What are Central Inverters?

Inverter, as we know, is the heart of every PV plant. It converts direct current produced by the solar panels and converts it into AC electricity which required by the appliances. In addition to this, it additionally monitors and controls the PV system.

The types of inverters available in the market are:

Central inverter: Here individual solar panels of the entire system are connected in series and DC power from these is taken to the inverter for conversion.
String inverter: Here, individual solar panels are connected in series to form strings. DC power is taken from these strings to multiple inverters instead of one central unit and is then converted to AC power
Micro inverter: Micro inverters are small inverters attached to the back of each and every panel of a PV system.

Now, what exactly are central inverters?

A typical central inverter is located in a protected environment, away from harsh climatic conditions and usually near the main electricity service panel. In this architecture, DC power is taken from all the solar panels into one combiner box and then is taken to the central inverter to be converted into AC power. As a result, voltages can be quite high in the central inverter, sometimes as much as 600 volts DC.

Central inverters are the ones usually used for large-scale industrial applications and have larger capacities than string inverters and micro inverters. A 5 MW PV system necessitates the need for a central inverter with a minimal rating of 5 MW itself.

What are the advantages of central inverters over the string and micro inverters?

With central inverter comes a few advantages that the other inverters don’t have. Some of them are listed below.

Credibility:

Central inverters have been around for a long time now. And because of this, more real-world field data is available regarding its performance. This factor gives the central inverter more credibility than the others and people are more willing to place their trust in a proven technology.

Lower costs:

The investment for central inverters is less per watt when compared to string or micro inverters. This is because of the fewer components and connections involved along with lesser installation costs.

Reliability:

Usually central inverters are housed in protective environments, subject to how well maintained they are. Hence there really isn’t a risk of them being exposed to harsh climatic conditions.

What are the negatives of central inverters?

There are several disadvantages when it comes to central inverters when compared to string and micro inverters. Some of the most prominent ones are discussed below:

Potential for a single point of failure

The biggest disadvantage of using these inverters is that even if one panel is shaded or fails due to some other reason, it will affect the performance of the entire system. In a set up where solar panels are attached in series, the panels act like one unit. Here, if one panel under-performs, the whole array will be affected. Industry experts say that shading of as little as 10% of a solar system connected to a central inverter, can lead to a system-wide decline in power output with as much as around 50%.

Higher risk factor

Solar panels, when connected in series, together produce DC voltage of high rating. This power needs to be conveyed for a long distance to the central inverters. Handling of this DC power of high rating could be life threatening to both the installers and owners.

Higher Replacement Cost

In a centralized architecture, if the central inverter fails, the replacement costs incurred will be higher than in the case of string inverters or micro inverters owing to its high rating.

So, as we have seen above central inverters have its pros and cons. Central inverters works best in areas with no shading concerns and are suitable for large photovoltaic systems and non-residential applications.

Related Articles

Industrial Rooftop Solar, Solar forHotels

Ask Solar Mango

Sweet Answers to Solar Questions