| Nowadays,thermal power plants in China generate electricity by igniting coal powder.The materials for combustion are rare ones such as heavy oil.Under the circumstance of growing energy crisis,plasma ignition becomes the first choice for thermal power plants to due to its advantages of economy and environmental protection. The power supply system of arc heater is the key to guarantee the stability in the ignition process.To develop a power supply system for plasma ignition with proper structure,reliability and good control performance shares great practical value.This paper designs a three-phase SCR rectifier based power supply scheme whose main part is SIEMENS SIMOREG DC-MASTER.According to the parameters of arc heater,control function of 6RA70 is finished by the software of Drive Monitor.The system applies PLC as the core of the whole control system to realize automation control for the power supply system.The system realizes the S7-200PLC's control on 6RA70 by USS protocol.This paper designs the I/O interface circuit between S7-200PLC and 6RA70 and compiles the logic control program.The existing plasma arc heater adopts motors to pull electrodes for arc-generation. This existing technology leads to the complex structure and increases the cost of the system.Therefore,this paper designs an arc generation circuit based on Flyback converter at HF.This paper carries out research on the match between the power supply and loads as well as conditions and demands for stable ignition.This paper also proposes a complex control method which combines current feed-forward and feed-back control. This method satisfies the needs of arc heater both in stable and dynamic state.This control method is realized by the configuration and optimization of 6RA70's parameter.The power supply system is debugged and the key factor of arc generation is analyzed by experimental results.In the experiment the power supply system operates stably and the flame burns steadily.The feasibility of system scheme is proved.
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