使用三电平变流器拓扑结构,可有效降低单个开关器件所承受的电压等级,为碳化硅(SiC)器件在高压大功率牵引变流器领域的应用提供解决方案.文章根据牵引逆变器的应用需求,针对三电平二极管中点箝位(Neutral-Point-Clamped,NPC)型逆变器拓扑的电流谐波最小脉宽调制(Current harmonic mini-mum pulse width modulation,CHMPWM)策略开展了研究,通过求解不同开关角个数下开关角度随调制比的变化曲线,实现了三电平逆变器脉冲数较低情况下的电流谐波的总体优化,理论分析了CHMPWM不同开关角个数下的各次电流谐波和加权总谐波畸变(weighted total harmonic distortion,WTHD)特征,介绍了CHMPWM的脉冲产生方式及基于定子磁链偏差矢量的调制模式切换方法.最后,利用小功率试验平台对三电平逆变器CHMPWM及调制模式切换策略进行了试验研究,结果表明,三电平逆变器CHMPWM策略具有较好的动态和稳态性能,能满足牵引逆变器的技术应用需求.
Current harmonic minimum PWM strategy for traction inverter based on three-level topology
The three-level converter topology stands out as an effective way to reduce the voltage level borne by individual switch-ing devices,which provides a solution for the application of silicon carbide(SiC)devices in high-voltage and high-power traction con-verters.This paper explores the current harmonic minimum pulse width modulation(CHMPWM)strategy based on the three-level diode neutral-point-clamped(NPC)inverter topology,tailored to meet the specific application requirements of traction inverters.Through a solving process,this study generated the curve of switching angle variations with modulation ratios at different numbers of switching an-gles,leading to overall optimization of current harmonics under low pulse counts of three-level inverters.Subsequent theoretical analysis revealed the characteristics of current harmonics at diverse orders and the weighted total harmonic distortion(WTHD)at different num-bers of switching angles within the CHMPWM framework.Further exploration in this study delved into the pulse generation method of CHMPWM and the modulation mode switching method based on the flux linkage deviation vector of stators.In addition,experimental research was carried out on a small-power experimental platform,to verify the three-level inverter CHMPWM and modulation mode switching strategy.The experimental results showcased the good dynamic and steady performance of the three-level inverter CHMPWM strategy,demonstrating its suitability for the technical application requirements of traction inverters.
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