Abstract In this paper, a new control approach using an optimal linear control with prescribed degree of stability for modular multi-level converters (MMC) is presented and analyzed. The proposed controller relies on a linear quadratic regulator with integral action which brings the ability of state variable reference tracking for modular multi-level converters. Since MMC is a complex system with several state variables, a unified control system design for this system is vital. The proposed controller of this study is designed to obtain wider stability margin thanks to the implementation of prescribed degree of stability concept to minimize the quadratic performance index of the control structure. By means of this method, the poles of the closed-loop system will be shifted to the desired places in the left half side of the S-plane. The main advantages of this control strategy compared to previous methods are that it will be possible to control the state of energy for each phase separately, while there will be superior tolerance to nonlinearities and the enhanced stability margin with less sensitivity to plant-parameter variations. The performance of the designed controller is verified through MATLABTM simulations (The MathWorks, Natick, MA, USA) with the nonlinear model of MMC.

中文翻译：

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具有规定稳定性的模块化多电平转换器的最优线性控制

摘要 在本文中，提出并分析了一种新的控制方法，该方法使用具有规定稳定性的模块化多电平转换器 (MMC) 的最优线性控制。所提出的控制器依赖于具有积分作用的线性二次调节器，这为模块化多电平转换器带来了状态变量参考跟踪的能力。由于 MMC 是一个具有多个状态变量的复杂系统，因此该系统的统一控制系统设计至关重要。由于实施了规定的稳定度概念，以最小化控制结构的二次性能指数，本研究中提出的控制器旨在获得更宽的稳定裕度。通过这种方法，闭环系统的极点将移动到 S 平面左半边所需的位置。与以前的方法相比，这种控制策略的主要优点是可以分别控制每个相位的能量状态，同时对非线性具有更高的耐受性，并且稳定性裕度更高，对设备参数变化的敏感性更低。设计控制器的性能通过 MATLABTM 仿真（The MathWorks，Natick，MA，USA）与 MMC 的非线性模型进行验证。