Research On Novel Continuous Co-phase Power Supply Scheme And Its Power Supply Capacity Of Electrified Railway

The rapid development of Chinese electrified railway fully reflects the superiority of the existing power frequency single-phase AC 25 k V power supply system of Chinese electrified railway,but the existing traction power supply system still has certain shortcomings.In order to minimize or avoid the safety risks when the train passes through the neutral section,improve the power supply capacity and the direct utilization rate of the regenerative braking energy of the traction power supply system,and solve the power quality problem of the current electrified railway which is dominated by negative sequence,it is necessary to study the novel continuous co-phase power supply scheme of the electrified railway to solve the shortcomings of the current traction power supply system,so that the advantages of power frequency singlephase AC 25 k V power supply system can be further exerted.The novel continuous co-phase power supply scheme and its power supply capacity of electrified railway will be studied,and the research contents and results are as follows:Research is carried out on the composition of the novel continuous co-phase power supply system.According to whether the negative sequence compensation device is installed,there are two types of operation schemes.The first type of operation scheme is mainly composed of single-phase transformer,and the second type of operation scheme is composed of single-phase transformer and negative sequence compensation device.According to the different topological structure of the system scheme,it can be divided into the continuous power supply scheme of traction substation group,the continuous power supply scheme of high-voltage special line and the continuous power supply scheme of traction cable.For the second type of operation scheme,according to the different compensation principles of the compensation device,the compensation scheme is divided into reactive compensation scheme and active compensation scheme.According to the different locations of compensation devices,it can be divided into centralized compensation scheme and distributed compensation scheme.Based on the study of different compensation schemes,a reactive power compensation scheme based on a novel T-connected balance transformer is proposed.By comparing various compensation schemes,the application scope of different compensation schemes of the novel continuous co-phase power supply system is obtained.Aiming at the second type of operation scheme of the novel continuous co-phase power supply system,the negative sequence compensation model,capacity allocation scheme and compensation strategy are studied to provide reference for system operation.Taking the limit of three-phase voltage unbalance at point of common coupling and the limit of power factor of the traction substation as constraints,starting from the transformer wiring relationship,a general mathematical model for negative sequence and reactive power comprehensive compensation of the novel continuous co-phase power supply system is constructed.For the negative sequence compensation schemes given by the topology including reactive power compensation schemes based on YNd connection transformer,Dd connection transformer and T-connected balance transformer with static var generator,and active power compensation schemes based on combined co-phase power supply devices,based on the model,the negative sequence and reactive comprehensive compensation models of centralized compensation scheme and distributed compensation scheme are constructed respectively.And a distributed compensation strategy with coordinated control is proposed,which the strategy is consistent with the negative sequence current to be compensated by centralized compensation.For various compensation schemes,the maximum reactive power compensation is defined,and a method of selecting compensation scheme is proposed to realize the capacity configuration of compensation scheme.Based on the constructed comprehensive compensation model and instantaneous reactive power theory,the compensation control strategy of the centralized compensation scheme is proposed.The correctness of the comprehensive compensation model,capacity allocation scheme and control strategy is verified by example analysis.Based on the scheme and operation strategy of the novel continuous co-phase power supply system,the integrated power flow calculation model and solution method are studied to provide technical means for the analysis of the power supply capacity of the system.According to the composition of the novel continuous co-phase power supply system,the different components are modularized,and the integrated power flow calculation model of the system is constructed,including the external power supply,the traction network model(singlebranch and multi-branch),the negative sequence compensation device,energy storage devices and new energy models.The model has good universality and is also applicable to unilateral traction power supply system.For the solution of the constructed power flow calculation model,according to the load types involved in the calculation in the iterative calculation process,it can be divided into current source iterative model and power source iterative model.For the current source iterative model solving method,in addition to the common sequential linear power flow algorithm,an improved model solving method is proposed.For the power source iteration model solving method,the basic and improved solution methods of the power source iteration model are proposed.Compared with the current source iteration model,it has a wider range of applications.For the case with negative sequence compensation device,energy storage device and new energy,an alternating iterative power flow algorithm is proposed.The correctness of the model and solution algorithm is verified by comparing the measured data and simulation.Based on the integrated power flow calculation model,the ability of the novel continuous co-phase power supply scheme to provide qualified electric energy to the train load under load conditions is studied,and the traction network voltage under no-load conditions is evaluated.Aiming at the voltage rise and equalizing current of the traction network under no-load condition of the novel continuous power supply system,the equivalent circuit model of the system under no-load condition is constructed,and the voltage and equalizing current under no-load condition are analyzed,and the influencing factors of equalizing current are revealed.Taking the voltage level of the traction network as the main constraint,a method to evaluate the power supply capacity under load conditions from the power supply distance of the traction network and traffic level is proposed,and the influencing factors of the power supply capacity is analyzed.In addition,a method to solve the equivalent impedance of the system by Thevenin’s theorem is proposed,which the derivation process is simplified and has a wider range of applications.Taking an actual line as an example,the novel continuous co-phase power supply scheme and power supply capacity improvement measures are applied to the line scheme design.Based on the power flow calculation model constructed in this paper,the power supply capacity for the novel continuous co-phase power supply scheme is verified and compared with the existing power supply scheme,and the comparison results show that the novel continuous co-phase power supply scheme is technically progressiveness.Based on the simulation results,the power supply capability and the applicability of the novel continuous co-phase power supply system are analyzed.The novel continuous co-phase power supply scheme studied in this paper involves technical innovation in external power supply and traction power supply system.At present,there is relatively little research on this technical scheme.Based on the research of the system topology and scheme operation strategy,an integrated power flow calculation model of the novel continuous co-phase power supply system is constructed,with which the power supply capacity of the system can be evaluated.The research content of this paper can provide technical support for the engineering application,energy consumption evaluation,design and optimization and system operation of the novel continuous co-phase power supply scheme,which has great engineering practical significance.