A photovoltaic grid connected inverter with current source characteristics and maximum power tracking

A novel design of a photovoltaic grid connected inverter is presented. The inverter is realized so as to attain current source characteristics for simple connectivity to the grid. The advantage of this realization is simplified system due to the fact that no voltage amplitude matching or modulating is required and the wave shape of the grids voltage has no influence. The inverter´s current polarity must be taken care of, to match the voltage polarity of the grid. The simple realization yields simplicity in the switching circuitry and control. The design includes an H-bridge topology that is switched by the AC grid itself. Therefore, no synchronization is required. Consequently, this simple switching scheme inherently suits all wave shapes and all frequency changes of the power grid. The system is combined with a maximum power point tracker (MPPT) with only output current control. The paper presents the theory, technology and the circuit of the new inverter.