New Modulation Techniques for Single Phase to Three Phase Matrix Converter

Single phase to three phase $(1\phi-3\phi)$ power conversion is of particular interest in rural electric systems and in the operation of three phase motor drives from a single phase supply. Conventionally, the conversion is brought about by AC to DC rectification, followed by generation of three phase voltages from a voltage source inverter (VSI). However, such a conversion requires a large DC link capacitor, making it unsuitable in applications where space and/or size constraints exist. Moreover, the presence of an energy storage element such as capacitor in the DC link, compromises on the reliability of the system. An alternative topology for $ 1\phi-3\phi$ power conversion is a $ 1\phi-3\phi$ direct matrix converter $(1\phi-3\phi\ {\mathrm {MC}})$, which brings about static power conversion from single phase to three phase without any intermediate DC link, hence eliminating the need for any energy storage element. Matrix converters are successfully used in three phase to three phase power conversion, however, $ 1\phi-3\phi$ MCs have not gained significant popularity due to their low output voltage ratio and also due to the presence of lesser order harmonics in their output voltages. This paper presents two novel strategies for the modulation of a $ 1\phi-3\phi$ matrix converter driving an inductive load, both addressing the problem of lower order harmonics in the output. It deals with delta-sigma modulation (DSM) for $ 1\phi-3\phi MCs,$ which is a voltage control technique at variable switching frequency. Further, modulated model predictive control (MMPC) is discussed as an alternative current control based modulation for the same converter. MMPC is an improvised variant of model predictive control that offers the benefit of a fixed switching frequency besides having a fast dynamic response.