随机对流条件下全密封变换器负载能力的动态评估方法

Load Capacity Dynamic Assessment Method for Fully-sealed Converter Under Random Convection

在环境随机对流作用下,全密封变换器的功率器件热安全性难以准确判断,影响了变换器负载能力评估的有效性。为此,文中提出一种随机对流条件下的全密封变换器负载能力动态评估方法。该方法首先基于历史运行数据和热网络模型,提取变换器外壳对流热阻的随机样本;再通过小波包变换和马尔科夫链原理,对外壳对流热阻的变化进行随机模拟;接着基于对流热阻模拟序列和不同负载电流等级,模拟功率器件的结温波动情况;最后基于皮尔生长函数,计算功率器件过温风险,实现变换器最大负载电流动态评估。以全密封H桥变换器为对象,设计一个环境对流可控的实验平台。实验结果表明,所提方法能够有效提升全密封变换器运行的可靠性与经济性。

It is difficult to accurately assess the thermal safety of power devices in fully-sealed converter due to the random convection, which seriously affects the validity of the load capacity evaluation of the converter. Therefore, this paper proposed a load capacity dynamic assessment method of power devices for fully-sealed converters under random convection.Firstly, the random sample of convective thermal resistance of a converter shell was extracted, based on historical operation data and thermal network model. Next, the random simulation of the convective thermal resistance of the shell was realized by using wavelet packet transform and Markov chain principle.Then, the junction temperature fluctuation of the power device was simulated, based on the sequence of convective thermal resistance and load current levels. Finally, the optimal load current limit of the converter was determined by the over-temperature risk of the power devices and growth function. An experimental platform for H-bridge converter with controllable environmental convection was designed. The relevant experimental results show that the proposed method can effectively improve the reliability and economy of the fully-sealed converter.