Mechanism Analysis And Power Supply Design Of Dielectric Barrier Discharge Powered By Bipolar Square Current

Dielectric barrier discharge device,which can generate low-temperature plasma with high activity under the condition of normal temperature and pressure without expensive and slow vacuum pumping operation,is widely applied in fields of surface modification,ozone synthesis,plasma sterilization and volatile organic gas treatment.The current injected into the DBD is one of the key factors to control the load discharge.Constructing power supply of current type to control the current injected into DBD load can not only control the discharge products of DBD load,but also effectively prevent the inevitable peak current from damaging the power supply and DBD load under the action of power supply of voltage type.It is regrettable that few literatures are available to analyze the internal mechanism of DBD load under the action of power supply of current type.Still,few literatures are available to construct power supply of current type for DBD load and analyze the load characteristics under this power supply.In view of the situation,this thesis studied the following contents:(1)A DBD one-dimensional fluid model was established,which took pure helium as working gas and contained 6 kinds of micro particles and 27 chemical reactions.The correctness of the model was verified by driving the DBD load with sinusoidal voltage and from the perspective of macro parameters concerning voltage and current and micro parameters concerning electric field and particle density.The model can be applied to analyze the internal mechanism of DBD under the action of subsequent bipolar square current.(2)The internal mechanism of DBD under the action of bipolar square current was analyzed.It was suggested by the research:Under the action of power supply,it was shown by the field intensity of the discharge air gap and the temporal and spatial distribution characteristics of the particle beam current that helium DBD was a phenomenon of uniform discharge;Current played the key factor to control the density of helium ion He⁺and voltage played the important factor to control the density of helium atom He^*;Although increase of current amplitude I_mpromoted the discharge,it divulged the He^*in space;The increase of current pulse width t_wpromoted the discharge,but excessive t_wwould significantly increase the terminal voltage of DBD load and cause damage;The increase of current rise time t_rinhibited the discharge,but shorter t_rsignificantly improved the performance of DBD load;The increase of air gap width d_gcan allow the discharge of a fall-rise pattern,but it would make the He^*more divergent in space;The increase of dielectric thickness d_binhibited the discharge and delayed the time of air gap breakdown.Therefore,thinner dielectric materials should be selected;The increase of dielectric constant?_bpromoted the discharge and shortened the time of air gap breakdown.Therefore,the dielectric material with higher dielectric constant should be selected.(3)Depending on the characteristics of DBD load under the action of bipolar square current,the DBD was tantamount to a diode clamping equivalent circuit to support the design of power supply.This thesis expounded the advantages of bipolar square current power supply compared with sinusoidal voltage power supply based on the equivalent circuit.A bipolar square current power supply composed of direct current power supply,two quadrant chopper circuit,filter inductance,current inverter circuit,high-frequency transformer and diode clamping equivalent circuit was designed.The working principle and model of the circuit were analyzed and deduced.Besides,the influence of transformer excitation inductance L_mand parasitic capacitance C_son load power was discussed.(4)The software and hardware circuit were designed and the relevant components were selected.The experimental platform that can generate bipolar square current was established and an excimer lamp load based on DBD principle was lit.It was suggested by the research:The working waveform of the load basically conformed to the expected effect.f=70k Hz was the best working frequency under the experimental conditions.The ultraviolet radiation intensity UV of the excimer lamp under this frequency was higher than that under other frequencies;The current duty cycle D was always positively correlated with UV,but the excessive value of D would shorten the idle time when the current was zero,which was not conducive to the composite reaction between micro particles and the continuous operation of excimer lamp;Under the action of the power supply,around 10%of the error can be controlled between the experimental power and the theoretical calculated power of the load.