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Unformatted text preview: C HAPTER 1. I NTRODUCTION 1.1 I NTRODUCTION The matrix converter is AC/AC converter which uses an array of controlled bidirectional switches to create a variable output voltage system with unrestricted frequency. It does not have any DClink circuit and does not need any large energy storage elements, which contribute to a compact size and can work with unity power factor. The matrix converter consists of nine bidirectional arranged in three groups. Each group consists of three switches as shown in figure 1.1. A bidirectional switch is able to control the current flow and voltage blocking in both directions. This arrangement of bidirectional switches allows any of the input phase to be connected to any of the output phase. The converter diagram looks like a matrix and hence this type of converter is termed as matrix converter. In order to provide safe operation of the converter, when operating with bidirectional switches, two basic rules have to be followed. Do not connect two different input lines to the same output line. This causes short circuit of the mains Do not disconnect the output lines. This interrupts inductive current causing over voltage. Figure 1.1: Matrix Converter 1.2 A DVANTAGES 1. The power loss in nine switch matrix converter is less. 2. The total harmonic distortion in nineswitch matrix converter is less and hence the input and output filter rating are small. 3. Three phase matrix converters are capable of providing simultaneous frequency and voltage transformation and needs less reactive component as compared with conventional AC/DC/AC converters. Since matrix converter uses bidirectional switches and hence are capable of regenerating energy back to the source and hence unity power factor operation is possible. 4. Independent control of rectification and inversion and hence simple control logic and independent control of input power factor and output current THD under different load conditions. In view of these advantages, the nine switch matrix converter topology will provide higher efficiency and higher density as compared with conventional acac converter, which is the main aim of the project. 1.3 L IMITATION The main limitation of the matrix converter is that the o/p voltage is always less than the input voltage. For any modulation methods the envelope of the o/p voltage must be contained within the continuous envelope of the input voltages. Thus the maximum o/p voltage cannot be more than 0.5 of the peak input voltage. By injecting 3 rd harmonic the o/p voltage can be increased to 0.866 of the peak input voltage 1.4 B ASIC TOPOLOGY OF T HE M ATRIX C ONVERTER The basic concept of the matrix converter is that the output voltages are related to the input voltages by a switching function matrix T ij as shown in figure 1.1 and equation 1....
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 Summer '09
 Frequency, Volt

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