Advanced modeling of center-node unified power flow controller in NR load flow algorithm

A new and versatile member of flexible AC transmission systems (FACTS) controller is center-node unified power flow controller (C-UPFC). The C-UPFC is capable to control various system parameters independently, e.g., the active power through the line, the reactive powers at the ends of line and the magnitude of the voltage at the mid-point of the line. Applying C-UPFC device may increase the power transfer capability of a transmission corridor. This paper presents a proposed power and current injections model of C-UPFC. The developed model is incorporated in Newton-Raphson (NR) based on combined mismatches load flow algorithm. The shunt and series voltage control variables of C-UPFC are updated during the iterative process. This model contrary to some existing models of FACTS devices, keeps the original structure and symmetry of admittance and Jacobian matrices. The model presents a simple approach for implementation the C-UPFC in load flow code without any modification in Jacobian matrix. The approach is tested on the IEEE 30-bus and 57-bus systems using C++ load flow engine, proving its effectiveness in incorporating the C-UPFC in load flow algorithm.