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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。
Insulated gate bipolar transistor (IGBT), turn off the over-voltage problem is always a major problem to be solved by the designer. Rely on the rational design of multi-layer composite busbars is not enough to eliminate the IGBT turn-off voltage spikes caused by the stray inductances of the large current transformer neutral point clamped (NPC) three-level IGBT inverter. Therefore, it is necessary to design an effective IGBT absorption circuit. In this paper, Undeland absorption circuit is extended in NPC three-level inverter. Combined with NPC three-level inverter operation mode, the working principle of LRCD absorption circuit is analyzed in detail. The quantitative relation and influence between LRCD absorption circuit and inverter circuit performance are studied. The mathematical expression is given and the design principle of absorption circuit parameter is proposed. The correctness of analysis and parameter design is verified by simulation and experiment. LRCD absorption circuit will be successfully applied to 1.4MW level NPC three-level inverter prototype. The results show that the LRCD snubber circuit achieves the “soft” turn-on and the “soft turn-off” of the main switching device IGBT and the clamp diode in the NPC three-level inverter. By reasonably designing the absorption parameters, The quantitative control of the rate of change (di / dt) and the rate of change of turn-off voltage (dv / dt) of the turn-on current of the main switch can effectively restrain the over-voltage spikes of the switching device and optimize the transient characteristics of the switch. The absorption circuit for large-capacity NPC three-level IGBT inverter applications.