How to improve the life of PV inverter?

PV inverter is the core equipment of the photovoltaic system. Its main function is to change the direct current from the photovoltaic modules into the alternating current which meets the requirements of the grid.

But in fact, the inverter is not only the inverter, but also the safety housekeeper of the pv power station. The pv inverter also undertakes the monitoring and protection of the phv array and the grid, and has system-level functions such as external environmental protection and human-computer interaction.

Why do pv inverters dissipate heat?

PV inverter as a power electronic equipment, and all electronic products are facing the challenge of temperature.

Of all electronic product failure cases, 55% were caused by temperature.

The electronic components inside the inverter are also very sensitive to temperature. According to the 10-degree rule of reliability theory, the temperature rises by 10 degrees and the lifetime decreases by half from room temperature, so the inverter cooling design is very important.

Several ways of inverter cooling

PV inverter cooling system mainly includes radiator, cooling fan, thermal conductive silicone grease and other materials.

At present, there are mainly two ways of inverter cooling: natural cooling and forced air cooling.

1) Natural cooling

Natural cooling refers to the realization of local heating device cooling to the surrounding environment without any external auxiliary energy to achieve the purpose of temperature control, which usually includes heat conduction, convection and radiation of three main heat transfer modes, in which convection is dominated by natural convection.

Natural heat dissipation or cooling is often suitable for low power devices and components with low temperature control requirements, low heat flux density of devices, and sealed or densely assembled devices that are not suitable (or need not) to use other cooling technologies.

At present, most of the mainstream single-phase inverter and three-phase inverter under 20 kW in the market adopt natural cooling mode.

2) Forced air cooling

Forced air cooling is a method to take away the heat emitted by the device by forcing air flow around the device, such as fans.

This method is a simple and effective heat dissipation method.

If the space between the components in the component is suitable for air flow or local radiator installation, this cooling method can be used as far as possible.

The method of improving the forced convection heat transfer capability enlarges the heat dissipation area and produces a relatively large forced convection heat transfer coefficient on the heat dissipation surface. Increasing the radiator surface area to enhance the heat dissipation of electronic components has been widely used in practical engineering.

In order to enhance heat transfer, fins are mainly used to expand the radiator surface area. The choice of radiator material is directly related to its heat dissipation performance.

At present, the radiator is mainly made of copper or aluminum, and its expanded heat transfer surface is made by folding fin / stamping thin fin process.

3) Comparison of two cooling methods

Natural heat dissipation has no fans, low noise, but slow heat dissipation, and is generally used for small power inverters.

Forced air cooling should be equipped with fans, with large noise, but fast heat dissipation.

In the medium power series inverter, there are two ways.

By comparing the heat dissipation ability of series inverter, it is found that the forced air cooling is better than the natural cooling. The temperature rise of the key components, such as the capacitor and IGBT, is reduced by about 20, which can ensure the inverter to work long life and high efficiency.

The temperature of inverter with natural cooling mode is increased and the life of components is reduced.

Forced air cooling also uses two types of high-speed fans and medium speed fans.

The use of high-speed fans can reduce the volume and weight of radiators, but increase noise, fan life is also relatively short;

Using medium speed fan, radiator slightly larger, but at low power, the fan does not turn.

At medium power, the fan operates at low speed.

Actually, the full power operation time of the inverter is not very large, so the life of the fan can be very long.

Attention should be paid to heat dissipation when installing the system.

PV inverter itself is a source of heat, all the heat must be released in time, can not be placed in a closed space, otherwise the temperature will rise higher and higher.

PV iinverter must be placed in an airtight space, and avoid direct sunlight.

When multiple inverters are installed together, there should be enough distance between the inverters and the inverters to avoid mutual influence.