Research On MPPT Technology Of Thermoelectric Energy Harvesting For Wireless Sensor Network Node Power Supply

At this stage,many wireless sensor network(WSN)nodes still use battery-powered methods.Battery-powered has the disadvantage of requiring manual battery replacement.Energy harvesting technology is a promising alternative to battery-powered.There are many different energy sources in the environment for energy harvesting technology,such as solar energy,wind energy,vibration energy,etc.However,due to the abundant heat sources in industrial sites,this research focuses on thermoelectric energy harvesting.Since the output power of the thermoelectric generator(TEG)is not enough to directly supply the WSN node at this stage,it is extremely important to improve the energy conversion efficiency of the TEG.For TEG,the most commonly used method to effectively improve its output efficiency is to perform maximum power point tracking(MPPT)on its output.The most classic MPPT methods applied to TEG are internal resistance matching method and perturb and observe method.These two methods have their own advantages and disadvantages.The advantages of the internal resistance matching method are simple implementation,fast tracking speed,and stable output after reaching the maximum power point(MPP);the disadvantage is that the TEG and the load need to be disconnected during the tracking process,resulting in energy waste and output fluctuations.The advantage of the perturb and observe method is that there is no need to disconnect the TEG and the load and the tracking accuracy is higher;the disadvantage is that the introduction of perturb makes the output of the system reach MPP with a small range of fluctuations and slow tracking speed.This paper proposes a new MPPT method and verifies it through simulation and actual experiment.The method combines coarse and fine adjustment to improve the energy conversion efficiency of TEG.The specific work content of this paper is as follows:1.Based on experimental fitting,the temperature-output voltage model of TEG-287-1.0-1.3 thermoelectric module is obtained,and the model expression is a simple two-dimensional planar linear equation.The coefficient of determination of the fitting function obtained is~2=0.9992,which is the most consistent with the experimental results under the existing experimental conditions compared with the models obtained in other studies.2.Based on the obtained TEG output characteristic model,a new MPPT method is proposed,and Simulink simulation experiments are carried out on this method.The MPPT method is composed of two parts:coarse adjustment and fine adjustment.The coarse adjustment is an improvement of the internal resistance matching method based on the obtained TEG temperature-output voltage model;the fine adjustment is an improvement of the perturb and observe method.The improvement of both methods overcomes the shortcomings of the classic method and combines the advantages of the two.The simulation experiment verifies that the proposed MPPT method is accurate,stable and fast.3.Set up an experimental platform to conduct a feasibility experiment on the coarse adjustment part of the MPPT method,under the experimental conditions that the heating temperature of the experimental platform is 150℃and the TEG cold end naturally dissipates heat.Compared with no MPPT,the MPPT circuit increases the power obtained on the load by 99.31%,and the output is stable.This proves the feasibility and stability of the proposed coarse adjustment method.