Summary: A solar inverter is the brain for a solar power plant.

While the solar panels are the most visible part of a solar power plant, the component that actually “administers” the entire power plant is the solar inverter. What are the different types of solar inverters, and how do they work?

An inverter’s core function is to convert direct current generated by the solar PV panels into alternating current required by the grid. However, their role goes far beyond that, and it can be considered that inverters are the brain of a solar power plant.

In addition to converting DC to AC, the capabilities of the inverter are vital to reliably integrate solar with other sources such as grid or backup diesel generator.

A solar inverter is the brain of a solar power plant.

The inverter has long been considered the brain of the PV system, and advancements in inverter technologies are making them even smarter and more critical to the success of solar power generation.

Questions from the curious cat

What are the different types of inverters used in solar power plants?

The three main types of inverters used in solar power plants are:

  • Central inverters – these perform the function of DC to AC conversion and other power management functions from one central device. A large solar farm could have multiple central inverters, but each of these could of the sizes 1 MW and above.
  • String inverters – string inverters distribute the load of central inverters into multiple inverters. Typically, string inverters could be of sizes of a fourth of central inverters.
  • Micro-inverters – Micro-inverters are small sized inverters attached to individual solar panels.

How much do inverters cost?

Inverters typically cost about 7-15% of the total solar power plant cost. For large solar farms, cost of inverters will be 7-10% of total cost; for smaller rooftop solar power plants, the cost could be 10-15% of total.

Which of the three types – central, string, or microinverters – are best for my solar power plant?

There is no single right answer to this question. Each type of inverter brings different strengths and benefits.

Central inverters are usually more efficient and less costly than string and micro-inverters. String inverters provide a balance of redundancy and size, while microinverters enable panel level optimization, as well panel level monitoring.

As of 2014, most large solar farms use central inverters, and to a certain extent string inverters. Very few large solar farms use microinverters.

At the rooftop level, both central and string inverters find equal favour.

Microinverters are quite new and they are hence used only in a small percentage of solar installations.

Do inverters have anything to do with the extent of monitoring I can have for my solar power plant?

Yes. Most of the monitoring of a solar power plant is done by the inverters. Thus, the extent to which you would like to monitor a solar power plant will depend on the type of inverter used. A central inverter might not be in a position to monitor what’s happening at an individual panel level, while a micro-inverter which is attached to each panel will be able to do this.

What are the largest capacities inverters come in?

As of 2014, solar inverters are available as large as 2 MW. Most solar farms use inverters of sizes between 250 kW to 1 MW.

What are the smallest capacities inverters come in?

Microinverters, the smallest of the solar inverters available in the market, come as small as 150 W.

Do inverters require significant maintenance?

Good quality inverters require only minimum inspection and maintenance. That said however, inverter life and operating quality also depend on the quality of the grid (if it is a grid-tied solar power plant), where the inverter is kept (is it inside a cool room or in the hot sun) and also how it is cooled (especially for central inverters used in large scale ground mounted power plants).

What is the lifetime of an inverter?

Central inverters typically can work without a need for replacement for 10 years. In many cases, these inverters have done well up to 20 years.

String inverters can also work without problems for 10 years

It is said that micro-inverters can have a lifetime of upto 25 years

Some nice videos for you

A short but easy to understand video on microinverters

A nice illustration of a central inverter, from ABB


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