| The dielectric barrier discharge(DBD)system composed of high-voltage power and discharge electrode unit contains multiple second or multi-order circuits,and shows resonance phenomenon at a specific frequency(resonant frequency).The Variation of the resonant frequency with the discharge parameters means that the impedance matching between the high-voltage power and the plasma load is unstable,and the discharge stability is also affected.Therefore,it is very meaningful to study DBD discharge system resonance.In order to achieve impedance matching and improve discharge efficiency,it is necessary to measure the plasma load capacitance.The general method for measuring load capacitance is the Lissajous figure method.The load capacitance is determined from the slopes of adjacent sides of the Lissajous figure.It is difficult to determine the slopes of adjacent sides when Lissajous figures are not regular parallelograms.A new method for determining the load capacitance is required.In this thesis,the following studies were carried out on the DBD discharge system resonance,resonance load capacitance,resonance power and so on:In order to study the DBD discharge system resonance,the current resonance curve in the discharge circuit was measured.We find that the discharge current decreases with the increase of the power frequency,which proves that the discharge circuit has parallel resonance characteristics.Whether argon discharge or helium-argon mixture discharge,the discharge circuit resonates only when it is in wire discharge.With the increase of electrode gap,the resonant frequency increases,the resonant current decreases,and the half-width of current resonance curve increases.When the content of argon is more than 30%,the resonant frequency and resonant current decrease with the increase of argon content,and the half-width of the current resonance curve increases;The resonance phenomenon disappears,when the content of argon is less than 30%.The half-width variation of current resonance curve is explained by the power frequency range corresponding to the isolated wire discharge.A method to calculate the load capacitance of electrode gap discharge based on capacitance probability histogram is presented.The influences of oscilloscope time base,storage length,smoothing method,window number and polynomial order on load capacitance are analyzed.It is found that before making the load capacitance probability histogram,the data collected by oscilloscope should be processed as follows: 1.Nonlinear interpolation is carried out to ensure the same data points in each full voltage cycle;2.Savitzky-golay smoothing is performed on the voltage data after interpolation,and select appropriate smoothing window points(200)and polynomial order(2)during smoothing.Finally,the influence of the screening interval width and statistical cycles number on the characteristic capacitance of capacitance probability histogram is discussed.It is found that only when the screening interval width is appropriate and statistical cycles number is sufficient,two obvious characteristic capacitors will appear in the capacitance probability histogram.The influence of electrode voltage and argon content on resonant load capacitance was studied based on capacitance probability histogram method.It is found that with the increase of electrode voltage,the electrode capacitance is almost constant,the resonant dielectric capacitance increases,but the resonant gap capacitance decreases.With the increase of argon content,the electrode capacitance changes slightly,the resonant dielectric capacitance decreases,and the resonant gap capacitance increases first and then decreases.The variation of resonant dielectric capacitance and resonant gap capacitance is explained by the discharge area and intensity.In addition to,the resonant discharge power and resonant argon atomic spectral intensity were also studied,and it is found that they have similar variation characteristics to the resonant dielectric capacitance. |
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