逐级独立优化的MMC模型预测控制

Stagewise Independent Optimization Model Predictive Control of Modular Multilevel Converters

模型预测控制(MPC)方法应用于模块化多电平换流器(MMC)系统时存在计算负担大、配置加权因子困难等难题。在分析MMC离散数学模型的基础上,利用系统输出电平作为控制项,提出了简化有限控制集的无加权因子的逐级独立优化模型预测控制策略。通过设计独立目标函数来逐级实现交流输出跟踪以及环流抑制的控制目标,并在环流抑制环节中引入误差补偿模块以抵偿桥臂误差电压。此外,提出的基于BFPRT算法的子模块电容电压均衡策略能够在保证电容电压控制精度的同时,避免在每个控制周期对桥臂子模块电压进行完全排序,从而提高了系统运行速度。最后MATLAB/Simulink仿真结果和MMC样机实验结果均验证了所提方法的可行性、有效性以及出色的计算效率。

There are several problems in the application of the available model predictive control(MPC) method to modular multilevel converter(MMC) system, such as high calculational burden and difficulty in configuring weighting factors. Based on an analysis of the MMC discrete mathematical model, using the output voltage level as the control set, a model predictive control method of stagewise independent optimization with a simplified finite control set and without weighting factors is proposed. The control objectives of tracking the alternating current and suppressing the circulating current are achieved by establishing independent objective functions, and the error compensation module is introduced in the circulating current suppression section to compensate for the arm error voltage. Besides, the capacitor voltage of submodule balancing method based on the BFPRT algorithm is proposed for avoiding the complete sorting of the arm submodule voltages in each control cycle without reducing the control accuracy. Finally, the simulation results of Matlab/Simulink and the experimental results of a MMC prototype both verify the feasibility, effectiveness and excellent calculation efficiency of the proposed method.