The Study On The Recovery Strategy Of Grid Frequency Under Power Grid Accident

The frequency is an important operation parameter, as it is an important indicator ofthe quality and safety conditions of the power system. And so, preventing the frequencysharp drop from the fault situations and maintain the stability of the system frequency, is acrucial problem of the power system. UFLS(Under Frequency Load Shedding)is an lastand effective way to be used.UFLS plan now is often through the simulation technology to be set up. In this paper,an evaluation method based on the degree of closeness between the frequency simulationtrajectory and the measured trajectory, which was the mathematical model of the errorevaluation between the frequency simulation trajectory and the measured trajectory, wasproposed to evaluate the simulation accuracy of the system frequency synthetically. Theeffectiveness of the error model and evaluation method proposed was verified according tothe calculation analysis of the frequency measured trajectory and the simulation trajectoryin the several frequency decreasing events of northeast china power grid.The simulation analysis of the traditional UFLS scheme was made based on the aboveadjusted frequency simulation trajectory, The load shedding scheme whose frequency wasestablished without over-adjustment according to the set contents and requirements ofpower system UFLS scheme, and the effectiveness of this scheme was verified accordingto the simulation calculation of a simple system.In order to eliminate the over cut or under cut of the load by UFLS, the ant colonyoptimization algorithm and optimization the UFLS scheme is developed. The mathematicaloptimization model of the UFLS device was established after comprehensively consideringthe operational constraints and operation modes of the system. The practical calculationexample was made a simulation calculation to verify feasibility and validity of this method.