Modeling and Sizing of Hybrid Energy Storage System for Virtual Synchronous Generator

Renewable energy sources (RESs) play a major role in the modern power system to meet the increasing demand and to reduce environmental effects. But they are unable to perform frequency regulation resulting in higher frequency deviations with higher integration of RESs. To overcome this problem power converters are modified as synchronous generators using proper control mechanisms called as Virtual Synchronous Generators (VSGs). Energy Storage Systems are required to absorb and deliver excess energy. We have used a battery/ultracapacitor hybrid energy storage system (HESS) to achieve this. Power allocation for the two storage units is modeled such that fast-varying power fluctuations are compensated by ultracapacitor (UC) and low frequency power fluctuations are compensated by the battery. This is achieved by emulating the inertia by the ultracapacitor and emulating reheat turbine model, droop control etc. by the battery. Some research produces the modelling details of HESS but not the sizing considering required performance. To fulfil this research gap sizing of the HESS is presented through this research paper. Eventually, the proposed system was implemented and simulated in MATLAB Simulink. Results were analyzed to verify the proposed concept for different cases to prove that it gives outputs similar to conventional synchronous generator.