Study On Uninterrupted Voltage Regulating Power Supply With Wide Range Input Voltage For Downhole Tools

With the development of oil and gas exploitation technology,there are more requirements to power supply for downhole tools such as log-while-drill instruments and downhole guided control tools.Turbogenerators have become their main power supply equipment because they can adapt to the extreme downhole environment and have a long working life.However,the drilling fluid flow required by the drilling technology varies widely,which makes the output voltage of the turbo generator change in a wide range.Not only will the quality of power supply decrease,but even the function of downhole tools become invalid.In the event of the turbogenerator failure,it will cause power interruption,which will affect the reliable and stable operation of downhole tools.Aiming at the above problems,an uninterrupted voltage regulator scheme with wide range input voltage for downhole tools is proposed by combining theoretical analysis,circuit design and simulation analysis.The correctness and effectiveness of the scheme are verified by experimental tests.The main contents and phased research results are as follows:1^st.The adaptability of downhole power supply to wide range input voltage caused by large range fluctuation of drilling fluid flow is studied.The voltage stability characteristics and application scope of common DC-DC converter topology are compared and analyzed.A two-stage DC-DC voltage stabilization topology of isolated SEPIC converter cascade BUCK converter is proposed.Under wide range input conditions,stable DC voltage output is finally achieved.2^nd.The reliability of underground power supply caused by the extreme environment in the downhole and turbo damage is studied.The lithium battery pack is selected as the backup power supply,and an uninterrupted switching control method based on power multiplexer chip for downhole tools with two independent power sources is presented.Ensure that the backup power supply of the main power failure can be put into the power supply system quickly,and ensure the high reliability of the downhole power supply.3^rd.The circuit parameters of the front and back converters of the main circuit are designed,and the control loop of the isolated SEPIC converter based on peak current control is constructed.The MATLAB simulation results show that the SEPIC converter can maintain a stable 45 volts output in the range of 15?120 volts input voltage.The small signal model of BUCK converter circuit is established,and the control loop and loop compensation network of BUCK converter based on single voltage control are designed.The 45 volts voltage is further converted to a stable 12 volts output.4^th.The hardware circuit is designed,the principle prototype is made,and the experiment is carried out.The experimental results show that when the input voltage varies from 15 to 120volts,the output voltage is stable at 12 volts and the maximum ripple of output voltage is 183millivolts.When the main power supply fails,it can switch to the backup power supply automatically,and the switching time is less than 3.1 microseconds.The validity and feasibility of the uninterrupted regulated power supply system scheme with wide range input in oil and gas wells are verified.These results can provide technical reference for further research on the downhole power supply technology with turbogenerator as input.