Photovoltaic inverters are electronic products, which are limited by internal electronic components and must have a certain lifespan. The life of the inverter is determined by the quality of the product, the installation and use environment, and the later operation and maintenance. So how to improve the service life of the inverter through correct installation and later operation and maintenance?
The main factors affecting the service life of the inverter are: 1. The internal temperature of the inverter; 2. The input voltage and current parameters of the inverter; 3. The external environment for the inverter to operate.
Inverter's internal temperature
The temperature inside the inverter is the most important factor affecting the life of the inverter. Too high temperature will reduce the performance and life of the components. The capacitor inside the inverter is the key factor affecting the life of the inverter. There is a simple basic principle: the ten-degree rule, that is, for every 10-degree decrease in ambient temperature, the life of the capacitor is doubled; for every 10-degree increase in ambient temperature, the life of the capacitor is shortened by half.
The inverter itself is a heat source. The power modules, inductors, switches, cables and other circuits inside will generate heat. All the heat must be dissipated in time, otherwise the internal temperature will rise. Therefore, the heat dissipation design of the inverter is a key link in the product development and design. At present, the inverter industry basically adopts natural cooling and air cooling. The low-power models are mainly natural cooling, and the medium and high-power models basically All are air-cooled. In order to ensure the stability of the internal temperature of the inverter, in addition to product design considerations, special attention should be paid to the following matters during installation and use:
(1) The inverter must be installed in a well-ventilated space to maintain good ventilation with the outside world. If it must be installed in a closed space, an air duct and exhaust fan must be installed, or an air conditioner. It is strictly forbidden to install the inverter in a closed box.
(2) The installation location of the inverter should avoid direct sunlight as much as possible. If the inverter is installed outdoors, it is better to install it under the eaves on the back side or under the solar modules. There are eaves or modules above the inverter to block it. If it can only be installed in an open place, it is recommended to install a sunshade and rain shelter above the inverter.
(3) Whether it is a single installation or multiple installations of the inverter, it must be installed in accordance with the installation space size given by the inverter manufacturer to ensure that the inverter has sufficient ventilation and heat dissipation space and operation space for later operation and maintenance.
(4) The inverter is installed as far away as possible from high temperature areas such as boilers, fuel-fired hot air blowers, heating pipes and air-conditioning external air outlets.
Inverter input voltage and current parameters
Improper matching of the input voltage and current parameters of the inverter will also affect the life of the inverter. The higher the voltage or current that the components inside the inverter are subjected to, the shorter the life of the components. We take the MAX 100-125KTL3-X series inverter as an example. The input operating voltage range of this series of inverters is 200-1000V. In this range, the inverter can work. If the voltage is too low, the current will be too high, close to the critical state. If the input voltage is too high, the current will become smaller, but the voltage will be close to the critical state. In this case, it will not only affect the power generation efficiency of the inverter, but also affect the inverter. The service life of the inverter, therefore, we generally recommend that the input working voltage of the string be configured to a rated voltage of about 600V. Considering the electrical parameter characteristics under the NOCT condition of the module, the input working voltage of the string should be configured to about 650V, which can take into account the high efficiency of the inverter. and service life.
If the input working voltage of the string is configured at about 800V, not only the power generation efficiency will be reduced, but the power devices and current bus capacitors will be under high voltage, and the life of the insulating layer will be reduced, which will affect the life of the inverter. If the input working voltage of the string is configured to 500V, the current will increase by 20% compared with the rated voltage, and the heat of the inverter will mainly come from the current. In this case, the heat will increase by 20%, and the temperature of the inverter will increase. resulting in reduced service life.
In addition, although the capacity ratio restriction has been loosened in the current project approval, excessive over-provisioning will make the inverter run at full load for a long time, which will naturally affect the life of the inverter. For this reason, when we design the capacity ratio, in addition to In addition to economic factors, the life of the inverter should also be fully considered.
The external environment in which the inverter operates
The external environment in which the inverter operates is also an important factor affecting the life of the inverter. At present, the protection level of string inverters on the market can reach IP65 or even IP66. It is dustproof, rainproof, and has the ability to resist salt spray corrosion. It can adapt to harsh external environments. In many places, because the dirt falls on the radiator, it will affect the function of the radiator. Dust, leaves, sand and other fine objects may also enter the air duct of the inverter, which will also affect the heat dissipation, thereby affecting the service life. In this case, it is particularly important to regularly clean up the dirt on the inverter or cooling fan so that the inverter has good cooling conditions.
One end of the inverter is connected to the photovoltaic array, and the other end is connected to the power grid. The power quality of the power grid will also affect the life of the inverter, especially the voltage of the rural power grid is unstable, high and low, and the power grid harmonics are high, which is easy to trigger the inverter. If the inverter starts the protection mechanism, the inverter will stop running when the voltage exceeds the range, and resume operation when the voltage is normal. However, if the inverter is restarted frequently, the service life of the inverter will be reduced.
Summarize
After the inverters are shipped in batches, after a series of quality inspections, their design life is almost the same, so system design, installation and post-operation and maintenance are the key factors. In order to improve the actual service life of the inverter, on the one hand, it is necessary to create a good operating environment for the inverter to protect it from wind, sun and rain; The cooling air duct is unblocked to avoid over-temperature derating and other failures.