Research On The LLC Resonant Converter For Sewage Treatment

OH advanced oxidation sewage treatment power supply is a medium-power rectifier equipment, whose main function is to provide the electric field in the mixed aggregation of boron diamond electrodes, and thus produce strong oxidizing free radicals of OH around the electrode. The organic matter in sewage is completely oxidized to carbon dioxide and water by the free radicals.Firstly, this thesis gives a brief analysis of the development status of the sewage treatment power supply. Compared with the PWM converter, the series resonant converter, the parallel resonant converter and the series-parallel resonant converter, the LLC resonant converter is proposed to have a wide input voltage range and can achieve zero voltage switching(ZVS) in the whole load range. Meanwhile, the secondary rectifier diodes can achieve zero current switching (ZCS). It has the advantages just like high efficiency and high power density that can meet the requirements of the OH oxidation on the power source perfectly.This paper focuses on the research and development of the sewage treatment power supply by the LLC resonant converter. On the basis of detailed analysis of its work process, the steady-state mathematical model of the converter is established by the use of first harmonic approach (FHA). The thesis deduces the input impedance, input output gain, no-load and short-circuit characteristic of the inverter and analyses the effect and influence of the system parameters on the converter process.A simulation model of LLC resonant converter is built by PSIM, whose results show that the main power switches and the secondary rectifier diodes of the LLC resonant converter can achieve zero voltage switching (ZVS) and zero current switching(ZCS) in a large load range. The simulation results verify the accuracy of the theoretical analysis.On the basis of theoretical analysis and simulation, the paper gives comprehensive design of the LLC resonant converter for a further verification. This converter can handle150V/40A power, and chooses TMS320F28035as the core of control system. Experimental results and data verify the converter is designed reasonably.