Research And Development Of Plasma Surface Treatment Digital Resonant Power Supply

Atmospheric low-temperature plasma can change the hydrophilicity and viscosity of the surface of the materials,and is widely used in manufacturing,metal,medical,plastic,and other fields.At present,the plasma power supply has disadvantages such as large loss,low power factor,and poor current control ability,and the digital plasma power supply has not been fully studied.The thesis takes the Plasma Digital Power Supply as the research object.Based on the plasma load equivalent model,the series resonance and phase-shifting full-bridge ZVS circuit is designed,and the Digital Peak Circuit Mode Control(DPCMC)and software control system is developed using DSP and STM32 dual-core system,and a Plasma Surface Treatment Digital Resonant Power Supply is therefore developed.The main work content is as follows:(1)By analyzing the discharging principle of the plasma generator,the thesis proposed the generator load equivalent model,which is simulated and verified by the PSIM tool,and attained the breakdown characteristics and frequency characteristics of the nonlinear variable capacitive load.Based on the above,a series resonant circuit was designed to compensate for the reactive power generated by the capacitive load,which effectively improves the power factor of the power supply,and the maximum power factor is greater than 0.98.(2)DSP is used to realize the digital control of the "Boost+Phase-Shifted Full-Bridge ZVS+Transformer" series resonance topology.The CCM-Mode Boost circuit is designed to increase the power range of the power supply to 1.5k W.The Phase-Shifted Full-Bridge ZVS circuit is designed to reduce switching loss,and the efficiency is greater than 95% when the set power is above 600 W.Transformer leakage inductance is used to form a series resonance topology,through resonance boost increases the voltage across the load.(3)The CMPSS and EPWM modules of the DSP is designed to develop the DPCMC control mode to improve the dynamic response and current control performance of the Digital Resonant Power Supply,and realized the Cycle-By-Cycle control of the current.The overcurrent protection response time is as low as 10?s while the switching frequency is 40 k Hz.DPCMC is used to modulate the Phase-Shifted Full-Bridge PSPWM drive,and the PSPWM coincidence angle ? is modified by adjusting the set power to achieve better linearity of power modulation.(4)The digital resonant power supply control and software system are accomplished by designing the "DSP+STM32" dual MCU digital platform.A state machine power management system is developed based on DSP to realize accurate and reliable sequence control.STM32 is used to develop Free RTOS operating system to realize the Human-Computer interaction interface and serial Modbus-RTU communication.(5)Performance of the Digital Resonant Power Supply is tested,and the influence of generator parameters,process parameters,and power supply parameters on the plasma surface treatment effect is explored.The results showed that: the Digital Resonant Power Supply is suitable for three loads: Direct Jet,Rotating Jet,and DBD generator,and realizes ZVS with a maximum efficiency of 96.3%.Among the three generators,the Direct Jet generator got the best surface treatment effect under the same test conditions,and the minimum contact angle is12.229°.The surface treatment effect will be worse when the gas pressure,processing height,and speed become greater.And an optimal combination of resonance inductance and switching frequency was found to maximize the output power and thus achieve the best treatment effect.