Improvement of output voltage control performance for low speed operation of matrix converter

The matrix converter (MxC) is an ac-to-ac conversion device that can generate variable frequency, variable voltage output. Nine bidirectional switches of MxC allow PWM control of input currents and output voltages. PWM switching needs "switch commutations" from one switch to another. During the switch commutations, however, unwanted voltage error occurs like a dead time effect in voltage source inverter (VSI). When PWM pulse widths are narrower than the time for completing a commutation sequence, voltage error rapidly increases. In the low speed range, PWM pulses become narrower and voltage distortions become larger due to incomplete commutations. Moreover these errors are critical in the low speed operation because system is sensitive to even a small voltage error. In this paper, a new PWM strategy is proposed for improving voltage control performance in the low speed range. Based on the input and output voltage information, PWM pulse widths are controlled to avoid incomplete commutation. The feasibility of the proposed method is proved through simulation and experimental results.