Influences of Power Electronic Converters on Voltage–Current Behaviors During Faults in DGUs—Part I: Wind Energy Conversion Systems The growing interest in clean and sustainable electric energy pushes toward increasing the interconnection of wind energy conversion systems (WECSs) to utility grids. The designs of the majority of WECSs employ power electronic converters (PECs), which generally have nonlinear and switched characteristics. The characteristics, operation, and control of PECs in WECSs can result in nonconventional voltage-current behaviors during faults. This paper investigates the voltage-current behaviors during faults that occur in grid-connected WECSs. Two types of WECSs are considered in this paper, which are the doubly fed induction generators and permanent magnet generator based WECSs. The voltage-current behaviors are investigated in experimentations for different faults occurring in different parts of the test grid-connected WECSs.