Multilevel dynamic voltage restorer

This letter presents the implementation and control of a high voltage dynamic voltage restorer (HVDVR) for use in power distribution network to compensate for sags in utility voltages. The proposed HVDVR is implemented using a multilevel inverter topology with isolated DC energy storage, allowing the direct connection of the HVDVR to the distribution network without using a bulky and costly series injection transformer. A control algorithm, incorporating P+resonant and Posicast compensators, is also presented for controlling the HVDVR with perfect reference voltage tracking and effective damping of transient voltage oscillations at the instant of sag compensation. Finally, simulation results are presented to verify the performance of the proposed multilevel HVDVR.