75kVA三电平背靠背变流器的散热分析及优化

摘要

For the 75kVA three-level back-to-back converter, the heat sources including the busbar are analyzed and calculated first. Secondly, the equivalent thermal resistance circuit is given. Based on the circuit, a forced-air cooling system is designed for the power converter. After that, a three-dimensional geometric model of the converter is built, and a computation-fluid-dynamics finite element software is used to simulate the cooling system. The impact of the dissipated power of the busbar, power semiconductor devices and the air volume of the cooling fan is also investigated. According to the simulation results, an optimized cooling method through setting up the appropriate aperture opening ratio of the inlets and active wind shields is presented. Finally, some experimental verification is also offered with infrared thermometer in a 75kVA laboratory prototype. Comparing the experimental results with the simulation results, it is shown that the designed cooling system cools the converter well and every power device has almost the same temperature distribution. The provided design methods for the cooling systems may be useful for other power converters.%以75kVA三电平背靠背变流器为对象,先对包括功率母线在内的热源进行分析计算,而后给出了系统的等效热阻网络,并根据热阻网络为变流器设计了基于强迫风冷的散热系统。接着在建立该变流器三维几何模型的基础上用计算流体动力学有限元软件对其进行模拟仿真,分析了母线功耗、器件功耗和风机风量对变流器内热分布的影响规律,并提出了通过配置进风口开孔率和活动挡风板改进散热的措施。最后结合变流器实验装置,利用红外测温仪对带载稳定运行的变流器测试,进行实验验证。实验结果和仿真结果的对比表明,所设计的散热系统可以满足变流器的散热要求,同时各半导体器件散热均匀。所提出的散热设计方法和优化措施,对其他变流器的散热设计有一定的借鉴意义。