一种基于直流电容取电的多电平变流器电容动态均压方法

A Capacitor Voltage Dynamic Balancing Method for Multilevel Converters Based on Taking Power from Capacitors

多电平变流器的电容电压不均问题影响装置容量利用率、稳定运行以及电能质量。提出一种基于直流电容取电的多电平变流器动态电阻均压装置及控制方法。该装置由低压金属氧化物半导体场效应管(metal oxide semiconductor field effect transistor,MOSFET)与电阻串联构成动态均压电阻,通过宽范围电压输入型DC-DC电源从直流电容获取功率,并采用滞回比较、占空比控制等方法控制低压MOSFET的开通和关断,实现多电平变流器各电容电压的动态均衡控制。该装置增加的成本较低,控制方法较为简单,易于实现,适用于各种多电平变流器结构,通用性较强。基于PSCAD/EMTDC的仿真表明,提出的动态电阻均压装置和控制方法能够良好地实现多电平变流器直流电容的动态均压控制。

The capacitor voltage balancing problem of multilevel converters may result in the reduction of capacity utilization,the unstable operation and the deterioration of power quality.Based on taking power from capacitor,a dynamic resistance balancing device for multilevel converters and its control method were proposed,in which the dynamic equalizing resistance consisted of a low-voltage MOSFET and a resistance in series,and the power was taken from the capacitor through a DC-DC convertor with wide range voltage input.The turn on/off of low-voltage MOSFET was controlled by hysteresis comparison method or duty ratio control method, which could implement the dynamic balance control of multilevel converter＆#39;s capacitor voltage.The increased cost of the device is very low,the control method is simple and easy to implement;it has strong universality and can be applied in all kinds of multilevel converters.Based on PSCAD/EMTDC, the results show that the proposed dynamic resistance balancing device and control method can well realize the dynamic balancing control for the capacitor voltage of multilevel converter.