Research On Continuation Power Flow Calculation Method For Power Network With Intermittent Power Supply

With the development of society and the progress of science and technology,the scale of power system is increasing,in addition to the traditional thermal power and hydropower,wind power and photovoltaic power generation as the representative of the renewable energy power generation is gradually increasing,power grid structure is becoming more and more complex.As one of the key technologies to study the operation state of power system,how to improve the power flow algorithm and improve the reliability of the algorithm has become a hot issue in the current research area.Fixed growth mode is used for power injection of conventional power flow calculation method,which make the Jacobian matrix has a singular problem near the critical value.It does not suitable for large scale intermittent power supply access network.The continuation power flow of nonlinear power injection method compared with the traditional power flow calculation method does not need to consider the problem of singular Jacobian matrix,the calculation speed and accuracy of power flow algorithm are improved.The main work of this thesis is as follows:1.The model of power flow calculation of power system with intermittent power supply is established,and the corresponding equivalent circuit is given.Through the comparison and analysis of several kinds of common power flow model,it's concluded that the P-Q decomposition method is more representative and more applicable for power flow calculation in power systems with intermittent power supply.But the P-Q decomposition method in the vicinity of the critical values still has the Jacobian matrix singularity problem.2.According to the conventional power flow calculation method is easy to cause the singular Jacobian matrix near the limit point of the problem,In this thesis,the concept of load power change parameter is proposed.The load power is introduced to the power flow calculation and construct the nonlinear flow balance equation.This equation not only reflects the changing trend of the power of the injected nodes,but also makes the convergence of the power flow equation from the N+1 dimensional space to the exact solution.3.In order to improve the convergence speed and computational efficiency of the continuous power flow algorithm and solve the problem that the step size change drastically during the convergence process,make accuracy of the algorithm be guaranteed.In this thesis,an improved LMS variable step size algorithm is proposed and use the iteration number as feedback,and the control strategy of step size control factor is proposed to adaptive change step size,improve the accuracy of the algorithm,reduce the number of iterations of the correction process and enhance the speed of the calculation of the power flow.4.Analyzing the voltage stability margin of power system with nonlinear power injection and proposing a continuation power flow modeling and calculation method based on the fuzzy model for nonlinear power injection,and the load margin of the power network is presented.Through the choice of the key points on the load forecasting curve to obtain Multiple linear curves.The nonlinear load model is established by the TSK fuzzy method,which guarantees the smooth and continuous of the nonlinear load model,accurately reflect the physical characteristics of the actual,so that the power injection of the continuous power flow equation is more in line with the direction of the load variation.