Research And Design Of DC-DC Converter For Vehicle Power Supply

At present,most of the electric locomotives use the 750V DC for the supply.But it cannot be used directly in the electric locomotive,as a result,it is necessary to research a DC-DC converter for on-board power supply of electric locomotives,in order to convert the voltage of DC and supply power for locomotive composite energy storage system,control system and lighting system.Firstly,the research of DC-DC converter for electric locomotive vehicle power is discussed in detail.It chooses the isolation type full bridge DC-DC converter topology,adopts the single phase shift modulation method,analyzes the converter under the principle of energy transmission and single phase shift control the working principle.The resonance characteristics and power characteristics of the converter are studied,and the stability of the converter is determined.In order to further verify the rationality of the designed single-phase shift control dc-dc converter,the input voltage waveform data used in the experiment was input into Matlab for simulation experiment.However,the simulation results show that the ripple is larger after the output voltage is stabilized.FFT analysis shows that the harmonic content of 100Hz is much higher than other high-order harmonics,so it is necessary to filter the voltage ripple of double grid frequency.In most cases,LC filter circuit is added to the input of dc-dc converter,but this will increase the cost and volume of the converter.This paper focuses on the output ripple voltage suppression method without LC filter circuit.In order to realize the closed-loop control system design of the converter,small signal modeling of bidirectional dc-dc converter is carried out in this paper.Two main influencing factors of output voltage pulsation are analyzed and summarized:input voltage pulsation and control closed-loop.In view of the current MPS hybrid phase-shifting control adopted at home and abroad,all sampling parameters must be very accurate,otherwise the system’s dynamic performance will further deteriorate the defects were improved,a VDPC direct virtual power control method was derived to improve the system’s dynamic response performance.Combined with the advantages of PI closed-loop control method of input voltage feedforward,a virtual power control method of input voltage feedforward is proposed.In order to further verify the accuracy of the designed control method,a simulation experiment was carried out in Matlab,and the simulation results showed that the control strategy met the accuracy requirements of the system.Then,this paper completed the design of on-board power bi-directional DC-DC converter system,choose the freescale MC9S12XF512 chip microcontroller as the control module,with appropriate peripheral circuit,including the auxiliary power supply module,drive module,voltage and current sampling circuit implements the system power supply,data acquisition,PWM output,closed loop control,etc.The parameters of the high frequency transformer used in this paper are designed,and the methods of electromagnetic interference suppression are analyzed.The design of the software control part includes the main control program and the closed-loop control program.Finally,in order to further verify the accuracy of the designed control method and simulation,a bidirectional dc-dc converter experimental system platform was built,and the experimental results were analyzed.