An experimental research on comparison of two kinds of voltage sag generators

With the extensive use of power quality compensator and wind power generation system, various voltage sag generators (VSG) have been designed to achieve the performance test of power quality compensator and satisfy the requirement of low voltage ride through (LVRT) experiment of wind power system. Two methods to simulate the sag of grid voltage are proposed, one is to use autotransformer regulator and switches, and the other one is based on the topology of power electronic device. Both of them have been analyzed on their work principles and topology in detail. Then, on the basis of the result, experimental prototype is built for functional verification. Experimental results make out that the autotransformer regulator based VSG has simple structure, but it fails to achieve the phase angle jump and needs electronic switches to take place of contactor to avoid the control delay; the power electronic based VSG is more flexible that it can produce various voltage faults with controllable amplitude, phase and duration time. Moreover, the power electronic based VSG has a transient process with smooth transition.