Modeling and Analysis of VSC Based DC Lines in AC Power Flow Problems

Abstract

Integration of renewable power generation has emerged as a critical challenge facing electric power systems. Increasing the penetration of such energy sources, while maintaining stability, will require creative solutions infused with new technology. Advancements in voltage source converters (VSC) make the device a viable option for high voltage DC (DC) transmission. Utilization of VSC based DC lines could improve stability performances impeding large wind farms connected to the grid by improving reactive power support. This thesis introduces a detailed method for incorporating VSC transmission lines into AC power flow models, and simplifies the proposed method into a combination of AC components. The simplified model will benefit grid planning efforts by reducing computation time through smaller Jacobian matrices, while the detailed method offers insights into the VSC’s operating condition and proximity to capability boundaries. In addition, the flexibility provided by VSC transmission is analyzed through the generation of PQV capability regions. Comparing the regions for a conventional AC connection versus a VSC-DC line shows the latter does not necessitate a change in voltage at a load bus when the power demand varies.