The Research Of Shedding Load Order Scheme Based On Fuzzy Analytic Hierarchy Process

Under frequency load shedding is the important means to inhibit the frequency decreas and maintain the frequency stability of power system. Reasonable and effective to shed load can make power system recover to a stable conditions in the shortest time,that is an important means to insure safety operation of power system.From the definition of frequency, on the foundation of full understanding power system static frequency characteristics,the power system dynamic frequency characteristics of the stand-alone system and multi-machine power system is analysed by the method of simulation analysis.The functions of static frequency characteristics is restrain the system frequency changes,but which not influences the initial system frequency variation.And the dynamic characteristics of the frequency is more complicated, several factors contribute to it such as system network structure,mode of operation and distribution location and the other factors.The system frequency dynamic process has a obvious spacetime distribution.In the course of under frequency load shedding shedding,the rescovered level of system frequency has a closely associated with load adjusting effect coefficient. Therefore, this paper focuses on the the impact of load frequency adjustment coefficient on the recovery of system frequency during under frequency load shedding.And through the mathematical deduction.it has access to the rule that load frequency adjustment effect coefficient is changed during under frequency load shedding. A under frequency load shedding scheme based on load frequency adjustment effect coefficient was proposed, and digital simulation is given for the proposed scheme.The simulation demonstrates the effectiveness and reasonable of the proposed method.During under frequency load shedding,the reality is that the importance and cost of load shedding bus(line) must be considered apart from load frequency adjustment effect coefficient of load shedding bus(line).This paper use fuzzy analytic hierarchy to make a comprehensive evaluation for each load shedding bus (line) during under frequency load shedding and get the sequence of load shedding with the integrated weight. Combined with the example the simulation was carried out,the simulation result show that the sequence of load shedding can make the system frequency quickly recover to the range of safe operation,and it is reasonable and effective.Therefore,the method that is proposed by this paper with integrated effect is superior to the traditional method.