模块化多电平变流器(Modular Multilevel Converter,MMC)日益广泛应用于高压直流输电(High Voltage Direct Current,HVDC)技术中,但MMC的多变量、强非线性特性,使其稳定控制问题成为拓展应用的瓶颈所在.从能量耗散和环流抑制的角度出发,基于MMC动态数学模型,直接在abc静止坐标系下建立双线性Lagrange方程.以均衡子模块电容电压为目标设计能量函数,结合PI控制简单架构,提出新型的无源性PI控制方法,使系统沿Lagrange积分最小化轨迹移动.在满足系统全局渐进稳定的前提下,实现期望轨迹的快速跟踪.针对MMC-HVDC环流产生的变流器损耗增加问题,设计MMC环流控制器,获得无源性PI控制环节桥臂电压补偿量,实现电容电压平稳和环流有效抑制.仿真结果表明所提出的方法具有响应快速、稳定性高、鲁棒性强的特点.%Modular multilevel converter (MMC) is widely used in high voltage direct current (HVDC). However, the multivariate and strongly nonlinear characteristics of MMC make the stable control problem become the key to their application. From the perspective of energy dissipation and circulating current suppression, the bilinear Lagrange equation in a-b-c synchronous reference frame is developed directly on the basis of the dynamic mathematical model of MMC to analyze strictly passive features of the system. Energy function for balancing capacitor voltage is designed. Combining the simple architecture of PI control, a novel passivity-based PI control method is proposed to ensure the whole system along Lagrange integration minimization trajectory. The desired trajectory fast tracking can be realized under the premise of global asymptotic stability. For the increase of converter losses generated by the circulation of MMC-HVDC, this paper designs circulating current controller of MMC to obtain arm voltage compensation in passivity-based PI control and achieves that the capacitor voltage comes to smooth and circulation is effectively suppressed. The simulation results show that the proposed method has the advantages of quick response, high stability and strong robustness.
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