METHOD FOR CONTROLLING A PHOTOVOLTAIC INVERTER FOR NETWORK FAULT RIDE-THROUGH AND A PHOTOVOLTAIC INVERTER SYSTEM

摘要

A method of controlling an inverter, which is connected between a photovoltaic generator and a power supply network for ride-through of a network fault, is disclosed. A voltage dip is detected in the network voltage and the voltage (U_dc) of a DC voltage link of the inverter is monitored. When it is detected that the DC link voltage (U_dc) exceeds an upper limit value (U_THup), an operating mode for ride-through of the network fault (FRT) is started. The upper limit value (U_THup) corresponds to a saturation voltage U_dc,nom(max) in the specific I_ac/U_dc characteristic curve of the inverter, above which the maximum AC output current I_ac,max of the inverter decreases. In the FRT operating mode, an energy dissipation device is activated, which is adapted to dissipate power from the DC voltage link, if necessary, and is controlled to keep the DC link voltage (U_dc) within a range (U_dc−ΔUU_dcU_dc,nom(max)) below the saturation voltage (U_dc,nom(max)). An inverter system for a photovoltaic plant which implements the method is also disclosed.