Study On Relay Protection Of Distribution Network With Distributed Photovoltaic

In recent years,the use of solar photovoltaic technology has been rapid development,and matures in commercial and industrial applications.Expected in the next few years,the number of PV in China's power grid will grow significantly.However,the distribution of a large number of distributed PV makes the traditional distribution network structure and power flow distribution change,distribution network fault characteristics change.Therefore,the access of distributed PV may cause the misoperation or rejection of the traditional protection device in the distribution network.In this paper,the fault characteristics of distribution network with distributed PV supply are analyzed theoretically,and simulate it.On this basis,the protection of photovoltaic power supply distribution network is improved,to make the protection of distribution network can adapt to the access of distributed photovoltaic power supply.In this paper,the low voltage ride through control strategy of photovoltaic grid connected system is studied,and get the equivalent model of voltage controlled current source for distributed PV.In this model,the output current of distributed PV has nonlinear relationship with the grid voltage,failure analysis of distribution network with distributed PV can not be carried out using traditional fault analysis method.Based on this model,this paper studies the fault characteristics of distribution network with distributed PV,The analysis method proposed in this paper considered the control strategy and characteristics of PV.It is the basis of the following research on the protection of power grid with PV.According to the fault characteristics of PV distribution network,this paper analyzes the causes of the malfunction of the traditional directional element.On the basis of analyzing the relationship between voltage and current phase of PV with low voltage ride through,this paper studies the directional component criterion for low voltage through type PV distribution network.Finally,on the basis of correctly identifying the fault direction,This paper presents an adaptive sequence current distribution network suitable for containing a plurality of PV overcurrent protection.The protection scheme is verified by simulation,can effectively improve the scope of local protection.