Study On Protection Of Active Distribution Network Based On Distributed Wind Generation Transient Characteristics

Renewable energy distributed access to distribution network,forming a new type of active distribution network,and increasingly become one development trend of power system.The structure and flow direction of active distribution network are not certain with the network operation mode and distributed generator(DG)supply power state,especially the DG is subjected to power electronic converter c.ontrol and showing the unique transient characteristics.The original three section current protection of distribution network should not be used again,and the differential protection of the high voltage power network will not be adapted.Therefore,it is very important theoretical significance and application value to study the protection of active distribution network.Based on the transient characteristics of' distributed wind generator as the breakthrough point,the paper studied the line protection of active power distribution network which contains motor type and inverter type distributed wind power generation.Firstly,the transient model of the doubly fed induction generator and permanent magnet synchronous generator are analyzed.Qualitatively and quantitatively research the effect of current protection and differential protection after distributed wind power access to distribution network.Secondly,the paper derived the fault current AC component attenuation characteristic of DFIG,which is significantly difference from the fault current slow attenuation characteristic of large system.So the protection scheme of the distribution network based on the comparison of the current attenuation factor at both ends of the line which can distinguish between internal and external faults is proposed.Among them,the current attenuation factor is extracted and characterized by Prony algorithm.Then,the fault current limiting characteristics of the permanent magnet synchronous generator in low voltage ride through are derived,which is significantly different from the characteristics of the fault current increases several times of large system.The protection scheme of distribution network with inverter type wind power is formed,by comparing the current amplitude difference of the two ends of the line.Finally,the simulation model of active distribution network with distributed wind power is built in the power system electromagnetic transient analysis software PSCAD.A lot of fault simulation tests are carried out for the line protection of distribution network,and the results show that the feasibility of the proposed scheme and the effectiveness of the protection algorithm.