Research On The Inverter-based Electromagnetic Detection Transmitting System

The electromagnetic detection method is an important geophysical detection method that is able to characterize the electrical properties of materials,and it has good detection effects and wide application scenarios.This method is based on the principle of electromagnetic induction,which has unique advantages in the acquisition of the electrical and magnetic conductivity of the target,the inversion and interpretation of the data.In geological and hydrocarbon exploration,the electrical and magnetic conductivity information of the target to be surveyed is the key information for the exploration task,so the electromagnetic detection method has a high application value in geological and hydrocarbon exploration.According to the different time-frequency domain characteristics of the transmitting signal,the electromagnetic detection method is subdivided into the frequency-domain electromagnetic method and the time-domain electromagnetic method.The transmitting signal of the frequency domain electromagnetic method is a sinusoidal voltage signal,which has the advantages of strong lateral detection capability,high detection resolution and accuracy,while the transmitting signal of the transient electromagnetic method is a trapezoidal current signal,which has the advantages of large detection depth,high mobility and strong terrain adaptability.For different application scenarios and application requirements,this paper carries out the design work of electromagnetic detection transmitting system,which has important value and significance to the development and application of electromagnetic detection technology.In both of the above-mentioned electromagnetic detection applications,the transmitting system needs to generate high-power alternating signals.The generation of highpower alternating signals is very suitable for inverters,so this paper uses three different inverter technologies as technical means to generate transmission signals,and designs three transmission electromagnetic detection transmission systems that meet different application scenarios to overcome the shortcomings of different transmission systems,such as large size,high switch losses,and long shutdown times.In the theoretical part,this paper analyzes the working principle of the transmitting circuit,establishes a model,and theoretically analyzes and deduces formulas for the voltage and current in the transmitting coil.In terms of engineering implementation,this paper completes the construction of the main circuit in the hardware design of the system,and designs supporting modules such as power supply modules,drive circuit modules,capacitor voltage detection modules,and control circuit modules,making the circuit have the hardware foundation for transmitting target voltage signals.In the software design of the system,this paper completes the design of the RTL program in the FPGA to achieve functions such as communication,protection of hardware circuits,and control of power devices,enabling it to have software compatibility with the hardware.This paper has completed the following research work to address the above issues:(1)An cross-well electromagnetic transmitting system was designed based on IPM.In the paper,intelligent power modules were used to replace power devices to build a single-phase inverter,and a matching software and hardware system was designed.Pulse width modulation technology was used to convert the input DC voltage into a sine wave voltage signal for output,and single-frequency sine wave voltage signals with multiple frequencies in the frequency range of 15.625Hz～2k Hz can be transmitted.The maximum voltage amplitude is up to 500 V,and the maximum current is up to 10 A.(2)A transient electromagnetic transmitting system was designed based on a ninelevel inverter,which can output multiple positive and negative voltages of different amplitudes to achieve an adjustable turn-off time of the transient electromagnetic emission current.The feasibility of the design was verified through simulation,and a matching software and hardware system was designed.Through experiments,it was verified that when the peak transmission current is 1.7A,three different cutoff times of 162,142,and129 can be achieved,and the switching frequency is less than 100 times per second.(3)A transient electromagnetic transmitting system was designed based on a constant voltage double-clamping inverter.The system uses the charging and discharging characteristics of capacitors to generate an instantaneous high-amplitude bipolar voltage,which shortens the cutoff time of the transmission current to achieve better detection results.The feasibility of the design was verified through simulation,and a matching software and hardware system was designed.Through experiments,it was verified that when powered by 5V,the peak transmitting current is 8A,the turn-off time is about 150.2,and the frequency is less than 100 times per second.