Safe operating range dynamic analysis, and tuning of the temparature and reactant utilization control for solid oxide cells

Abstract

Solid Oxide Cells systems (SOCs) are increasingly being considered as an electrical energy storage method and therefore as a means to boost the penetration of Renewable Energy and to improve the grid flexibility by power-to-gas electrochemical conversion. However, temperature and reactant utilization control become crucial if the systems are to be used in dynamic operation with intermittent electrical power sources. In the present work, two 1D models of SOC stacks are built and used to study the dynamic behaviour of such stacks, and to select and tune the best control systems. After having compared with literature the accuracy of the models, safe operating ranges are determined to respect the thermal constraints of the stack. The dynamic analysis points out that inputs (m_fuel, m_atr) and outputs (U, ΔT max) are strongly decoupled; therefore, proportionalintegral control strategy has a good potential to prevent dangerous operating conditions in dynamic operation. Finally, the controllers are tuned and their transfer functions are reported.