Active balance of a solid oxide electrolysis cell stack tower: Circuit design and control strategy

Solid oxide electrolysis cell (SOEC) technology is characterized by high efficiency and reversibility, yet it encounters significant challenges in scaling up. A common approach to scaling up involves piling up multiple stacks to form a stack tower, which increases voltage and reduces power converter loss. However, as the number of stacks increases, ensuring homogeneity within the stack tower becomes increasingly challenging. Issues such as gas maldistribution and resistance inconsistency can accelerate degradation by inducing local hotspots and reactant starvation, highlighting the urgent need for online balance methods. Inspired by the active balance technology used in battery systems, this study introduced an active balance circuit to enhance the homogeneity of SOEC stack towers. A current tracking controller was designed for this circuit to enable independent current control for series-connected stacks, with Simulink simulations demonstrating a response time to reference current signals within 0.2 s. A voltage balancing strategy was proposed to generate the reference current signal for this controller, which was implemented and validated using a multiphysics stack tower model. The results showed that the balancing strategy effectively reduced temperature inhomogeneity by over 10∘C under conditions of gas maldistribution and resistance inconsistency, underscoring the potential of the active balance circuit to improve the durability of SOEC technology.