Model Segmentation Of Complex Distribution Network And Its Application Research

Complex distribution network is a major part of the power system.The main characteristics of the current distribution network are a large number of nodes and equipment,a wide range of applications,and a complex network structure.The subsequent popularization of distribution automation,the installation of intelligent terminals,the integration of distributed power sources,and the huge investment in power electronic equipment have made the distribution network an exponential increase in complexity,which has all contributed to the corresponding distribution network.Real-time simulation brings many challenges.At the same time,with the introduction of the concept of digital twin distribution network,it is particularly important to be able to match the real-time simulation of the complex distribution network.The question is that the traditional single-core electromagnetic transient simulation can no longer meet the requirements of fast real-time simulation.This thesis is to solve the above problems and realize the electromagnetic transient real-time simulation of complex distribution network.Therefore,the author studies the model segmentation method and interface algorithm to improve the electromagnetic transient simulation rate.At the same time,the model segmentation application research is carried out in the complex distribution network with distributed power sources and in the case of distribution feeder automation.First of all,the thesis expounds the current research status of model segmentation technology from the domestic and foreign perspectives,analyzes the development status and prospects of distribution network,and analyzes the research significance of model segmentation in the background of complex distribution network.In the next step,this thesis explains the overall architecture and interface algorithm of the model segmentation interface,including the realization principle of the model segmentation interface,electromagnetic transient network calculation methods,and analyzes the serial and parallel calculation timing of the power system model segmentation.Furthermore,several commonly used model segmentation methods are introduced: long-distance transmission line decoupling method,state space node(SSN)method,node split method,ideal transformer model(ITM)method,and combined with complex distribution network,this thesis analyzes the advantages and disadvantages of each interface method.After that,based on the parallel calculation sequence,this thesis puts forward the transfer function formulas and stability criterion for the voltage-type ITM interface and the current-type ITM interface under various line conditions for the ideal transformer model(ITM)method,and discusses several measures of improving the stability of the interface.However,these types of improvement measures cannot fundamentally break through the limitations of the ITM interface stability criterion.Therefore,according to the proposed transfer function of the voltage-type ITM interface and the current-type ITM interface,it is concluded that when the voltage-type ITM interface does not satisfy the stability,the current-type ITM interface must be stable,and vice versa.Finally,according to the conclusion,the ITM interface conversion algorithm is proposed,and corresponding simulation verification is made.Subsequently,studying the applicability of the split interface in the complex distribution network,this thesis discusses the existence and grid connection methods of distributed power generation(DG).The existence method is that distributed generation cannot exist alone,while as a part of the micro power grid.Therefore,this thesis chooses the droop control method to simulate the control module of the distributed micro power grid.The simulation modules are divided into three parts: micro power supply module,filter circuit module and the droop controller.The micro power grid model is composed of three peer DGs,and based on MATLAB/Simulink,a distribution network model with DG is built.This model uses a single interface to divide the system into two subsystems,and uses the grid-connected operation mode and island operation mode of the distributed micro power grid to divide the application of the model by using the ITM interface and RT-LAB’s own SSN interface,and respectively the simulation results are analyzed.Ultimately,the access of distributed power sources will affect the flow of power and current in the distribution network.The traditional ITM interface will not meet the stability characteristics of the interface,resulting in simulation failures.In order to study the applicability of different segmentation interfaces in this situation,the SSN algorithm and ITM conversion algorithm were used respectively,based on MATLAB/Simulink,and droop control was used to build a distribution network model with DG,and a single interface was used to split the system into two.The sub-systems,using the grid-connected operation mode and island operation mode of the distributed microgrid,respectively verified the segmentation characteristics of the ITM conversion interface and the RT-LAB built-in SSN interface in this case,and analyzed the corresponding simulation results.Finally,in the same way,in the case of a feeder failure in the distribution network,feeder automation will cause switching actions in the distribution network,which will inevitably change the topology of the distribution network,and the traditional ITM interface will also no longer be applicable.Therefore,in the face of this situation,the article designed its control strategy for intelligent distributed feeder automation,and based on MATLAB/Simulink to simulate and model the intelligent terminal(STU)with different functions in the distribution network.Automatic function of fault detection,fault isolation,and power supply restoration of non-faulty section.In order to verify the applicability and stability of the SSN interface and the ITM conversion interface,two split interfaces were used to split the IEEE33 node into two subsystems.Under the condition of Intelligent Distributed Feeder Automation(FA),comparative verification experiments were carried out respectively.