A novel method of power flow analysis with UPFC considering limit violations of variable

In this paper, with respect to power flows of power systems with UPFC (Unified Power Flow Controller), a relatively detailed analysis and comparison to the models and algorithms reported in the open literature are made. A new power injection model and algorithm for power flow calculation of power systems with UPFC is proposed, and its principles and deriving processes are expatiated. The capacitance of line to ground is considered in the model. This model based on power injection method, is intuitive, convenient and versatile, and can be used for various functional modes of FACTS devices and all FACTS devices. A sequential iteration algorithm to solve the power flows with UPFC is developed based on the Fast Decoupled Load Flow(FDLF), in order to conveniently handling limit violations of the UPFC internal state variable but little modification to mismatch equations and Jacobian matrix. How to determine the initial start conditions and to handle limit violations is also discussed. Finally, the numerical examples shows that this model still has good convergence performance even using the zero value as an initial state for this external variable.