Danfoss Solar Inverters recommends string inverters for PV power plants
The inherent modular nature of PV modules means that a PV plant of any size is modular. Therefore, it is common sense to look at alternative ways to structure a PV plant than conventional ones. By using the inverter as a modular element in the plant, the built-in functionalities of the inverter can take over many of the additional functions that are needed when choosing a central inverter station. By using inverters that can handle 1000 V input, junction boxes and distribution boxes can be omitted, as the DC cables are laid directly from the string of modules to the inverter. Installations can be realised at a cost wich is 10 % lower than installations based on central inverters.
In addition to the cost savings, higher energy yields can be reached due to lower cable losses without extra cabling efforts. To achieve the best value for money solution, up to 1 % yield losses in the DC cabling of PV plants are generally accepted. Using string inverters, 0.3 % DC cabling yield losses and 0.1 % AC cabling yield losses are a-chievable at the same cost. Individual MPP tracking for every string, which is a major advantage of string inverters, enables maximum energy yield per string. If the rows of modules per PV substructure are connected to their own MPP tracker, the risks of losses due to shading are greatly reduced.
String inverters have the benefit of being a commercially available standard component. This enables a local installer or plant supervisor with no special training to carry out an inverter exchange if required. Therefore, the service contracts required with central inverters are not necessary for string inverters.
Further information on the benefits of string inverters in power plants is found on our dedicated website. Here you can also download a concept paper and a film on the subject: www.stringinverters.com