中点钳位型三电平逆变器通态损耗分析

Analysis of Conduction Losses in Neutral-Point-Clamped Three-Level Inverter

研究了中点钳位型三电平逆变器通态损耗的一种简单计算方法。根据电流、电压关系确定器件导通规律,进而计算出器件导通占空比,由此推导出用于分析计算的导通损耗表达式。该表达式与器件静特性、功率因数、调制度及负载电流有关,利用其计算不同载波调制下通态损耗时只需改动导通占空比。另外,采用该损耗模型对正弦波调制和三次谐波注入法调制下的三电平逆变器通态损耗进行了分析比较,所得结论为三电平逆变器损耗研究奠定了基础。

An effective and straightaway conduction-loss-analysis method, which is one of the important considerations in neutral-point-clamped （NPC） three-level inverter, is investigated. The conduction loss expressions are derived based on the knowledge of conduction devices, which are determined by the working condition and the conduction duty cycle. The results clearly show conduction losses are the function of semiconductor static characteristic, power factor, modulation depth and load current. They can be utilized to calculate conduction losses for different carrier-based modulation methods. The loss model is used for analysis and comparison on two different modulation strategies, sinusoidal PWM （SPWM） and third harmonic injection PWM （THIPWM）, in the paper. This approach should benefit the prediction and further investigations of power semiconductor losses for three-level inverter.