The Study On Voltage Stability Of Power System With Wind Farms Considering Dynamic Response Of Components

With the economic and social development,the social power consumption is growing rapidly,and some power networks are already in an overloaded state.The operating point of the power system has increasingly approached its stability limit,and voltage stability problems are getting worse.In recent years,in order to meet the requirements of sustainable development between economy and environment on a global scale,China’s power system has entered the era of large power grid where multiple distributed energy sources coexist.As a rich and clean energy,wind power is widely used in the large power grid.However,the wind speed is random,which leads to the uncertainty and has a non-negligible impact on the operation of the power system.Therefore,it is of great significance to study the voltage stability problem of power system with wind farms.In the existing literature,there are many research methods on voltage stability.Among them,online monitoring based on the Thevenin equivalent plays an important role in the study of voltage stability of power systems,and how to accurately calculate the Thevenin equivalent parameters which are considered to be complex and variable is the key to applying this method.On the other hand,the large scale access of wind power increases the proportion of power electronic equipment connected to the power grid,and the nonlinearity of the power system is aggravated too.At the same time,dynamic response of components which are important to medium and long-term voltage stability are also nonlinear factors in the power system.Therefore,the nonlinear dynamic characteristics in today’s grid must be fully considered when studying voltage stability.However,the traditional Thevenin equivalent method is essentially a linear equivalent and cannot fully reflect the dynamic response in power system.Therefore,from the above two perspectives,this paper studies the Thevenin equivalent parameter calculation method and the medium and long-term voltage stability analysis method of power system considering the dynamic response of components.In order to solve the limitations of the traditional Thevenin equivalent parameter method in the calculation,this paper proposes a tracing algorithm of Thevenin equivalent parameters for power systems based on power series expansion from the perspective of improving the assumptions of traditional method.The algorithm which can be calculated without initial value avoids the phenomenon of parameter drift,and is suitable for the transient recovery process after system fault clearing.Besides,simulations in the simple double bus system and the IEEE39 node example system verify that the proposed algorithm can effectively avoid the interference of measurement error,which shows good robustness and accuracy.The simulation in three-node system with wind power verifies the effectiveness of the proposed algorithm for voltage stability analysis.In the process of studying the long-term voltage stability considering the dynamic response of components,two nonlinear dynamic factors of generator over-excitation limitation and OLTC tapping action are involved.At the same time,the existing single-port coupling equivalent model is modified from the perspective of the maximum transmission power.Combined with the voltage stability index,a medium and long-term voltage stability analysis method considering dynamic response is proposed.Finally,the simulation results in the three-machine nine-node example system and the IEEE39-node example system show that the modified equivalent model can fully reflect the dynamic process of the interaction between generation OEL and OLTC tapping action.The voltage stability index can effectively warn the medium and long-term voltage collapse caused by the process.The simulation in the three-node nine-node system with wind farm shows that the modified single-port coupling equivalent model is suitable for voltage stability analysis of power system with wind power.