Research On RF And Vibration Hybrid Energy Supply System Of Power Transformer Low Power Monitoring Node

With the rapid development of China’s social economy,the demand for electricity consumption in various sectors of society is rising,making the scale of the power system more and more huge.As the key equipment in power system,the stability of power transformer is very important to the safe and stable operation of power system.Therefore,it is necessary to monitor the running state of power transformer to prevent transformer sudden failure from affecting production and life.With the development of Internet of Things technology,many low-power sensors have emerged in power transformer monitoring nodes.These traditional power supply methods have the disadvantages of high cost and environmental pollution.Therefore,it is of great significance to design a radio frequency and vibration hybrid energy supply system to collect energy in the environment to power the sensor.In this thesis,the RF and vibration hybrid energy supply system of low power monitoring node of power transformer is studied.Firstly,the design theory of RF energy harvesting antenna and vibration energy harvester is analyzed.A metamaterial unit is designed,and an improved RF energy harvesting antenna is proposed based on this unit.The influence of different size parameters on the antenna performance is analyzed by simulation software,and the optimized antenna is obtained.The resonant frequency of the optimized antenna is 2.45 GHz,the value of S₁₁ at the resonant frequency is-34.95 d B,the value of voltage standing wave ratio is 1.036,and the gain is 0.65 d B.Compared with the antenna before improvement,its performance has been greatly improved.Secondly,a vibration energy harvester based on piezoelectric cantilever beam structure is designed,and the vibration energy harvester is analyzed and optimized by finite element simulation software.The final output voltage of the vibration energy harvester at the first-order natural frequency of 100 Hz is 5.97 V,and the output power is 1.5 m W.Then the energy collection circuit of the hybrid energy supply system is designed.By analyzing different topologies of rectifier circuit and matching circuit,a single-order Cockroft-Walton voltage doubler rectifier circuit and a double-branch matching circuit are designed.The whole circuit composed of matching circuit and single-order voltage doubler rectifier circuit is simulated and analyzed by microwave simulation software,and the component parameters in the circuit are determined.The influence of the input power and frequency of the signal source on the rectification efficiency,output voltage and output power of the circuit is analyzed.When the input power is-10 d Bm,the output voltage of the RF rectifier circuit at 2.45 GHz is 429 m V,the rectification efficiency is 24.5%,and the output power is 24.48μW.At the same time,a power management circuit based on BQ25504is designed,in which the vibration energy collection adopts a bridge rectifier circuit.Finally,the physical production and testing.In general,there is a certain gap between the experimental results and the simulation results.The test results show that the S₁₁parameter curve of the antenna and the RF rectifier circuit has shifted,but the change trend is basically consistent with the simulation.When the input power is-10 d Bm and the load is7500Ω,the output voltage is 318 m V,the output power is 13.48μW,and the rectification efficiency is 13.5%.The output performance curve of the vibration energy harvester is basically consistent with the simulation.The output voltage at the first-order natural frequency is 4.68 V and the output power is 0.74 m W.The experimental results show that the hybrid energy supply system can meet the power supply requirements of low-power sensors.