模块化多电平直流变压器的傅里叶级数建模与控制器设计

Fourier Series Modeling and Controller Design of Modular Multilevel DC Transformer

研究模块化多电平直流变压器,其由两相模块化多电平桥臂、高频隔离变压器和并联全桥模块组成.模块化多电平桥臂采用准方波调制,并联全桥模块采用方波调制,基于傅里叶级数分析单移相控制下的工作原理和功率特性.采用傅里叶级数求和的方法建立模块化多电平直流变压器在单移相控制下的数学模型,求得单移相控制到输出电压的传递函数,在开环传递函数的基础上设计PI控制器,以达到控制输出电压的目的.最后在MATLAB/Simulink中搭建模块化多电平直流变压器的仿真模型.仿真结果表明,利用该数学模型设计的PI控制器可使直流变压器输出电压稳定.

The modular multilevel DC transformer is studied,which is composed of two phase modular multilevel converter,high frequency isolation transformer and parallel full-bridge module.The modular multilevel bridge adopts quasi-square wave modulation,and the parallel full-bridge module adopts square wave modulation.Based on the Fourier series analysis,the operating principle and power characteristics under single phase shift control are analyzed.The mathematical model of modular multilevel DC transformer under single phase shift control is established by using the method of Fourier series summation,and the transfer function from single phase shift control to output voltage is obtained.Based on the open loop transfer function,the PI controller is designed to control the output voltage.Finally,the simulation model of modular multilevel DC transformer is built in MATLAB/Simulink.The simulation result shows that the output voltage of the DC transformer is stable with designed PI controller.