NPC五电平Z源逆变器的设计研究

传统NPC五电平逆变器不具有单级升压的功能,直流电压利用率低,不允许上下桥臂直通,需引入死区时间,造成逆变系统安全性下降。Z源逆变器(ZSI)利用特殊的X型LC网络实现单级升压功能,同时允许桥臂直通,提高逆变器的可靠性。为此提出一种双Z源NPC五电平逆变器拓扑,分析其直通工作状态,并说明了此拓扑结构的合理性。基于传统NPC五电平逆变器的同相载波层叠PWM调制原理,设计了一种适用于五电平ZSI的同相载波层叠PWM调制法。仿真分析验证了此调制方法的合理性及NPC五电平Z源逆变器在提高直流电压利用率方面的优势。

Research on neutral-point-clamped five level Z source inverter

The utilization rate of DC voltage of traditional neutral-point-clamped ( NPC ) five-level inverters without voltage-boost capability is low .The dead zone is needed in order to avoid shoot-through state , which causes the de-cline in the system security .With a unique X-shaped LC network , a Z-source inverter can gain boost ability and im-prove the reliability utilizing the shoot-through state .The topology of NPC five-level Z source inverter with two Z-source networks was proposed .Its shoot-through state was analyzed and the rationality of this topology structure was il-lustrated.Based on phase disposition ( PD) pulse width modulation ( PWM) algorithm of conventional NPC five-level inverter , a practicable PD PWM algorithm was designed for five-level Z source inverter .The simulation results demon-strate the rationality of this modulation method and the advantage of NPC five-level Z source inverter on improving the utilization rate of DC voltage .