Measured interconnected behavior of wind turbine inverters

As an overvoltage protection for the HVDC thyristor valve a method of connecting a unit arrester to each thyristor is presented. A study was conducted to investigate how far the necessary thyristor series number in the valve could be reduced by this method. For this purpose, the valve voltage design is discussed when the gapless arresters are used to protect the valve. Then, an anlysis on a 12 pulse convertor was performed with digital simulation. The evaluation on the results of analysis under reasonable assumptions showed possibility that the necessary thyristor series number can be reduced by more than 10% compared with that of the conventional method.