Inverter failure of the hottest photovoltaic syste

Inverter failure with low power generation of photovoltaic system

after the installation of photovoltaic system, users are most concerned about the power generation, because it is directly related to the return on investment of users. There are many factors that affect the power generation, including the quality of components, inverters, cables, installation orientation azimuth, tilt angle, dust, shadow shading, component and inverter proportioning system scheme, line design, construction, electric voltage and other factors. This series of articles will explore various factors one by one based on actual cases. This paper mainly discusses the influence of inverter fault on the system

photovoltaic system inverter

photovoltaic system is composed of components, supports, inverters, cables, distribution cabinets and other equipment. The support is a structural equipment, which will not be damaged except for wind damage; Components and inverters are power generation equipment, but the power density of components is low. For example, a 10kW power station uses 40 components, with a total area of 64 square meters, but these energy are concentrated in an inverter with an area of 0.25 square meters. The inverter has high power density, which is high temperature, high voltage and high current

in addition, the inverter needs to deal with a lot of things. In addition to converting DC into AC, it also undertakes the tasks of detecting the status of components and electricity, system insulation, external communication, etc. the amount of calculation is large and easy to make mistakes

photovoltaic inverter is composed of circuit board, fuse, power switch tube, inductance, relay, capacitor, display screen, fan, radiator, structural parts and other components. The service life of each component is different. The service life of the inverter can be explained by the "barrel theory". The maximum capacity of the barrel is determined by the shortest wood board, the service life of the inverter is determined by the component with the shortest service life, and the most prone to failure of the inverter are the power switch, capacitor, display screen, fan and other four components

power switch tube

power switch tube is the main device to convert DC into AC, and it is the heart of inverter

at present, the power switch tubes used by the inverter include IGBT, moset, etc., which are the most vulnerable components of the inverter. It has three fears: first, it is afraid of overvoltage. A 600V withstand voltage tube will explode in less than 0.1 seconds if the voltage at both ends exceeds 600V; Second, fear of overcurrent. A pipe with a rated current of 50A will explode in less than 0.2 seconds if the current is greater than 50A; Three fears are over temperature. Ig can also be waterproof and ash proof. BT section can be reduced. The specific temperature of diesel and steam is not usually 150 degrees or 175 degrees. Generally, it is controlled below 120 degrees. Heat dissipation design is one of the most key technologies of the inverter

if the power device is damaged, it means that the inverter needs to be replaced. However, there is no need to worry too much, because many experiments and problems in the design of the inverter are often caused by the improper operation of the staff. These factors have been fully considered. Under normal circumstances, the service life of the inverter to 20 years is no problem. When installing the inverter, it is necessary to consider leaving a heat dissipation channel for the inverter. In addition, if there are too high harmonics and too frequent voltage mutations in the electricity, it will also cause overvoltage damage to the power devices

electrolytic capacitor

capacitor is the component of energy storage, and it is also one of the essential components of inverter

capacitors include electrolytic capacitors, film capacitors, etc., each with its own characteristics, which are required by the inverter. There are many reasons that affect the service life of electrolytic capacitors, such as overvoltage, harmonic current, high temperature, rapid charge and discharge, etc. under normal use, the biggest impact is temperature, because the higher the temperature, the faster the evaporation loss of electrolyte. It should be noted that the temperature here does not refer to the ambient or surface temperature, but refers to the working temperature of aluminum foil

manufacturers usually mark the capacitor life and test temperature on the capacitor body. The volatilization of electrolyte limits the life of electrolytic capacitors. Japan NCC capacitor is one of the best capacitors in the world, and its longest life is 15 years in the specification

LCD

the LCD of the inverter can display the instantaneous power, power generation, input voltage and other indicators of the photovoltaic power station. If you can show the cause of the failure, it will be a good part for the equipment manufacturers of recycled plastic granulator

most inverters have displays, but some do not. In addition to the above advantages, LCD has a fatal defect - short service life. If the LCD with average quality works for 10000 hours, it will be seriously attenuated and cannot be used. According to the working time of inverter 6:: 00, the LCD works 14 hours a day and 5000 hours a year. Assuming that the service life of LCD is 40000 hours, its service life is 8 years

at present, the display is generally reserved for household inverters. For medium and high-power series inverters used in power stations, there is a trend that there is no LCD

fan

the heat dissipation methods of series inverter mainly include forced air cooling and natural cooling

forced air cooling requires fans. Through the heat dissipation capacity comparison experiment of series inverter, it is found that the heat dissipation effect of forced air cooling is better than that of natural cooling for medium and high-power series inverter. Forced air cooling can reduce the temperature rise of key components such as the internal capacitor and IGBT of the inverter by about 20 ℃, which can ensure the long-life and efficient operation of the inverter, while the temperature rise of the inverter with natural cooling can reduce the service life of components. The service life of high-quality fans is about 40000 hours. The inverter with intelligent heat dissipation generally starts to work when the power of the inverter reaches more than 30%. The average working time is about hours a day, about 1800 hours a year, and there is no problem in using it for 20 years

the most common fault of the fan is that the power supply of the fan is broken, or foreign matters enter the fan, which hinders the rotation of the fan

summary

as an electronic product, photovoltaic inverter has certain limitations in use, which should be paid attention to in design and installation. The inverter failure rate of experienced EPC installers is more than 30% lower than that of inexperienced installers, so experience is very important. When transporting and installing the inverter, handle it with care to avoid loosening the connector inside. Temperature has a great impact on the service life of the main components of the inverter. The inverter should avoid direct sunlight and be installed in a ventilated and heat dissipation place; Attention should be paid to the matching of components and inverters. Inverters should not work under full load for a long time; The inverter should not be installed in an electrical environment with high harmonics, which can significantly reduce the probability of inverter failure and prolong its service life