Development Of Driving Power For Dual-ultrasonic Compression System Based On STM32 And Experimental Research

Energy is the important material base of human activity. With the speeding up of industrialization, the demand for energy in China is becoming higher than ever before, while more than 50% of the consumptions are dependent on imports, which makes China’s energy security issues highlighted. There is a huge development space in new energy resources and renewable energy resources, and a bright future of the industry. In renewable energy production, biomass occupies a large proportion. Cellulose biofuel is one of the most promising biofuels, which can be made from abundant crops straw, forestry processing waste, waste paper, city garbage and other cellulosic biomass.Studies have shown that ultrasonic vibration assisted pelleting of biomass can significantly improve the biomass density, strength, impact resistance, pretreatment efficiency, and reduce the cost, compared with traditional methods. Obviously, ultrasonic power supply is one of the most important factors influencing the biomass compression effect in the process of the pelleting cellulosic biomass. Therefore, combining with the excellent performance of STM32 MCU and DDS chip AD9850, this paper put forward a design of digital ultrasonic power supply, which simplifies the circuit structure of the power supply to the maximum extent and improves the stability and reliability of the ultrasonic power supply.First of all, the overall scheme is designed based on the function of the ultrasonic power supply. The control chip which is suitable for the ultrasonic power supply, the inverter form and the PWM control scheme are determined. Eventually the overall solution is determined which the STM32 is chose as control core.Secondly, hardware system of the ultrasonic power is designed according to the overall scheme, including the rectifier and filter circuit, BUCK chopper circuit, inverter circuit, feedback circuit, drive circuit and design of high-frequency transformer.Thirdly, ultrasonic power control system based on STM32 is designed, including the STM32 minimum system, DDS module, the dead zone control module, phase detection module, over current and overheating protection module, and the corresponding programs.Finally, the ultrasonic power supply PCB drawing, proofing, welding, debug and test are completed and experiments are done on the press machine developed by our team with the ultrasonic power supply designed in this paper. The results show that pressure hold maximum importance on the density of the biomass pellet, followed by moisture content and compression time. The maximum density of the biomass pellet can be obtained under the condition of 0.4 MPa pressure,60s compression time,5% moisture content. The results also show that moisture content hold maximum importance on the mass loss rate of the biomass pellet, followed by pressure and compression time. The minimum mass loss rate of the biomass pellet can be obtained under the condition of 0.3 MPa pressure,90s compression time,5% moisture content.