Mechanism,Implementation And Optimization Of Dielectric Barrier Discharge Energy Compression

Dielectric barrier discharge(DBD)is a typical approach to produce the room temperature plasma,which is widely used in the material surface modification field.With a growing threat from the energy waste and the environmental pollution,the DBD plasma surface modification has attracted more and more attention in the material processing industry and has a wide application prospect in other fields due to its high-efficiency and pollution-free.The high voltage resonant converter is a key part of the DBD surface modification system.Unfortunately,the interaction between the circuit parameters and the surface modification effect are not yet fully clear,which affects the resonant converter design optimation and its engineering applications.Therefore,how to shape the resonant converter output waveforms and control the energy transfer mode so as to realize an efficient plasma treatement has become the main concern in the surface modification field.This research topic is an interdiscipline of plasma,material and power electronics.By focusing on the effect of the energy transfer time in each period,this dissertation investigates the DBD load parameter extraction,the modification effect modeling,the resonant circuit parameter design and the power source performance optimization.Firstly,a piecewise DBD load model is built and a concept of DBD energy compression is proposed.By clarifying the formation mechanism of the DBD load equivalent capacitances,a piecewise DBD load model is established,which has different dielectric equivalent capacitances during the two different working stages of the DBD load.The parameters of the piecewise DBD load model are extracted by measuring the q-v Lissajous figures at different air gap spacings.The piecewise load model describes the transition conditions between the discharge and non-discharge stages more accurately than the tranditional DBD load models,which is more suitable for the precise calculation of the effective discharge time.Based on the piecewise load model,a concept of DBD energy compression is proposed,which can be used to describe the discharge time regulation effect of the power source.By exploring theimpact of the load current wavform on the discharge time,a resonant converter in the discontinuous-current-mode(DCM)is employed to realize the energy compression.The DCM resonant converter also achieves the decoupling control of the discharge power,the discharge time and the switching frequency.Then,the optimizating effect of the DBD energy compression on the surface modification is revealed.By adopting the DCM energy compression in DBD,the polymer material surface is treated.And then,the relationship between the surface modification effect and the energy compression degree is revealed,which shows that polymer surface wettability,roughness and polar function group percentage are all improved by increasing the energy compression degree with the same energy density.It is also speculated that the energy compression can achieve a higher reactive species density and a more efficient energy transfer.By comparing the energy compression effects at different frequencies,a three-dimensional model of surface modification is established,which represents the synthetic effects of the energy compression degree and the switching frequency on the surface wettability.The three-dimensional model also reveals the relationship among the reactive species density,the free electron energy and the reactive species lifetime.Meanwhile,the optimal surface modification conditions and the power source design optimization direction are clarified.Furthermore,an advanced technique of DBD energy compression with the third harmonic circulating current generation is proposed.A virtual current injection analytical approach is presented,which makes the resonant converter equivalent to a virtual excitation current signal injected into the DBD piecewise load model.With this virtual current injection approach,the energy compression is realized by injecting a third harmonic current into the DBD load.A current-fed parallel-series resonant converter is then established,which generates a third harmonic current component and achieves the energy compression.The third harmonic current only circulates inside the parallel-series resonant tank and does not flow into the inverter,which solves the contradiction between the energy compression and the power device current stress.With the natural anti-short-circuit ability,this current-fed parallel-series resonant converter is suitable for the industrial surface modification applications.Additionally,a method of rectifier-compensated fundamental plus third harmonic approximation(RCFTHA)is introduced to describe the current-fed parallel-series resonant converter by superposing two equivlanet linear circuits operating at the fundamental and third harmonic frequencies,respectively.Consequently,the circuit parameter design and optimization are realized with the energy compression degree as a design target.The experimental results form a 350W prototype substantiate the effectiveness of the energy compression with the third harmonic circulating current and the accuracy of the RCFTHA.Finally,the energy compression stability,the soft switching achievement and the high power application examples of the current-fed parallel-series resonant power source are presented.By reversely utilizing the RCFTHA,a judgement method of the energy compression stability at different powers is deduced.It is proved that the current-fed parallel-series resonant converter can achieve a stable energy compression and an overall surface modification improvement over the full power range.And then,with the bypass auxiliary capacitors added into the inverter,the current bypass channels are established to achieve the power device zero-voltage-switching and the inverter high-efficiency operation over a wide power range.Furthermore,the 15kW and 30kW current-fed parallel-series resonant power sources are built,and their experimental results verify that the current-fed parallel-series resonant converter is a viable candidate for the high power DBD surface modification applications.By employing the concept of energy compression,the dissertation establishes an interaction between the high voltage resonant converter parameters and the DBD surface modification effect.Consequently,the effective resonant converter solutions are proposed to achieve the high-efficiency plasma treatment.This study provides siginficant guidance for the optimal design of the plasma power source output waveforms,and it also has high practical value in the energy consumption reduction and the industrial production efficiency enhancement.