Design of new nonlinear optimal predictive controller for Unified Power Flow Controller

Unified power flow controller (UPFC) is one of the most effective flexible AC transmission systems (FACTS) devices for controlling power flow and improving stability of power system. However, to achieve such functionality, a proper and sufficient control system should be designed for this device. This paper proposes a novel nonlinear multiple-input multiple-output (MIMO) predictive control system using optimal control approach to control UPFC. The proposed control scheme is applied to the overall mathematical model of UPFC which consists of the d-q representation model of shunt and series parts of UPFC, in addition to the DC link voltage dynamic model. To validate the proposed control scheme, we perform simulations on single-machine double line infinite bus power system installed with UPFC using PSCAD/EMTDC software package. Steady-state and dynamic stability of the system are investigated under the proposed controller. The simulation results are encouraging and show the robustness and superiority of the proposed controller compared to conventional PI controller. The new controller guarantees the closed-loop stability system and has a good tracking behavior.