Cooperative Control Strategy of Multiple DC Electric Springs in DC Microgrid Based on Model Prediction

For the problem of voltage quality degradation and low inertia of the power system caused by the high penetration of renewable energy access to the power grid and load switching, the adaptability of the traditional inertial control decreases with the expansion of the power grid scale. Therefore, a coordinated voltage control strategy of DC microgrid with multiple DCESs (DC electric springs, DCESs) is proposed. Firstly, the distributed consensus algorithm is used to exchange the local information and the adjacent information through the sparse communication network, offering the global average bus voltage. The integration link is introduced to improve the convergence of classical consensus methods. Considering the sudden changes of voltage caused by the system switching and the source-side power fluctuation, a predictive model is built based on the bidirectional full bridge DC/DC converter in the DCESs in order that each DCES can adaptively offer the optimal virtual capacitance value according to the power fluctuation state of the system, smoothing the dynamic response process of DC bus voltage. The convergence and stability of the system voltage are analyzed. Finally, the effectiveness of the model is verified through the MATLAB/Simulink in three aspects, i.e. the voltage quality, the plug-and-play performance, and the system inertia, under the random fluctuating loads and the actual photovoltaic scenarios. The proposed control strategy has a better dynamic response ability while ensuring the stable system voltage. © 2024 Power System Technology Press. All rights reserved.