A MOSFET-based series-resonant indirect-matrix-type power electronic transformer (PET) consists of line-frequency-switching folding–unfolding bridges and series-resonant dc–dc converters (SRCs), which is an attractive choice to achieve ac–ac conversion due to its high efficiency and high power density. However, the conduction losses, switching losses, and core losses in each of the high-frequency switching cycles T_s are different due to the pulsating dc voltage |ac|, which introduces difficulties in the calculation of losses. In addition, the small dc capacitors also participate in the resonance, and the resonant current shape deviates from a pure sine. Therefore, the conventional loss model is not suitable for PETs. In this paper, the time-domain analysis of SRC resonant current considering the dc capacitor is developed. Then, the analytical expression of the resonant current RMS value in grid cycle T_g is derived, which is more accurate in calculating conduction loss than the conventional model. In addition, it avoids the calculating losses in each T_s. Next, an analytical switching loss model is developed based on the curve fitting of the capacitance–voltage relationship. A simplified analytical core loss model is provided. Each part of the loss of the PET is verified by thermal simulations, and the total losses are verified by efficiency tests on an experiment prototype.

基于 MOSFET 的串联谐振间接矩阵型电力电子变压器 (PET) 由工频开关折叠展开桥和串联谐振 dc-dc 转换器 (SRC) 组成，这是实现交流的有吸引力的选择交流转换由于其高效率和高功率密度。然而，每个高频开关周期T _{s 中}的传导损耗、开关损耗和磁芯损耗由于脉动直流电压|ac|，这给损耗计算带来了困难。此外，小直流电容也参与谐振，谐振电流形状偏离纯正弦。因此，传统的损失模型不适用于 PET。在本文中，开发了考虑直流电容器的 SRC 谐振电流的时域分析。然后推导了谐振电流有效值在电网周期T _{g 中}的解析表达式，比传统模型计算传导损耗更准确。此外，它避免了每个T _s的计算损失. 接下来，基于电容-电压关系的曲线拟合开发了分析开关损耗模型。提供了一个简化的分析磁芯损耗模型。PET 的每一部分损耗都通过热模拟验证，总损耗通过实验原型的效率测试验证。