The Development Of NMR Transmitter Based On Parallel Charging Technology

Nuclear Magnetic Resonance(NMR)water-seeking method,as a direct,noninvasive physical water-seeking method,has significant advantages such as high resolution,rich information,and unique interpretation.It's widely used in China's arid areas.JLMRS,as the only NMR groundwater detection instrument product with core technology independent intellectual property,has achieved good application effect in China.However,with the increasing demand for deep groundwater detection,the environmental impact of strong electromagnetic noise is increasingly intensified,the JLMRS transmitter system has obvious problems such as slow charging speed of storage capacitor units and low charging voltage accuracy,which in turn greatly reduces the system detection efficiency and accuracy.In order to solve the above technical problems,this paper proposes a development scheme of a NMR transmitter system based on parallel charging technology.The main research work is as follows:1.Analyze the output current of the power supply in the transmitter system,and influence the working state of the system during the entire launch process.The output current of the power supply,the charging current of the storage capacitor unit,is a major factor that restricts the working efficiency of the transmitter system.By analyzing the necessity of the adjustable charge current and the demand characteristics of high-power supplies,a design proposal for using a parallel DC/DC switching power supply to constitute a high-power charging power supply is proposed;2.Study the current-sharing technology and charging current self-adjustment algorithm for parallel DC/DC switching power supplies.Based on the double closedloop feedback loop of voltage and current,the fuzzy PID algorithm is used to realize the parallel current sharing of the dual power supplies;the adaptive adjustment of the charging current is realized by using digital pulse width modulation technology;and a parallel power supply module is developed based on the above technology.The ability to quickly and accurately charge the capacitor lays the foundation;3.Transient launch bridge units and transmitter control units are designed.Highpower IGBTs are used to build transient transmission bridges,and the IGBT buffer absorption circuit is optimized to reduce the switching loss and suppress the turn-off peak voltage;the STM32-FPGA hardware architecture is used to realize the transmitter drive and control;Based on the above hardware unit,large Power supply requirements;Finally,the transmitter system performs laboratory and field verification tests,respectively.The results show that the parallel DC/DC switching power supply has a reasonable design,the current unevenness is less than 1%,and the current sharing effect is ideal;the higher power supply is increased from the original 450 W up to 1500 W,and the output charging current is increased from the original fixed 1.3A 1~3.5A adjustable;Transmitter control unit communication without error code,emission,energy release,acquisition,drive,synchronization and other key timing logic is reasonable;launch voltage has good consistency,accuracy up to 0.1V;especially in the larger launch voltages,the efficiency of the transmitter system has increased by nearly 50%.In summary,the performance indicators of various aspects meet the design requirements of the NMR instrument transmitter and provide important technical support for deepwater detection.