Control of a Four-Port DC–DC Converter for Photovoltaic Systems Integrating Batteries and Supercapacitors

The integration of batteries and supercapacitors into a photovoltaic (PV) system using a multiport dc-dc converter offers an attractive alternative to conventional configurations with multiple two-port dc–dc converters. However, the high-order, cross-coupled, and multivariable nature of most multiport converters poses significant control design challenges. This paper proposes a digital control strategy based on state feedback, decouplers, and PI controllers to efficiently regulate a four-port dc-dc converter topology that interfaces a PV module, batteries, supercapacitors, and a load. The proposed approach achieves reduced settling times for PV and load voltages, as well as for battery and supercapacitor currents, while minimizing overshoots and undershoots. Experimental results demonstrate smooth transitions between operating modes, highlighting the ability of the system to simultaneously perform MPPT, regulate charge and discharge currents, and maintain stable load voltage control. With settling times for reference changes of less than 20 ms for all controlled variables and a cross-coupling deviation of less than 2 % between PV and load voltages, the proposed control strategy ensures robust and stable performance in all operating modes studied.