An adaptive droop-based control strategy for fuel cell-battery hybrid energy storage system to support primary frequency in stand-alone microgrids

Abstract

Abstract Frequency fluctuations arising from high penetration of renewable energy resources in stand-alone microgrids (SAMGs) compromise their stable operation. To this end, battery energy storages are widely used to regulate frequency fluctuations in SAMGs. However, the battery should be charged and discharged constantly to compensate power imbalances which dramatically reduce its lifetime. Moreover, to support primary frequency, the sudden and deep power changes of battery are inevitable which accelerate its lifetime reduction. To addresses this issue, in this paper a hybrid energy storage system including fuel cell (FC) as main and battery as complementary power source is introduced. In the proposed hybrid energy storage, the utilization factor concept and the flow rate of hydrogen fuel are incorporated to enhance dynamic response of the FC. Accordingly, the FC achieves the ability to compensate fast power transients and therefore, coordinates with the battery using a dynamic droop-based control strategy. The aim of the control strategy is to prioritize power sharing between FC and battery of the hybrid energy storage such a way that the primary frequency in the SAMG is effectively supported. The performance of the proposed control strategy for the FC-battery hybrid energy storage system is evaluated using digital time domain simulation studies in MATLAB /SIMULINK software environment. The simulation results indicate that the proposed dynamic droop-based control strategy leads to a proper power sharing between FC and battery, forming a complementary hybrid energy storage system which has better primary frequency support than the battery in SAMGs.