Design of a Single-Input Triple-Output Hybrid Converter With Decoupled Control for Reverse Electrodialysis Systems

Reverse electrodialysis (RED) is a promising membrane-based technique on extracting salinity gradient power (SGP) from river water and seawater. Despite the prominent advantages of direct electricity conversion and abundant storage, RED stacks suffer from a low energy conversion efficiency, which renders optimized utilization of the attained power quite essential. Consequently, this article presents the design of a single-input triple-output hybrid converter with three independent control variables to address this issue. The hybrid converter integrates a buck converter and two switched-capacitor-based resonant converters (SCRCs) to deliver power from the RED stack to three output ports, including a water pump, a 48-V dc microgrid, and batteries. To avoid cross-coupling of power flow control among these ports, a decoupled control scheme is developed to achieve voltage regulation for the water pump, maximum-power-point-tracking (MPPT) of the RED stack, and battery charging current regulation independently. Moreover, the selection principles of resonant inductors and battery charging current are elaborated to derive the zero-voltage-switching (ZVS) operation regions of six switches under different operating conditions of RED stacks. Simulation and experimental results of both steady-state tests and dynamic tests validate the effectiveness of the proposed decoupled control scheme and ZVS regions.