不平衡电网下MMC-UPFC的反演-滑模控制策略

Backstepping-based sliding-mode control strategy of MMC-UPFC under unbalanced power grid

针对模块化多电平变流器(MMC)-统一潮流控制器(UPFC)采用的控制方法存在的问题,本文提出了一种基于MMC-UPFC的反演控制(BSC)与滑模控制(SMC)组合而成的反演-滑模控制(BSC-SMC)非线性控制策略,这种控制策略既保留了SMC的抗干扰能力强等性能,也兼具BSC响应速度快等优点。首先,根据MMC-UPFC的拓扑结构,建立并联侧MMC变换器、串联侧MMC变换器的数学模型;其次,在不平衡条件下进行了正、负序分解,并设计了MMC-UPFC在不平衡条件下BSC-SMC控制器,并证明了控制系统的稳定性;最后,在MATLAB/Simulink软件平台搭建MMC-UPFC仿真模型进行仿真验证,通过把本文所提BSC-SMC控制策略与PID控制策略在接收端电源电压单相跌落、串联侧注入电压两种不同工况下进行了仿真比较,验证了BSC-SMC控制策略除具有SMC控制策略的抗扰性强特点外,还同时具有BSC控制策略的响应速度快和超调量小特点,且本文控制系统的稳定性更强、鲁棒性更好,从而验证了本文所提BSC-SMC控制策略的有效性和优越性。

In response to the problems of the control method used in modular multilevel converter(MMC)-unified power flow controller(UPFC),a nonlinear control strategy combining back stepping control(BSC)and sliding mode control(SMC)based on MMC-UPFC is proposed in this paper.This control strategy not only retains the strong anti-interference ability of SMC,but also has the advantages of fast response speed of BSC.Firstly,according to the topology of MMC-UPFC,the mathematical models for the parallel-side and the series-side of MMC converter is established.Secondly,positive and negative sequence decomposition is carried out under unbalanced conditions,and the BSC-SMC controller for MMC-UPFC under unbalanced conditions is designed,and the stability of the control system is proved.Finally,a MMC-UPFC simulation model is established on the MATLAB/Simulink software platform for simulation verification,by comparing the BSC-SMC control strategy with PID control strategy under two different operating conditions:Single-phase drop of power supply voltage at the receiving end and injection voltage on the series-side of MMC,the proposed BSC-SMC control strategy not only has the strong anti-interference characteristics of SMC control strategy,but also has the characteristics of fast response speed and small overshoot of BSC control strategy,the stability and robustness of the control system are stronger,the effectiveness and superiority of BSC-SMC control strategy is verified.