Load Sharing and Arrangement through an Effective Utilization of SOFC/Super-capacitor/Battery in a Hybrid Power System

Abstract

Solid oxide fuel cell (SOFC) provides several benefits such as high efficiency, modularity, quiet operation and cogeneration alternatives. Nevertheless, the main weakness in SOFC-based power plant has the slow dynamic response during transient situations in peak demand since this problem can be addressed by using complementary system such as a super-capacitor (SC). This paper provides an optimal load sharing and arrangement strategy (LSAS) for a hybrid power system which combines a SOFC stack, a SC module and a battery bank that support local grid. According to LSAS, the SOFC is the primary power source. The SC module is utilized as a backup and complement device to take care of the load following problems of SOFC during transient. The battery bank is added as a high energy density and/or backup device to stabilize the DC bus voltage, while an electrolyzer (ELYZ) is used as a dump load during surplus power. The LSAS operates in two layers. The external layer accomplished the overall power management system. Depending upon load demand, this layer generates references to the internal layer. The internal layer controls the individual subsystems, i.e., SOFC, ELYZ, SC and battery according to the references coming from the external layer. A complete MATLAB/Simulink model has been established to check the performance of the proposed system for the real load conditions. Simulation results show the effectiveness of the proposed system in terms of power transfer, load tracking and grid stability.