Power System Security Assessment Based On Transient Energy Function

With the economic development of our country and the improvement of daily life, people demand more and more electric power as well as much higher reliability. To ensure the security operation of the power system, the power system security assessment is urgently demanded. The purpose of power system security assessment is to protect the system to operate continuously in safe and stable when any identify faults occurs. Its task is to assess the operating modes and faults modes which may cause the system unstable from the view of system and evaluate the load shedding amount which may lead the system stable. Transient energy margin sensitivity is used to calculate the limits of system operation conditions and the interface flow is used as a parametric variable. The transient energy margin sensitivity to the interface flow is established, and the power flow distribution factor is used to rapidly calculate the interface flow limit. Thus, the dynamic load shedding of the system in unstable state can be calculated. The power system transient stability assessment model is formed. Monte Carlo Method is used to sample the test system fault. Use the transient energy function to analyze the state of the system. Considering power system fault location, fault type and other statistical characteristics of random factors, the power system security assessment index is formed.The example used in this paper is 10-machine 39-bus test system. The system dynamic load shedding amount is calculated under specific failures and the probabilistic stability of the system is analyzed. The system security assessment is achieved. The result of the example confirms the validity and rationality of the improved system safety assessment by using both transient energy margin sensitivity method and the Monte Carlo method. And it also shows that the combined method is practical and useful in power system security assessment.