Design And Research Of Phase-shifted Full-bridge Digital Power Supply For High-power Subway Screen Doors

The digital control technology attracted a lot of attention in modern high-frequency and high-power power system research.With the advantages such as simplifying the complexity of the control loop,increasing the robust of the power system,the digital control technology can enhance the performance of the power system,improve the control flexibility and the module efficiency,and reduce R&D costs either..With the actual application of the driving power supply for subway screen doors,this thesis combined the soft-switching technology and the digital control technology.A phase-shifted full-bridge soft-switching power supply based on digital control is proposed.A detailed analysis was carried about the designed digital power supply system,such as the topology circuit,the working mode,the device parameter design,the loop compensation analysis,and the digital controller,etc.the simulation and experimental verification were presented in this thesis.The specific work content is listed as following:Firstly,the technical indicators of the driving power supply for subway screen doors are presented with the digital control scheme.The main topology of the DC/DC power supply adopted a phase-shifted full-bridge ZVZCS topology,while the primary winding is connected in series with a blocking capacitor and the lag arm is connected in series with a reverse current blocking diode.The theoretical analysis a of the working modes is proposed in detail.Moreover,the calculation and the selection of components are presented,including the front-stage input circuit,converter circuit,resonant network,and output LC filter a.In order to solve the problems of DC bias and secondary side oscillation of high-frequency transformers,a DC blocking capacitor is used to prevent the transformer from being saturated,and the mathematical model of the secondary side oscillation of the diode is derived in detail,while various suppression measures are discussed.Finally,RC and RCD are used to suppress the network from absorbing secondary side oscillating voltage spikes.Secondly,a theoretical analysis is performed to the resolution,loop delay,and pulse width modulation of digital control technology,which is verified by the simulation;Further,the small-signal analysis and PI compensation are presented with the open-loop and closed-loop transfer functions of the main circuit topology.By using the frequency domain analysis method,and the Bode diagram,the compensated system closed-loop cutoff frequency and phase can be obtained.The phase margin and the cross frequency have been improved to meet the requirements of system dynamic response speed and steady-state accuracy.Based on the differential transformation,the control algorithm is realized by the incremental PI algorithm,which is performed with the DSP(TMS32028335).The software design,such as the sampling,digital filtering,protection,and loop control algorithms,is presented in detail with the flow chart of th main program,PI Control algorithm,soft start,and AD interrupt service function.Finally,a simulation model of the complete power supply system is built in Matlab/Simulink,the preliminary theoretical analysis,calculation and parameter design were verified.Moreover a power supply prototype with a rated power of2.2k W and an instantaneous power of 3.3k W was developed.The prototype,With the relevant test results of the power supply prototype,such as the key experimental data and waveforms of the power supply module,the rationality and engineering practicability of the proposed digital power module is verified.