Modeling and Control Design for a Bidirectional DC-DC Converter System for Cyclic Operation of a Reversible Solid Oxide Electrolysis Cell Stack

This paper presents a design of a bidirectional
DC-DC power electronic converter system enabling cyclic
operation for a Reversible Solid Oxide Electrolysis Cell
(RSOEC) stack for steam electrolysis. The cyclic operation
of the RSOEC stack is investigated, and two different equivalent
circuit models are presented for the mathematical
representation of the stack’s electrical dynamics: The wellestablished
steady-state Resistive model and a novel Voigt
model. From these, two combined mathematical models
of the bidirectional Buck-Boost converter supplying the
RSOEC stack are derived using the small-signal averaging
technique. For tracking the cyclic output current reference
to an RSOEC stack, two Proportional Integral Derivative
with derivative Filter (PIDF) controllers are designed
using the two combined mathematical models derived.
Finally, the performances of the two PIDF controllers for
the bidirectional DC-DC converter systems are compared
and validated through simulations. The simulation results
confirm the bidirectional Buck-Boost converter’s ability to
deliver cyclic bidirectional output current and demonstrate
that the control tuned based on the Voigt mathematical
representation of the RSOEC stack yields superior closedloop
performance in accordance with the control design
requirements.