Unsymmetrical three-phase voltage sag compensation through no energy stored voltage boosters

It is known that short-circuits on MV overhead distribution lines are the main origin of voltage dips at the customer equipment. The consequence on the phase voltages of both symmetrical and unsymmetrical short-circuits is not an amplitude reduction only, but a phase angle change as well. Static voltage boosters (SVB), with no energy stored, can very simply and quickly regulate the voltage amplitude. Through a proper design, such devices can also perform the phase angle regulation, action that could be required for some category of sensitive loads. The paper deals with the above topic. First, the expected voltage phase shift at customer delivery during a typical sag is estimated, by utility modeling and simulation. Then, a possible solution for a phase compensator SVB is analyzed and discussed