基于一致渐近稳定观测器的模块化多电平变流器控制系统设计

为了实现模块化多电平变流器(MMC)各模块之间电容电压均衡，减少电压传感器数量，设计非线性的降维状态观测器，并提出基于该观测器的系统控制方法.依据三相MMC拓扑结构，以三相环流、交流输出电流和所有模块电容电压为状态变量，建立状态空间模型. 结合模型，提出观测器的设计方法，该观测器通过测量MMC电路中6个桥臂电流和6个桥臂投入模块总电压，结合开关信号观测得到各模块电容电压. 利用无源理论和持续充分激励条件，证明在载波移相调制策略和最近电平调制策略下，观测器误差模型是一致渐近稳定的. 以该观测器为基础，设计MMC功率电流双闭环控制器. 通过搭建的仿真模型验证所设计观测器的观测值能够准确跟踪实际值，系统鲁棒性和动态性能较好.

Design of modular multilevel converter control system based on uniformly asymptotically stable observer

A non-linear reduced-order state observer was designed and a system control method based on the observer was proposed, in order to achieve capacitive voltage balance among modules of the modular multilevel converter (MMC) and reduce the number of voltage sensors. According to the three-phase MMC topology, a state-space model was established with three-phase circulating current, alternating output currents and capacitive voltages of all modules as state variables. Combining the model, an observer design method was proposed. The observer measured six bridge arm currents and six bridge voltages in the MMC circuit, and combined switching signals to obtain capacitance voltage of each module. Using the passivity theory and the persistently and sufficiently exciting condition, it is proved that the observer error model is uniformly asymptotically stable under the carrier phase shift modulation strategy and the nearest level modulation strategy. A MMC power and current double closed-loop controller was designed based on the observer. Simulations show that the observed values of the designed observer can accurately track the actual values, and the system has good robustness and dynamic performance.