Hybrid Energy Storage Capacity Configuration of the Isolated DC Microgrid Based on Improved VMD and Decomposition Domain

For the bus voltage volatility and hybrid energy storage capacity optimization caused by special loads in isolated DC microgrid, a hybrid energy storage capacity configuration of the DC microgrid based on improved variational mode decomposition (VMD) and decomposition domain is proposed. The strategy adopts an improved VMD for the hybrid energy storage power, which adaptively optimizes the parameters K and α of VMD using the Northern Goshawk Optimization (NGO) algorithm and allocates the power decomposed by frequency to hybrid energy storage. Hilbert transform is used to find out the partition of low frequency, intermediate frequency band and high frequency, where the low-frequency part and high-frequency part are provided by the battery and supercapacitor (SC) respectively, and the intermediate frequency domain is shared by the battery and supercapacitor. Subsequently, a capacity optimization model of the hybrid energy storage system with the minimum annual average configuration cost of the energy storage system as the objective function is established and solved to obtain the energy storage capacity configuration scheme. Simulation and analysis are carried out on Matlab/Simulink to verify the effectiveness and economy of the proposed strategy.