Grid integration of Solar energy system can be pursued in two different ways, (i) Solar Photovoltaic generator, and (ii) solar thermal generators. The solar thermal route is pretty straight-forward, because in this case thermal energy will be used to drive a turbine to generate electricity. Parallel connection of alternators are well known in the literature and you can read any standard book to understand it. In solar PV generation  route, solar power is converted into DC electricity and is usually operated to track the maximum power point of solar generation. This DC is then converted into AC system by means of inverters. And so, you need to understand parallel operation of inverters in this regard, and brief description of which can be found at http://mypages.iit.edu/~qzhong2/LoadSharing_web/LoadSharing_web.html . You must understand that these inverters are usually controlled to mimic the existing generators, and so, you will find several terms such as droop-control, to explain the parallel operation of these inverters.

You can connect two solar inverter outputs (AC) together in parallel, but they must be frequency and phase locked and made to be grid-tie if they are to also be paralleled with the larger power grid. There are many ways of doing this, but a master-slave approach works quite well with one master and up to several slave inverters, all synchronized. It can be done with either analog or digital control.

thanks for all.