Abstract
Direct AC/AC converters have been investigated for miniaturization, high efficiency and harmonics reduction of mains current. These converters are classified into direct switch AC/AC converter (matrix converter) and PWM rectifier-inverter AC/AC converter in view of each circuit configuration.
Firstly, this paper proposes averaged DC link voltage control of direct AC/AC converters, and details of the control method are described. In this method, averaged DC link voltage is derived from two selecting phase-to-phase mains voltages and the duty ratio of these selecting voltages for each modulation period. The averaged DC link voltage is used for the calculation of modulation index at each output phase.
Secondly, this paper discusses a compensation method of output voltage error from commutation in case of applying the averaged DC link voltage control. Generally, the output voltage error occurs in direct AC/AC converters from commutation sequence consisting of two or four steps. And the compensation method reduces the error by analyzing commutation pattern created by the averaged DC link voltage control.
Finally, experimental results are demonstrated, and it is confirmed that the harmonic distortion of the output current is efficiently reduced with the proposed compensation method.
