| Microgrid is a small power generation and distribution system composed of energy storage device,distributed generation,energy conversion device,load,monitoring and protection device,which can maximize the use of renewable energy and effectively solve the problems caused by the access of distributed generation to the distribution network.The operation and fault characteristics of microgrid are complex,so the traditional protection scheme of microgrid can't adapt to this situation.In this paper,two protection schemes of microgrid are designed.In this paper,the internal line protection scheme of AC microgrid with inverter-based distributed generation is studied.Through the research on the mathematical model of the inverter-based distributed generation,the control strategy of the inverter-based distributed generation is formulated.Based on this,the simulation model of the microgrid line protection scheme is studied.The simulation research is carried out for the fault characteristics of the inverter-based distributed generation and the microgrid.At the same time,the influence of the fault characteristics of the microgrid on the traditional current protection is analyzed.In view of the complex operation and fault characteristics of microgrid and the problems existing after the conventional adaptive current quick break protection is connected to the distributed power supply,an adaptive current quick break protection based on the real-time fault information is designed,and the effectiveness of the scheme is verified by simulation.According to the difference of positive sequence differential impedance in the protection zone,a pilot protection scheme based on positive sequence differential impedance is designed,and the positive sequence current differential protection is added as the backup protection,so as to eliminate the influence of the dead zone when the metallic three-phase short circuit occurs in the line.Finally,the effectiveness of the scheme is verified by simulation. |
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