Research On The Topology And Control Of DC-DC Converter For Current-Source Type Controlled-Source Electromagnetic Detection Transmitter

Mineral resources are very important to the development of national economy,but with the increasing of mining intensity,the mining resources in shallow surface are gradually reduced,and the exploration of mineral resources begins to move from the surface of the earth and mature areas to deep areas of the earth and difficult to explore.As the key equipment of electromagnetic geological exploration,electromagnetic detection transmitter directly affects the accuracy and depth of exploration.At present,the main topology of the electromagnetic detection transmitter at home and abroad uses the voltage source structure.However,the transmitting current of voltage source electromagnetic detection transmitter is prone to be affected by the transmitting load during geological exploration,which results in current distortion and further affects the accuracy of the detection results.Therefore,this thesis focuses on the current source electromagnetic detection transmitter to study the current source DC-DC converter topology and control technology.The specific research contents are as follows:Firstly,considering the problem that the transmitting current of voltage source electromagnetic detection transmitter is prone to be affected by transmitting load and further leads to distortion,a current source electromagnetic detection transmitter is used,in which the current source phase shift full bridge converter is used for DC-DC level,and the current source type H-bridge converter is used for DC-AC level.On this basis,the working principle,soft switching characteristics,the problem of duty cycle loss and output current characteristics of current source phase shifted full bridge converter under light load condition are analyzed.The control method of current source H-bridge converter is given.The simulation models of voltage source and current source electromagnetic detection transmitter are built respectively to verify the feasibility of current source electromagnetic detection transmitter.Secondly,in order to solve the problem of duty cycle loss in the current source phase shifted full bridge converter,the controlled rectification circuit is applied to the secondary side of the converter,and the mechanism of voltage spike is analyzed.On this basis,combined with the causes of voltage spike in that converter and duty cycle loss,a converter control method is proposed.The working principle,soft switching characteristics,output current characteristics and switching tube stress of the converter are analyzed in time domain.The realization conditions of soft switching,eliminating voltage spike and duty cycle loss are given.Then,a small signal model of output current source DC-DC converter based on the secondary side controlled rectifier is established by using the state space average method.The input voltage-output current transfer function and shift ratio-output current transfer function of the converter are derived and analyzed On this basis,taking the output current as the control target and using the single current loop based on PI control,the closed loop control parameters of the converter are designed and the dynamic performance,steady state performance and anti-input disturbance capability of the converter under closed loop control are analyzed.meanwhile the control parameters are verified by simulation.Finally,this thesis designs and builds the experimental platforms of current source phase shifted full bridge converter and the output current source DC-DC converter based on the secondary side controlled rectifier.And,the effectiveness and feasibility of the proposed control method to eliminate voltage spike and duty cycle loss are verified by comparing the experimental waveforms of the two converters.Meanwhile,the soft switching characteristics of the two converters are verified.