Abstract
This article presents a developed method to improve the representation of a voltage-controlled bus in the current injection load flow method. This improvement is based on a hybrid current and power mismatches formulation, where the load bus equations are represented by current mismatches and voltage-controlled buses bus equations are based on power mismatches. In this method, the advantages of the NewtonRaphson method and current injection mismatches method are collected. The total number of equations is reduced, where only one equation is required for each voltage-controlled bus. This article also describes direct modeling of voltage/power control devices in the developed load flow method. The static synchronous compensator can be represented as a voltage-controlled bus node in terms of power mismatch. The static series synchronous compensator and unified power flow controller are modeled by series impedance and two current injections at the corresponding nodes. In the case of unified power flow controller, additional power injection is included at the sending-end node to represent the voltage-controlled node. This modeling reduces the complexities of the computer program codes and enhances the reusability by avoiding the modifications in the Jacobian matrix. The IEEE data as well as systems from literature are used to validate the developed method and flexible AC transmission systems models.