First, the requirements of the components After the on-site component arrives, the owner, constructor, and supervisor will verify the component. The verification contents mainly include: appearance inspection, qualified labels, cargo documents, certificate of conformity, etc. If the owner or the constructor has questions about the key parameters of the module, a third party inspection may be conducted and the supervisor is responsible for witness sampling. Second, the best tilt angle of the PV array According to the "Specifications for photovoltaic power plant design" (GB50797-2012) Appendix B PV array optimum inclination reference: Latitude Φ is 39.8°, and the recommended inclination angle of grid-connected system is Φ39.8-7=32.8° Longitude County's latitude than Beijing High 2 degrees, so the tilt angle of the PV module of this project is equal to 35°, but during the construction process, the actual installation tilt angle of the PV module must be checked, and the tilt angle of the PV module bracket should not be adjusted. The lowest edge of the PV module is higher than the design elevation. 60 cm. Third, pull the experiment According to the local maximum wind pressure and the area of ​​photovoltaic modules, the pull-out force of typhoon can be calculated. The basis of photovoltaic modules in this project is spiral/pouring piles. After the construction of spiral piles is completed, a certain number of samples must be drawn according to the requirements of the specifications. Spiral piles were subjected to a pull-out test and comparisons were made between the pull-out test data and the design data to determine whether the photovoltaic module foundation was safe and reliable. The pull-out force of this project is 2000kg>1400kg (design data), and the basis of photovoltaic modules is solid and reliable. Fourth, cable selection Since this project is located at 42 degrees north latitude and belongs to cold mountainous areas, the cables should be made of flame-retardant and cold-resistant cables. The cables used in this project are: (1) Cables for string-to-confluor box use PFG1169-1×4 PV special cable, which is laid along the bracket. ZRC-YJV2-1KV cold-resistant type copper-core XLPE insulated cable is used for the convergence box to inverter. Buried laying. (2) ZRC-YJV-1KV cold-resistant copper core XLPE insulated cables lead to transformers in the AC outlet of the inverter. (3) The cable shall enter the entrance of the room from the outside, and at the joints of the cable, the holes through which the cables pass shall be fireproof and waterproof. The fire resistance limit shall be ≥1 hour. V. Lightning Protection and Safety (1) The frame of the assembly is reliably connected to the steel bracket. The steel bracket between different arrays is reliably connected to the 40×4mm hot dip galvanized flat steel and connected to the entire grounding system. (2) Ground power station grounding system adopts integrated grounding, artificial grounding electrode, 2.5m long 5# angle steel as vertical grounding body at a certain distance, and 40×4mm hot galvanized flat steel for reliable connection between angle steels. A 40×4mm hot-dip galvanized flat steel is laid around the array as a horizontal grounding body, and the grounding resistance is less than 4Ω. After the construction is completed, if the requirements are not met, the artificial grounding electrode is further increased to meet the requirements and buried underground. Hot-dip galvanized flat steel should be placed vertically because the vertical placement is smaller than the horizontally placed flow resistance. Sixth, the maximum power point tracking At a certain light intensity and ambient temperature, the photovoltaic array can operate at different output voltages, but only at a certain output voltage value, the output power of the photovoltaic array can reach the maximum value. At this time, the working point of the photovoltaic array reaches The highest point of the output power voltage curve is called the maximum power point. The electrician principle tells us: When the internal resistance of the photovoltaic array is equal to the load resistance of the electricity, the output power of the photovoltaic array can reach the maximum value, this is the maximum power point. After the load is determined, the load resistance is determined and will not change. Therefore, we only continuously adjust the voltage and current of the PV array according to different external light intensity and ambient temperature and other conditions to make it work at the maximum power point, which is called maximum power point tracking technology. The goal of the maximum power point tracking is to allow the solar module to output the maximum power in real time so as to maximize its efficiency. This is a key technology in the operation control of the solar photovoltaic power generation system. There are many ways to achieve the maximum power point tracking and there are many applications. The typical ones are the constant voltage method based on the parameter selection method, the interference observation method based on voltage and current detection, the three point gravity comparison method and the conductance increment method, and so on. The task of adjusting the working point of the photovoltaic cell is the power conversion system in the photovoltaic power generation system, which is the controller of the photovoltaic power generation system mentioned on the market. The core of the photovoltaic power generation system is the power electronic conversion circuit, supplemented by either simple or complex protection. Display, communication and energy management functions, for our users, the only thing that can be done is to choose a good controller in the market. Domestic brands have better "Huawei" and so on. The maximum power tracking point of the inverter imported from Germany is better. In this project, Huawei grid-connected PV inverters are used, and the inspection report for the site shows that the maximum efficiency of the inverter is not less than 98%. 7. Anti-islanding effect Under normal circumstances, the grid-connected photovoltaic power generation system supplies active power to the power grid in parallel on the power grid, but when the power grid is in a power failure condition (such as a power grid outage), these independent grid-connected power generation systems may continue to operate with local loads. The connection is in an independent operating state. This phenomenon is called the islanding effect. The major hazards of the islanding effect include: (1) The hazards to the grid load or personal safety, users or maintenance personnel do not necessarily realize the existence of a distributed power supply system. (2) Power supply quality: Without the support of large power grids, the quality of distributed power supply systems is difficult to meet the requirements. (3) When the grid recovers, the distributed power supply system will encounter difficulties in reconnecting to the grid, and non-synchronous grid connection will cause large current impact. (4) The power company's management requirements for the power grid. This kind of operation mode appears to be uncontrollable and has high hidden troubles in the power management part. Therefore, when an island phenomenon occurs, it is necessary to detect this phenomenon in a timely manner and remove the potential power supply from the grid-connected photovoltaic system. This can avoid the existence of an island phenomenon. Island detection methods can be divided into passive and active detection two categories. Passive detection methods usually include: voltage and frequency detection method, voltage harmonic detection method, phase jump detection method. In order to solve the problem of passive blind island detection with large detection blind spots, active detection methods have been proposed. The main methods are frequency/phase offset method, output power compensation method and insertion impedance method. When the grid is powered off, when the grid-connected PV system and the local load form an island, the voltage, frequency and phase of the grid-connected PV inverter output are detected. The grid-connected photovoltaic system and the local load are separated in time. The methods for de-listing are: (1) To stop providing active power to the inverter by closing the DC/DC circuit. (2) Block the inverter switch number and wait for the grid system to return to normal. When the grid returns to normal, the grid-connected PV system should transmit power to the local load at the same time. For our users, the only thing that can be done is to choose inverters with good anti-islanding effect in the market. The result of the anti-islanding protection experiment for grid-connected PV inverters used in this project is: When the inverter When the state of islanding is reached, the grid on the AC side of the inverter is disconnected under certain power conditions, and the inverter should be automatically protected within the specified time. Eight, equipment and system testing and debugging After the installation of the equipment, the test of PV modules and inverters shall be carried out according to the requirements of 6 "equipment and system commissioning" in the "Specifications for construction of photovoltaic power stations". The insulation resistance shall be measured in the order of the DC combiner box, inverter, AC distribution cabinet and cables. The measured values ​​shall meet the design and acceptance specifications. The test tool can be used with a 500V rocker. Low voltage electronic components should be released during testing. The test standards for other electrical equipment shall comply with the relevant provisions of the current national standard “Testing standards for electrical equipment installation engineering electrical equipment handover†GB50150. IX. The archives information that should be provided and prepared by the supervision unit during inspection and acceptance (1) Project supervision data (2) Record of quality defects (3) Project Construction Supervision Work Report The above contents are all important quality control points in the supervision of grid-connected photovoltaic power generation projects. By seizing these quality control points, the construction quality of the grid-connected photovoltaic power generation project can be guaranteed. Emergency Led Drivers,Emergency Battery Backup Led Driver,Led Emergency Backup Driver,Emergency Light Drivers Foshan Nai An Lighting Electric Co.,ltd , https://www.articalight.com