大功率三电平变频器损耗计算及散热分析

Losses Calculation and Heat Dissipation Analysis of High-Power Three-Level Converters

准确计算功率器件损耗可优化变频器的散热设计。功率器件的导通和开关特性对温度比较敏感,损耗计算必须考虑结温的影响。本文分析了中点钳位式(NPC)三电平变频器功率器件导通和开关规律,在此基础上建立了一套实用的损耗计算方法。通过热阻等效电路计算了功率器件的结温。对一台1MVA NPC三电平变频器在逆变和整流两种典型工况下进行了试验分析,采用红外热成像仪对功率器件的温度进行测量,计算和测量结果误差率在5%以内,验证了损耗计算的准确性。

Thermal design of the converter can be optimized if the power losses are precisely known.The device＇s conduction and switching characteristics are very sensitive to the temperatures,so the influence of junction temperatures must be taken into consideration when calculating the power losses.In this paper,a practical loss calculation method is derived based on the analysis of the conduction and switching principles of the neutral point clamping three-level converters.Using thermal resistance equivalent circuit,the devices junction temperatures are acquired.An 1MVA NPC converter is tested in inverter and rectifier operating modes,and the infrared thermal imager is used to measure the devices temperatures.The error rates between measured and calculated temperatures are within 5% range and thus the validity of the loss calculation method is verified.