Research On Key Technology Of Locomotive Auxiliary Power Supply Based On Phase Shift Full Bridge Converter

With the rapid development of railway industry,China has achieved remarkable achievements in railway technology,including running speed,transport volume and equipment technology.The progress of power electronics technology and railway transportation industry are developing towards "Green,Energy saving,Environmental protection",the technology of electric locomotive is getting more and more attention.The auxiliary power supply system provides the power supply demand for all kinds of equipment on the electric locomotive except traction system.Therefore,To keep the auxiliary power operating efficiently and reliably is a critical condition for high-speed operation of electric locomotives.In this paper,the auxiliary power supply of electric locomotive based on phase shifted full bridge(PSFB)DC-DC converter is taken as the research object.It is difficult to achieve the dynamic response and stability requirements of the nonlinear and time-varying isolated DC converter by using the traditional integer order PID control.In view of this problem,a dual closed loop fractional order PID(FOPID)controller based on average current mode is adopted to improve the dynamic performance of the system.In addition,PSFB converter is the main structure of the auxiliary power,because of this structure,it has complex fault type and large amount of fault information.A new fault diagnosis method for PSFB convert based on wavelet packet transform and optimization of extreme learning machine is proposed.The main research contents of this paper is as follows:(1)The status and difficulties research of auxiliary power in electric locomotive.The advantages of the PSFB converter as the main circuittopology of high-frequency isolated locomotive auxiliary power supply is summerized by consulting the relevant literature.In the next,To solve the problems in the control method and fault diagnosis technology of the locomotive auxiliary power supply based on the PSFB DC-DC converter,the key research content of this paper is put forward.(2)The characteristic analysis and modeling of locomotive auxiliary power supply based on PSFB converter.The working principle and inherent characteristics of PSFB converter are analyzed.Analyzing the influence of duty cycle loss phenomenon,a small signal model of PSFB DC-DC converter is established based on the state space averaging method.Finally,the necessity of designing closed loop control system is obtained by analyzing the open-loop stability of the transfer function.(3)The FOPID controller of PSFB converter based on particle swarm optimization algorithm.In order to improve the performance of PSFB converter controller,a dual closed loop FOPID control strategy based on average current control mode is designed.The parameter design of FOPID controller is more complex owing to the introduction of integral order ? and differential order ?.Particle swarm optimization algorithm is applied to optimize parameters of fractional order PI?D?-PI?controller,and the performance of the optimized controller is ananlyzed by Bode diagram.Finally,the simulation of different controllers based on Simulink shows that the FOPID controller has better control characteristics,including fast response and strong robustness.(4)Fault diagnosis strategy of locomotive auxiliary power supply based on PSFB DC converter.Firstly,the fault characteristics of PSFB converter are analyzed,and various fault types of main circuit power switch tube are determined.Secondly,the wavelet packet transform(WPT)is used to extract the feature vector of the output voltage of PSFB converter.Finally,the extreme learning machine(ELM)is used to classify the feature vector of the output voltage,and the Firefly algorithm(FA)is introduced to optimize the input weights and the hidden layer of the ELM,it improves the classification performance of ELM.The simulation results show that the proposed method has high accuracy and stability for fault diagnosis of PSFB converter.(5)The design and experiment of prototype platform.According to the main performance index of auxiliary power supply of electric locomotive based on PSFB converter.The relevant circuit of the prototype platform are designed,including the main power circuit,isolation drive circuit and signal sampling.The dual closed loop FOPID control program is tested based on DSP TMS320F28335.Finally,the FOPID digital control strategy and correlation performance is verified on the prototype platform.