EPE Journal Volume 131  
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EPE Journal Volume 131  Editorial EPE Journal Volume 131  Papers


EPE Journal Volume 131  Editorial  
A Special Issue on Matrix Converters
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By Prof. Johann W. Kolar Editorial of EPE Journal Volume 131  A Special Issue on Matrix Converters, written by Prof. Johann W. Kolar  
EPE Journal Volume 131  Papers  
Analytically Closed Calculation of the Conduction Losses of ThreePhase ACAC Sparse Matrix Converters
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By F. Schafmeister; M. Baumann; J.W. Kolar For threephase a.c.a.c. power conversion a conventional matrix converter (CMC) or a d.c. side connection of a current DC link rectifier and a voltage d.c. link inverter comprising no energy storage components in the d.c. link could be employed. The combination of d.c. link converters does show a lower number of turnoff power semiconductors and, therefore, has been denoted as Sparse Matrix Converter (SMC) or Very Sparse Matrix Converter (VSMC). A limitation of the phase displacement of the current and voltage fundamentals at the input and at the output to ± ð/6 does allow a further reduction of the system complexity, accordingly the respective topology has been introduced in the literature as Ultra Sparse Matrix Converter (USMC). In this paper a novel concept for the analytical calculation of the current stresses on the power semiconductors of the Sparse Matrix Converter Topologies (SMC, VSMC, and USMC) is proposed. As a comparison to a digital simulation shows, the analytical results do show a very good accuracy in a wide modulation range and for widely varying load current phase angle and widely varying ratio of output and mains frequency. Therefore, the analytical results provide an excellent basis for the dimensioning of the SMC, VSMC or USMC and/or for the determination of the rated output power and efficiency which could be achieved by employing given power transistors and diodes.  
Minimization of Matrix Converter Commutation Times
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By P. Wheeler; J. Clare; L. Empringham This paper describes the design, construction and testing of a 10kVA threephase to threephase Matrix Converter induction motor drive. The converter has been built using discrete 65Amp MOS Controlled Thyristors (MCTs), although the techniques applied could be used with most power semiconductor switching device. The commutation time has been minimized to avoid an unnecessary waveform distortion, this is particularly important at low frequencies. This minimization gives the Matrix Converter superior waveform quality in comparison to a conventional inverter. The commutation time minimization has been demonstrated using the MCT Matrix Converter with a 12 HP induction motor load, results are presented.  
Design of Pulse Patterns for Matrix Converters
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By O. Simon; M. Bruckmann; H. Schierling; J. Mahlein For the matrix converter (Fig. 1) two basic methods are known to calculate the switching states and turnon times necessary to generate the average output voltage and input current desired. One modulation technique is the direct method of Venturini and Alesina which controls each output phase separately and the other one is the space vector modulation or indirect method proposed by Huber, Borojevic and Burany which treats the complete converter as a whole. The paper presents a new pattern optimisation principle for the space vector modulation which reduces the switching losses of the matrix converter significantly. Already published optimisation techniques try to minimise the number of commutations within a switching period by different choice of the switching states for the zero voltage and by different arrangements of the switching states. These principles lead to pulse patterns which are quite similar to the FlatTop Modulation or to the symmetrical use of zero switching states known from voltage source converters. The new optimisation method also takes into account the commutation voltage which is different for each individual switching operation and which has a strong influence on the switching losses. To minimize the commutation voltage it is necessary to follow a certain phase sequence, i.e. the input voltages must be connected to each output phase in a certain order. This order depends on the actual values of the input voltages. For the direct modulation technique this loss optimised sequence can be realized quite easily but for the space vector modulation no arrangement of switching states follows the loss optimised sequence. The paper proposes a technique to obtain the Loss Optimised Pulse Pattern out of the result of the space vector modulation by a subsequent phase oriented rearrangement of the switching states. The influence on switching losses and on harmonic distortion both on the input and on the output side will be discussed.  
A Direct Power Electronic Conversion Topology for MultiDrive Applications
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By C. Klumpner; F. Blaabjerg The matrix converter (MC) is known as a single stage ac/ac converter, which is able to provide sinusoidal PWM output voltages and input currents, inherent bidirectional power flow and no reactive elements (bulky dccapacitors and large line inductors). However, the increased number of active switches (18), as well as the need of a protection circuit involving twelve diodes with rated voltage/current ratings used only during faulty situation, makes this topology not so attractive. In this paper, a twostage converter topology consisting of a threephase to twophase matrix converter directly linked to a Voltage Source Inverter (VSI) that provides direct power electronic conversion (DPEC) is analyzed. While the functionality is similar to a matrix converter, the analysis of the conduction losses shows a different shape of the efficiency curve, which in HVACapplications may be an advantage. In addition, a new topology is proposed where several VSIs are connected to the same dclink and their switching patterns are synchronized, which is especially useful for multidrive applications. The functionality of the proposed twostage multidrive DPEC topology is analyzed by simulations and proven by experiments.  
Robust Control of Discrete Bidirectional Switches in Matrix Converters Based on Rectifier Theory
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By M. Ziegler; W. Hofmann Due to the nonexistence of natural freewheeling paths the commutation in matrix converters is more complicated than in voltage source converters. The proposed interlockfree control for the bidirectional switches where both current directions can be controlled independently is based on the knowledge of the signs of the line to line input voltages and the load current directions. The suggested policy is compared with multistep commutation methods. Finally some measurement results of the forward recovery effect of new reverse and non reverse blocking IGBTs are presented.  
Implementation of a Matrix Converter Space Vector Control in Programmable Logic
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By J. Weigold; O. Simon; J. Mahlein; J. Igney To control a matrix converter different modulations are possible. To benefit from the new topology the rectifying and inverting vector modulation (RIVM) can be used. It is a complex theory but this article presents a realization in one single programmable logic device. Additionally pulse pattern execution (PWM, commutation strategies and input voltage/current filtering) are situated in the same device. This was possible after the optimization and the reduction of the necessary calculation steps. This new solution works without an extra microcontroller or a digital signal processor (DSP). It allows great reduction in costs of matrix converter control's implementation and increases the performance.  
Comparison of Losses in Voltage Source Inverters and Direct ACAC Converters
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By M. Bland; P. Wheeler; J. Clare; L. Empringham This paper is concerned with modelling, predicting and experimental measurement of semiconductor losses in direct ACAC (matrix) converters. All of the commutation scenarios possible in a matrix converter topology using two or four step commutation are identified and studied. A complete loss model for both switching loss and conduction loss for the purposes of comparison with other converter technologies is developed and the matrix converter compared with an equivalent backtoback inverter employing the same devices. 