| Lead-acid storage batteries have the recurrent recharging characteristic, and have many advantages such as low price, facility and non-pollution. In present industrial and mining enterprises, communications and transportation fields, demands for them are enlarged, and their power levels are greatly inceased. The traditional charger technologies, due to utilizing phase control SCR technologies, have some drawbacks such as long charging time, lower life of batteries. Therefore they are not suitable for the demands of modern production and daily life. To meet the modern theme of energy-saving and environmental protection, chargers with complete functions and good performance should be designed by the state of art of the power electronics and control technologies. In view of this, the following researching work has been carried out in the respect of application object of coal mine traction-engine powered by lead-acid storage batteries.Concerned with the times theme of energy-saving and environmental protection, the application prospects of lead-acid batteries, the development status and inefficiencies of chargers are summarized and analysed wholly. The researching target is selected as a novel full digital switch-mode high-power charger with on-line monitoring function by means of the PWM converter technology.Theoretical analysis of switching mode charger is depicted, and the working principle of the intermediate high-frequency link DC-DC converter is analysed. In addition, PID control theory to stabilize the DC voltage, the design of the PWM control strategy, and simulation analysis based on MATLAB / SIMULINK are performed.Hardware design of switching mode charger is designed systematically including power circuit, control circuit, and human-machine interface circuit and serial communication circuit. The power circuit basically consists of rectifier circuit, high-frequency transformer and the output filter reactor. The control circuits are built up by PWM pulse-generating circuit, IGBT driver circuit, I~2C bus circuit, and so on. Taking some factors like cost, EMC and efficiency into account, some relevant schematics and PCBs are drawn.Software design of switching mode charge constitutes software design objectives and arrangements of the program structure and the design of major functional modules. The major functional blocks includes the incremental PID control subroutine, the Modbus communication protocol subroutine, data acquisition and processing subroutine, charging process control subroutine, HMI subroutine, fault handling subroutine. By using mixed C and Assembly Language programming method, the whole program's edit, compilation and debugging are completed.System debugging of switching mode charger is described. In the different stages of hardware circuit design, the corresponding control procedures are developed and debugged step by step. Eventually the whole program's compilation and debugging are completed. A number of problems, such as jitterring elimination of the keyboard, PID control parameters matching, and so on, are encountered and solved during debugging the system. The prototype of a novel 30 kW high-power full-digital switch-mode charger, with on-line monitoring function, is produced and experimented in some coal mines. The measured results show that the charger has good effects satisfying the purpose of the design.Improvement of the input power factor of switching mode charger is designed. Since charger's power is high enough, the various methods relevant to the existing three-phase converter power factor correction and the criteria IEC61000-3-12 with phase current larger than 16A, are analysed. On the basis of the analysis, a new magnetic energy recovery switch (MERS) series compensation technology is chosen in order to correct the power factor of three-phase uncontrollable rectifier. The working principle of MERS is described, involved some problems such as non-chopping, PWM chopping and dead zone handling. Moreover related simulation analyses and experimental researches have been carried out, and the power factor correction is completed in large by using MERS.
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