Emergency transmission line switching to suppress power system inter-area oscillation

Electromechanical oscillation is an inherent property of ac power systems which can occur in the forms of local and inter-area oscillations. The inter-area oscillations may impose a serious threat on the system if they are not controlled properly. Over the past two decades, many methods have been introduced to control and suppress electromechanical oscillations. This paper proposes a new supplementary emergency damping control (SEDC) to suppress inter-area oscillations. In the proposed approach, a system brittleness index (SBI) is introduced which can show system risk for splitting into uncontrolled islands. Following a sever fault, the value and sign of SBI is used as an indicator for activation of SEDC. By using sensitivity analysis of the inter-area mode with respect to line switching, the most effective transmission line switching (TLS) is utilized as an emergency damping control for suppressing inter-area oscillations. For this purpose, by offline studies, a priority list of the effective lines switching is prepared. Then, in the real time operational environment, by using an optimization algorithm, the most effective line switching is implemented as SEDC activation. The optimization algorithm guarantees system operation against any potential violation due to line switching. The proposed SEDC has been demonstrated on IEEE 39-buses system with promising results.