Transient Instability Detection And Coherence Analysis Based On Multi-Source Trajectories

The topology of modern power systems is becoming complex and the electrical connection between regional power grids is greatly enhanced.So the stability characteristics of power grids are becoming more complicated.This puts higher requirements on the transient stability analysis method of power systems.Traditional transient stability analysis methods are difficult to meet the requirements of online applications.With the construction of smart grid,the information sources that can be used for transient stability analysis become more abundant.The wide-area phasor measurement system based on phasor measurement unit can obtain real-time information of each bus in the system,which provides a new direction for power system transient stability analysis.The disturbance trajectory of the system contains rich information,and the information can be analyzed and summarized to judge the transient stability of the system as early as possible.This paper studies how to apply multi-source trajectory information for transient stability analysis and generator coherency identification.Wide-area measurement information has the characteristics of global and real-time,and the amount of information is enormous.In order to obtain the characteristics of the power system transient stability detection,we need to divide the massive measurement information at first.One is to obtain the trajectory information from the generator bus,and the other is to obtain the trajectory information from the transmission line.The disturbed trajectories of these electrical quantities are studied to clarify the characteristics that reflect the transient stability of the system.Based on the research about the characteristics of the disturbed trajectory and the out-of-step oscillation recognition methods,the disturbed trajectory features with good adaptability and reliability are extracted,and construct the corresponding criteria based on these characteristics.In order to make good use of multi-source trajectory information,this paper proposes a transient instability detection method based on the integrated multi-source trajectory information,which combines various criteria via the discriminate speed difference in time sequence and forms a comprehensive transient instability detection method.The essence of this method is to combine the judgment results given by different criteria to form a comprehensive criterion of early warning and post judgment.While judging the transient instability of the system,it is also necessary to identify the coherent generators of the disturbed system,which provides an important reference for the subsequent control measures of the disturbed system.This paper proposes a generator coherence analysis method that does not require system state matrix calculation and only gives corresponding results based on the dynamic response trajectory of each generator.Based on the Locality In-between Polylines method,the trajectory similarity measurement method is constructed by calculating the area enclosed by the trajectories.Then the method uses hierarchical clustering to obtain the cluster of the coherent generator and the coherent index of the whole system.The proposed methods are verified by simulation in IEEE118 bus standard test system.The simulation results show that the proposed methods have good reliability in various scenarios and has certain practical application value.