Power Allocation and Unit Configuration Strategy for Hybrid Energy Storage of Supercapacitors

In view of the problems of random power allocation and difficulty in determining unit configuration parameters for the application of HESS in the field of frequency regulation, this paper focuses on the power allocation and unit configuration strategy of Hybrid Energy Storage System (HESS) composed of supercapacitors and lithium-ion batteries. In this paper, a virtual synchronous generator (VSG) control method is used to simulate the rotational and excitation characteristics of a synchronous motor in the power conversion system (PCS) of the HESS in order to cope with grid frequency deviation caused by load power fluctuation and provide the converter with inertia and damping characteristics. On this basis, a method of HESS power allocation is proposed to adjust the virtual moment of inertia according to the power fluctuations at different frequencies in order to suppress the high-frequency power perturbation and the medium- and low-frequency power perturbation of the hybrid energy storage, and to realize the coordination between supercapacitors and lithium-ion batteries. In order to realize the optimal configuration of HESS units, this paper analyzes the influence of different inertia constants and damping coefficients on the physical constraint mechanism of energy storage, and designs the optimal capacity and power parameters of energy storage units under different damping ratios to realize the optimal configuration of HESS units. In this paper, Matlab/Simulink simulation analysis is used to verify the control strategy and the parameter configuration method of the energy storage unit proposed in this paper. The simulation results show that the crossover frequency control strategy of the hybrid energy storage virtual synchronous machine can realize the coordination between the supercapacitor and the lithiumion battery, and the parameter configuration of the HESS unit is accurate and reasonable, which can meet the frequency regulation performance requirements.