级联型电力电子变压器电压与功率均衡控制方法

对于模块级联型电力电子变压器,如果整流级直流输出电压不均衡或各双有源DC-DC变换器(DAB)模块传递的功率不均衡,可能导致开关器件电压或电流应力分配不均。因此提出在整流级采用电压均衡控制,在DAB级采用功率均衡控制来解决整流级输出电压的不均衡问题和因各DAB模块参数不匹配导致的功率不均衡问题。对于该功率均衡控制,是利用各整流模块占空比的有功分量作为反馈量来调节各DAB模块占空比实现的。电压均衡控制与功率均衡控制共同作用,以使系统达到整流级直流输出电压均衡和各DAB模块功率均衡的目的。此外,该功率均衡控制可以很容易由DSP实现,且不需要任何电流传感器。该控制方法已得到仿真验证,并在模块级联型电力电子变压器实验平台上得到实验验证。

Voltage and Power Balance Control for Cascaded Multilevel Converter Based Power Electronic Transformer

For cascaded multilevel converter based power electronic transformer (PET), the unbalance of DC output voltage of each rectifier or power transmission in each dual active bridge (DAB) module may lead to uneven voltage or current stress among switches. This paper presents a strategy to solve voltage imbalance and power imbalance caused by parameter mismatch of each DAB module. Wherein, a voltage balance control strategy is adopted in multilevel rectifier stage, while a sensorless power balance control strategy is adopted for the modular DAB converter. Regarding the power balance realization, the active power component of the duty cycle in the rectifier stage is used as power feedback to adjust the duty cycle of each DAB module. These two control methods operate coordinately, to balance the DC output voltage of each rectifier and transfer power in each DAB module. Furthermore, the power balance control algorithm can be easily realized by DSP without current sensor. Finally, simulation and experimental data in a cascaded multilevel converter based PET have verified the proposed strategy.