Suppressing noise peak single phase to three phase Ac-ac direct converter introducing deltasigma modulation technique

For ac-ac power conversion, a combination of converter and inverter is usually used. But this method increases the power conversion stages, and increasing conversion stage becomes disadvantage in respect of the conversion efficiency. Moreover, using two converters enlarges the equipment and results in a high cost converter. Ac-ac direct converter converts ac power to ac power directly and can reduce power conversion stage. By the way, according to extension of power electronics fields, the necessity of single phase to three phase power conversion increases. For the purpose of reducing high frequency output voltage noise peaks, this paper proposes a single phase to three phase ac-ac direct converter. The proposed converter introduces delta-sigma modulator and output voltage characteristics are compared with a PWM converter. As a result, it was proved that the proposed converter could reduce high frequency noise peaks and had an advantage of keeping noise regulation.

I. Introduction

Usually, a combination of converter and inverter is used for ac-ac power conversion. But this approach needs more power conversion stages and leads to large power conversion loss. Ac-ac converter converts ac-ac power conversion directly with one conversion stage. On the other hand, with extending power electronics fields, the necessity for single phase to three phase power conversion increases. The authors have proposed delta-sigma modulated converters [1], [2] and have proved that the proposed converter could have suppressed noise levels and have had an advantage of keeping a noise regulation. Focusing on obtaining low noise peak output voltage with a simple control scheme, this paper proposes a delta-sigma modulated single phase to three phase ac-ac direct converter. To determine the switching pattern of the ac-ac converter, delta-sigma modulator is introduced. In comparison with PWM scheme, it is proved that the output voltage high frequency noise peaks, which appear in case of PWM scheme, can be suppressed by using the proposed converter.