Virtual Impedance-Based Control Strategies for Voltage Supporting in LCL-VSC Converters
Distributed generation systems, LCL-VSC convertion, power flow control, virtual impedance
The advances in power electronics and environment restrictions have driven the insertion, as distributed generators (DG), of renewable energy based systems on the power grid, the main one being those who use the photovoltaic and wind systems as primary energy sources. The interconnection of these sources with the power grid is generally obtainedbyVSCconvertersandLCorLCLfilters,beingcalledasLC-VSCorLCL-VSC systems. Such systems are highly variable in power generation, which may cause voltage fluctuation and frequency deviation in the electric grid. LC-VSC systems are controlled to operate as a controlled voltage source connected to the grid and they can regulate the amplitude and frequency of the voltage of the point of common coupling (PCC). LCLVSC are controlled to operate as controlled current source connected to the grid and they are still the most common system employed currently. Therefore, in this doctoral qualification, are proposed virtual impedance-based control strategies applied in LCL-VSC systemsforPCCvoltageregulation. Thevirtualimpedanceisusedforshapingtheequivalent DG system impedance connected to the grid and regulate the power flow of these systems for achieving the required PCC voltage regulatio