Research And Design Of A New Medium-frequency Constant-current Power Supply For Electrostatic Precipitator

With the continuous development of modern industry,effective control of soot emissions from coal,chemical and other industries has become an important issue in global environmental protection.As an important equipment for industrial dust control,electrostatic precipitator(ESP)system can better filter and control the dust particles in industrial field.The regulation mode,output performance and loss characteristics of the power supply for ESP system have a significant impact on the dust removal efficiency.The traditional ESP power supply has the defects of high voltage pulsation,slow dynamic response and large resonance loss.The medium-frequency ESP power supply has become a more ideal choice due to its high safety,high power density,low power loss and low transformation cost.In order to improve the dust removal efficiency of the medium-frequency ESP system,this thesis focuses on the static characteristics,transient characteristics and loss thermal characteristics of the new medium-frequency constant-current power supply for ESP system.The main research contents are as follows:1.The main circuit topology of the new medium-frequency ESP power supply and the empirical parameters of the equivalent load of the dust collector are given.The Medium-Frequency PWM modulation strategy of single-phase full-bridge inverter in new power supply is studied and classified.Considering the influence of different modulation strategies on the system current harmonic distortion factor and the extra loss of the medium-frequency high voltage rectifier transformer,the SPWM natural sampling modulation is introduced for comparison.According to the state equation of the new EXP power supply,the system open-loop simulation model is established,and the static characteristic index difference of the output characteristics,harmonic characteristics and switching loss characteristics of the new power supply under different modulation strategies is analyzed.The phase shift modulation is selected as the new ESP power supply modulation method and the soft switching technology of the power switching tube is realized.2.According to the working principle of the new medium-frequency constant-current ESP power supply under phase shift modulation,a large signal model of the power supply is established in the complex frequency domain.The full state feedback control is applied with the goal of the minimum dynamic response error square product,and the current inner loop is preferentially designed and equivalent to the new power module.The adjustment compensation network of the power supply system is designed according to the influence of the control object and the typical link on the transient characteristics of the system.The power supply system closed-loop simulation model is established.Considering the conditions of power starting process,DC voltage sudden rise and drop,and equivalent load sudden increase and unloading,the transient characteristics of the system are analyzed by using the time domain transient performance index.It is verified that the new power system has stable,accurate,fast and anti-interference performance under large signal disturbance.3.The two types of resistive power loss of the bus capacitor and the intermediate frequency rectifier transformer in the new power supply are analyzed.The ESR extraction method of the capacitor is proposed by decoupling the resistive ripple voltage of the bus capacitor,and the intermediate frequency transformer winding loss and core loss are analyzed according to Dowell's assumption and no-load test.The semiconductor switching losses caused by the inverter switching tube and the high voltage rectifier tube are also analyzed.According to the actual selected device,the total heat loss and total average power loss expression of various semiconductor switches are derived,and the 3D and 2D loss models are established in the Thermal Library.The simulation analysis of the power loss and thermal characteristics of each module in the power supply system under the normal operating state is realized.4.On the basis of theoretical analysis and simulation verification,the hardware architecture and software program of the new power supply system are designed and prototyped.The DSP-CPLD main control program and spark protection program are written to realize the closed-loop control and protection strategy of the new power supply experimental prototype.According to the experimental data of the normal operation and flashover of the experimental prototype,the feasibility and rationality of the project design scheme are verified.