模块化多电平换流器电容电压新型优化平衡方法

A Novel Optimized Capacitor Voltage Balancing Method for Modular Multilevel Converter

针对传统电容电压平衡方法计算量大、器件开关频率较高的问题,提出一种适用于MMC-HVDC系统的直流电容电压新型优化平衡方法。首先分析了传统排序算法存在的问题并给出其优化方法,提出采用随机选择算法进行MMC均压排序,以大幅度地优化排序效率。在此基础上,提出基于随机选择算法的电容电压优化平衡方法,根据引入的重新排序判据,使MMC控制器在电容电压变化不大的控制周期避免排序并保持触发脉冲不变,在需要排序的控制周期采用效率更高的随机选择算法排序,从而既进一步减少了控制器运算量,又能有效降低换流阀损耗。最后通过Matlab/Simulink仿真验证了所提优化平衡方法的可行性和有效性。

Aiming at problem of large calculation amount and high switching frequency existing in traditional capacitor voltage balancing method, a novel balancing optimization method for DC capacitor voltage in MMC-HVDC system is proposed. Firstly, existing problems in traditional sorting algorithm are analyzed, and the optimization method is given. Randomized selection algorithm is proposed for MMC voltage balancing, able to greatly improve sorting efficiency. On this basis, capacitor voltage balance optimization method is proposed, making MMC controller avoid sorting and maintaining trigger pulse unchanged in control cycle when capacitance voltages experiences small change. Capacitor voltages are sorted with randomized selection algorithm with higher efficiency according to introduced renewed sort criterion. Thus calculation amount of controller can be further decreased, and device loss of converter valve can be effectively reduced. Finally, feasibility and effectiveness of the proposed optimization method is verified with Matlab/Simulink simulation.