Comprehensive UPFC models for power flow calculations in practical power systems

A hybrid unified power-flow controller (UPFCs) model for power flow calculations is developed: an ideal voltage source model is used to represent the series part while an ideal current source model is used to represent the shunt part. Static relationships among real power and reactive power transfers, series transformer and shunt transformer losses are considered in detail. Equivalent relationships among our new models and existing models are also investigated. Since only one extra state variable is included in our developed UPFC models, it can be easily incorporated into existing Newton-type power flow solvers. Even with flat start initial conditions, this new model can be easily converged within a few iterations. We have tested our new models in IEEE 300-bus power systems. Simulation results demonstrate the efficiency and the accuracy of our proposed model.