Power Flow Calculation And Its Convergence Analysis For Energy Interconnected System

As the basic tool of analysis,the power flow calculation plays an important role in the energy interconnected system.Energy interconnected system are integrated with a large number of distributed energy generation devices and load devices,so the energy interconnected system would have a variety of node types.And there are many uncertainties in the device,leading to the distribution of power flow are not determined.Therefore in this thesis,the research on the various devices and the power flow calculation for energy interconnected system are carried out as follows:At first,analysis for various components of the energy interconnected system.The devices are mainly divided into the power generating device,the energy storage device,the load device,the communication and detection control device.By analyzing the structure,working principle and working status of these devices,laying a foundation for the next step to analyze the power flow calculation models for the various devices.Next,according to the existing types of nodes analysis various devices expansion node of energy interconnected system,in this thesis,a power flow calculation algorithm for different node types is proposed.Through establish power flow calculation model of transmission line,load and distributed generation in energy interconnected system,then,analyze power flow calculation for all kinds of nodes using Newton power flow algorithm.Above all,the Newton method general steps of the expansion node type for energy interconnected system are given,and the method is feasible through the verification by IEEE118 standard nodes system.And then,for the uncertainty problems of the energy interconnected system,a Fuzzy-Newton method for energy interconnected systems is proposed.Application of the fuzzy set theory for Newton power flow calculation method,among them,trapezoidal fuzzy number respectively to generator output,availability and the size of the load uncertainty modeling.To solve the problem of balancing nodes and linear programming,a new symmetric Fuzzy-Newton power flow algorithm is proposed,which is improved by the traditional Fuzzy-Newton method.And based on this,the branch constrained index is added,which makes the calculation result more satisfied with the adaptability of the system.Select the standard IEEE 118 node to verify the method.By comparing the simulation analysis of the three kinds of trend calculation method for the validation of the method can not only well solve the energy Internet system flow distribution of uncertain problems,but also can make the system of the device and branch to rational use,and the calculation results accord with the real power system.Finally,in order to solve the convergence problem of fuzzy power flow calculation,an analytical method based on Levenberg-Marquardt method is presented for improving the convergence of Fuzzy-Newton method.By analyzing the convergence theorem and convergence trend of Fuzzy-Newton method,found that Fuzzy-Newton method cannot convergence if the initial value selected inappropriate.Then several commonly used to improve the convergence of the method are compared,and select the Levenberg Marquardt method to improve the convergence of the Fuzzy-Newton power flow calculation.The method by adding the damping factor limiting the size of iterative correction to solve the initial value deviation.Because the Jacobian matrix is an important factor of affecting the power flow convergence,in this thesis,through reconstruct the Jacobian matrix to expand the areas of convergence.The verification of the IEEE118 standard nodes shows that the method can solve the initial value deviation problem well,and enlarge the convergence region,thus it can improve the convergence.