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Writer's pictureJaime Ventura Energy Consultant

STRING OR CENTRAL INVERTERS, PROS AND CONS

FOR ON-GRID SOLAR SYSTEMS


String or Central Inverters, Pros and Cons

Let's continue using our Integration Coefficient IC, one of our strongest business and manufacturing tools that gives us a profound differential advantage in the solar supply chain: education for maximum customer satisfaction.


Let's talk about an On-grid solar system with string or central inverters and their Pros and Cons. The picture above shows a typical connection diagram for these systems.


Transformerless grid-connected inverters, lighter and more efficient than their counterparts with isolation transformers, are now very popular in Eurasia and the USA, as they have shown more than proving their reliability versus the concern that existed at the beginning of this trend.


That was based on the possibility of transformerless electrical systems feeding the utility network due to a lack of galvanic isolation between the DC and AC circuits, which could eventually allow the passage of dangerous DC faults that would be transmitted to the AC side. This risk has been remedied with high-frequency galvanic isolation systems that exist today, making these central inverter grid-tie systems still widely used.


In the same picture, a “matrix combination” box is also shown that is used to wire and combine parallel or series chains of photovoltaic modules, and in this way, connect solar panels in groups, without exceeding the maximum DC input voltage allowed by the Inverter. However, many grid-tied inverter models now offer the possibility of multiple photovoltaic DC input connectors which can help avoid using these “combiners”.


This kind of solar panel connection in series brings us to one of the most common disadvantages of this central inverter-based system: they are relatively expensive to maintain since the installation can only be monitored at the system level and not at each solar module level. Then, when finding a defective or shadowed solar module, this job becomes an arduous, time-consuming task that is usually very expensive as done by experts.


On the other hand, string inverters never reach the useful life of a photovoltaic module. This fact causes a relatively limited warranty term of 5 or 10 years for these inverters compared to the 25 or 30-year warranty for solar panels. Any return on investment calculation for this kind of solar system must consider at least one or two replacements of this expensive component, plus the labor cost involved in those processes. For this reason, you need to add more than double the inverter cost due to its lower reliability to ROI calculations.


The best way to overcome all the disadvantages mentioned above is to use Solar Microinverters instead of String or Central Inverters, as we do when offering our On-Grid Solar Kit solutions.


For more information please do not hesitate to Contact Us.

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