Architectural and Control Contributions for PV Grid-Connected Systems Applying Dual-Stage Inverters

This paper presents a PV grid-connected system constructed with a three-phase dual-stage inverter. A special attention is destined to DC-DC stage. For this position, a three-phase series resonant converter is chosen, amongst other interesting alternatives. The application of this converter is studied through simulation. The dual-stage inverter tracks the maximum power operating point (MPOP) through a technique of maximum power point tracking (MPPT) that uses perturbation and observation algorithm (P&O) to maximize the inverter output power. With the used technique, any acquisitions in the photovoltaic array and in the DC-DC converter are necessary. The variables in the inverter stage to control the grid current are the same used in the MPPT. The simulation of a 12kW three-phase system discloses a fast dynamics and extremely efficient tracking. The DC-DC converter operates with constant duty cycle and frequency. The isolation is performed by a high-frequency transformer becoming the system most compact.