Research On The Key Technologies Of Power Supply For High-voltage High-power Electromagnetic Transmitter

As essential equipment for electromagnetic exploration, electromagnetictransmitter reverse the steady power supply with desired frequency and transmit thepower through grounding electrodes, in order to obtain effective electromagneticfield for deep geophysical exploration. To obtain effective geophysical data duringdeep exploration, the transmitter needs to be high-voltage, high-current, withhigh-accuracy output, and yet compact and light. The researches on the powersupply technologies for high-voltage high-power electromagnetic transmitter is ofsignificant importance to the deep geophysical explorations in China.Through the engineering research project, and based on switching powertechnology, we conducted in-depth study on the topology, modeling methods, andsystem controlling methods of high-voltage high-power electromagnetic transmitters,as well as the series-parallel integrated voltage/current sharing controlling methods,in order to address the issues in the power supply for high-voltage high-powerelectromagnetic transmitter.After analyzing the basic characteristics and current research status of thepower supply technology for high-voltage high-power electromagnetic transmitter, anew approach for theoretical study and technical development for the power supplytechnology based on switching power technology was proposed. From theperspectives of both controlling method and controlling performance, conventionalswitching power supply technology could not fulfill the special requirements for thetransmitter. For this limitation, we conducted detailed analysis on the basiccharacteristics, research status, and individual characteristics of the modeling method,controlling method, and modularized series-parallel integrated voltage/currentsharing method of switching power supply technologies, and summarized andcompared the existing issues in each of the technologies in order to identify the focusof this study.For the special usages and technical indicators of high-voltage high-powerelectromagnetic transmitter, the power topology of series-parallel two-passfull-bridge converter modules is adopted for the designing of two-pass magneticintegrated high-frequency transformer as well as the parameters of the power circuitdevices. The simulation analysis of the high-frequency voltage transformer modeland the magnetic transmitter power circuit model validated the feasibility of thedesign and the reasonability of the parameter choices.The modeling for transmitters at continuous working mode was studied.Transmitter was treated as equivalent to full-bridge converters. For full-bridge converter with on-state loss considered, energy conservation averaging method wasemployed for modeling, while for full-bridge converter with transformer inductionloss considered, equivalent controlled source method was employed for modeling. Forthe full-bridge converters with both on-state and transformer induction lossconsidered, a modeling method was proposed which combining energy conservationaveraging method and equivalent controlled source method. The large-signal averagedmodel, DC circuit model, small-signal circuit model and transfer function atcontinuous working mode were established for each type of converter respectively.The simulation showed that the model for converter with on-state and transformerinduction loss considered could more accurately reflect the characteristics ofnon-ideal full-bridge converters, and proved the accuracy and effectiveness of theproposed transmitter modeling method.Since fractional-order PID controller was adopted for the transmitter, a genetickernel-based particle swarm optimization algorithm (GA-PSO) was proposed totuning parameters of fractional-order PID controller. A method was proposed that theadopting of filter approximation and optimized degree reduction within the requiredfrequency band in order to obtain the integer-order model of the lower order ofapproximated fractional-order PID controller. In addition, the fractional-order PI-PDcontrolling approach for the transmitter with inner current loop, outer voltage loopand load current forward feedback was designed. The simulation showed that theapplying of GA-PSO algorithm to the parameter tuning for fractional-order PIDcontroller accelerated the convergence and improved the accuracy. The two-orderinteger-order model after approximation and degree reduction has consistentcharacteristics with fractional-order PID controller within the required frequencyband and can be used in practical application. The transmitter employingfractional-order PI-PD control has very good stability and dynamic performance,validating the effectiveness of the adopted controlling method.The relationship between the input voltage/current sharing and the outputvoltage/current sharing of each module in the series-parallel integrated system wasstudied in detail. It was found that when voltage sharing or current sharing controlapproaches are adopted for series integrated system, the system is unstable, whereaswhen they are adopted for parallel integrated system, the system is stable; from theperspective of the converter module’s input impedance, this phenomenon wastheoretically demonstrated. Making the converter module’s input impedance bepositive resistant by adopting a type of input matching network was proposed, in order to achieve voltage/current sharing to ensure the balance between the four typesof series-parallel integrated system. It was proposed to employ digitalvoltage/current sharing method for the transmitters, so that based on CAN busdesign, the voltage/current sharing of the transmitter could be realized using digitalcontrollers. And the effectiveness of the voltage/current sharing method was provedfrom the perspective of simulation.Lastly, based on the employed topology of transmitter, high-frequencytransformer and power equipment, as well as the result of the theoretical studies, a25KW prototype was produced. The comprehensive performance tests conducted tothe prototype validated the effectiveness of the theoretical study and simulationresult in this dissertation.This study focused on the technical requirements on the power supply fortransmitter, the practical factors in engineering applications were taken intoconsideration, and theoretical study and experimental validation were performed, itwas also verified in practical application.