Cooperative converter for improving the performance of grid-connected photovoltaic power plants

This study presents a new single-phase topology for the power injection system of a grid-connected photovoltaic generation system that is based on the parallel association of two voltage-source inverters: one is a three-level inverter with clamping diodes (or neutral point clamped) with a low switching frequency strategy (equal to the grid frequency) and the other is a two-level inverter which operates with a current hysteresis band strategy and an usual switching frequency (5-20 kHz). The main advantage of the proposed topology is to optimise the system design, allowing high power injection with a significant reduction of system losses (mainly switching losses) and achieving an increase of the energy injected into the grid. The performance of the proposed topology and its control algorithms are tested and validated using a laboratory prototype.