Performance evaluation of dynamic voltage restorer for power quality improvement in distribution network

Abstract

newlineA power quality problem is defined as any manifested problem in voltage current leading to frequency deviations that result in failure or misoperation of customer equipment Depending on the electrical distance related to impedance the type of grounding and connection of transformers between the faulted load location and the node there can be a temporary loss of voltage or temporary voltage reduction sag or voltage rises well at different nodes of the system Among the several novel custom power devices the Dynamic Voltage Restorer DVR is the most technically advanced and economical device for voltage sag mitigation in distribution systems The DVR functions by injecting AC voltages in series with the incoming three-phase network the purpose of which is to improve the voltage quality by an adjustment in the voltage magnitude wave shape and phase shift The voltage sag compensation involves the injection of real and reactive power into the distribution system The reactive power requirement can be generated electronically within the voltage source inverter of the DVR Voltage disturbance is the common power quality problem in industrial distribution systems The voltage disturbance mainly encompasses voltage sags voltage swells voltage harmonics and voltage unbalance The voltage disturbance notoriously affects voltage sensitive equipment that eventually leads to malfunction Voltage sag is one of the most severe power quality problems because of its adverse financial impact on customers Conventional Dynamic Voltage Restorers DVRs are connected to the power grid through power frequency transformers These bulky and costly transformers cause voltage drop and power losses In this concept a High Frequency Link Dynamic Voltage Restorer HFL DVR is proposed based on transformer isolated topologies