Sub-envelope modulation method to reduce total harmonic distortion of ac/ac matrix converters

An AC/AC matrix converter is an array of power semiconductor switches that connects directly a three-phase AC source to another three-phase load. It can convert an AC power source with certain voltage and frequency to another AC load with variable voltage and variable frequency directly without a DC-link and bulk energy storage component. Classical modulation methods such as the Venturini method and the space vector modulation method using AC-network maximum-envelope modulation, implement matrix conversion successfully. However, they also cause very high total harmonic distortion (THD). A novel approach, the sub-envelope modulation (SEM) method, is presented to reduce THD of matrix converters effectively. The approach is extended to an improved version of matrix converters and the THD can be reduced further. The algorithm of the SEM method is described in detail. Simulation and experimental results are also presented to verify the feasibility of the SEM approach. The results will be very helpful for industry applications.