Research On Internal Lightning Over-voltage Protection Of Large Centralized Grid Connected Photovoltaic Power Generation System

Lightning is a serious natural calamity factor that endangers the safe and reliable operation of grid-connected photovoltaic(PV)systems.The transient overvoltage caused by lightning in the system,namely lightning surge,will damage various electrical and electronic equipment through various ways,resulting in outage accidents and economic losses.Therefore,the protection of the transient over-voltage is a crucial problem.In view of the transient over-voltage in PV system,a complete set of protective measures should be taken.Installation of SPD(surge protective device)is an important one of them.As far as the published literature is concerned,the lightning surge protection design in PV systems is implemented according to the relevant specifications and experiential approaches in many engineering projects at present,lacking quantitative design calculation and sufficient reference basis.The simulation research and experimental investigation of DC SPDs applied in grid connected PV system are carried out in this paper.Firstly,based on PSCAD simulation software,the simulation model of DC SPD is established.The single-stage and doublestage SPDs are simulated respectively,and their protection characteristics are analyzed.The circuit structure,parameter selection and energy coordination are further discussed.The performance test is conducted on the assembled prototype of the SPDs.The relevant protection indexes are measured and compared with the simulated results to check the validity of the simulation model.Furthermore,the design is finalized for the SPDsSecondly,the simulation model of SPDs at both ends of the cable is established,and the energy cooperation is analyzed.The influence of the cable length on the overvoltage suppression effect is investigated.The feasibility of the simulation method is verified by theoretical calculation of the parameter range of the cable for connection.Then,the transient simulation model of the PV power generation system is built,and the installation scheme of the SPDs in the system is discussed.The protective effects of SPDs are inquired for the lightning surges intruding from PV module and 35 k V grid sides,respectively.The research results reported in this paper can provide quantitative reference for the design and application of the SPDs in photovoltaic power generation system.They are of practical significance for the lightning overvoltage protection in photovoltaic power generation systems.