| The constant improvement of modern industry has brought about great development for our society and economy, but at the same time, the industry dust particle has been one of the sources of air pollution. The electrostatic precipitators(ESP) which are high efficient dust removal equipments have done great contribution for solving air pollution problem. As its key part, the high-power high-voltage ESP power supply has been the research focus in this field. This paper applies the VIENNA rectifier and LCC resonant technology to the ESP power supply and this is one of the best technical solutions now and has significant value in theory and industry application.This paper begins with the principle and electrical characteristics of electrostatic precipitator, and it further indicates that the high-frequency ESP power supply is the main development direction of ESP power supplies for its many advantages in improving the dust removal efficiency and the system reaction speed, and so on.In this paper, the principle of soft-switching of the LCC series-parallel resonant converter is clearly analysed, it proves that it is the best topology for the output stage converter for it can efficiently remove the adverse impact of leakage inductor and distributed capacitor of the high-frequency high-voltage transformer to ESP power supply. The advantages of the discontinuous current mode for LCC resonant converter is discussed for that it can realize the destination of zero-current switching on and zero-voltage zero-current switching off for the switch and reduce switching loss greatly and improve output power, which can get the international level to reach 1.2A current in high voltage output side.Based on the electric circuit model of converter in this mode, the mathematical description analysis is done, and the analytical expression for the characteristics is deduced. The way to realize soft-switching and the voltage adjusting characteristics are discussed. The method to choose the factors that impact the energy circulation in the resonant loop and efficiency and peak value of resonant current is deeply studied and it indicates that the converter will work in the best condition when it works in the double-impulse critical mode and the output is the maximize limit. To work as the guide for parameters choice, the design curves of critical frequency with voltage output factor and equivalent load factor with voltage output factor and capacitor ratio are plotted. Based on these curves, the parameters of LCC resonant converter are designed and the validation is done in Saber system by building simulation model. With the use of 72 kV and 30 kW high-voltage high-power ESP power supply experimental prototype which is based on the TI company control chip TMS320F28035, the frequency adjusting test is done. The simulation and experimental results both prove the correctness of the mathematical description and characteristics analysis in discontinuous mode for the LCC resonant converter, which is good guidance for industry practice. But it also proves the shortcomings in adjusting voltage and improving power near critical frequency mode when traditional rectifiers are applied in the input stage in the experimental prototype system now and the output voltage and power can only be adjusted by changing frequency, and the peak value of resonant current is very large.For the problems in disadvantages to match with output stage converter and impact on the grid brought about by the ESP power supply systems that widely apply traditional rectifiers in the grid side now, this paper adopts the three phase VIENNA rectifier as the front-end stage, which can improve the power factor in grid side, and its DC bus voltage can be used to be new factor in adjusting the output voltage and power. The mathematical model is built, based on which the control methods are studied. The simulation model in Saber is built to verify the theory analysis which will be the reference for the use of VIENNA rectifier in high-power ESP power supply system.To get 80kV/80 kW output voltage and power to reach the requirement of this project, the circuit parameters are separately designed for two ESP power supply systems that apply three phase diode bridge rectifier and VIENNA rectifier in the grid side separately. The two systems are compared and analysed, and the result proves that it can not only overcome the problem to the grid and reduce the ratio of high frequency transformer greatly, but also overcome the shortcomings in matching with the characteristics of LCC resonant converter in the output stage brought about by adopting the traditional rectifiers as the front-end stage when the VIENNA rectifier is used in the grid side in the ESP power supply system for the DC bus voltage can be controlled and improved. This technical solution has good prospect for industry application. |
PDF Full Text Request