中间直流环节杂散参数对变流器支撑电容电流的影响分析

Analysis of Influence of Stray Parameters of Intermediate DC Link on Converter Support Capacitor Current

在牵引变流器的主电路设计过程中,由于采用多重四象限并联供电,使中间直流环节无法完全实现低感连接,导致线路杂散阻抗引入,多重支路电容之间产生谐振,引起电容电流额外增加等情况。为此,文章通过搭建牵引变流器主电路的等效仿真模型,结合中间直流环节增加线路杂散参数的两重并联主电路结构,推导得出了中间直流环节引入线路杂散电感的主电路传递函数。根据传递函数的幅频特性可知,线路杂散电感会使主电路存在除二次谐振点外还会增加1个高次谐振点,并且杂散电感越大,谐振增益越大,造成支撑电容电流增大。

In the main circuit of traction converter, due to the using of multiple four quadrant parallel power supply, the middle DC link can not fully realize low inductance connection and introduce line stray inductances, which leads to the resonance between multiple branch capacitors and the increase of capacitive current. In this paper, by building the equivalent simulation model of the main circuit of traction converter, combined with the double parallel main circuit structure of adding line stray parameters in the middle DC link, the main circuit transfer function of introducing line stray inductance into the middle DC link was derived. According to the amplitude frequency characteristics of the transfer function, the stray inductance will make the main circuit have a higher order resonance point besides the secondary resonance point, and the larger the stray inductance is, the larger the resonance gain is, resulting in the increase of the support capacitance current.