模块化多电平型高压DC/DC变换器的研究

模块化多电平型(modular multilevel)高压DC/DC变换器采用模块化结构,能够很容易通过子模块串联的方法得到较高的电压和功率等级,适用于高压大功率直流变压场合。该DC/DC变换器采用由两个模块化多电平换流器MMC(modular multilevel converter)组成"面对面相连"的结构,其本身具有直流侧故障保护的功能,无需采用直流断路器进行保护,变压器的存在可实现了电气隔离。目前针对此拓扑结构的研究尚处于起步阶段,其基本运行方式仍是研究的重点和难点。本文具体描述了模块化多电平型高压DC/DC变换器的拓扑结构,并且分析了其本身具有直流侧故障保护功能的作用机理。在此基础上,从调制策略、电容电压平衡策略及功率控制策略三方面对控制器进行设计。最后,通过建立仿真模型和搭建单相结构的实验平台,验证了所提基本运行方式的有效性。

Research on Modular Multilevel High Voltage DC/DC Converter

Due to the modular configuration, modular multilevel high voltage DC/DC converter can obtain high voltage level and high power level by connecting submodules in series. The converter is suitable for high voltage and high power DC transformer applications. The DC/DC con-verter is a front to front structure constituting of two modular multilevel converters (MMC). Because of its inherent DC fault isolation capacity, the DC/DC converter does not need a DC circuit breaker. Besides, the transformer between the two MMCs can support electric isolation. At present, studies based on the DC/DC topology structure are still at an initial stage. The basic operation mode has become the difficulty and the key point of the research.This paper detailedly describes the topology structure of modular multilevel high voltage DC/DC converter, and ana-lyzes of the working principle of its inherent DC fault isolation capacity. Based on the topology, develops a controller according to modulation strategies, submodule capacitor voltages balancing methods and power control strategies. Finally, a single phase DC/DC converter simulation model has been established in Simulink of MATLAB. An experiment of prototype has been designed and built to verify the validity of the basic operation mode and the power control method of the DC/DC converter.