中文摘要：

MMC的控制策略通常采用双闭环PI控制,而PI环节参数设计没有固定设置方法,调节不易。文中提出了一种基于线性二次调节（linear quadratic regulator,LQR）理论的控制策略,该策略具有参数易设定、反应迅速、自适应性强等优点,将LQR控制取代双闭环中的内环控制。为了消除LQR控制中的稳态误差,采用在LQR控制的基础上加入积分控制的线性二次型最优控制（LQRI）。最后在MALAB/Simulink构建了MMC-HVDC仿真模型,并对双闭环PI和LQRI控制性能对比,验证了LQRI控制方法可行性和优越性。

英文摘要：

The control strategy of modular muhilevel converter （MMC） generally adopts double closed loops PI control, while there is no fixed way to design the PI parameters and the adjustment is difficult. This paper presents a control strategy which is based on linear quadratic optimal （LQR）theory. The strategy has such advantages as simple parameters, quick response and strong adaptability etc. The LQR control is used to replace the inner ring of the double closed loop control. In order to eliminate the steady-state errors of LQR control, the integral control is added to the LQR, constitute the linear quadratic optimal control strategy （LQRI）. Finally, the MMC-HVDC systems are simulated in MALAB/Simulink, the control performances of the LQRI controller are compared to the double closed loops PI control. The simulation results validate the feasibility and superiority of the proposed control strategy.