Stability Analysis And Design Of A High-voltage Direct-current Power Supply For Electrostatic Precipitator

In recent years,with the national attention to environmental protection and the increasingly stringent emission standards,it has become an urgent problem for all heavy emission enterprises to reduce the dust emission caused by coal combustion effectively and reasonably.Among all kinds of dust control methods,ESP(electrostatic precipitator)has gradually become an ideal method to solve this problem.The high-voltage medium-frequency ESP power supply stands out from all kinds of ESP power supply because of good dedusting effect,high safety and low transformation cost.According to the above background,in order to improve the stability of high-voltage medium-frequency ESP system,this paper focuses on the switch control strategy of ESP power supply.Firstly,this paper introduces the working process of ESP,and then analyzes the development status of ESP briefly.Meanwhile,according to the principle of ESP,the conclusion that the dust removal efficiency is related to the driving speed of dust particles is derived.So the best working voltage and current of ESP can be deduced from the conclusion,which lays a foundation for the design of the control strategy.This paper also analyzes the main circuit topology and the working principle under unipolar PWM(Pulse Width Modulation)modulation of high-voltage medium-frequency ESP power supply.After that,static characteristics under open-loop of the ESP power supply is studied.Then,according to the working principle,the large signal mathematical model is established by using the state space average method.Since the ESP power system is a timevarying and non-linear dynamic system,the use of traditional PID control will make the system dynamic response slower and lead to low system stabilityAfter understanding the principle of the sliding mode control,the natural applicability to non-linear systems is recognized.This paper decided to carry out the closed-loop sliding mode control for the ESP power system.Selecting appropriate state variables and sliding mode is the premise of adopting sliding mode control for ESP power supply.After that,the arrival condition,existence condition and stability condition of the sliding mode control are analyzed,and the parameters of the sliding mode control are determined according to the mentality of PWM modulation.With purpose of verifying the improvement of sliding mode control on the dynamic stability of the system,this paper adds the traditional voltage control method to compare with it and analyzes the advantages and disadvantages of the two control methods by building a PLECS simulation model.In this way,the effect of sliding mode control on improving the dynamic response speed of ESP power supply system is clarified.After analyzing the working principle of the ESP power supply and the control strategy,this paper designs the experimental prototype and the main control program.Then,this paper selects the chip model of the main control processor and designs the detection and protection circuit when the ESP power supply system encounters over-current and other faults.At last,the experimental results show that the scheme designed in this paper really improves the operation stability of the ESP power supply system.