Design Of Wireless Power Transmission System For Solar Greenhouse Based On Microwave Technology

The solar greenhouse covers all parts of the country.Judging from the development trend of solar greenhouses,its scale is constantly increasing,and it is expected to increase by 33.33% in 2020.Traditional solar greenhouse sensor acquisition systems usually use wired methods for transmission.Wired power transmission improves the stability of the system.However,the humid environment and the high p H environment of the greenhouse can easily cause aging and damage of the transmission line.The increase in the operating time of the system also increases the failure rate,which makes the sensor work uncertain.And for most large-scale solar greenhouses,the large number of internal sensors leads to the need to lay a large number of electrical-level networks,which poses a problem for the maintenance of power-level networks.Therefore,this paper proposes to solve the problem that the transmission of the sensor d rive circuit inside the solar greenhouse is restricted by wired transmission by means of wireless transmission,so that the sensor installation and its transmission design are modular and simple.Starting from the distribution of internal sensors and opera ting parameters of the solar greenhouse,the spatial distribution of the wireless power transmission device and the design indicators that should be met are determined.Select the appropriate wireless transmission principle by designing indicators.Using wireless transmission and microwave transmission technology,the electrical energy emitted by the photovoltaic panel is converted into electromagnetic waves through the transmitting antenna.The electromagnetic wave is converted into electrical energy throu gh the receiving antenna.In the generation mode of the waveform,a frequency synthesis technique is used to design a microwave generator with a working frequency of 2.4 GHz.The self-feedback RC varactor phase modulator is designed by the linear operation of the varactor.In this way,the problem of the same phase of the transmitted signal is solved.The receiving end uses a microwatt-level energy harvesting circuit to make energy more efficient.In the design of the microstrip antenna array,a one-to-one connection relationship between the excitation source and the radiation unit is proposed.The system transmit and receive antenna dimensions were designed using Ansoft HFSS.The relationship between the number of radiating elements and the radiation gain of the antenna is obtained,and the microstrip antenna array structure that meets the requirements is designed to determine its radiation gain.The receiving antenna uses a paraboloid for signal enhancement.In the analysis of the factors affecting the rece iving power of the system,through the selection of the experimental environment,the construction of the experimental collection link is carried out.The relationship between the receiving distance in the ideal environment,the scattering effect of vegetation in the solar greenhouse and the receiving power is theoretically derived.And introduce the influencing factors of environmental electromagnetic waves.Finally,3 trials were conducted.In the process of transmitting from the transmitting end to the receiving end,the effects of vegetation scattering and spatial electromagnetic wave environment on transmission efficiency are explored.The energy conservation law and microwave transmission technology are used to derive the approximate influence of vegeta tion scattering on transmission efficiency.Taking the solar greenhouse dominated by cucumber at different distances and different time periods in Harbin in winter as the test object,the influence of the microwave power transmission system on the receiving power of the photovoltaic microwave wireless power transmission system was tested and analyzed.The test results show that when the system's transmit power is 20 W,the antenna gain is 15.28 d B,and the operating frequency is 2.4GHz,the sensor equipment i n the range of 1.4m can be transmitted.In this range,the power value that the receiving antenna can receive decreases with increasing distance,and the range is between 7.63 and 0.0034W;the received voltage is between 7.38 and 0V,and the current is between 1.04 and 0A.between.The receiving antenna output parameters in the range satisfy the working conditions of the microwatt level energy harvesting circuit.It is capable of collecting microwatt-level energy.Secondly,the closer the receiving point is to the transmitting antenna,the more obvious the effect of receiving power on the scattering of vegetation in the solar greenhouse.The total received power of the receiving point near the analysis of the transmitting antenna needs to be included in the scattering component.