The project is located in Jinrun Avenue West, Danyang City, Zhenjiang City, Jiangsu Province. Jiangsu Weiyi Heat Exchanger Co., Ltd. has a production plant with colored steel tile roofs, a factory canteen with concrete roofs, and a newly built car shed roof. This photovoltaic power generation system adopts single crystal silicon 450Wp photovoltaic modules, with a planned installed capacity of 0.8991MWp. The proposed power generation method is "self use, surplus electricity connected to the grid", and the grid connection voltage level is 0.4kV low-voltage grid connection.

Equipment Selection

Component:

By comparing the table, it can be concluded that

The use of 550Wp components to form a 0.8991MWp photovoltaic array requires a relatively small number of components, which means a small footprint, reduced cable and bracket usage, and reduced investment. However, as this project is a multi-point low-voltage grid connection project, the direct current MPPT input current of the 1000V low-voltage grid connected inverter is about 26A, and the optimal power point current of mainstream high-power 500Wp and single chip power 500Wp or above single crystal silicon modules is more than 13A, The short-circuit current is about 14A, which exceeds the maximum input current of the inverter MPPT. Therefore, 450Wp single crystal silicon module is selected for this project.

Inverter:

This project is a rooftop power plant with scattered roofs and low-voltage grid connection. The series inverter helps to save the cost of collecting line cables, and there are many MPPTs, which can reduce the parallel distribution on the DC side caused by the distance between the collecting lines and improve power generation. Based on the actual situation of this project, it is recommended to choose a 50kW series inverter and a 100kW series inverter.

Design of Color Steel Tile Roof Support:

The photovoltaic support of the colored steel tile roof adopts lightweight materials as the support and foundation, and suitable fixtures and guides are used. The fixture is fully compatible with the roof and is firm and reliable. The support structure adopts an aluminum alloy support system, and the aluminum alloy material is required to be 6005-T5; All aluminum alloy materials are subjected to anodizing treatment, and the film thickness after anodizing is 15&# 956; M; The bolts connecting components to guide rails, components to pressure blocks, and pressure blocks to guide rails are made of 304-2B stainless steel bolts.

design scheme

String design principles:

The output voltage range of a string formed by series connection of solar cell components must be within the allowable input voltage range for normal operation of the inverter.

The total power of the solar cell components connected to the DC input side of each inverter should be greater than the rated input power of the inverter and should not exceed the maximum allowable input power of the inverter.

After 3 solar cell modules are connected in series, their maximum output voltage is not allowed to exceed the maximum allowable system voltage of the solar cell module itself.

The DC cable path from the solar panel to the inverter should be as short as possible to reduce DC losses.

Design of solar cell module string:

The maximum allowable input voltage of the inverter selected for this project is 1100V, and the input voltage MPPT has a full load working range of 550V to 850V. The temperature range of the module operation is -40 ℃~+85 ℃, and the ambient temperature is -10 ℃~50 ℃. The series number of the module is calculated to be 15 ≤ N ≤ 18. After correction based on factors such as the optimal input voltage of the inverter and the working environment of the battery module, the final determination of the series number of single crystal silicon solar cell modules is N=18.

String array design:

This project adopts 450Wp high-efficiency single crystal silicon components, with a total of 1998 installed components and a peak power of 899.1kWp. Each 18 components are connected in a series, with a total of 111 series. Every 7 series are connected to a 50kW series inverter; Every 14 or 15 series inverters are connected to one 100kW series inverter, and every 4 inverters are connected to one 400V AC grid connected cabinet. The two grid connected cabinets are arranged in the distribution room on the first floor of the production plant in the factory area, and the outgoing lines are connected to the low-voltage side busbar of the 1 # and 2 # transformers in the distribution room for grid connection.

Support structure scheme:

The layout of concrete roof components in this project is planned to use single row component brackets, with a component inclination angle of 23 degrees;, assembly

The lowest point shall be no less than 0.3m from the roof. The structural support adopts thin-walled steel structural support, and the diagonal beams of the support columns are all made of U-shaped steel. The columns are connected to the prefabricated concrete support piers with pre embedded U-shaped bolts through a customized base, and SBS waterproof rolls are installed under the prefabricated concrete support piers. The support purlins use U-shaped steel as component guides, and the components are fixed to the purlins through compression blocks.

System solution:

The planned installed capacity of this project is 0.8991MWp, adopting a block based power generation and centralized grid connection scheme. The battery module adopts 450Wp single crystal module, the colored steel tile roof is laid flat along the slope, and the optimal inclination angle of the concrete roof is 23 degrees; Fixed installation on the bracket, and the shed components installed on the purlins also serve as the shed roof, with the azimuth angle consistent with the original building. Each sub array is composed of several solar cell arrays in series and parallel. Each solar cell subarray is composed of a solar cell string, inverter equipment, and grid connected equipment.

The power generation income is the product of the online electricity consumption and the online electricity price. After the normal power generation of the power station construction, the online electricity consumption decreases year by year, and the average annual online electricity consumption during the normal operation period is 8303.24 million kWh.

According to policy requirements, the comprehensive electricity price for the newly built photovoltaic power station in the power plant is 0.6345 yuan/kWh, and the total power generation income during the calculation period is 11.6558 million yuan.

system safety

Roof waterproofing:

For roofs in areas with severe water leakage, cover them with waterproof rolls; Local water leakage areas shall be sprayed with integrated waterproof rolls locally; For the leakage of cracks caused by the structure itself, grouting sealing is adopted.

Lightning protection, grounding, and overvoltage protection design:

1. Grounding and lightning protection of photovoltaic array area

The frame of photovoltaic modules should be grounded using yellow green wires or stainless steel bidirectional puncture plates (concrete roofs), and the installation purlins of modules should be directly connected to the grounding grid. Grounding of photovoltaic cell array bracket. Each series inverter output is equipped with lightning protection devices, which can effectively avoid equipment damage caused by lightning strikes and grid surges. All cabinets should have good grounding. The grid connected cabinet is arranged in the original substation and distribution room, and is reliably connected to the grounding system of the original substation and distribution room.

The grounding adopts a square hole grounding grid, and the grounding resistance should be selected according to the provisions of the "Code for Design of Grounding of AC Electrical Installations" GB50065-2011, which should not exceed 4;. Install lightning strips in areas such as photovoltaic arrays to prevent direct lightning strikes. The service life of the grounding grid is calculated as 30 years. The grounding device complies with the provisions of "Overvoltage Protection and Insulation Coordination for AC Electrical Equipment" GB/T50064-2014 and "Code for Construction and Acceptance of Electrical Equipment Installation Engineering".

2 Insulation coordination

According to the "Overvoltage Protection and Insulation Coordination for AC Electrical Installations" GB/T50064-2014, for equipment of 110kV and below, the insulation level of the main equipment is mainly determined based on the lightning impulse voltage, namely the lightning impulse withstand voltage and short-term power frequency withstand voltage. Determine the insulation level of the main equipment economically and reasonably based on the protection level of the lightning arrester.

Photovoltaic power station relay protection:

1. Inverter protection

The grid connected inverter is a complete set of equipment supplied by the manufacturer, which includes undervoltage protection, overvoltage protection

Low frequency protection, island protection, short circuit protection, and other functions.

2 Grid connected switch protection

1) Overload long delay inverse time protection, short circuit short delay inverse time protection, short circuit short delay definite time protection

Protection, short-circuit instantaneous protection, and ground fault protection functions;

2) Setting function;

3) Overload alarm function;

4) Fault memory function, contact loss indication, MCR function;

3 Fire alarm system

4 Security system

5 (Construction) Fire Protection System

Operation and maintenance plan

After the completion of the construction period, the function of the photovoltaic power generation system project department will be transformed into project operation, with project construction personnel and streamlined personnel responsible for project operation management, and the photovoltaic power generation system operation department will be established. The operating company shall carry out the operation, daily maintenance, and regular maintenance of the photovoltaic power generation system. The overhaul of the photovoltaic power generation system, cleaning of battery components, repair and maintenance of steel bracket paint for battery components, greening maintenance, and hygiene cleaning shall all be carried out through outsourcing to reduce management costs and improve economic benefits.

Maintenance management plan:

Due to the large area of the photovoltaic array, the installation of lightning rods in the array will have a significant impact on the array. According to relevant provisions, after comprehensive consideration, it is determined that lightning rods will no longer be installed in the photovoltaic array of this photovoltaic power generation system. Instead, direct lightning protection will be provided through the connection of battery components and brackets to the station grounding grid through the solar cell array. To prevent damage to electrical equipment caused by lightning intrusion waves and internal overvoltage, lightning arresters are installed step by step in box transformers and DC distribution cabinets.

The maintenance of battery components adopts daily inspection, regular maintenance, regular dust removal, and cleaning.

Auxiliary technical solution:

1 Environmental monitoring plan

In order to ensure the normal operation and data analysis of the photovoltaic power plant, a set of environmental monitoring instrument is installed inside the photovoltaic power plant. The device is composed of wind speed and direction sensors, sunlight radiation meters, temperature measurement probes, control boxes, and brackets, which can measure wind speed and direction, surface temperature of photovoltaic modules, environmental temperature, and total solar radiation in real-time.

2 component cleaning plan

The pollution on photovoltaic modules has a significant impact on power generation, mainly manifested as: firstly, it affects the transmittance of light, which in turn affects the amount of radiation received by the module surface; The second issue is the turbidity on the surface of the module, which can form shadows due to the close proximity to the battery cells, and cause local hot spot effects in the photovoltaic module, thereby reducing the power generation efficiency of the module and even burning the module.

The main pollution sources of the environment where this photovoltaic power station is located are bird droppings and a small amount of small sand and gravel. During the operation of the power station, it is necessary to clean the battery components to ensure their power generation efficiency and prevent thermal spots caused by dirt from burning the battery components.

The cleaning of the surface of photovoltaic array battery modules can be divided into regular cleaning and irregular cleaning.

Regular cleaning is generally carried out every two months and a cleaning route is established. The cleaning time is arranged before sunrise or after sunset. Irregular cleaning is divided into cleaning after harsh weather and seasonal cleaning. Cleaning after severe weather conditions such as strong winds or rain and snow. Clean promptly after each windy weather. Timely inspection should be carried out after rain and snow, and mud spots and accumulated snow on battery surface components should be cleaned. Seasonal cleaning mainly refers to the cleaning of bird droppings in the power generation area located under the migration route of migratory birds in spring and autumn. During this season, daily inspections should be conducted and any contaminated battery components should be promptly cleaned. Daily maintenance mainly involves conducting daily inspections to check the cleanliness of battery components. Those that do not meet the requirements should be cleaned in a timely manner to ensure the cleanliness of the battery surface components.

Due to the fact that this project is a rooftop photovoltaic power plant and manual cleaning is difficult, the component cleaning system is considered in this project. The water source for the flushing system is connected to the existing water supply system in the factory area, and the specific connection point is determined on site. The measured water pressure at the roof where solar energy is installed should not be less than 0.15MPa. If the actual water pressure does not meet the cleaning requirements, a pipeline booster pump should be added. The booster pump is set at the starting point of the water supply connection. The flushing system will construct a new water distribution network to supply water to each quick water intake valve. Each water intake valve can cover a circular area with a maximum radius of 30 meters, and the spacing between water valves will be determined based on the current situation of the roof and the layout of the solar panel, not exceeding 46 meters. Equipped with water hoses and matching flushing water guns, maintenance personnel carry the matching hoses and connect them to the nearby water intake valve when flushing photovoltaic panels. The hoses and matching water guns are used for manual cleaning. The insulation material is made of high foaming rubber plastic foam, which is flame retardant B1 grade. The insulation layer is 45mm thick, and the protective layer is made of 0.3mm aluminum alloy sheet. A drain valve is installed in the water distribution pipeline system to vent the pipeline for water storage during maintenance. When the winter temperature is below 5 ℃, it is not suitable to use water for flushing during the time period. The drain valve should be opened to vent the water stored in the water pipe to prevent pipeline freezing and cracking. Roof solar panel cleaning water drainage system: When cleaning the solar panel, try not to use cleaning agents or other chemicals. Wastewater that does not use chemical cleaning can be directly discharged into the rainwater system of the roof. For locally heavily polluted areas, environmentally friendly cleaning agents can be used and manually wiped locally.