Advanced steady-state models of UPFC for power system studies

In this paper, focus is on the UPFC steady-state modeling for the implementation of the device in the Newton-Raphson load flow algorithm. Two models, deriving from the known voltage source model (VSM), are presented and analyzed in detail. One is a power injection model (PIM) and the other one is the new shunt admittance model (SAM). Each one of these models represents a more robust and feasible alternative to the VSM because it bypasses the difficulties arising from the VSM, maintaining its advantages, though. Different simulations are presented in the paper to test and compare the models: Newton's quadratic convergence of the load flow algorithm is guaranteed by implementing the PIM and the SAM, with high convergence speeds.