Control strategy of an Indirect Matrix Converter with modifying DC voltage

The indirect matrix converter (IMC) consists of an input matrix converter stage and an output voltage source inverter (VSI) stage. The input matrix converter provides the DC voltage needed for the output stage. Usually, the switching sequences of the input and output stages are arranged to have soft switching commutation at the input stage. The capability of the input matrix converter to generate produce different DC voltages is exploited in this paper. If the converter can operate at a reduced DC voltage then commutation of the VSI can take place at lower voltages. Depending on the required output voltage, the modulation of the input matrix converter is changed in order to obtain a lower/higher DC voltage without causing over modulation The strategy could be applied to a cage induction machine drive, operating at low speed and therefore requiring low voltage, or a doubly-fed induction machine drive operating near synchronous speed where the required rotor voltage is smaller. The strategy is experimentally validated controlling the output current of the IMC feeding a resistive-inductive load. Experimental results are shown for step changes in demanded reference currents and current regulation at different modulation strategies of the input converter.