Photovoltaic power conditioning and maximum power point tracking by means of a self commutated inverter

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 a 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 in order 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 special synchronization scheme 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.