| The research and analysis of large power grid must be based on digital computation and simulation,and load model is the key factor to determine the credibility of calculation results.With the development of global integration,the proportion of energy storage capacity in the power grid is increasing.Various factors such as physical characteristics,distribution position,charge and discharge depth,charge state and control mode of various energy storage elements have different influence on the characteristics of integrated load.It is of great theoretical and practical significance to study the generalized composite load model including the influence of energy storage elements.In this paper,all-vanadium redox flow battery(VRB)is studied as the research object.The simulation model of the VRB energy storage system is constructed and verified by the Matlab/Simulink simulation platform.Based on this,the external characteristics of the VRB energy storage system are studied and the external characteristics can be described equivalent by the step response of the first order inertial system order.The model can effectively describe the force limit of the VRB energy storage system with few parameters and relative structure.Simple,can be easily implemented in the simulation software.Simulation results show that the model is correct and effective,and the parameter identification results are stable,which is suitable for power grid simulation.The classical integrated load model(Classic Load Model(CLM)model and generalized integrated load model(Generalized Synthesis Load Model,GSLM)are constructed.The latter considers the effect of VRB energy storage system,distribution network parameters and reactive power compensation,and the structure is more reasonable.A simple single node 5 node simulation system is built,and the CLM model and GSLM model are tested on this basis.The results show that when the capacity ratio of VRB energy storage system is higher than a certain value(40%),the ability to describe the comprehensive load characteristics of the distribution network is significantly reduced by the CLM model.The GSLM model can effectively describe the integrated load characteristics of the distribution network,whether it is the discharge state or the charge state.In the same working state,the higher the VRB energy storage capacity ratio,the better the identification effect of the GSLM model than that of the CLM model.A more complex IEEE-14 node simulation system is constructed to further verify the GSLM model.The influence of access capacity and geographical location on integrated load characteristics of VRB energy storage system is studied when centralized and distributed access.The results show that the influence degree of VRB energy storage on the distribution network characteristics increases with the increase of the capacity ratio of the power grid,and the influence degree of the centralized VRB energy storage on the distribution network is affected by the negative r atio of the access point and the branch of the distribution network,that is,the access point and the distribution network of the distribution network with the different geographic location of the centralized distribution network.The closer the electrica l distance at the end is,the smaller the load proportion of the branch is,the more obvious it has on the comprehensive load characteristics of the distribution network;the impact of the distributed access is obviously less than the centralized access;t he impact of the capacity ratio is obviously greater than the effect of the geographical location.On this basis,the GSLM model proposed by the above data is further verified.The results show that the GSLM model proposed in all cases can effectively fit the comprehensive load characteristics of distribution network with VRB energy storage system,and has a strong applicability. |
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