Stability improvement of VSC-HVDC based multi machine power system using optimized super twisting sliding mode controller

Abstract

This article presents application of an optimized robust and nonlinear controller approach for dynamic stability of a multi machine power system integrated with VSC-HVDC transmission. To improve dynamic stability of the system, a super twisting Sliding Mode Control approach, whose gains are optimized by multi objective flower pollination algorithm is designed to enhance the system stability over a various operating conditions, such as three phase fault, dc link fault, converter and inverter parameter change, increase of the mechanical input of the generator and change of active and reactive power. The super twisting sliding mode controller is designed for its superiority in robustness and chattering free actions over conventional siding mode controller in which a hyperbolic tangent function is chosen for the sliding surface. A multi objective flower pollination algorithm is applied to find optimized gains of the super twisting Sliding mode controller, in order to improve the capacity of the controller and the dynamic stability of the system. The results are compared with STSMC and conventional PI controller. It is shown from the result that the proposed controller is more capable in settling the system in steady state from any abnormal condition quickly than SMC and PI controller.