STATCOM

as an important flexible AC transmission system（FACTS）

has been used widely in the reactive power compensation of power system thanks to its fast response.During the manufacturing period of STATCOM

each function of full-bridge sub module must be tested

in which rated current testing commonly at present is that the power is supplied to the DC side capacitor of the sub-model through the diode rectifier

while a big reactor is connected to the AC side of the sub module.The magnitude of current is adjusted by adjusting the output voltage magnitude of AC side.With this method

only one sub module can be tested at the same time.It is a time consuming and inefficiency process in the batch production of the STATCOM.In this paper

a batch testing method of the sub module is proposed with which a group of sub modules can be tested simultaneously by way of series of the sub-model and addition of grading control algorithm of the sub-model

thus improving significantly the testing efficiency of the submodel and saving labor cost.