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What is the inverter in a photovoltaic installation?

What is the inverter in a photovoltaic installation?

We already know that all types of photovoltaic solar installation produce electricity thanks to solar panels from the sun’s rays, but in order to power homes, companies or warehouses, the appropriate elements must be placed.

What is the inverter in a photovoltaic installation? Different types of photovoltaic or isolated inverters. What inverter do I need?

These elements are necessary because the photovoltaic panels produce direct current but most supplies are connected to alternating current. For this reason, inverters are needed, which are the electronic equipment in charge of converting electricity from direct voltage to alternating current, just as we have in any electrical supply.

How do the two types of currents work?

DC

Direct current is one whose electrical charges or electrons always flow in the same direction in a closed electrical circuit, moving from the negative pole to the positive pole of a source of electromotive force, such as occurs in batteries, dynamos or in any other source that generates that type of electrical current.

Direct current is usually used in any small electronic device such as mobile phones, tablets or laptops, for which they always incorporate batteries and are powered by them or use power supplies that transform electricity from alternating current to direct current.

Alternating current

However, in alternating current during an instant of time one pole is negative and the other positive, while in the following instant the polarities are inverted as many times as cycles per second that current possesses. However, even if there is a constant change of polarity, the current will always flow from the negative pole to the positive.

What equipment is needed to convert direct current to alternating current?

As we have said before, solar panels produce electricity in the form of direct current. And for their part, batteries also store electricity continuously. For this reason, to be able to use it in our usual household appliances, most of which are designed to be connected to alternating light (the light that we have in the plugs in our houses), we will need equipment that converts direct current into alternating current.

This device is called an inverter. In the case of inverters that transform direct current directly from solar panels to alternating current, they are called solar or grid-connected inverters.. And when the panels are used to charge batteries (by means of a charge regulator) and the inverters transform the energy of the batteries into alternating current, they are simply called inverters or for isolated installation.

The solar inverter is used in self-consumption installations connected to the electricity grid and is a key part of our photovoltaic installation because, in addition to converting direct current into alternating current, it also performs other functions.

Additional functions performed by solar inverters

  • They protect the installation: By regulation, in the event of a network problem or short circuit, they are disconnected and stop power generation.
  • They optimize the production of electricity: They can adapt production to the solar situation that exists, to the need for energy that we have or …
  • They are synchronized with the electrical network and/or the batteries: so that everything works perfectly and we have the most convenient energy at all times from among the different sources in our installation.
  • They collect and offer useful information regarding the energy production and performance of the installation: In addition, in the event of a problem, the inverter provides valuable information.

There are several types of solar inverters, depending on the type of installation: There are normal or string inverters (both single-phase and three-phase), there are micro-inverters and hybrids, which allow batteries to be incorporated in addition to panels.

There are also several types of inverters for installation isolated from the electrical network, that is, in installations where there is no connection to the normal electrical network. In this case the inverters are basically differentiated by the voltage we have for the batteries, there are inverters for 12V batteries, others for 24V batteries and others for 48V batteries. An inverter of 12 will not work for 24 or 48V, and vice versa either. Also in any of these voltages we find inverters, inverter-chargers and hybrid inverters.

Below we detail its characteristics and functions, so that you can choose the most suitable type of inverter according to your needs.

Types of inverters for use in photovoltaic installations

Inverter type chain or string

In solar installations with string inverters, the solar panels are connected by strings or lines and each inverter has one or more inputs for strings of photovoltaic panels. These inverters are the most widely used and the most economical on the market, their main use being in installations without the presence of shadows and with panels that are all the same for each string.

In each chain of panels, the power produced by all the panels can be affected if one of the panels in the chain has leftovers or a drop in performance for some reason, since the same intensity will pass through all the panels in the same chain, and Therefore, if one lowers the intensity produced, the same intensity will pass through all of them as that of the panel that generates less at each moment. In addition, like all inverters, this type of inverter also has a maximum conversion power, so if we want to install more solar panels in the future, we will have to add another inverter or change the existing one for a more powerful one.

This type of inverter (if accessories such as optimizers for each panel are not added) does not include panel monitoring of the photovoltaic system, so if a panel decreases its performance, it will not be possible to know which panel it is and we will have to review all the panels to find the problem.

Microinverter

These are smaller inverters than conventional ones. As a general rule, microinverters are only connected to one or two solar panels, so they transform direct current into alternating current individually for each panel. This model offers better features than string models, since they can always get the maximum power from each panel, but the investment is also higher. Microinverters are installed next to or below each solar panel. Its main advantages are:

  • Possibility of obtaining the maximum power of each solar panel
  • Decreased shadow effect or other objects on the panels
  • These inverters allow panel-by-panel photovoltaic system monitoring, which allows us to verify that the entire installation is working properly. Microinverters are recommended when there are different panels and/or different orientations, shades, etc. in the installation, which may affect the performance of the panels differently at any given time.

Isolated installation inverter

Its mission is to invert the direct voltage of the batteries from 12, 24 or 48V to convert it into the 230V alternating voltage that we use in our homes. These inverters have security measures against overvoltage, excess temperature and output short circuit. In addition, they prevent excessive discharge of the batteries by cutting consumption if the battery voltage is very low.

Inverter-charger

These inverters are the same as the previous ones but also incorporate a battery charger that can charge the batteries from an alternating current input and that can normally be a generator set or gasoline electric generator. This type is the most used in installations of habitual use, since it allows to have an auxiliary electrical generation system for when there is not enough photovoltaic production.

hybrid inverter