With the installation of distributed photovoltaic systemsRongThe rapid growth of quantity has increasingly highlighted the problem of power grid backflow. When the photovoltaic power generation exceeds the local load power, excess electricity will flow into the grid, forming a reverse flow. This not only leads to an increase in voltage in the power grid system, affecting the quality of power supply, but may also damage equipment on the user side and photovoltaic power generation side, threatening the safe and stable operation of the power grid system.plus‌Issued by the National Energy Administration《Management Measures for the Development and Construction of Distributed Photovoltaic Power Generation》In the middle,Propose that large-scale industrial and commercial distributed photovoltaics should generally choose the mode of all self generation and self use. According to this policy,The demand for anti backflow in large-scale industrial and commercial distributed photovoltaic projects has emerged.

1 Project Overview

The distributed photovoltaic project of Fengcheng Qujiang Coal Development Company is located in Yichun City, Jiangxi Province,installed capacityfor5.8MW，Adopting a spontaneous self use mode with surplus electricity not connected to the internet.

Fengcheng QujiangCoal Development CompanyDistributed Photovoltaic Projectfor35/10kVproject，35kVThe side adopts a dual power supply single busbar segmented system, with one incoming line from the State Grid Xian curve incoming line and the other incoming line from the user's own power plant switch curve incoming line. This project has a total ofplace1a10kVConsolidation point, under consolidation pointbelt3A photovoltaic boost box transformer with a fairy curve incoming line distance connected to the gridpoint100-200mThe incoming distance of the electrical curve is connected to the gridpoint6Kilometers. For the connected photovoltaics, the project requires self use and no surplus electricity connected to the grid. The backflow detection point is set at the Qujiang substationplace35kVXian curve incoming line, power plant substation Xian wire incoming line. Based on the above basic conditions and the original construction drawing design, the following is developed to achieve photovoltaic grid connection without grid connection through anti backflow master-slave machines.

2 Project Requirements

measureWhen the power at the two incoming lines of the Liangxian curve and the electric curve is too low when the power of the grid is too low，Step by step jumpopen3Low voltage side switch of a photovoltaic boost box transformer; When the power of the grid is gradually restored, manually close it3Low voltage side switch of a photovoltaic boost box transformer.

3 product solution

This project is based on user needsuseAM5SE-PVSeries master-slave anti backflow protection, connectedpassGOOSEThe communication scheme implements anti backflow rigid tripping, and the detailed plan is as follows.

Picture1 Product Configuration Diagram of Fengcheng Qujiang Coal Project

asPicture1forProduct configuration diagram of this project，Distribution of incoming power lines in the power plant substationplace1Taiwan anti backflow mainmachine1#AM5SE-PVM-GOOSECollect incoming current and voltageCalculate workratePpcc1；At Qujiang Substationplace35kVXian curve incoming line configurationplace1Taiwan anti backflow mainmachine2#AM5SE-PVM-GOOSECollect incoming current and voltage,Calculate workratePpcc2；Install on the low voltage side of the boost box transformerplace1Anti backflow measures from TaiwanmachineAM5SE-PVS-GOOSEUsed for opening and closing low-voltage side switches.A local area network is formed between the anti backflow host and the anti backflow slave through an optical port switch via the fiber optic network of the mobile company's base station.

The rigid anti backflow protection strategy is as follows:

1）Power plant substation Xian wire incoming:

WhenPpcc1And the power is affected bynumberPF＞0When, bymainmachine1#AM5SE-PVM-GOOSEthroughpassGOOSESend commands from the communication network tomachineAM5SE-PVS-GOOSEFrom the machineskip1#Boost box to low voltagesideQF1；

WhenPpcc1And the power is affected bynumberPF＞0When, bymainmachine1#AM5SE-PVM-GOOSEthroughpassGOOSESend commands from the communication network tomachineAM5SE-PVS-GOOSEFrom the machineskip2#Boost box to low voltagesideQF2；

WhenPpcc1And the power is affected bynumberPF＞0When, bymainmachine1#AM5SE-PVM-GOOSEthroughpassGOOSESend commands from the communication network tomachineAM5SE-PVS-GOOSEFrom the machineskip3#Boost box to low voltagesideQF3；

2）Qujiang Substation Xian Curve Incoming Line:

WhenPpcc2And the power is affected bynumberPF＞0When, bymainmachine2#AM5SE-PVM-GOOSEthroughpassGOOSESend commands from the communication network tomachineAM5SE-PVS-GOOSEFrom the machineskip1#Boost box to low voltagesideQF1；

WhenPpcc2And the power is affected bynumberPF＞0When, bymainmachine2#AM5SE-PVM-GOOSEthroughpassGOOSESend commands from the communication network tomachineAM5SE-PVS-GOOSEFrom the machineskip2#Boost box to low voltagesideQF2；

WhenPpcc2And the power is affected bynumberPF＞0When, bymainmachine2#AM5SE-PVM-GOOSEthroughpassGOOSESend commands from the communication network tomachineAM5SE-PVS-GOOSEFrom the machineskip3#Boost box to low voltagesideQF3；

4 Project topology scheme

1） Scheme topology diagram

Picture2 Topology diagram of project proposal

2） Anti backflow protection

Product Image

AM5SE-PVM-GOOSE AM5SE-PVS-GOOSE

3） Project List

5 On site installation pictures

this projectAnti backflow host and slave bothadoptWall mounted boxInstallation method，sceneThe installation image is as follows.

Picture2Qujiang Substation Photovoltaic Grid Connectionpoint Picture3Power plant substation Xian wire incoming line

6Product association scheme

Apart from abovenarrate, recount, stateGOOSEOutside of communication plan，AM5SE-PVThe series also supports fiber optic direct jump solutions, mainly divided intoforAM5SE-PVMhostTheAM5SE-PVSFrom the machineTheAM5SE-PVS2The slave, master, and slave are connected through optical fiber, and can choose multimode or single-mode optical fiber. Multimode optical fiber is suitable for the distance between the mains incoming line and the grid connection pointleave100m-1.5kmSingle mode optical fiber is suitable for the distance between the incoming and grid connection points of the mains power supplyleave1.5km-20km. ItsmiddleAM5SE-PVSSlave machine is suitable for single city power input line，AM5SE-PVS2Suitable for multi city power supply lines, the following are the application scenarios for single city power supply lines and dual city power supply lines:

Single line incoming fiber optic direct jump anti backflow

Dual power incoming line fiber optic direct jump anti backflow

7 Conclusion

The anti backflow master-slave machine introduced in this article can gradually disconnect the photovoltaic boost box transformer during high photovoltaic power generation or heavy load shedding, achieving photovoltaic grid connection without grid connection. sametimeGOOSEThe communication scheme and fiber optic direct jump scheme can ensure the collection of current and voltage signals and accurate anti backflow function when the incoming and connecting points of the mains power are far away, which is helpful for the implementation of spontaneous self use and residual power off grid mode in subsequent large-scale industrial and commercial photovoltaic projects.