Carrier-based control of matrix converter in linear and over-modulation modes

Since the inception of matrix converters, various modulation schemes have been proposed for their control. But the explanation of matrix converter operation is complex, and so is the control methodology. In this paper a 3-phase to 3-phase matrix converter is explained from the point of view of multi-level inverter topology. The matrix converter is represented as a three-level inverter and a switching cycle average model of the converter is presented. A simplified carrier-based modulation scheme is proposed where the need for sector information and corresponding look-up tables is avoided. The theoretical maximum output to input voltage transfer ratio of 0.866 is attained when the input power factor is unity. The voltage transfer-ratio is increased at the expense of low frequency harmonic distortion in the output voltages and input currents, by operating the converter in the over-modulation mode. Both input-side over-modulation and output-side over-modulation are analyzed and their limits of operation are derived. The voltage transfer-ratio is found to be 0.95 with output-side over-modulation and 0.908 with input-side over-modulation. Theoretical calculations of the maximum output voltages in the linear and over-modulation modes presented in the paper are supported by simulation results.