Development Of Mining Digital AC Stabilized Power Supply With High Power Factor Based On STM32

The project in this thesis is one part of the National Key Technology R&D Program of China during the Eleventh Five-year Plan Period (serial number: 2007BAK29B05; 2007BAB13B01). The work is proposed in accordance with the problems of low power factor, high input current distortion rate, high harmonic content, serious harmonic pollution and so on for the nonlinear loads, such as monitoring and control equipments in underground coal mine. At present high precision and high stability equipments are very common in the modern high production and high efficiency mine, which are an important guarantee for the coal mine safety production. However, the traditional mining power supply have the drawbacks of low input power factor and poor stability, and are vulnerable to the influence of the coal mine grid voltage fluctuations, poor power quality, load nonlinearity and impact and so on, which could cause monitoring and control equipments instability, malfunction and shutdown. It is of important practical significance to conduct the research on mining digital AC stabilized power supply with input high power factor and output voltage stabilization and reliablity.The designed digital AC stabilized power supply consists of three-phase voltage source PWM rectifier and single-phase voltage source PWM inverter. The principles and control strategies and the implementation of specific functions of them are further studied in this thesis, the main contents of this thesis are as follows:Combining with the field requirements, the system’s functions, such as power factor correction and AC output voltage regulation, are established. The research status of power factor correction and AC regulated power supply are investigated by consulting documents, then the system’s performance indexes and main structure are determined, and detailed implementation plan is developed as well.The key factors influencing on power factor correction and the important technologies of realizing power factor correction are analyzed, and the topology and principle of PWM rectifier are introduced, the low-frequency mathematical model of PWM rectifier in the three phase static coordinate is established, then direct current control strategy of fixed switching frequency are described in detail and their regulators are designed. Finally, simulation verification for the proposed plan of PWM rectifier is carried out on matlab platform. It has been shown by the simulation results that the system’s input current is sinusoidal wave and in-phase with power network voltage and the effect of its correction is very obvious.The open-loop mathematical model of single-phase inverter is presented based on the detailed analysis of inverter topology and working principle. The double-loop control strategy of outer output voltage and inner inductor current is studied and its equivalent mathematical model is also constructed. It has been shown at last by matlab simulation results of different modulation modes and double-loop control strategy that single-phase inverter has the good load adaptability and the ability of outputting stable voltage.The hardware control circuits based on STM32 has been developed and debugged, which include several circuits such as signal processing circuit, communication circuit, phase-locked multiplier circuit and so on. It is proved by experimental results that the designed circuits are of strong anti-interference ability and stability.System software architecture is planned on the designed hardware platform. The software of data sampling and closed loop control algorithm calculating and SPWM generating and system protection have been written. It is verified by the debugging results that the software has the reasonable division and could operate stably to meet the system requirement.The steady and dynamic performance experiments of PWM rectifier and PWM inverter are carried out respectively on the experimental platform which has been developed. It has been shown that the results are basically identical with the simulation results and the performance indexes of digital AC stabilized power supply with high power factor have been met the requirements and the system scheme is of feasibility and rationality.