An optimal six vector switching pattern in matrix converters for reducing harmonics and switching loss

Abstract

This paper analyses harmonic distortion caused by the narrow pulse problem in matrix converters, and presents an improved switching pattern that is based on the basic five vector switching pattern. With limited switching frequencies, the improved pattern solves the narrow pulse problem by applying an additional zero vector and adjusting the sequence of the four active vectors at the same time to minimize the switching times. Simulation results show that in the six vector switching pattern, a) the low-frequency harmonics caused by the narrow pulse problem is greatly reduced; b) the average switching frequency is reduced compared with the five vector pattern; c) the sampling frequency harmonics are apparently attenuated though a little 1/2 and 3/2 sampling frequency harmonics are produced; d) THD of output current is improved to the same level of the three zero vector switching pattern (TZVSP); e) The proposed switching pattern has benefit in both normal and unbalance input voltage conditions. Experimental results on a matrix converter platform verify the benefits of the six vector switching pattern. Faster dynamic, lower harmonics and lower loss can be achieved by using the proposed six vector switching pattern.