1. General provisions for BIPV system design
BIPV system design generally has the following provisions.
①Industrial and civil building photovoltaic systems should be specially designed or used as part of the building electrical engineering design.
②The selection and design of photovoltaic modules or square arrays should be combined with the building. Under the premise of comprehensive consideration of power generation efficiency, power generation, electrical and structural safety, and application and aesthetics, component-type and building-material photovoltaic modules should be reasonably selected and matched with the building model. The numbers are coordinated to meet the requirements of installation, cleaning, maintenance and local replacement.
③The cables for power transmission, distribution and control of photovoltaic system should be arranged in a coordinated manner with other pipelines, safe, shielded, and centrally arranged to meet the requirements of installation and maintenance.
④ The photovoltaic module or square array connecting cable and its total output power shall comply with the relevant regulations of “Photovoltaic (PV) Module Safety Setting Part 1: Structural Requirements” GB/T20047.1.
⑤A warning sign for preventing electric shock should be set up at the position where people may come into contact with or approach the photovoltaic system.
⑥ The grid-connected photovoltaic system shall have corresponding grid-connected protection functions.
⑦ Photovoltaic system should be installed with metering device, and should reserve detection interface.
⑧ The photovoltaic system should meet the requirements of the “Technical Requirements for Grid-connected Photovoltaic System” (GB/T19939) on power quality indicators such as voltage deviation, flicker, frequency abundance deviation, harmonics, three-phase unbalance and power factor.
⑨ The independent photovoltaic system of the high grid should meet the relevant requirements of “Technical Conditions and Test Methods of Household Solar Photovoltaic Power System” and “GB/T 19064”.
2. BIPV system design requirements
①It should be based on factors such as the use function of new buildings or existing buildings, power grid conditions, load nature and system operation mode. Determine whether the photovoltaic system is a building material type, a component type or an installation type.
②The photovoltaic system is generally composed of photovoltaic array, photovoltaic junction box, inverter (limited to including AC line system), battery and its charging control device (limited to the system with energy storage device), electric energy meter and instrument displaying electric energy related parameters .
③ The performance of each component in the photovoltaic system should meet the relevant requirements of national or industry standards, and should obtain relevant certification.
④The design of photovoltaic array should follow the following principles.
a. Determine the type, specification, installation location and installation site area of photovoltaic modules according to the building design and its power load.
b. Determine the installation method of photovoltaic modules according to the principle of adopting the best inclination angle as much as possible, easy to remove dust, and ensuring good ventilation of the modules.
c. According to the rated DC voltage of the inverter, the maximum power tracking control range, the maximum output working voltage of the PV modules and its temperature coefficient, determine the number of PV modules in series (or PV modules or strings).
d. Determine the parallel number of PV modules according to the total installed capacity and the capacity of PV module strings.
e. The electrical performance parameters of components within the same string and the same sub-array should be as consistent as possible, and the dispersion of the maximum output power Pm and the maximum working current lm should be less than ±3%.
f. During architectural design of building material photovoltaic system and component photovoltaic system, it is necessary to consider the installation and layout of electrical circuits, and at the same time ensure the reliable grounding of the metal frame of each building material photovoltaic module and component photovoltaic module.
⑤The setting of photovoltaic junction box should follow the following principles.
a. The photovoltaic junction box should be equipped with copper busbars or terminals.
b. Each PV module string should be led by cables to the busbars. Set up DC sub-switches and DC main switches before the busbars.
c. Lightning protection devices should be installed in the photovoltaic junction box.
d. The location of the photovoltaic junction box should be convenient for operation and maintenance, and an indoor dry place should be selected. The photovoltaic junction box installed outdoors should have waterproof and anti-corrosion measures, and its protection level should be IP65 or above.
⑥ The total rated capacity of the inverter of the independent photovoltaic system should be selected according to the maximum power of the AC side load and the nature of the load.
⑦ The total rated capacity of the grid-connected photovoltaic system inverter should be determined according to the installed capacity of the photovoltaic system; the number of grid-connected inverters should be determined according to the installed capacity of the photovoltaic system and the rated capacity of a single grid-connected inverter. The selection of grid-connected inverters should also follow the following principles.
a. The grid-connected inverter should have automatic operation and stop function, maximum power tracking control function and anti-islanding function
b. The grid-connected inverter without the power frequency isolation transformer shall have the DC detection function.
c. The grid-connected inverter without isolation transformer shall have the DC grounding detection function.
d. It has a grid-connected protection device, and has the same voltage, phase number, phase, harmonics, frequency and wiring mode as the power system.
e. It should meet the requirements of high efficiency, energy saving and environmental protection.
⑧ The selection of DC line should follow the following principles.
a. The withstand voltage level should be higher than 1.25 times of the photovoltaic array voltage.
b. The rated current-carrying current should be higher than the setting value of the short-circuit protection appliance, and the setting value of the short-circuit protection appliance should be higher than 1.25 times the nominal short-circuit current of the photovoltaic array.
c. In the full power state, the line voltage loss should be controlled within 3%.
⑨ The lightning protection and grounding protection of the photovoltaic system shall meet the following requirements.
a. The measures for preventing direct lightning strikes and electromagnetic pulses from lightning strikes in photovoltaic systems should strictly comply with the relevant provisions of the Code for Design of Lightning Protection for Buildings (GB50057).
b. The lightning protection and grounding measures for photovoltaic systems and grid-connected interface equipment shall comply with the relevant regulations of “Guidelines for Overvoltage Protection of Photovoltaic (PV) Power Generation Systems” (SJ/T11127).
⑩Building-material photovoltaic system should follow the following principles.
a. Building material photovoltaic modules must have the inherent functions of the building materials themselves, and have no effect on the original building materials functions.
b. The system structure of building materials-type photovoltaic modules must comply with the “Technical Regulations for Solar Photovoltaic and Building Integration Application” (hereinafter referred to as “Regulations”).
⑪ Component photovoltaic system should follow the following principles.
a. Component-type photovoltaic modules must have the inherent functions of the building components themselves, and have no effect on the original functions.
b. When the component-type photovoltaic system retains the inherent functions of the building components, if the consistency of the solar radiation received by the components is affected, each string of components needs to be isolated with blocking diodes, or a controller or inverter should be used alone.
c. The structure of the component-type photovoltaic system must meet the requirements of the “Regulations”.
3. Power distribution system
①The design of grid-connected photovoltaic system distribution and substation should not only comply with the “Regulations”, but also in accordance with “Code for Design of Substations of 10kV and Below” (GB50053), “Code for Design of Substations of 35~110kV and Below” (GB50059) related requirements.
②The distribution and substation of the photovoltaic system should be arranged in a centralized or decentralized manner according to the scale of the photovoltaic array and the form of the building.
③ The transformer of the photovoltaic system should be a dry-type transformer.
4. The system is connected to the grid
① The grid connection of the photovoltaic system to the public power grid shall meet the relevant regulations and requirements of the local power supply agency.
② When the photovoltaic system is connected to the public grid in a low-voltage manner, it shall comply with the relevant regulations of the Technical Requirements for Grid-connected Photovoltaic System (GB/T19939).
③ When the photovoltaic system is connected to the public grid by medium voltage or high voltage (10kV and above), the power quality and other related parts should refer to the “Technical Requirements for Grid Connection of Photovoltaic System” (GB/T19939), and should meet the following requirements.
a. When the operating voltage of the grid-connected point of the photovoltaic system is 90%~110% of the rated voltage, the photovoltaic system should be able to operate normally.
b. The photovoltaic system shall provide the power supply agency with a test report on the operating characteristics of the photovoltaic system within 6 months of grid-connected operation to indicate that the photovoltaic system complies with the relevant regulations of the connected system.
④An isolation device should be installed between the photovoltaic system and the public power grid, and should meet the following requirements.
a. An isolation device should be set up between the photovoltaic square and the inverter, and between the inverter and the public grid.
b. The photovoltaic system should be equipped with a special low-voltage switch box (cabinet) for grid connection at the grid-connected place. Special signs and prompting words and symbols such as “warning” and “dual power supply” should be set up.
⑤ The safety and protection requirements of grid-connected photovoltaic systems can refer to “Technical Requirements for Grid-connected Photovoltaic Systems” (GB/T19939), and should meet the following requirements.
a. The grid-connected photovoltaic system should have automatic detection function and grid-connected cut-off protection function.
b. The photovoltaic system should select and install grid-connected protection devices according to the system access conditions and the requirements of the power supply department, and should comply with the relevant regulations of (Grid Interface Characteristics of Photovoltaic (PV) System) (GB/T20046) and the “Relay Protection and Safety Automatic” Functional requirements of “Technical Regulations for Devices” (GB/T14285).
c. When the power quality of the public grid exceeds the limit, the photovoltaic system should automatically stop supplying power to the public grid. Within a period of time after the power quality of the public grid returns to the normal range, the photovoltaic system shall not supply power to the grid. The delay time for restoring grid connection is determined by the power supply department according to local conditions.
⑥ The control and communication of the grid-connected photovoltaic system shall meet the following requirements.
a. According to the requirements of the local power supply department, configure the corresponding automatic terminal equipment and communication devices, collect the telemetry and remote signaling data of photovoltaic system devices and grid-connected lines, and transmit the data to the corresponding dispatch master station in real time.
b. The power quality real-time online monitoring device should be configured at the grid interface/public contact point of the well grid photovoltaic system, and all measurable power quality parameters (voltage, frequency, harmonics, power factor, etc.) should be transmitted to the corresponding dispatcher stand.
⑦ The grid-connected photovoltaic system shall determine the electric energy metering point according to the principle of the gateway metering point setting of the local power supply department, and shall meet the following requirements.
a. The photovoltaic system is equipped with a special electric energy metering device at the electric energy gateway metering point.
b. Electric energy metering devices shall comply with the relevant regulations of “Technical Regulations for Design of Electricity Measurement and Electric Energy Metering Devices” (DL/T5137) and “Technical Management Regulations for Electric Energy Measurement Devices” (Dl/T448).
⑧ The photovoltaic system as an emergency power source shall meet the following requirements.
a. It should be ensured that the photovoltaic system is disconnected from the public grid in an emergency, and the non-specific loads supplied by the photovoltaic system should be cut off.
b. The emergency circuit in the switch cabinet (box) should be provided with corresponding emergency signs and warning signs.
c. The automatic switch between the photovoltaic system and the power grid should be selected in the non-self-recovery mode.
5. Electric energy storage system
①The electric energy storage system should choose batteries with long life, high charging and discharging efficiency, and small self-discharge.
②The electric energy storage system should meet the relevant requirements of “Technical Regulations for Design of DC System of Electric Power Engineering” (DL/T5044) and “Technical Conditions and Test Methods of Household Solar Photovoltaic Power System” (GB/T19064).