Research On Adaptive Protection Of Coal Mine Power Grid Based On Digital Modeling Technology

The coal mining industry is the pillar industry of China’s economic development,and a stable power supply system is the guarantee for the safety production of coal mining.The operation mode of coal mine distribution network is varied,the load line is short,and the working conditions are harsh,which adds difficulty to the relay protection.In response to these issues,based on traditional protection,this thesis studies an adaptive current protection scheme and a voltage-current interlock protection scheme based on digital modeling technology,and researches a fault line selection scheme based on fault transient characteristic quantity and artificial neural network,and finally carries out software design for protection setting and fault line selection functions.The main research conducted in this thesis includes the following:Firstly,this thesis elaborates the concept of digital modeling technology,analyzes and compares two modeling methods,model driven and data driven,and designs the digital model and digital logic model of the coal mine distribution network,in order to achieve the description and verification of the target function.Based on the PSO particle swarm algorithm,a real-time online updating method for digital model parameters was studied,the effectiveness of the verification method was verified,and certain improvements were made to the algorithm.The theoretical analysis of grounding faults in coal mine distribution network was carried out,and simulation verification was conducted using MATLAB/Simulink.The setting principles of traditional three-stage current protection were introduced and its shortcomings were analyzed.The adaptive protection scheme based on digital model is studied,and the improvement of protection performance and setting workload is verified by a case.In view of the short load line and low impedance of coal mine distribution network,there is often no protection area for current velocity break protection.Considering the situation that current increases and voltage decreases at the same time when short circuit occurs,a digital model based voltage and current interlocking instantaneous speed break protection is studied,and the effectiveness of protection is verified by an example.In response to fault line selection,based on the designed digital model,the fault fusion line selection method based on the zero sequence transient characteristics and neural network is adopted.The wavelet packet is used to decompose the fault zero sequence current simulated by the distribution network model by three-layer wavelet packet.The wavelet packet coefficient on the third layer is calculated and used as the input to train the BP neural network.The output result of BP neural network is used as the criterion for fault line selection.Finally,based on MATLAB GUI,this thesis has designed an adaptive protection application software for coal mine distribution network.The protection setting and line selection methods studied in this paper are integrated into the software and the reliability and stability of the software are tested.