Research On Static Voltage Stability Of Grid Structure Based On Generalized Tellegen’s Theorem

Currently, UHV power grid construction that the characteristics focus on new energy consumption has laid a foundation for the development of smart grid. However, the structure of the electric network becomes increasingly complex, and safe and stable operation of power system has potential problems. In recent years, one of the main reasons for the domestic and foreign large-scale blackouts is the weak link of the power grid structure. Starting with the network structure, this thesis focuses on weak link of the electric network and the problem of static voltage stability. The main work is as follows:This thesis mainly discusses "virtual short virtual open" phenomenon of electric network during the static voltage stability critical state and proposes a method of looking for weak node and key branch. Critical load impedance modulus value of each node in electric network is calculated by critical impedance modulus method. The first load node to reach the critical value is a weak node that needs be found in the way of the corresponding load change. After determining the weak node, the load at the weak node is increased and power flow calculation is run. The key branch of the system are obtained, which is corresponding to the weak node and seriously affects the static voltage stability of the system.Based on the generalized Tellegen’s theorem and considering the influence of the node load on the admittance matrix, the self-admittance correction of the weak node load on the key branch node is calculated; the equivalent factor is introduced and the mutual-admittance correction of the weak node load on the key branch is obtained by the equal slope method; The trend of the weak link is obtained from the change of the key branch admittance.With the trend of the weak link, the voltage stability of the system is studied by calculating the minimum eigenvalue of the system under each load condition of the weak node. Taking the IEEE-30 node system as an example, the correctness of the static voltage stability analysis method based on the network structure is verified.