Novo conversor isolado de múltiplas entradas e múltiplas saídas multidirecional para arquiteturas modernas de distribuição de energia CC de baixa tensão

Abstract

This work presents the modelling, analysis, and simulation-based evaluation of a multidirectional, multi-winding, multiport flyback DC-DC converter proposed for the integration, within a single conversion stage, of sources and loads operating at different voltage levels in low-voltage DC architectures. By doing so, the need for intermediate DC-DC converters and the losses inherent to multistage power processing are reduced, thereby favoring higher power density. As a proof of concept, a three-port configuration composed of a photovoltaic source, a DC load, and a battery energy storage system was adopted to develop the analytical formulations, the control strategy, and the validation studies. For converter operation, an operating scheme is adopted in which the magnetization and demagnetization processes of the coupled inductor take place individually for each port, thereby reducing the dynamic coupling among ports, increasing the flexibility of the turns-ratio design, and simplifying control implementation. Energy coordination is performed through a Power Flow Control Strategy (PFCS), in which the voltage of port 2 acts as the global coordination variable and is maintained within a band delimited by four voltage levels, from which the operating modes are selected according to the balance among photovoltaic generation, load demand, and the power-exchange capability of the storage system. Within this framework, port 1, connected to the photovoltaic system, operates either in Maximum Power Point Tracking (MPPT) mode or in voltage-droop-based power-limiting mode, referred to as Voltage Droop Control Mode (VDCM). For this port, a Finite Control Set Model Predictive Control (FCS-MPC) strategy is employed to track the photovoltaic array voltage reference, which is generated either by the MPPT algorithm, featuring an adaptive step size and based on observer-estimated photovoltaic current without the need for a current sensor, or by the VDCM, depending on the system operating mode. Port 3, associated with battery energy storage, is bidirectionally controlled through two voltage-droop strategies, one dedicated to the charging process and the other to the discharging process. Under surplus-energy conditions, the system selects the Battery Voltage Droop Control by Charging Mode (BVDMcha), in which the battery absorbs power; under power-deficit conditions, it selects the Battery Voltage Droop Control by Discharging Mode (BVDMdis), in which the battery supplies power to the system. When no energy exchange is required, port 3 remains in a standby state characterized by the IDLE mode. In a complementary manner, port 2, associated with the DC load, incorporates protection functions that allow the load either to remain connected or to be disconnected. Simulation results under islanded operation and different irradiance and load-demand conditions showed that the voltage of port 4 2 remained within the specified range under both surplus- and deficit-power scenarios, with port 3 transitioning between the BVDMcha and BVDMdis modes to absorb or supply energy as required. In addition, a comparative evaluation of alternative control strategies for port 3 was carried out, highlighting differences in dynamic compatibility with the photovoltaic control loop. In summary, the obtained results indicate that the proposed multiport topology, together with the new operating scheme and the developed control strategy, constitutes a technically viable solution for integrating, within a single conversion stage, elements operating at different voltage levels in DC architectures.