一种适用于大容量中点钳位型三电平逆变器的绝缘栅双极型晶体管吸收电路研究

Research on a Insulated Gate Bipolar Transistor Snubber Circuit for the High Power Neutral Point Clamped Three-Level Inverter

绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT),关断过压问题始终是设计者亟待解决的主要问题。单单依靠合理的多层复合母排设计不足以消除中点钳位型(neutral point clamped,NPC)三电平IGBT逆变器大换流路径杂散电感所引起的IGBT关断电压尖峰。因此,必须设计有效的IGBT吸收电路。该文将Undeland吸收电路在NPC三电平逆变器中进行扩展应用,结合NPC三电平逆变器运行模式,详细分析LRCD吸收电路工作原理。研究LRCD吸收电路与逆变器电路性能之间的定量关系与影响,给出了数学表达式,提出吸收电路参数设计原则。通过仿真与实验验证了分析与参数设计的正确性。将LRCD吸收电路成功应用于1.4MW级NPC三电平逆变器原理样机。研究结果表明,LRCD吸收电路在NPC三电平逆变器中实现了主开关器件IGBT和钳位二极管的"软"开通与"软"关断,通过对吸收参数的合理设计能够定量的控制主开关管的开通电流的变化率(di/dt)和关断电压的变化率(dv/dt),有效抑制开关器件的关断过压尖峰,优化开关管的瞬态特性。该吸收电路适合大容量NPC三电平IGBT逆变器应用。

The overvoltage at insulated gate bipolar transistor（IGBT） turn-off switching is a major challenge for the designers at all time. Only by the multi-layer bus-bar, the high turn-off transient voltage because of the stray inductance in the long current loop in neutral point clamped（NPC） three-level IGBT inverter could not be restrained thoroughly. Thereby, the design of the snubber circuit for IGBT is absolutely necessary. The Undeland snubber circuit was expanded into the NPC three-level inverter. Based on the operation mode of NPC three-level, the principium of LRCD snubber circuit was analyzed in detail. The quantitative relation and between the system performance of inverter and the LRCD was studied, and the mathematics expression was presented. The design principle of LRCD parameter was brought out and verified with the simulation and experiment. The LRCD snubber circuit has been successfully applied in 1.4MW NPC three-level inverter. The study shows that the soft-switch of IGBT and diode in three-level inverter could be achieved with LRCD, the switch-on di/dt and the switch switch-off dv/dt of IGBT can be specified quantitatively with the appropriate parameters of the snubber circuit, the overvoltage at IGBT turn-off switching can be reduced, and the transient characteristic of IGBT can be optimized. The snubber is usable for high power NPC three-level inverter.