模块化多电平变流器的直接功率控制仿真研究

新型模块化多电平变流器(modular multilevelconverter,MMC)通常采用双闭环矢量控制策略,针对该方法存在的需调整控制参数较多、动态响应慢等问题,研究MMC的直接功率控制策略及电容电压平衡方法。首先,将现有的桥臂模块电压排序法与参考信号中叠加平均值控制量的方法进行综合,控制电容电压平衡;然后,在桥臂内电容电压相互平衡的基础上,利用双闭环PI调节器控制桥臂间各电容电压保持一致并跟踪给定,使电压波动范围明显减小,提高变流器输出波形质量;最后,将变流器虚拟磁链直接功率控制策略应用于MMC。研究该种拓扑结构下的功率估计方法,并利用Matlab对所设计系统进行仿真验证,结果表明所提控制方法正确、有效。

Simulation Research on Direct Power Control of Modular Multilevel Converters

The strategy of double closed-loop vector control is commonly used for new modular multilevel converter(MMC),but this control method has the problems of too much parameters needed to be adjusted and dynamic response is unsatisfactory and so on.For these,direct power control strategy of MMC and the strategy of balancing capacitor voltage were researched.First,the method of sorting arm module voltage and adding average control signals to reference were combined.Then,the double-loop proportion regulators were used to make capacitor voltage be consistent and track the given value which made the fluctuation range of capacitor voltage to be significantly reduced.It improved the quality of converter output waveforms.Finally,the strategy of virtual flux direct power control was used for MMC.Research focused on the method of power estimation for this kind of topology.Finally,simulation research of the designed system was implemented with Matlab.The results show that the proposed methods are correct and effective.