基于ADRC的柔直系统交流侧不对称故障穿越控制OA

When a multi-terminal flexible DC transmission system based on a modular multilevel converter is connected to the grid,If the system fails,it will prevent the normal transmission of power and thus threaten its safety,so how to ensure its continued operation in the event of a system failure has become a hot topic of research today.In this thesis,a control method combining negative sequence current suppression and DC voltage fluctuation suppression is studied for asymmetric faults occurring on the AC side of flexible DC transmission systems.By deriving the AC side expression of the MMC under asymmetric faults,the corresponding negative sequence current controller is designed to achieve the suppression of negative sequence currents.An active disturbance rejection controller has been introduced to control the DC voltage in response to the diametrical pulsations generated by asymmetric faults,Effective suppression of DC voltage fluctuations is achieved by adding the DC voltage diphasic component to the extended state observer of the active disturbance rejection controller.