EPQU Journal Volume 11 Issue 1

Wieslaw JALMUZNY

This article presents the effect of secondary circuits of inductive current and voltage transformers on measuring accuracy in HV power networks. The basic parameters of instrument transformers were defined, such as errors or rated output. The impedance effect of the leads connecting secondary terminals with measuring instruments and the impact of burden power on the energy measuring error were analyzed. The calculation samples illustrate the procedure when assessing energy (power) measuring error. The algorithm may be applied, with positive results, by the operating personnel of measuring circuits with instrument transformers.

Saša DJOKIĆ and J. V. MILANOVIĆ

General testing procedures for testing different types of electrical equipment against various types of voltage sags and short interruptions are proposed and described in this paper. The recommendations for testing are discussed with respect to a number of sag and interruption parameters, non-ideal voltage supply characteristics, type of equipment, operating/loading conditions of the equipment and multiplicity of the malfunction criteria of the equipment. Presented analysis is illustrated using the examples of equipment sensitivity identified in tests.

The paper deals with the new method of analysis, synthesis and experimentation of single-phase power active filters. By using a new particular transformation theory, the ordinary single-phase system can be transformed into an equivalent two-axes orthogonal one. The new original thought is based on the idea that ordinary single-phase quantity can be complemented by fictitious second phase so that both of them will create an orthogonal system, as is usual in three-phase systems. Application of the above theory makes it possible to use complex methods of analysis as the instantaneous reactive power method, which have not been usable for single-phase systems so far. Both the active and reactive powers can be determined by this method. Practical application of the method is outlined for the case of reference current determination for single-phase power active filter. The paper shows some examples of the simulation verification results, which proved a high accuracy and extremely fast response of the single-phase active filter with control, based on the introduced method. The effectiveness of proposed control algorithm is also demonstrated by experimental results, which were carried out on the single – phase active parallel filter, power rate of 25 kVA and controlled by 32 – bit floating point digital signal processor TMS 320C31.

Shu-Jen Steven TSAI, Yilu LIU, Michael R. INGRAM

Voltage flicker caused by the electric arc furnace (EAF) and the mitigation using the superconducting synchronous condenser (SuperVAR) by the American Superconductor Corp. are considered in this paper. The modeling of EAF, SuperVAR and the system used are discussed. Fast reactive power support to reduce voltage flicker problem by an EAF is desirable. We use the voltage fluctuation amplitude as an index to evaluate the effectiveness of SuperVAR for two different MVar levels. It is found that at the PCC (point of common coupling) bus, the application of the SuperVAR can improve the voltage flicker by 6% and 19% by applying DC1A type and AC4A type exciter to the SuperVAR. With an DC1A type exciter, the SuperVAR can output only between +1 and -2 MVAR and with an AC4A type exciter the SuperVAR can provide its full rated power (8MVAR) to the system, therefore the voltage flicker becomes less severe.

Antoni ROZOWICZ

This article presents the results of research carried out on the formation of light parameters of the phosphor coatings and surfaces of fluorescent lamps. Particular attention has been paid to those parameters which influence the formation of light parameters such as light efficacy and ripple. The results of the measurements of light efficacy and light ripple are given in terms of the thickness of coatings and some of the physical parameters of phosphors used in AC powered mains frequency fluorescent lamps. On the basis of attained results the conclusions are given concerning the efficacy of light and the depth of light ripple in the function of the thickness of phosphor coating

Grzegorz RADOMSKI

It is common to find the inexpensive but robust electric power rectification method to fulfil the demands of clean power conversion. The Vienna rectifier structure is one of the hopeful construction to fulfil these demands. It may be classified as the Clean Power Converter. It lets us obtain PFC rectification in simpler than the PWM converter system. The Vienna rectifier has three control points. In addition the Vienna rectifier is the three voltage level system with less current ripples than in the case of the PWM converter. However, it has some disadvantages. The Vienna rectifier system is an unidirectional converter. It can function only in the rectifier mode, the working in the inverter mode is impossible and the generation of the reactive power is strongly restricted. Usually the Vienna rectifier is controlled on the basis of the direct current control method. However, this method is not perfect because it lets the improper control sequences appears. In this paper the mathematical model of the Vienna rectifier is derived. The voltage space vectors and their dependencies to the phase currents are defined. The range of the phase displacement angle and the maximum voltage space vector module v. phase displacement angle is drawn out for the case of the sinusoidal space vector modulation. The drawn out relations are proven by simulation results.

Elzbieta SZYCHTA

The article discusses class E zero-voltage-switching resonant inverter (ZVS). The resonant circuit of the inverter is subject to mathematical analysis using the method of state variables with the aid of MATLAB software. Results of simulation testing, based on Simplorer software, of an inverter at the operating frequency of 100kHz are presented.

Chunchun XU, Zhian ZHONG, Virgilio CENTENO, Richard CONNERS, Yilu LIU

To maintain power system operation in a balanced and stable condition, the frequency deviation and the rate of frequency change information are highly desired in monitoring and protection applications of the power grid. How to obtain frequency information more accurately and efficiently has been the topic discussion for decades. PMUs (Phasor Measurement Unit) are the most widely-used devices for measuring phase angle differences and they also provide very accurate frequency information. However, the high installation cost of PMUs limits their applications for wide area control and stability analysis of power system. Thanks to commercial GPS receivers and the fast developments in Ethernet networks, an affordable wide area, quasi real-time, GPS synchronized frequency measurement is now possible. This paper introduces a portable networked Frequency Disturbance Recorder (FDR) device, which can be used at any 110V wall outlet and transmit measured frequency data remotely via the Ethernet. The practical issues and challenges of the device design and implementation are analyzed and discussed. Based on these low cost FDRs, a US-wide Frequency Network (FNET) has been implemented at Virginia Tech and some power system monitoring applications are being developed by taking fully advantage of the FDRs.

Ehab. F. EL-SAADANY, Hatem. H. ZEINELDIN

The installation of electronic devices, digital equipment, and nonlinear loads in both industrial and domestic applications have dramatically increased in recent years, which in turn increased the level of harmonics in the system. Harmonic distortion is widely recognized as a significant cause of damage to, and mal-operation of electrical equipment. A harmonic filter can eliminate the potentially dangerous effects of harmonic currents created by nonlinear loads. There are two types of harmonic filters: passive filters and active filters. Passive filters are inexpensive compared with most mitigating devices. In this paper, reactance one-port compensator is designed for current harmonic mitigation. The optimal parameters of the filter are determined using the Branch and Reduce Optimization Navigator (BARON) Nonlinear Programming Solver in the General Algebraic Modeling System (GAMS).

Piotr MYSIAK, Piotr JANKOWSKI

The design method and results of the simulation and laboratory tests.

The article presents the principle of operation, design method, and results of laboratory and simulation tests of a 24-pulse power network converter system with direct-voltage output, the concept and practical realisation of which was worked out within the framework of a research project financed by the State Committee for Scientific Research. The presented converter allows significant reduction of undesirable higher harmonics in the power network current, including the elimination of harmonics of an order 23 and 25. The 24-pulse nature of operation of the system is obtained using three sets of coupled three-phase power network reactors (CTR).

Janusz BIALEK, Andrzej WASOWSKI

The criteria for estimating the asymmetry of arc furnace circuit impedances, referring to the theory of symmetrical components, have been presented. In contrast to the criteria recommended as yet by IEC and CENELEC, they give homogeneous estimation of asymmetry of circuit impedances, heating powers and unbalance of arc currents. Moreover they make it possible to take into account functional dependences among them and, consequently, to improve the analysis of unbalanced operation states of EAF, as well as their balancing.

Edwin HAESEN, Marcelo ESPINOZA, Bert PLUYMERS, Ivan GOETHALS, Vu Van THONG, Johan DRIESEN, Ronnie BELMANS, Bart de MOOR

In this article the authors describe how genetic optimization algorithms can be used to find the optimal size and location of distributed generation units in a residential distribution grid. Power losses are minimized while the voltage profile is kept at an acceptable level. The methods is applied on a system based on an existing grid topology with production and residential load data based on measurements. Different scenarios are chosen to run the algorithm. The obtained optimal location and size prove to depend strongly on the given conditions.