A Single Phase to Single Phase Step-Down Cycloconverter for Variable Speed Drive Applications

Abstract

In industrial community, there is a growing interest of using single-phase cycloconverters for variable speed drive applications. To employ cycloconverter in variable speed drive applications, the harmonic components of cycloconverter output voltage which is always expressed in terms of total harmonic distortion (THD) should be low to ensure good power quality. Different type of switching pulse width modulation techniques is available to compensate the THD, but the complex modulation techniques increase the complexity of gate drive circuit and hardware implementation process. In this paper, a modified single-phase to single-phase mid-point type cycloconverter topology is proposed which significantly reduces the THD of output voltage for one-third and one-four of 50 Hz frequency conversion without using any type of pulse width modulation techniques for switching. The proposed topology offers promising performances in terms of THD and it also lowers the complexity of gate drive circuit compared to existing solutions. To verify the feasibility of the proposed converter, a laboratory prototype is developed besides MATLAB/Simulink simulation.