| The continuous expansion of the power grid,the large-scale interconnection of the power grid,and the integration of high proportion of clean energy represented by wind power into the power grid have become an inevitable trend of power systems development.It is of great significance to study the development and evolution of power network with the large-scale wind power integration and its cascading failures to improve the reliability and safety of power grids.Therefore,the space-time evolution model of the complex power grids with wind power is proposed.Based on this,the space-time evolution model of wind power integrated power system considering the characteristics of different voltage levels of nodes is proposed.By introducing the joint entropy,the risk of system cascading failure in the evolution process is evaluated,revealing the impact of wind power penetration and network topology on the probability of grid cascading failure after wind power integration.To explore the impact of wind power fluctuation on the grid evolution,a space-time evolution model of complex power grids with wind power is proposed in this paper.The slow dynamic process and fast dynamic process are considered in this model.In the slow dynamic process of space-time evolution,a probability model for wind farm integration is established based on the characteristics of wind resources in different regions;in the fast dynamic process,the fluctuating power is described and the flow distribution of the system is optimized after wind power integration in the interval DC power flow mode.The IEEE-118 node system is used to verify the proposed model.By introducing the load rate and the power flow entropy indicators,it is concluded that the higher the wind power penetration,the greater the system's load loss,and the more uneven and disordered the system's power flow distribution.When the wind power penetration is close to 15%,the power flow entropy increases faster.To reveal the impact of wind power integration under different voltage levels,a space-time evolution model of wind power integrated power system considering the characteristics of different voltage levels of nodes is proposed.Considering the regional characteristics of the power grid,the effects of the original network node degree,the distance between nodes,and the voltage level characteristics of the nodes are considered comprehensively and the newly added nodes are distributed at different voltage levels in the process of slow dynamic node access based on the space-timeevolution model of complex power grids with wind power.It can be concluded from simulation that the system node degree distribution is more uniform and the system robustness is enhanced when the influence of different voltage level characteristics are considered in the access process of new nodes in the system;finally,the analysis of the power flow entropy in the process of the system evolution shows that with the consideration of the influence of voltage level characteristics in the access process of new nodes in the system,the influence of wind power fluctuation on the system power flow can be effectively alleviated when the wind power penetration increases to 10%.When the wind power penetration of the system increases to nearly 15%,the power flow entropy of the system increases faster,but the increase rate of the power flow entropy considering the voltage level characteristic is smaller than that of the power flow entropy when the voltage level characteristic is not considered.In order to analyze the risk of cascading failure during the evolution of wind power integrated power system,a cascading failure risk assessment method for wind power integrated power system based on joint entropy is proposed.The method comprehensively takes into account the weighted network topological entropy affected by the degree and the weighted power flow entropy affected by the load rate.The joint entropy can not only measure the stability of network topology,but also measure the uniformity of system power flow distribution revealing the risk level of cascading failure in system evolution.Finally,the risk and conditional risk are used to evaluate the blackouts in the process of system evolution,and compared with the joint entropy,which shows the effectiveness of the analysis of the cascading failure evolution process based on joint entropy. |
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