Discussion on the selection and maintenance of photovoltaic grid connected inverter

Date: 2019-10-29

Visits: 9

  First, classification


  The photovoltaic grid-connected inverter is a special device that converts the DC power generated by the photovoltaic array (photovoltaic cell/component) photoelectric effect (solar energy into electric energy) into AC power and then merges into the public power grid. Different from conventional inverter products, it can follow the changes of sunshine conditions to the maximum extent and keep running on the best power conversion efficiency and power output characteristics. It can be divided into three categories: photovoltaic grid-connected micro-inverters, string-type inverters and centralized inverters. The application scope covers large-scale ground photovoltaic power stations, wind-solar complementary street lighting, and household-use roof photovoltaic power generation. Photovoltaic farm irrigation and other fields. There are many styles of products, which can be divided into indoor and outdoor products. They can cope with different application environments, and their products have different shapes. At the same time, their output power ranges from tens of watts to hundreds of kilowatts or even megawatts to meet different applications. demand.


  Second, purchase


  Photovoltaic grid-connected inverter is one of the essential core components in photovoltaic power generation applications. The efficiency of a single photovoltaic power generation project and the annual power generation are all dependent on the product, and it is also the core component of the safe operation of photovoltaic power generation. Consumers (users) can choose different power levels and different types of products according to different functions, and can meet the needs of household photovoltaic power generation, industrial and commercial distributed power generation, and power generation for power generation enterprises.


  When purchasing a PV grid-connected inverter, first pay attention to the label on the package and the product, identify the input voltage range, voltage type, maximum input current of the PV grid-connected inverter; output voltage level, voltage type, frequency; maximum Continuous operating current, maximum output power, and inverter efficiency. Secondly, the random data of the product should be checked. The random data should include at least the following contents: product details (including technical parameter description), product installation instructions, operation instructions and maintenance instructions.


  As a general industrial product, PV grid-connected inverter products are recommended to be used by non-professionals. After purchasing the product by non-professionals, you should carefully read the random documents such as the product manual, and install and use it in strict accordance with the requirements of the random documents. If you have any questions, you need to contact the manufacturer or manufacturer to ensure proper installation and use.


  If you purchase foreign-imported products, you should pay attention to whether the foreign products declare the application of domestic standards. At present, the current effective product standards in China are NB/T32004-2013 "Technical Specifications for Photovoltaic Grid-Connected Inverters", especially paying attention to foreign countries. The output voltage and frequency of the product should be matched with the domestic public grid point where the product is connected. In addition, it is necessary to pay attention to the fact that the requirements for over-voltage protection of foreign products are significantly different from the domestic standards. When using foreign products, the products will be caused. Mistakes or refusal, there are huge security risks, and non-professionals are not recommended to purchase foreign imported products.


  For professionals to purchase PV grid-connected inverters, in addition to paying attention to the maximum conversion efficiency marked on the product nameplate, it is also necessary to pay attention to the maximum power point tracking efficiency of the product, and the product is at low to medium power (50% rated output power and below). ) Power quality conditions during operation (eg output harmonics, DC components, etc.) and their over/under voltage protection parameters. According to the different use environments of the products, the products should be differentiated and used. For example, household household products should pay attention to the electromagnetic compatibility and noise indicators of the products; products used in high altitude areas (the applicable products should not exceed 1 000 m above sea level). Pay attention to derating; products used in extremely low temperature and high temperature areas (the temperature range of conventional products is -25 ° C ~ +60 ° C) should pay attention to the climatic environment adaptability of the product, leaving sufficient safety margin for normal use of the product.


  Third, maintenance


  The service life of PV grid-connected inverters is generally 10-20 years. The quality level of products is uneven. If improper maintenance is used, the life of PV grid-connected inverters will be seriously shortened, and even huge potential safety hazards will be brought. .


  Firstly, the technical parameters of the products to be purchased must be determined by the professional according to the needs of the use, and then installed by professional and technical personnel, and the products can be connected to the grid and put into use after being qualified by the local power department.


  In daily use, it is necessary to regularly check the input and output terminals of the product. The connection should be firm. The input and output wires and cables are not aging or the skin is damaged or scratched. The grounding wire is firm, not broken or falling off. If problems are found, they should be replaced by professionals. Do not remove the input and output terminals at will. The input terminals have dangerous voltage generated during the daytime. The output terminals are always energized before the grid connection is disconnected. The live parts of the terminals should be avoided and not touched by personnel.


  In daily use, if the inverter is faulty, it should immediately disconnect the protection switch from the grid, and ask the professional to eliminate the fault before turning on the inverter again.


  Before performing any maintenance work, first disconnect the PV grid-connected inverter from the grid, then disconnect the DC side electrical connection and wait at least 5 minutes until the internal components are discharged before repair work is required. Professional and technical personnel complete.


  Non-professionals should not disassemble the product casing. Professionals should follow the warning signs on the product during maintenance. Wear anti-static gloves to avoid unnecessary board contact. Also, pay attention to the bare hand and do not directly touch the power of the inverter. The device and the heat sink, the product still has a high temperature for a period of time after the power is cut off, and should be protected from burns.


  In daily use of the product, the surface of the product and the dust at the inlet and outlet can be cleaned regularly with a clean and soft dry cloth to keep the product well cooled and the product is in a good ventilation environment. Maintenance of the product's unpacked enclosure is not recommended for operation by non-technical professionals.