Solar Power System: String inverter vs Central inverter

One of the most important components of a solar power system is the solar inverter. A solar inverter helps to convert the variable direct current (DC) to alternating 240V current (AC). This AC electricity is then used in homes and commercial spaces to operate appliances. The other key function of a solar inverter is to maximize energy harvested from the solar panels.

Inverter technology has advanced a lot over the years and in addition to converting DC to AC, they have several other functions, like data monitoring, advanced utility controls, application, and system design engineering.

There are two main types of inverters, central inverters and string inverters.

Central inverters ‘centralize’ the power that is produced by the plant in one place. They convert between 500 kW to 2.5 MW. Every power block at a solar plant will have one central inverter.

On the other hand, string inverters use a distributed architecture with small inverters for smaller sections of the array. They consequently convert much less power than a central inverter. One of the advantages, however, is that, should an inverter fail, only the power from one small section will be lost as opposed to an entire power block. At a solar PV plant, each power block consists of 10 string inverters. One can buy the best solar inverters online in India through various websites.

Benefits and Drawbacks of String vs. Central inverters

Many times it is assumed that the bigger, the better and cheaper. So, the Central inverter architecture is cheaper and is seen as having better performance as compared to string inverter architecture. However, this is not always the case. Both types of inverter architecture have their advantages and disadvantages.

String Inverters

Pros:

· System efficiency: The efficiency of a system depends a lot on its design. If a bigger inverter is chosen for a smaller set of solar panels, it results in an efficiency drop. Inverters work at their peak efficiency when the panel’s capacity is not under-designed. Therefore, it is better to choose a smaller solar string inverter in a case where the total solar panel capacity is under-sized.

· System uptime: In case one of the string inverters is shut down for any maintenance, the other inverters need not be turned off. This avoids a complete shutdown of the whole system and power can be generated from the other inverters too.

· Replacement Cost: Due to its size, it is much affordable to replace a string inverter with a central inverter.

· Panel Array Orientation: Every string inverter comes with a separate MPP (maximum power point) Tracker. Many of the commercial string inverters available today have two MPPTs. The panel array attached to an inverter needs to be oriented in the same direction and should also have the same shading conditions to avoid any significant losses and to create hotspots that will deter the panels in the long run. In a string architecture, there are many smaller inverters connected to a set of panels that are oriented similarly. This gives the freedom to have an array of panels on separate buildings in different directions each connected to a different string inverter.

· System Cost: It is much cheaper to transport and install a larger number of string inverters than it is for a big central inverter. Due to its weight and the amount of heat that it generates, a central inverter might need a concrete foundation, cooling chamber, etc. This is not the case in a string inverter that can be installed right below the solar panels.

Cons:

· System Cost: The cost of the whole system can go quite high in this type of architecture. So in the case of larger systems, using a central inverter makes more sense due to the cost.

· Maintenance: As there are multiple inverters in a system, each at different locations, it will require more maintenance than a single inverter. However, with a good monitoring system, this can be significantly reduced.

· Space: Since it is a distributed system, one needs more space to keep each inverter and separate cabling needs to be done to each inverter as well.

Central Inverters

Pros:

· Fewer Control boards: In a 500KW solar system, with 10 KW inverters, 50 control boards will be needed, each connected with a separate protection and connect switch. In a central inverter, however, an inverter of 500 kW will require just one control board. Thus there will be more collective consumption loss for string inverters as opposed to one single central inverter.

· Easy Monitoring: it is comparatively easier to monitor a central inverter as there are fewer of them.

· Panel Orientation: in cases where all the panels are oriented and angled in the same direction, central inverters offer the optimal production with lower DC Watt unit cost.

· Space requirement: Central inverters are better suited for places where there is less space. Using a large number of small inverters would use up a lot of space.

Cons:

· Maintenance: It requires separate cooling and filtration system, while a string inverter does not need extra fans.

· Installation cost: Although the cost of the inverter is less, a central inverter takes up a higher installation cost due to its size.

Considering the various advantages and disadvantages of the systems, one must evaluate the different site conditions and requirements before choosing one. The best solar inverters online in India can be bought easily by browsing through the extensive collection provided by the websites. ABB is a leading global technology company that has many great options for solar inverters. One can find a variety of ABB solar inverters online.