Solar PV rooftop systems: System configuration for the grid connected systems
Grid-connected systems can be conﬁgured in any of a number of ways . In the classic conﬁguration with a central inverter, the solar generator is composed of nSP strings that are parallel connected to nMS modules. This type of system, which entails extensive DC wiring and a special generator junction box , is sensitive to partial shading, as well as mismatch loss within the installation.
For more than a decade now, smaller one-string inverters have been on the market and are advantageous in that (a) wiring is limited to series connecting a number of modules and (b) a generator junction box can be dispensed with. For larger installations of this type, a series of such single-string inverters is used, although these devices need to be parallel connected on the grid side. Inasmuch as each string inverter can adjust to the speciﬁc insolation conditions at the module to which the inverter is connected, such systems are less sensitive to partial shading. Moreover, DC power loss is usually lower than with central inverter systems owing to the absence of a DC cable and the generally shorter string wiring runs. Based on these advantages, installation efﬁciency is on a par with or even superior to that exhibited by central inverter systems, despite the fact that the DC–AC conversion efﬁciency of smaller inverters is usually lower than that of larger inverters.