A review of minimisation of output DC current component methods in single-phase grid-connected inverters PV applications

Nowadays, it is a general trend to increase the Distribution Generator (DG) based on renewable energy such as photovoltaic (PV) system. This generator can affect the grid by causing a number of problems due to injection of DC current into the grid. If this DC current is not properly prevented, result problems in distribution network such as increased corrosion in underground equipment and transformer saturation. This paper reviews the minimization methods which employ to minimize the output DC current component in single-phase grid-connected inverters photovoltaic applications. These methods are categorized into four classifications. The basic approach is to make use of an isolating transformer to prevent the DC current. Another technique is to use a half-bridge inverter which has the capability of blocking the DC current flow to the AC side. It is also possible to use a DC blocking capacitor in the inverter output. A more recent method is to use current sensing and control techniques to monitor and calibrate the DC link current sensors.