Research On Power Supply System Of Ultra-high Voltage Transmission Line Monitoring Equipment Based On WPT Technology

In recent years,EHV transmission lines have become the main force of long-distance power transmission,an important way to realize power dispatching between the north and the south,and play an important role in national economic development.By installing on-line monitoring equipment on transmission towers,the EHV transmission lines can be monitored in real time,and abnormal situations can be dealt with in time to avoid accidents,thus ensuring the safe and stable operation of the power grid.However,with the development of online monitoring technology,how to provide stable and efficient power supply for online monitoring equipment in various complex environments has become an urgent problem to be solved.Taking electricity from the power line itself is an important way to solve the power supply problem of on-line monitoring equipment.However,the huge potential difference makes the on-line monitoring equipment of transmission towers unable to directly utilize the electric energy at the high voltage side,and the electric energy transmission can only be realized by overcoming the insulation safety distance by means of wireless power transmission.In view of the above phenomenon,this thesis designs a power supply system for on-line monitoring equipment of EHV transmission lines based on the emerging wireless power transmission technology of RF power acquisition.On the premise of not using the fundamental electric energy of EHV transmission lines,the system extracts and utilizes the harmonic energy in the power grid,and combines the electromagnetic induction principle and the new technology of wireless power transmission to convert the extracted harmonic energy into the form of radio frequency energy.It crosses the safe distance of EHV insulation in the way of wireless power transmission,and transmits the radio frequency energy to the radio frequency power taking device on the tower,which converts the radio frequency energy into stable direct current energy,thus achieving the stable and efficient power supply goal for the on-line monitoring equipment of transmission towers.The system extracts and makes reasonable use of the harmonic energy which is detrimental to the quality of the power grid,thus improving the utilization efficiency of electric energy and the quality of the power grid.The main research contents are as follows:(1)The power supply system of EHV transmission line monitoring equipment based on wireless power transmission technology is designed.The overall design is divided into four parts:the harmonic power extraction circuit design of EHV transmission line,the power supply design of RF power transmitter,the design of RF power transmitter and the design of RF power receiver.(2)Research on harmonic power extraction According to the basic principle of passive filter and the design method of related parameters,combined with the fundamental flux principle,a single tuning filter is connected to the primary side of a three-winding transformer,and a hysteresis comparison PWM current control method is adopted in the secondary winding.The fundamental compensation current with the same size and opposite direction as that of the primary side is generated by active compensation,so that the fundamental flux of the iron core is equivalent to zero as a whole,and the leakage impedance of the primary side of a series transformer to the fundamental wave is nearly zero,and the excitation impedance to the harmonic wave is very high.MATLAB is used to establish the simulation circuit model of single-phase harmonic power extraction,and the obtained waveform in the harmonic power extraction circuit is transformed by FFT,the spectrum distribution is observed,the effectiveness of the harmonic power extraction circuit is checked,and the extracted harmonic power is calculated.(3)The power supply design of radio frequency power transmitting device includes the design of coil turns,the selection of iron core materials,and the design of isolation protection circuit.The power supply uses electromagnetic induction principle to couple harmonic electric energy,which is converted by surge protection,rectification and filtering,voltage stabilization and DC-DC circuit,and then output to a stable DC voltage to supply power to the radio frequency electric energy transmitter.(4)The whole circuit design of RF power transmitting and RF power taking device is carried out by Altium Designer,and the board is cast to make the real thing.An integrated RF wireless transceiver chip is selected at the transmitter,which makes the whole RF transmitter more integrated,intelligent and miniaturized.The acquisition terminal of RF is based on the topological circuit structure of seven-order rectification and voltage doubling,which makes the RF power taking device have higher output voltage and power,and can provide stable DC power for monitoring equipment.Finally,the experimental data show that the power supply system of EHV transmission line monitoring equipment based on the wireless power transmission technology of radio frequency power acquisition can collect the working voltage of the online monitoring equipment when it runs normally outside the safe distance of EHV transmission line under the premise that the transmitting power of the radio frequency power emitting device is 7W,thus realizing the stable and efficient power supply goal of the online monitoring equipment.