10-04-2017, 08:55 PM
ABSTRACT
This paper proposes a shunt active filter to minimize the power quality impact instead of using the conventional fixed Filters of the matrix converters. Matrix converters inject significant harmonics and nonstandard frequency components into power systems. The proposed approach eliminates the total line current harmonics efficiently. By minimizing the Total Harmonic distortion the harmonic pollution in the power system will be reduced, and the power quality will be increased. The proposed approach has been tested and validated on the matrix converter using Mat lab/Simulink .The Simulation results are shown to demonstrate the advantages of the proposed scheme. Keywords Matrixconverter ,Shunt active filter,Power quality,Current harmonics
1. INTRODUCTION
The matrix converter with3 to3 configuration is one of the possible direct AC-AC converter topologies [1].Matrix converter has several advantages over traditional rectifierinverter type power frequency converters. It provides sinusoidal input and output waveforms. It has inherent bi-directional energy flow capability and the input power factor can be fully controlled. Last but not least, it has minimal energy storage requirements, which allows to get rid of bulky and lifetimelimited energy-storing capacitors. In spite of the advantages ,the matrix converter has also some disadvantages. It has a maximum input output voltage transfer ratio limited to 87 % for sinusoidal input and output waveforms. It requires more semiconductor devices than a conventional AC-AC indirect power frequency converter, since no monolithic bi-directional switches exist and consequently discrete unidirectional devices, variously arranged, have to be used for each bi-directional switch. It is sensitive to the disturbances of the input voltage system. But it will particularly produce higher order harmonics [2]. The matrix converter consists of 9 bi-directional switches thatallow any output phase to be connected to any input phase. The general architecture of the matrix converter is shown in Fig.1. Nine bi-directional switches in the matrix converter can theoretically assume 512 (29) different switching states combinations. But not all of them can be usefully employed. Regardless to the control method used, the choice of the matrix converter switching states combinations (from now on simply matrix converter configurations) to be used must comply with two basic rules. Fig. 1 General Architecture of Matrix Converter Taking into account that the converter is supplied by a voltage source and usually feeds an inductive load, the input phases should never be short-circuited and the output currents should not be interrupted. From a practical point of view these rules imply that one and only one bi-directional switch per output phase must be switched on at any instant. By this constraint, in a three phase to three phase matrix converter only 27 switching combinations are permitted.
2. POWER QUALITY ISSUES IN MATRIX CONVERTER
2.1 Power Quality Power quality is the set of limits or conditions of electrical properties that allows electrical devices to function in their planned manner without loss of performance. Without the proper power, an electrical utility or load may malfunction, fail permanently or not operate at well. There are many possible ways in which electric power can be poor quality. Ideally, voltage is fed by a utility as a sinusoidal wave is having a magnitude and frequency given by national, international standards or system specifications with impedance of zero ohms at all frequencies. Generally electrical power source is ideal and it can deviate in the following ways .Variations in the peak or RMS voltage are important to different types of equipment and load. When the RMS voltage goes beyond the nominal voltage by 10 to 80 percent for 0.5 cycles to 1 minute, the phenomena is called a "swell [3]. Sag is the opposite action: the RMS voltage goes below the rated voltage by 10 to 90 percent for 0.5 cycles to 1 minute [4]. Variations in the wave shape usually known as harmonics [5].
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