基于等效开关电路模型的三重化线电压级联型变换器控制

The Triple Line-voltage Cascaded Converter Control Based on the Equivalent Switch Circuit Model

线电压级联型功率变换器是一种以传统两电平六开关电压源型变换器为单元,通过线电压级联方式构成的多重化变换器。由于其具有易于模块化,扩展性强,所需隔离直流电源数少等优点,因此更适合作为网侧变换器用于风力发电系统。通过分析其工作原理与结构特点,提出一种载波移相空间矢量脉宽调制(space vector pulse width modulation,SVPWM)策略;并建立统一的等效开关电路模型;通过分析传统的采用集成控制思想所设计的控制系统的不足,从而提出一种改进的控制策略。该策略不仅具备集成控制的优点,且通过增加均压补偿控制环及负序电流抑制环,实现了对多重化变换器中各组成单元传输功率的控制,解决了因各单元传输功率不均衡而造成的直流侧电容电压不均等与交流侧三相线电流不对称等问题。实验结果表明了所提出的控制策略的正确性与有效性。

The multiple line-voltage cascaded power converter is composed of conventional two-level six-switch voltage source converters which are connected by line-voltage cascading method. It is applicable to wind energy conversion system as a grid-side converter, due to its easy modularization, strong scalability, and less isolated dc source requirement. In the paper, a kind of carrier phase-shifting SVPWM was proposed and the uniform equivalent circuit model was built by analyzing the operation principle of the converter. And then the paper proposed an improved control strategy through analyzing the inadequacy of the control system only based on the integrated control theory. The control strategy has the merit of integrated control theory, and meanwhile, it can realize the independent adjustment of the transmission power of each VSC and the depression of the negative components of line-currents. The availability of the proposed control strategy is proved by the experimental results.