Effect of a new parameter of voltage sag, i.e., phase angle jump, on invertors for PV System was surveyed by newly developed Voltage Sag Generator. The generator can reproduce actual voltage sags recorded past, and artificial voltage sag with controlled phase angle jump. It consists of PC, D/A converter and power amplifier. A program generating wave form of sag has been developed and improved considering interruption process of PC. Evaluation of the performance of inverters for PV system under various types of sags is carried out with this voltage sag generator.