Active Disturbance Rejection Control Based on an Improved Topology Strategy and Padé Approximation in LCL-Filtered Photovoltaic Grid-Connected Inverters

Although the smart grid, equipped with situational awareness and contextual understanding, represents the future of energy management and offers flexible, extensible, and adaptable intelligent grid services, it still shares similarities with traditional systems. For instance, the control performance of the DC (Direct Current) bus voltage will continue to be adversely affected by various uncertain interference factors in the future smart grid. In practice, this often leads to challenges, as inverters typically operate at high frequencies when connected to the grid. Therefore, the ability to effectively suppress fluctuations in DC bus voltage and mitigate their impact, as well as enhance the dynamic performance of the system, will be one of the key indicators for evaluating the upcoming smart grid. Consequently, this paper proposes DC-link Voltage Control using a two-stage Extended State Observer (ESO)-Cascaded Topology Structure in an LCL (Inductive-Capacitive-Inductive) Filtered Photovoltaic Grid-Connected Inverter based on Padé Approximation and Improved Active Disturbance Rejection Control. Results from both simulations and experiments demonstrate that the proposed algorithm performs effectively and is capable of suppressing fluctuations.