A NEW CIRCUIT FOR THREE-PHASE TO THREE-PHASE AC/AC MATRIX CONVERTERS

The conventional AC/AC matrix converter uses 9 bi-directional switches. The 3×3 switches give 512 combinations of switching states, which are decreased to only 27 feasible states, if the two basic rules (preventing the short-circuit and open-circuit) to operate the converters safely are applied. The output voltage of a basic matrix converter is limited to 866.0 2 3 ≈ of the input voltage. In this paper a new circuit for three-phase to three-phase AC/AC matrix converters is presented. This new circuit uses 10 bi-directional switches. Therefore the permitted states are increased to 45 combinations. The algorithm for controlling the matrix converter is based on Least Mean Square Errors (LMSE). The output voltage of the new circuit is increased to 15.1 3 32 ≈ of the input voltage. The other advantages of this circuit are: low THD, self operating under distorted and unbalanced conditions, minimum losses, simplified control algorithm and no limitations on frequency conversion. I. INTRODOCTION The matrix converter seems to be an universal converter because of its inherent bi-directional power flow and because of any desired number of inputs and output phases. In addition there is theoretically no need of energy storage elements, which are costly, space consuming and e.g. the energy stored in the dc-link of a voltage source inverter is difficult to control in case of fault. Other advantages of matrix converters are: • Sinusoidal input current waveforms with small distortion; • Provide independent control of the magnitude and frequency of the generated output voltages; • Adjustable input power factor regardless of the load, generally with unity power factor; • Has high-efficiency and fast-response; • And many other advantages [1], [2], [3], [4]. The matrix converter consists of nine bi-directional switches arranged so that any input line can be connected to any output line as shown in Fig. 1. The converter has inputs phase voltages 321,, iii vvv, and outputs phase voltages 321,, ooo vvv. The input voltages of the matrix converter are given by