Development of UPFC operating constraints enforcement approach for power flow control

This study proposes a comprehensive modelling for a unified power flow controller (UPFC) into a Newton–Raphson load flow algorithm. The developed UPFC model is based on the power injection approach considering four control modes to control the voltage magnitude of a specific bus, the active and reactive powers flow in a transmission line concurrently or selectively. The developed model avoids the modifications of the main part of the load flow algorithm (Jacobian matrix). This can be achieved by transforming the voltage sources of UPFC equivalent circuit into two injected loads at its sending and receiving buses. The required control values can be achieved by updating these injected loads as a function of them. Consequently, the complexities of incorporating UPFC in load flow algorithm are significantly reduced. The operating constraints of the UPFC model are enforced using the developed approach based on modifying and updating the specified values as a function of their maximum limits. The developed model with constraints handling approach is validated using standard IEEE 14-bus, 30-bus, and 118-bus test systems. The obtained results demonstrate the effectiveness of the developed model and its superiority to other reported conventional methods.