Comprehensive Control Strategy Considering Hybrid Energy Storage for Primary Frequency Modulation

Abstract

The increase in the number of new energy sources connected to the grid has made it difficult for power systems to regulate frequencies. Although battery energy storage can alleviate this problem, battery cycle lives are short, so hybrid energy storage is introduced to assist grid frequency modulation. In this paper, a hybrid energy storage system composed of battery energy storage and super-capacitor energy storage systems was studied, and a comprehensive control strategy was proposed. Firstly, by setting the frequency dead zone of the energy storage to be smaller than that of the thermal power unit, the frequent action of the thermal power unit was avoided. Secondly, virtual inertial control and virtual droop control were effectively combined. Then, the state of charge of battery energy storage and super-capacitor energy storage was considered so that they could operate in harmony. Finally, a simulation model was built in MATLAB/SIMULINK, and case studies were conducted to verify the proposed control strategy. Results showed that the proposed control strategy could effectively reduce the frequency deviation of the power grid, and maintain the state of charge, reduce the number of operated batteries, and improve cycle life.

Keywords

• hybrid energy storage
• primary frequency modulation
• virtual inertial control
• virtual droop control
• state of charge