Research On Power System Transient Stability Assessment And Control Strategy Based On Energy Transfer Function

With the power system interconnection projects under executed,the era of largescale power system is approaching.Although the allocation of resources is being optimized,the security and stability issues of the power system are more complex and severe.Once a fault occurred,it may spread to a wide-range area of the power system,even cause black-out,if there are no timely control measures taken.Therefore,based on the study of existing assessment methods for transient stability,in this paper,the power system transient stability is analyzed from the perspective of energy.Firstly,the power system transient stability analysis methods are analyzed in this paper and summarized that they contain the transient energy function,and the energy structure theory.Based on the transient energy function,the energy structure theory,alone with the concept of graph theory,the generator energy transfer function is proposed.It is used to describe the energy flowing between any two generators and the total transient potential energy of the power system after the fault cleared.Based on the generator energy transfer function and combining with the K-means clustering analysis method,this paper presents a method of coherent generator clusters identification and transient stability assessment for the power system.In this paper,two indicators are set: the generator port energy sum and the generator port energy change rate.The former is used to describe the energy output/absorption status of each generator at each time,and the status is used as the basis to divide the generator into the leading cluster or the lagging cluster.Meanwhile,the latter is used to describe the energy change rate of each generator at each moment.Through the K-means clustering analysis method,the generators are divided into two coherent generator clusters.Furthermore,combined with the port energy sum,the two coherent generator clusters are divided into the leading cluster and the lagging cluster.Then,the transient stability of the power system is evaluated by analyzing whether the port energy change rate of the leading cluster maintains a positive value.Afterwards,based on the sum of energy of generator ports and the EEAC method,a safety and stability control measure to prevent the power system instability is proposed,which is generator tripping.In this measure,the generator tripping sequence is based on the amount of port energy sum of each generator in the leading cluster,from large to small,and the tripping process ends if the amount of active power tripped meets the required amount calculated at first.Finally,through the simulation of the IEEE-140 node system and the Sanhua power grid system,the validity of both the coherent generator cluster identification and transient stability assessment method based on the generator energy transfer function,is verified.