单相控制型软开关逆变器的最小复位电流控制

基于电感电流临界导通模式(critical conduction mode, CRM)的控制型软开关技术可实现开关管零电压开通(zero voltage switching, ZVS),但传统恒定电流复位方法的反向电流大，开关管通态损耗高。文中以单相三电平中点箝位型(three-level neutral point clamped, 3L-NPC)逆变器为研究对象，提出一种具有最小电感复位电流的控制方法。首先，分析开关管ZVS的实现条件，建立谐振等效电路分析模型，推导出电感复位电流理论最小值，在保证整个工频周期内开关管ZVS的同时，降低复位电流导致的开关管通态损耗。然后，建立逆变器损耗分析模型，将文中方法与传统恒定电流复位方法进行损耗计算与对比。最后，搭建一台1 kW的单相3L-NPC逆变器样机进行实验，结果表明文中方法相比于传统恒定电流复位方法，降低了损耗，最高变换效率提升约0.5个百分点。

A minimum reverse inductor current control for single-phase controlled-type soft-switching converters

The controlled-type soft-switching technology based on critical conduction mode (CRM) is an effective way to achieve zero voltage switching (ZVS) of switches. However, the higher reverse inductor current of the convention-al constant boundary conduction mode (CBCM) method leads to higher conduction losses. In this paper, the sin-gle-phase three-level neutral point clamped (3L-NPC) inverter is taken as an example for analysis, and a minimum reverse inductor current control is proposed. Firstly, the requirement for achieving ZVS turn-ON of switches is quantitatively analyzed, and the model of the equivalent resonance circuit was built. Accordingly, the theoretical minimum reverse inductor current for achieving ZVS turn-ON in the fundamental period is derived, which lowers the conduction losses of switches. Then, by establishing the power losses analysis model of the 3L-NPC inverter, the power losses of the proposed scheme and the conventional CBCM method are calculated and compared in detail. Finally, a 1 kW single-phase 3L-NPC inverter prototype was built, and experimental results verify that the proposed method features lower conduction losses than that of the CBCM method. The maximum efficiency of the 3L-NPC inverter is increased by 0.5%.