Research On Micro Grid Power Monitoring System Based On Lora Communication

With the gradual advancement of the national goal of "carbon peak and carbon neutralization",the scale of new energy development and utilization is expanding day by day.Microgrid is conducive to solve the problem of new energy consumption.The reliability,power quality and economy of microgrid have attracted much attention.With the help of the current powerful Internet of things technology,this thesis designs a power monitoring system based on Lora communication for the microgrid application scenario to realize the comprehensive monitoring of power consumption information and power quality,reduce the operation and maintenance cost and improve the intelligent level of power consumption.The main research contents and work of this thesis are as follows:（1）This thesis expounds the target function and design principle of microgrid power monitoring system,and designs a complete network architecture of monitoring system.Based on the star network structure,the monitoring system is divided into three layers,including terminal equipment layer,communication layer and master station layer.Lora communication mode is adopted between terminal equipment layer and communication layer.（2）This thesis expounds the power quality evaluation standard of microgrid,studies the detection methods of harmonic,voltage rise,voltage drop and short-term voltage interruption in microgrid,and makes simulation analysis on MATLAB platform.It includes detecting the amplitude,frequency and phase of steady-state harmonic signal based on FFF and its improved algorithm,and comparing and analyzing the detection effect.The simulation results show that double window all phase bispectral FFT has better detection effect than windowed bispectral FFT;The method based on DB4 wavelet transform can effectively detect the start and end time of transient disturbance signal and the effective value under disturbance,and distinguish voltage sag,voltage sag and voltage short-term interruption according to the effective value;The combination of double window all phase bispectral FFT and DB4 wavelet is studied to decompose,denoise and reconstruct the harmonic signal under transient disturbance with noise.Matlab simulation shows that this method can detect the start and end time of mixed transient disturbance with noise and the content of each harmonic.（3）The software and hardware design and experimental prototype development of the intelligent power measurement and control instrument at the terminal are completed.The hardware includes MCU minimum system and its peripheral circuit,sampling and signal conditioning circuit and Lora communication circuit.In the software,the message format and content of the power monitoring system are designed first,and then the main program,sampling program and sx1278 transceiver function subroutine of the intelligent power measurement and control instrument are designed.（4）Considering and designing the software and hardware implementation of the system,STM32f407 and SX1278 are selected as the core processor of intelligent power measurement and control instrument and Lora communication RF chip.Based on these two chip selection,the hardware circuit of intelligent power measurement and control instrument is designed,including power supply circuit,Lora communication circuit,relay control circuit and sampling conditioning circuit.Based on sm32 cubemax and KEIL development environment,the main program and functional subroutines of intelligent power measurement and control instrument are designed and written.（5）A power monitoring Internet of things test platform based on One NET is built.The specific construction method is that the relay gateway is connected to the Internet of things platform as hardware equipment,and the intelligent power measurement and control instrument is connected to the relay gateway;According to the data uploaded by the relay gateway,the visual interface design of the monitoring master station is completed.The communication capability of Lora and the basic measurement function of intelligent power measurement and control instrument are tested,and the test results meet the expected requirements.