基于快速排序算法的模块化多电平换流器电容电压均衡策略*

模块化多电平换流器(Modular Multilevel Converter,MMC)在模块数较多时,传统算法实现电压均衡将占据大量计算资源,影响系统的运行速度甚至动态响应特性。为此,提出一种基于快速排序算法的电容电压均衡策略。采用分治技术,基于比较、划分的思想实现模块电容电压排序,根据电容能量变化选择触发模块实现电容电压均衡。推导快速排序算法的时间复杂度和排序效率,分析算法对系统特性的影响,研究不同情况下基于快速排序算法的均衡策略的适应性。采用DSP控制器TMS320F28335测量算法的执行时间并在PSCAD/EMTDC中搭建MMC仿真模型,验证了基于快速排序算法的电容电压均衡策略的有效性和正确性,表明快速排序算法可以有效降低排序计算量,减少仿真时间,并且随着模块数的增加优势愈加明显。

A capacitor voltage balancing strategy based on quicksort algorithm for modular multilevel converter

Excessive computation is required to realize the voltage equalization using traditional algorithm,in the controller of modular multilevel converter (MMC) when existing large amount of sub-modules per arm,this will also result in a decline in the running speed of the system and even affect dynamic performance.In order to solve this problem,a capacitor voltage balancing strategy based on the quicksort algorithm is proposed.Through dividing and conquering technology,the modular capacitor voltage sequences are realized based on comparison and division.The trigger modules put into operation are decided by capacitor energy variation to realize voltage balanced.Time complexity and sort efficiency are deduced and the effect on system performance is analyzed.The adaptability of the strategy under different circumstances is researched.The DSP controller TMS320F28335 is used to measure execution time of algorithms.The MMC model is set up on the PSCAD/EMTDC and the efficiency and correctness of the voltage balancing strategy based on quicksort are proved.The simulation results show that the quicksort algorithm can reduce computation time,lower the requirement of the hardware and its advantages become more obvious with the increasement of sub-module.