Research On Adapitive Directional Protection For Active Distribution Networks

With the continuous increase of the distributed power(DG),the distribution network transforms from the traditional passive network to the active distribution network.A large number of Inverter-Interfaced DG(IIDG)accesses have an increasingly important impact on the safe and stable operation of the power grid.In order to prevent the IIDG large-scale network disconnection during the power grid to bring serious adverse effects to ensure the safe and stable operation of the power grid,grid-connected regulations require that the distributed power supply in the power system accident or disturbance caused by voltage drop in a certain voltage drop Range and time interval,to ensure that no off-line continuous operation,or even to the grid into the additional reactive power,so as to support the grid voltage to achieve fault crossing.Moreover,the traditional distribution network in the probability of the highest asymmetric failure.Therefore,in order to ensure the safe and stable operation of the distribution network,this paper proposes an adaptive directional protection scheme suitable for active distribution networks,and discusses the implementation of the protection scheme under asymmetric fault faulty operation control strategy.Compared with the protection of high-voltage transmission network,the research on protection of distribution network is still weak.In this paper,firstly,the development of active power distribution network protection at home and abroad is sorted out,and a simple and economical relay protection scheme is proposed according to the characteristics of tree topology of active power distribution network.The scheme is adaptable to different fault components,DG type and permeability,distribution network operation mode,distribution network reconfiguration and so on.Compared with the differential protection,the protection scheme has better economy,suitable for active use in a large number of distribution network.Then,in order to meet the requirement of grid-connected regulation,this paper proposes a fault-tolerant distributed fault-tolerant distributed power control strategy to establish the equivalent circuit of inverter distributed power supply.Based on this,the optimization method of control strategy is studied.The effectiveness of the control strategy and optimization method is verified by simulation.The research results show that the control strategy can improve the running capability of the fault-tolerant distributed power supply,improve the fault characteristic and facilitate the fault analysis.The main difference between the proposed control strategy and the fault feature analysis method is that the different control strategies of the converter and the characteristics of the controlled current source of the distributed power supply can meet the requirements of the relay protection principle analysis and setting calculation need.Finally,this paper discusses the realization of the protection scheme,mainly studies the direction components of the key components and the communication standard IEC 61850.This paper analyzes the adaptability of traditional directional components in active power distribution network,and proposes a principle of directional components for distribution network in active distribution network.For IEC 61850,the information model of adaptive direction protection,the function realization of automatic configuration unit and the project configuration of distribution network protection are analyzed emphatically,and a preliminary exploration of IEC 61850 is introduced in the protection of distribution network.