The low voltage ride through test circuits include a DC source, the equipment under test, a grid fault simulator and the grid. A PV simulator (or PV array) provides input energy for the equipment under test. The output of the equipment under test is connected to the grid via a grid fault simulator, as shown in figure 1.Note MP1 is the measurement point between the grid and the grid fault simulator; MP2 is the measurement point at the high voltage side of the transformer; MP3 is the measurement point at the low voltage side of the transformer.