A Novel Junction Temperature Balance Control Method for Typical Three-Phase Converters Based on a Hybrid Modulation Strategy

Abstract

Unbalanced junction temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> ) distribution of a bridge leg can accelerate the development of aging defects and reduce the lifetime of the converter. Therefore, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> balance control (TBC) is important for high reliability operation. Conventional TBC methods based on parameter adjustment cannot avoid reducing the efficiency and the power quality of converters. Other TBC methods can only be used in some switching devices in special packages. In this article, a novel TBC method is proposed based on a hybrid modulation strategy. First, temperature distributions in three space vector pulse width modulation (SVM) methods are analyzed theoretically and verified by experiments. This is the basis for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> balancing. Second, a hybrid modulation strategy is proposed based on the bang-bang control. It can switch from these three SVMs adaptively according to the maximum <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> difference. In this way, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> difference of a bridge leg can be controlled to a fixed range. Third, the effectiveness of the proposed TBC method is verified by experiments. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> difference caused by unbalanced aging can be controlled from over 20 °C to 3 °C. Compared with conventional TBC methods, the proposed method has almost no effect on the efficiency and output power quality of the converter.