配电网中的电力电子变压器研究

A power electronic transformer applied to distribution system

针对电力电子变压器(PET)在配电网中的应用,采用三级拓扑结构,提出一种新方案。输入级高压为三电平整流电路,以降低元器件耐压等级,采用无功功率和高压整流输出电压闭环,以实现无功可调和稳定高压侧的直流电压;隔离级采用高频变压器,其高压侧为三电平拓扑,低压侧为二极管整流,实现从高压到低压的dc/dc变换和隔离目的,而且通过输出电压闭环控制确保低压直流侧电压恒定;输出级低压为二电平三相逆变电路,采用输出电压闭环以控制期望的电压。采用三级控制分别对应三级电路,以实现系统输入电流正弦、负荷侧供电电压恒定,灵活传输有功,向电网注入无功等功能。详细介绍了所提出的PET系统各部分工作原理,并基于Matlab/Simulink建立了仿真模型,以DSP TMS320F2812为基础构建了实验平台,仿真和实验结果验证了该PET系统可行、有效。

The paper proposes a new power electronic transformer （PET） for the application in the distribution system, which adopts the three-stage circuit topology. The input stage uses three-phase three-level PWM rectifier to reduce the voltage stress rating of components, where the reactive power and high-voltage de-link voltage closed-loop controls are adopted to adjust the reactive power and stabilize the de-link voltage at the high-voltage side. The isolation stage employs the high-voltage frequency converter which adopts three-level topology at high-voltage side and diode rectification at low-voltage side to realize de/de conversion and isolation from the high-voltage side to the low-voltage side, furthermore, the constant low de voltage is maintained by using output voltage closed-loop control. The output stage adopts three-phase two-level inverter at low voltage side which outputs the desired voltage and power to the load through the output voltage closed-loop control. With the three-stage control strategy responding to three-stage circuit, it can make the PET＇s input currents sinusoidal and the output voltages of load side constant, real power transmission flexible, and reactive power injected into power grid. The working principle of each component of the proposed PET system is explained in detail and the simulation model is established based on Matlab/Simulink, and this system is also implemented in laboratory based on DSP TMS320F2812. The simulation and experimental results verify the feasibility and validity of the proposed PET system.