Increasing inter-area available transfer capacity using controllable network transformers

Control areas are often interconnected to each other by tie-lines over which the operators have little or no real-time control. Congestion of any one of the lines in the transmission corridor limits its Available Transfer Capacity (ATC), even if there is available spare capacity in some parallel paths. Increasing inter-area ATC is key to increasing penetration of renewable generation, since the geographical location of renewable generation sites are often far from the load centers. Traditional methods of increasing inter-area ATC like transmission upgrade or FACTS installations are expensive and also require significant lead-time. Controllable Network Transformers (CNTs) are low-cost power flow controllers which can be realized by augmenting existing Load Tap Changing (LTC) transformers. The paper shows from a system level perspective, the application of CNTs to increase inter-area tie-line ATC, thereby allowing increased inter-area green energy transfer.