中压变换器关键部件绝缘设计与评估方法研究

Insulation Design and Assessment of Critical Components in MV Power Converter

基于SiC器件的中压变换器因外部绝缘问题限制了其功率密度的提高,迫切需要研究其外部绝缘设计与评估方法。本文首先提出了一种基于硅光电倍增管的局部放电光学检测传感器;然后,利用此传感器研究了2种外部绝缘结构在PWM激励下的局部放电(partial discharge,PD)特性,并总结了普适的电力电子高压绝缘设计建议;最后,以Si C中压变换器中2个关键绝缘部件的设计评估作为实例,利用所提传感器进行绝缘考核性试验。结果表明:Si PM光学传感器具有体积小、灵敏度高、抗电磁干扰能力强等优点,适合PWM激励下的电力电子应用;2种典型外部放电缺陷下,PD起始电压均随着器件开关切换速度和频率的提高而降低;对于沿面放电,PD脉冲主要分布于PWM激励的上升和下降沿,而对于尖端放电,PD脉冲主要存在于PWM激励的平坦区;实例结果验证了所提传感器在功率变换器绝缘系统离线评估甚至未来在线监测应用中的可行性。提出的电力电子绝缘设计建议和评估方法,对未来中压高功率密度变换器的绝缘设计与评估具有借鉴意义。

The increase of power density of Si C-based medium-voltage converters is limited due to external insulation problems,and it is urgent to study its external insulation design and evaluation.First,a novel silicon photomultiplier(SiPM)-based external discharge sensor is proposed.Then,the partial discharge(PD)characteristics of two external insulation structures under PWM excitation are studied using this sensor,and universal high-voltage insulation design recommendations of power electronics are summarized.Finally,by taking the design evaluation of two key insulation components in the SiC-based medium-voltage converters as examples,insulation assessment tests are carried out with the proposed sensor.The results show that SiPM optical sensor has the advantages of small size,high sensitivity,strong anti-electromagnetic interference ability,etc.,which is suitable for power electronic applications under PWM excitation.The PD inception voltages decrease as the switching speed of the device and the frequency increase,under two typical external discharge defects.PD pulses are mainly distributed on the rising and falling edges of PWM excitation for creeping discharge,while for tip discharge,PD pulses mainly exist in the flat area of PWM excitation.The results verify the feasibility that the proposed sensor could be used in offline evaluation of converter insulation system and even future online monitoring applications.The proposed power electronic insulation design recommendations and evaluation method can provide references to the insulation design and evaluation of future medium voltage high power density converters.