Assessment Of Power System Voltage Stability Under Small Disturbance

Voltage is an important indicator to measure the quality of power grid.Whether the voltage is stable or not,it has an important impact on the entire power system in order to operate safely and reliably.The sysface voltage collapse,but even develop into a more serious power outage.Therefore,in tem voltage drop will not only lead the power grid to order to ensure the safe operation of the power grid,it is necessary to avoid voltage instability events,and it is necessary to evaluate the stability of the voltage of the power system.In the past,the power industry relied heavily on traditional power processes for static analysis of voltage stability.The stability is determined by calculating the PV and QV curves of the selected load bus.These curves were often generated by conventional models,but Due to the divergence of power flow,it is impossible to fully generate QV and PV curves,so this research evaluates through the following three points:First,it is determined that most generators or branches consume more reactive power due to interference,modal-based analysis and its applications are used to evaluate the voltage stability of large-capacity power systems.Secondly,the positive and negative eigenvalues of the Jacobian matrix of the power system are used as indicators of system voltage stability.For small-interference steady-state power systems,positive eigenvalues indicate that the system is stable,while negative eigenvalues indicate that the system is unstable.The minimum eigenvalue indicates how close the system is to voltage instability.Finally,by correlating the eigenvalues with the Q-V sensitivity of each bus,the relationship between system voltage stability and the reduced Jacobian matrix eigenvalues is better understood.The reduced Jacobian matrix can be used as a symmetric matrix,so if all eigenvalues are positive and the QV sensitivity is positive,then the reduced Jacobian matrix eigenvalues are close to be pure real numbers,and the reduced Jacobian matrix’s minimum eigenvalues can be used for columns.The stable mode of the system is out,and the remaining eigenvalues are ignored because they are considered to be strong enough.At the same time,the participation factor can be effectively used to find the weakest node or bus in the system.