不平衡电网电压下MMC-UPQC的无源超螺旋二阶滑模控制策略

基于模块化多电平换流器(modular multilevel converter,MMC)的统一电能质量调节器(unified power quality conditioner,UPQC)在电网电压不平衡时,采用传统控制方法存在补偿效率和精确性较低的问题.针对这一情况,提出一种无源超螺旋二阶滑模控制策略.首先,基于MMC-UPQC的数学模型和无源控制理论,设计不平衡电网电压下基于欧拉-拉格朗日模型的正负序无源控制器;然后,加入超螺旋二阶滑模控制对无源控制器进行改善,抑制常规滑模存在的抖振,并解决无源控制对系统精度要求高的问题,提高系统的响应速度、补偿精度和抗干扰能力,提升系统的整体性能;最后,在Matlab/Simulink平台上进行仿真,并与PI控制和单独的无源控制对比,仿真结果验证了所提无源超螺旋二阶滑模控制策略的有效性和优越性.

Passive super-twisting second-order sliding mode control strategy for MMC-UPQC under unbalanced grid voltage

When the voltage of the grid is unbalanced, it is difficult to use traditional control methods for the unified power quality conditioner(UPQC) of a modular multilevel converter(MMC) to comprehensively control the power quality, and the compensation efficiency and accuracy are low. To solve these problems, a passive super-twisting second-order sliding mode control strategy is proposed. Firstly, based on the mathematical model of the MMC-UPQC and passive control theory, a positive and negative sequence passive controller based on the Euler-Lagrange model under unbalanced power grid voltage is designed. Then, super-twisting second-order sliding mode control is added to improve the passive controller, which suppresses chattering of the conventional sliding mode, and solves the problem that passive control requires high precision of the system. It improves the response speed, compensation accuracy and anti-interference ability of the system, and improves the overall performance of the system. Finally, the simulation is carried out on the Matlab/Simulink platform and compared with PI control and independent passive control. Simulation results verify the effectiveness and superiority of the proposed passive super-twisting second-order sliding mode control strategy.