Modeling and Control for the DC-DC Three-Port Series Resonant Converter in Power-to-X Application

Power-to-X technology provides an effective approach for renewable energy utilization, which prefers multienergy interaction systems to efficiently manage power flows among various sources and loads. As a solution, multiport resonant dc-dc converters show their advantages in terms of integration, power volume, and efficiency. However, their complex structure poses strict challenges in modeling analysis and control design works. This article explains the comprehensive modeling procedure of a three-port dc-dc converter with three series resonant windings, where the strategies of harmonic approximation, extended describing function method, and state variable reduction are used to properly simplify the original nonlinear high-order equations. In fact, the proposed modeling method is highly versatile and applicable to n-port resonant converters for a variety of power-to-X applications. After acquiring the large- and small-signal models, this article further develops general modulation and control principles for multiport resonant converters. A voltage control strategy based on inner phase shift ratio modulation is introduced, demonstrating a wide voltage regulation range and power decoupling performance. The effectiveness of the proposed models and control strategy is verified through simulation and experimental results.