Nondifferential AC Choppers Based Identical Bipolar Buck–Boost AC–AC Converter Without Commutation Issue

Abstract

This article proposes a new H-bridge structured bipolar pulsewidth modulation (PWM) buck–boost ac–ac converter based on the nondifferential ac choppers. The proposed converter can generate simple identical noninverting and inverting buck–boost voltage outputs by modulating one phase leg with single control duty ratio ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${d}_1$</tex-math></inline-formula> or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${d}_2$</tex-math></inline-formula> ). It can also provide flexible identical noninverting and inverting buck–boost operations by modulating both phase legs with two control duty ratios ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${d}_1$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${d}_2$</tex-math></inline-formula> ). In the proposed topology, the use of nondifferential ac choppers eliminates the complementary switching of ac switches and related inductor open-circuit issue. Moreover, half the switching devices are configured as switching-cell units to avoid shoot-through occurrence due to accidental turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> of complementary switches. Therefore, the proposed topology is free from commutation issue and can abolish PWM deadtimes to produce high-quality output with improved utilization of switch duty ratios. It also provides continuous input current and can perform normally with reactive loads. It has the potential to mitigate both voltage sags and swells (due to bipolar operation) when used as series voltage compensator; and unlike the existing nondifferential bipolar ac–ac converters, it can provide compensation for more intense voltage sags (of above 50%) as well. In-depth analysis of the proposed topology and hardware verifications are provided in this article.