Research On Single-phase Ground Fault Location Method Of Coal Mine Distribution Network With Photovoltaic Power Generation

With the access of Photovoltaic Power(PV),problems such as the power flow of the coal mines and the short-circuit current characteristics under single-phase ground failure are also complicated.To a certain extent,the topological structure and trend distribution of traditional low-voltage distribution networks are changed,and the power supply network of single power supply is transformed into dual power supply or even polygon.Therefore,the fault positioning method based on the traditional distribution network cannot be applied to the coal mines.This article conducts research on the fault positioning method of the power distribution grid of the photovoltaic power supply,and carried out the following research work:(1)The design and research of the photovoltaic power station system connected to the coal mine distribution network are carried out,and the principle and components of the photovoltaic power system are introduced.The simulation model of the photovoltaic cell is built in Matlab,and the influence of temperature and light intensity on the photovoltaic cell output power,open circuit voltage and short circuit current is simulated and analyzed.The photovoltaic cell type,bracket type and inverter type suitable for the photovoltaic system are selected.The photovoltaic system designed in this paper adopts two-stage three-phase photovoltaic inverter,which adopts voltage and current double closed-loop control.Through the analysis of the output voltage and current waveform of the grid-connected photovoltaic power generation system,it can be seen that the photovoltaic power supply can be equivalent to the voltage source connected to the coal mine distribution network.(2)The effects of PV power supply on fault currents after being connected to the coal mine distribution network,the effects of harmonics generated by PV on the coal mine distribution network when connected at different access points,and the effects of PV on fault location after being connected to the grid were analyzed.The optimal access point is found by comparing the magnitude of the third harmonic generated by PV at different access points to the coal mine distribution network.(3)A method based on zero-sequence current information is proposed to locate the fault line of the single-phase ground fault in the coal mine distribution network with photovoltaic power supply,and then the traveling wave distance method is used to locate the fault line.In this paper,the mode component of the fault line is decomposed by wavelet transform and reconstructed to obtain D1 component.The exact location of the fault point can be obtained according to the maximum value of D1 component after reconstruction.The simulation model was built in Matlab/simulink according to the power system diagram of a distribution network of a coal mine in Shandong province,and the photovoltaic power supply was connected to the optimal access point for simulation verification.It is proved that the proposed method can be applied to the single-phase grounding fault location of the coal mine distribution network containing photovoltaic power generation,and has a high fault location accuracy.