This paper addresses the switching transients in multibranch thyristor-switched capacitors (TSCs). The current transients\r\nfollowing the addition of a branch to a group of already connected ones are analyzed. Expressions for both its fundamental and its\r\noscillatory components are given in terms of the power network voltage, frequency, short-circuit level, and the switching angle. The\r\nrelations include also the compensator parameters such as its total reactive power rating, total number of branches, the number\r\nof already connected branches, and the initial voltage on the capacitor involved in the switching transient. An expression for the\r\ndistortion of the supply current is also given. A minimization procedure is presented for identifying the optimal switching angle\r\nleading to the least magnitude of the oscillatory current. Switching when the instantaneous supply voltage is equal to the initial\r\nvoltage will result in the least oscillatory current only in the two special cases of a single-branch compensator, or in the switching\r\nof the first branch of a multi-branch TSC. The effect of both the total number of branches and the branch switching steps on the\r\noscillatory current and on the optimal switching angle is also discussed. The advantage of the suggested procedure is demonstrated\r\nby investigating several case studies....
A dynamic voltage restorer (DVR) with no energy storage is studied. By using a matrix converter instead of the conventional\r\nAC/DC/AC converters, elimination of the DC-link capacitor is possible. The switching algorithm of matrix converter is the space\r\nvector modulation. There are different compensation algorithms to control the conventional DVR. These methods have been\r\nanalyzed in this paper for the proposed matrix-converter-based DVR. A deep analysis through different diagrams would show\r\nthe advantages or disadvantages of each compensation method. Equations for all methods are derived, and the characteristics of\r\nalgorithms are compared with each other....
This paper investigates the numerical issue of a discrete-time induction-motor emulator implementation. The stability analysis of\r\nthe finite-word-length implementation shows a coupling between required word length and the sample rate. We propose specific\r\nguidelines to analyze this coupling and to estimate the required data word length for both signals and coefficients of the model. To\r\nrespect algorithm requirements, an FPGA-based implementation was used for architecture development. The direct torque control\r\nis implemented to verify in real time the AC-motor emulator prototype....
This paper presents design consideration and performance analysis of novel reduced parts online three-phase uninterruptible\r\npower supply (UPS) system. The proposed UPS system is based on reduced switch count dual bridge matrix converter. It employs\r\nonly six power switches and results in reducing the cost of the system compared to conventional online UPS topologies, while\r\nachieving excellent performance. The performance of the proposed system is evaluated through simulation in terms of input/output\r\nwaveforms quality and shows the viability of topology....
The ferroresonance or nonlinear resonance is a complex phenomenon, which may cause overvoltage in the electrical power system\r\nand endangers the system reliability and operation. The ability to predict the ferroresonance in the transformer depends on the\r\naccuracy of the transformer model used. In this paper, the effect of the new suggested ferroresonance limiter on the control of the\r\nchaotic ferroresonance and duration of chaotic transients in a potential transformer including nonlinear core losses is studied. To\r\nstudy the proposed ferroresonance limiter, a single phase 100 VA, 275 kV potential transformer is simulated. The magnetization\r\ncharacteristic of the potential transformer is modeled by a single-value two-term polynomial. The core losses are modeled by third\r\norder power series in terms of voltage and include core nonlinearities. The simulation results show that the ferroresonance limiter\r\nhas a considerable effect on the ferroresonance overvoltage....
Loading....