A preliminary analysis of thevenin equivalent impedance match criterion of load shedding in specific scenarios

摘要

Voltage stability is a traditional and important study field. Load shedding is a normal method to enhance the voltage stability when system operates at limits. Estimating how close the load is to the maximum deliverable power of transmission system is an effective method to evaluate the voltage stability. The impedance match criterion based on Thevenin equivalent is considered as a necessary and sufficient condition whether the load approaches the maximum deliverable power of transmission system or not and can be used as a reference for load shedding. This paper presents a preliminary analysis of Thevenin equivalent impedance match criterion for load shedding in some specific scenarios which may lead to system collapse. A 3-bus simple system simulation is performed to show the potential collapse. And the simulation results show that the Thevenin equivalent impedance match criterion does not hold in some specific scenarios. The Thevenin Equivalent impedance of the system match the load equivalent impedance twice before the system collapse and the criterion would not be sufficient in the specific scenarios, which may lead misoperation on load shedding. Simulations on IEEE 39 also prove that the issue exists.