UPFCs control design for avoiding generator trip of electric power grid with barrier function

•A transient control scheme for UPFC is proposed for preventing generator trips.•An energy function based control scheme is proposed in UPFC controller design.•The generator trips are prevented by constraint control with barrier functions.

A novel transient control scheme for unified power flow controller (UPFC) devices is proposed for avoiding generator trip in electrical power grid. The control scheme is derived by an proposed control lyapunov function, which consists of energy function and barrier functions. Undesirable generator trips are prevented thanks to the barrier functions penalty imposed by UPFCs, because the value of the barrier function approaches infinity as generator frequency deviation approaches pre-set threshold. The control effects of the UPFC devices make the time derivative of control lyapunov function be negative for asymptotic stability. The attraction region of the system is reshaped by control system with the desired stable equilibrium point, and the generator trips are prevented in this region. Meanwhile, the attraction region and its design are discussed. Two numerical simulations are carried out using 3 bus and IEEE 162 bus test system, to demonstrate the effectiveness of the proposed method.