| As a kind of single-headed roadway,the mine tunneling face is prone to gas accumulation.If the gas concentration exceeds a certain value,a major explosion accident will be happened in the event of slight spark.The local ventilator is the main air supply device of the tunneling face,the reliability of its power supply is directly related to the safe production of coal mines.In order to ensure the local ventilator works continuously for 24 hours and realize exvacation equipment not stopping,this paper designs an energy storage device for emergency power supply of mine local ventilator that integrates charge and discharge,and its control technology is studied.Firstly,aiming at the "Three Specialties and Two Lockups " power supply system of local ventilator,the overall function and structure of the emergency power supply energy storage device is designed.The energy storage device can not only be used as an emergency power source when the power system faults,but also can achieve the reactive power compensation function during normal operation of the power grid.The working principle of the two-stage power convert system is analyzed,and the power circuit of the energy storage device is mathematically modeled.Secondly,the battery management system of the energy storage device is designed.Appropriate energy-storing batteries were selected according to the operating characteristics of different batteries.Aiming at the energy unbalanced during charging and discharging of the individual cells,a battery energy equalizer based on a bidirectional DC-DC chopper circuit is designed.The simulation results show that the energy inconsistency between the individual cells is significantly reduced after multiple charge and discharge cycles.Besides,the control strategy of the two-stage energy storage converter is analyzed.The front-stage DC-DC converter acts as a buck-boost,which adopts voltage and current double closed-loop control during emergency power supply and grid-connected operation to ensure the stability of the DC bus voltage.The rear-level PWM converter adopts droop control strategy based on low-voltage distribution network correction in emergency power supply mode.The power loop,voltage loop,and current inner loop are parameterized.To avoid the impact of voltage and current caused by different control strategies during mode switching,the PWM converter still adopts the droop control strategy in grid-connected mode.To avoid the influence of grid fluctuations on converter output power,the Q-f and P-U control loops is improved.A simulation model of the energy storage converter is built in Matlab/Simulink.The simulation results show that the control strategy adopted in this paper can make the energy storage converter operate stably in two modes.Finally,the mode switching control method of the energy storage device is studied.The third harmonic injection method is adopted to detect the islanding of the microgrid system composed of the energy storage device and the fan load.According to the common faults of the underground ventilator power supply system,the mode switching control strategy of the energy storage device is proposed based on the island signal and the mode switching signal and the transient switching process of the energy storage converter is studied.The simulation results show that the islanding detection technology used in this paper can determine the operating state of the microgrid system,and the single-mode control strategy can achieve smooth switching of voltage and current.There are 81 figures,9 tables and 92 references in this paper. |
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