Load-following active power filter for a solid oxide fuel cell supported load

While the integration of base-load fuel cells into the built environment is expected to provide numerous benefits to the user, the steady-state and dynamic behavior of these stationary fuel cell systems can produce an undesirable impact on the grid distribution circuit at the point of connection. In the present paper, a load-following active power filter (LFAPF) is proposed to mitigate the grid impact of such systems and instead improve overall local power quality. To evaluate the strategy, the LFAPF is integrated into a SOFC system inverter with one-cycle control (OCC) to provide the fundamental benefits of a traditional active power filter (APF) while also damping out short-term line current transients. The LFAPF benefit is illustrated through simulation of an SOFC interconnected with the utility electric distribution system and a building electricity demand that is modeled as a dynamic non-linear load. Three installation cases are examined: (1) a load-following SOFC, (2) a base-loaded SOFC, and (3) an offline SOFC. Without LFAPF, the load-following SOFC causes load transients due to the finite SOFC response time, and the base-loaded SOFC case has transients that appear more severe because they represent a larger overall percentage of the grid-provided load. The integration of an LFAPF improves the steady-state behavior over the base case and mitigates voltage sags and step changes. Thus integrating an LFAPF can, by providing useful services to both the utility and the end-user, facilitate the integration of an SOFC into the distribution system.