School of Automation and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Received: March 23, 2023 Accepted: May 6, 2023 Publication Date: June 13, 2023
Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.
Aiming at the voltage fluctuation of DC microgrid bus caused by the power fluctuation of distributed power supply and switching of constant power load (CPL), this paper proposes a model predictive control (MPC) strategy with nonlinear observer, which is applied to bidirectional DC-DC converter for energy storage. First, a small disturbance model of the system with converter control is established, the influence of photovoltaic unit and constant power load on the system stability is analyzed, and then the objective function is constructed according to the bidirectional DC-DC converter, the optimization equation is established and the optimal control rate is obtained. Second, a nonlinear state observer is established and a composite control strategy is designed to adjust the charging and discharging process of the battery, realize the power balance between the source and load of the DC microgrid, and ensure the stability of the DC microgrid. Finally, a simulation model is built in Simulink and the results are analyzed, and the simulation results show that the proposed control strategy has good dynamics and robustness compared with the traditional double-closed-loop PI control when the constant power load is frequently switched and the photovoltaic power generation power fluctuates.
Keywords: DC-DC bidirectional converter; Constant power load; Model prediction; Nonlinear observer
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