Six step modulation of matrix converter with increased voltage transfer ratio

Abstract

Conventional modulation strategies for matrix converters based on trigonometric transformations and space vector techniques have their voltage transfer capability limited at about 0.866 p.u. This leads to a derating of motor capability by 25% in the realization of variable frequency drives using off-the-shelf line-fed motors, or requires custom designed motors for operation at reduced voltage. In this paper, a six-step variable frequency modulation strategy for the matrix converter that is capable of providing more than 1 p.u. fundamental component of output voltage is presented. Six step operation suitable for the conventional 9-switch topology and the reduced switch dual bridge topologies are presented, with capability of unity displacement factor operation at the input and output simultaneously. It is demonstrated that by varying the switching angles, control of fundamental component of output voltage and input current is possible, with concomitant generation of reactive power at the input and output terminals of the converter, with bidirectional power flow. The paper presents analytical results, computer simulation results along with laboratory scale experimental results.