EPQU Journal Volume 12 Issue 2

Leonardo R. Limongi, Marcelo C. Cavalcanti, Francisco de Assis S. Neves, Gustavo M.S. Azevedo

This paper presents the implementation of an active filter configuration for harmonic compensation. The system can be controlled for current harmonics and reactive power compensations simultaneously by using a converter operating as active shunt filter. A synchronous reference frame based controller is compared to an instantaneous reactive power based controller. The synchronous reference frame method is chosen to control the converter due to the better performance when the supply voltage is distorted. A shunt active filter system has been designed and built to meet IEEE 519 recommended harmonic standards. Simulation demonstrates the good performance of the active filter configuration. Experimental results, corresponding to the operation of the digital signal processor-controlled shunt active filter are also presented.

Krzysztof P. Sozanski

This paper describes the sliding discrete Fourier transform (DFT) algorithm as an alternative for typical DFT used for spectrum analysis and synthesis. As an example a control circuit for a three-phase 75 kVA parallel active power filter (APF) is used. Such filters have been built and tested. Some illustrative, experimental results are also presented in the paper. The control algorithms of the proposed APF are implemented in the fixed-point digital signal processor TMS320C50. The presented control APF algorithm is a good alternative to classical APF control algorithms, because it allows easy selection of control parameters in mains currents: imbalance, reactive power or harmonics contents. In the proposed circuit transient performance of APF is improved using non-causal predictive current compensation.

Henryk Supronowicz, Andrzej Olszewski, Hubert Gawinski

This paper describes a control circuit for the active power filters working with three-phase AC power line. It describes logic circuitries as well as laboratory test results. The control circuit was realized with programmable logic devices, fast analog-to-digital and digital-to-analog converters. Proposed system working with open-loop control, it allows significantly simplifying its logic structure. Programmable logic devices do simultaneously a few independent tasks, so a control algorithm can be performing fast, improving considerably compensation dynamic. This paper includes results of laboratory tests of the active power filter consisted of proposed control circuit and a voltage-source converter.

Mieczysław Nowak, Juliusz Hildebrandt, Jacek Rabkowski, Roman Barlik

In the paper specification of a complex converter designed as an interface between a supercapacitor energy storage battery and other DC auxiliary links, with emphasis on its control system, and some laboratory investigation results, is presented. The converter applied in the solution contains a DC/DC power controller and a DC/AC/DC medium frequency intermediate link with a transformer, permitting good voltage matching. Specific control of both cooperating converters in accordance with the proposed solution gives the possibility of synchronized and phase controlled operation of DC/DC and DC/AC converters resulting in the impact on the AC current wave shape. In this way AC link switching and conducting loss minimize and improving of interface efficiency have been emphasized.

Sven Tschirley, Steffen Bernet

This paper describes the effect of series connected diodes and their balancing networks m the clamp circuit in IGCT converters. It is shown, that the balancing of the clamp diodes has other requirements than the balancing of the series connected freewheeling diodes in the switch cell. The dynamic and static balancing of the clamp diodes is analyzed in detail.

Babak Farhangi, Shahrokh Farhangi

In PV grid connected power conditioners, usually both stepping-up the PV array voltage, and stepping-down the dc bus voltage for injection of a sinusoidal current to the grid is required. In this paper the design procedure of Z-source converter as a single phase PV grid connected transformer-less inverter is presented. The converter has one switch less than the conventional two stage power conditioner, which leads to reduction of cost. An optimum modulation pattern for the switches is proposed, and the low frequency ripple of the converter is modeled. The design of the converter is verified by simulation.

Christian P. Dick, Klaus Rigbers Harald Radermacher, Rik W. De Doncker

This paper presents analytical and computer aided investigations on photovoltaic (PV) - generators connected to DC/DC converters for module integrated inverters. It shows the controllability and describes how to design the converters regarding requirements such as a wide variable input voltage range, a constant output voltage and a variable transferred power, depending on temperature, solar radiation and the PV-generator itself. Due to the high non-linearity of the PV-generator’s characteristic, a mathematic model is presented in a basic form and it is applied to several real systems showing the controllability and important information on the design.

Nikolaj Levin, Vladislav Pugachov, Leonids Ribickis, Anastasia Zhiravetska

A multipolar contactless doubly-fed asynchronous generator is considered where the primary and secondary generation windings are arranged on the teeth of the stator, while the rotor is tooth-like and without windings. Analytical treatment of such a generator has been performed and the basic equations that allow the parameters and performance of the machine to be calculated in generation mode of operation have been obtained. The results of experimental investigations are presented for the physical model of the generator and comparison with the calculation data is given.

Marcelo C. Cavalcanti, Gustavo M.S. Azevedo, Bruno A. Amaral, Francisco A.S. Neves

This paper presents a system that provides photovoltaic generation as well as the functions of a unified power quality conditioner. The system can be controlled for current harmonics and reactive power compensation simultaneously by using a converter operating as active shunt filter. The other converter is used as active series filter and it compensates voltage harmonics or voltage sags and swells. Using only an inverter in photovoltaic energy conversion process, the system presents increased efficiency when compared to the conventional systems. The synchronous reference frame method is used to control the three-phase converters. Simulation results demonstrate the good performance of the proposed configuration. Experimental results corresponding to the operation of the series filter as voltage sag compensator are presented.

Zbigniew Olczykowski, Andrzej Wasowski

Methods of voltage unbalance estimation based on the theory of symmetrical components and the method of differential — angular coefficients of asymmetry have been discussed. It has been proposed the last one to estimate the asymmetry of square absolute voltage value, as useful for distorted processes.

Kyung Soo Kook, Yilu Liu, Stanley Atcitty

The wind power which has been expected to be a promising alternative energy source can bring new challenges when it is connected to the power grid due to the fluctuation nature of the wind and the comparatively new types of its generators. This paper illustrates a possible solution to mitigate these integration issues of the wind power by application of the energy storage to the wind farm in power systems focusing on its short-duration perspective. The simulation model for the Energy Storage System (ESS) connected to the wind farm is implemented using the Power System Simulator for Engineering(PSS/E) which is one of the most widely used program for the power system analysis in US. Employing a sample power system, the control effect of the ESS for mitigating the wind generation related power quality issues by suppressing the power flow fluctuation of the wind farm, and improving power system stability is validated. The counteracting effect of the ESS in the wind farm to the disturbance on the grid is also shown.

Zbigniew Fedyczak, Maciej Jankowski, Paweł Szczesniak

This paper deals with a quadrature-booster phase shifter for power flow control and for transient stability improvement in AC transmission systems. The PWM AC bipolar matrix chopper (MC) is proposed for the control of the qudrature voltage component of the original voltage. There are presented in this paper both steady and transient state analyses of a transmission system with passive load based on averaged circuit models. Furthermore, simulation and experimental test results obtained in a three-phase 3 kVA laboratory model are also presented.

Elzbieta Szychta

The article presents properties of multiresonant ZVS Cuk converter. The control system of the converter is based on PWM technique. The operating range of the converter is defined where ZVS operation is assured. Control characteristics are given and the converter’s efficiency is defined. The converter’s operation is analysed on the basis of simulation testing.

Tadeusz J. Sobczyk

The paper presents possibilities of so-called circuital mathematical models of electric machines, in which the machine is treated as a set of magnetically coupled coils. It is a very popular class of models used for analysis of operational conditions of electric machines. However, the progress in numerical solutions of electromagnetic filed causes the interest of researchers to shift into so-called field-models. This paper shows the author’s opinion on extreme possibilities of circuital models putting main attention to their creation, simplification and solving.

Jean Claude Vannier, Robert Kaczmarek, Zhu-Yun Wang, Andry Randria

The subject of the paper is the comparison of four complementary methods of the rotor loss estimation in a PM SM, supplied by a PWM voltage source. An ANSYS based finite element model produces values of W, the magnetic energy stored, and P, the rotor losses. On analytical level the machine is represented by a parallel two elements equivalent circuit for each voltage harmonic. Its parameters are estimated using P and W values. Finally, the eddy current losses representation in the ANSYS code is verified for magnets under study by direct losses measurements. The calculation results are compared with some measured values resulting from analysis and harmonic decomposition of the machine total losses.

Uwe SCHUFFENHAUER, Hans KUß

Optimizing the efficiency of modern asynchronous machines requires the knowledge of the particular loss components. In this contribution a method shall be presented, where by the transient FEM-calculation the copper losses in the rotor bars by harmonic field effects and the consequential originating harmonic currents can be estimated. By this way the determination of the current density of the rotor current harmonics is carried out along the height of the rotor bar. The loss distribution from the bar bottom to the bar tip is derived from the effective current density and its spatial distribution. The calculation shows, that the additional losses represent a considerable quantum of the total losses, they are partly in the range of the fundamental copper losses and therewith they have a lasting effect on the efficiency of the machine. By convenient geometrical actions a reduction of the additional losses is possible.

Christoph Schlensok, Benedikt Schmülling, Michael van der Giet, Kay Hameyer

Disturbing vibrations and noise of electrical machines are gaining impact. Therefore, it is necessary to estimate the electromagnetic, structure-dynamical, and acoustic behavior of the machine during designing and before prototyping. An adequate tool is numerical simulation applying the Finite-Element Method (FEM) and the Boundary-Element Method (BEM) allowing for the structured analysis and evaluation of audible noise also caused by manufacturing tolerances. The methods developed and proved at the Institute of Electrical Machines (IEM) at RWTH Aachen University can be applied to any electromagnetic device in general.

LPQI and EPQU are pleased to announce a new issue for EPQU Journal.

The summary of EPQU Journal Volume 12 Issue 2 is now available.