Control of cyclic fluctuations in solid oxide fuel cell cogeneration accompanied by photovoltaics

Using numerical analysis, stabilization of the cyclic fluctuation (changes of several minutes or less) of PV (photovoltaics) was attempted by introducing governor-free control of a SOFC (solid oxide fuel cell), controlling air flow rate, and using a flywheel inertia system. The energy balance of the system element, mass balance, time lag, etc. were modeled, and the response characteristics of the proposed system were analyzed using MATLAB/Simulink 2013a. Consequently, the range of fluctuation in the electrical frequency within 0.2 Hz was controlled by introducing a flywheel inertia constant of 0.01 s. Interconnection electricity using PV with cyclic fluctuations can be supplied as high-definition electricity. That electricity is controlled using a flywheel and a proportional-integral-differential controller with suitable parameters by adjusting the governor-free control and rate of air flow in the SOFC. The SOFC and an inertia system provide a supply of backup power from renewable energy and serve to promote the increased use of clean energy.