模块化多电平换流器电容电压优化均衡法研究

An improved capacitor voltage balancing strategy of modular multilevel converter

在模块化多电平换流器的传统子模块电容电压排序均衡方法中,算法排序在子模块数目较多的情况下存在运算量大、开关动作频繁等缺陷。因此,为了减少子模块排序运算量,降低开关频率,该文提出了基于改进归并排序的 MMC电容电压均衡法。首先,对引入的归并排序算法均衡工作机理展开了简要叙述,在此基础上,针对算法单次排序比较次数高对算法进行优化处理,进而减少了单次排序运算过程中算法所需的比较次数;并立足于简化后的归并排序算法,引入子模块之间的最大电压偏差比例值,实现降低排序频率与开关损耗,从而形成了具有优越性能的改进归并排序均压控制方法。最后,运用 Matlab/Simulink仿真平台搭建了模块化多电平换流器的直流侧电容电压均压控制模型验证所提改进归并排序均压方法的可行性与有效性。

In the traditional sorting equalization method of sub-module capacitor voltage for the modular multi-level converter,the algorithm sorting has many disadvantages such as the large calculation and frequent switching action when the number of sub-modules is large.Therefore,an MMC capacitor voltage equalization method is proposed on the basis of the improved merge sorting in order to reduce the sub-module sorting operation and also reduce the switching frequency.Firstly,this paper briefly introduces the equilibrium working mechanism of the merged sorting algorithm.Then,the algorithm for the single-order sorting comparison is optimized to reduce the times of comparison in the single sorting process.Based on the simplified merge sort algorithm,the maximum voltage deviation ratio among sub-modules is introduced to reduce the sorting frequency and switching loss.Thus an improved control method based on the merge sorting equalization is then formed with superior performance.Finally,the feasibility and effectiveness of modified merging and equalizing method for capacitor voltage equalization control model at the DC-side of modular multilevel converter are verified by using the Matlab/Simulink simulation platform.