T型三电平逆变器的中点平衡建模与控制

T型三电平电路是一种新颖的钳位型拓扑,它通过双向开关实现直流侧中性点与负载的连接;与传统二极管钳位(NPC)相比,该电路器件少、器件损耗均匀、运行效率高,因此在光伏等新能源发电中得到大量应用。中性点电压平衡问题是该类电路的固有问题,需妥善解决。文中首先分析了T型三电平中点电位的产生机理和影响因素,接着建立了中点电位的数学模型,提出了一种基于调制波电压指令分区的分析方法,得到零序电压对中点电位的解析表达式,据此建立了中点电位的平衡控制策略,并对控制器进行了设计。最后通过仿真分析,验证了理论分析的正确性。

Modeling and Control of Neutral Point Voltage Balancing for T-Type Three-level Inverters

T-type three-level circuit is a novel clamp topology,which achieves connection of the DC side neutral point and the load through the two-way switch.Compared with the traditional Neutral-Point-Clamp (NPC),the circuit uses fewer components,the device loss is uniform,the operation efficiency is high,and therefore it is widely used in new energy power generation such as photovoltaic power generation.Neutal point voltage balance problem is the inherent problem of this type of circuit,which need to be properly resolved.In this paper,the generation mechanism and influencing factors of T-type three-level midpoint potential are analyzed,and then the mathematical model of midpoint potential is established.An analysis method based on modulation wave voltage instruction partition is proposed,and the analytic expression of the zero sequence voltage to the midpoint potential is established.Based on this,the balance control strategy of midpoint potential is established,and the controller is designed.Finally,the correctness of the theoretical analysis is verified by simulation analysis.