Improving the Transient Response of Hybrid Energy Storage System for Voltage Stability in DC Microgrids Using an Autonomous Control Strategy

In renewable microgrid systems, energy storage system (ESS) plays an important role, as an energy buffer, to stabilize the system by compensating the demand-generation mismatch. Battery energy storage system serves as a decisive and critical component. However, due to low power density and consequently slow dynamic response the lifetime of BESS is observably reduced due to high current stress, specifically experienced during abrupt/transient power variations. Hence, hybridization with supercapacitor storage system is conferred. Additionally, the controllers designed for energy storage systems should substantially respond for compensating the transient requirement of the system. In this article, we propose a decoupled control strategy for batteries and supercapacitors based on k - Type compensators and a nonlinear PI controller (NPIC) respectively. The formulated control design is tested for voltage regulation in a standalone microgrid. Furthermore, a comparative analysis is presented with benchmark low-pass-filter (LPF) based controller. The results obtained shows the proposed control technique possess a faster response with improved voltage regulation capabilities. For the test system regulated at 48 V for various abrupt load-generation various case studies presented, the proposed methodology maintains a significantly reduced voltage deviation between 47 V - 51 V in contrast to 45 V - 56 V observed in the LPF methodology. Furthermore, the complexity is simpler in comparison to LPF based control strategy and a comparative obviation of additional sensing devices is achieved, that inherently reduces the detrimental effect on ESS response during transient condition.