Sweet Answer from Solar Mango: (updated Jul 2015)
Inverters, as you will be knowing, are the brains behind solar PV power plants. In addition to converting the DC current generated by the solar panels into AC, the inverters also perform a number of management functions.
The three main types of inverters used in solar PV 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 or even smaller. A 1 MW solar power plant could have as many as 40 string inverters, each 25 kW.
Micro Inverters – Micro-inverters are small sized inverters attached to individual solar panels. Microinverter capacities could be as small as the solar panels they support, that is, as low as 240 W each.
Each of the above types of inverters has its own pros and cons. While central inverters provide the scale needed for large solar farms, these inverters require relatively significant maintenance overheads owing to their size when compared to smaller string and micro-inverters, both of which require almost no maintenance. String and micro-inverters also provide the prospect of much less of output with inverter break-down – for instance, while the breakdown of a 1 MW central inverter serving a 1 MW solar farm implies loss of the total output for the period of breakdown, the same solar farm served by 40 string inverters of 25 kW each has much less loss of output owing to the breakdown of 1 string inverter. However, per W, both string and micro-inverters are costlier than central inverters.
Currently, while central inverters are the usually preferred choice for large-scale solar farms, all three types are seeing demand for distributed, smaller rooftop solar installations.
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