Supporting frequency inside of each generation area as well as keeping proper synchronism condition between interconnected areas are two main challenges for grid operators. In this paper, after analysis of structure of Renewable Static Synchronous Generation unit based on Synchronous Power Controller (RSSG-SPC) for holding and control of frequency, it is shown that how a renewable unit based on SPC can contribute to frequency support inside of generation areas and in this way it will support synchronism of neighbor areas. Results of mathematical analysis and state space modelling, as well as time domain investigation then real time test of two area system in presence of RSSG-SPC confirm that by reducing Rate of Change of Frequency (ROCOF), increasing level of Frequency Nadir (FN) and providing stiffer Center Of Inertia (COI) for whole of the grid, the RSSG-SPC not only supports frequency on the generation areas, furthermore it will cover synchronism of these interconnected areas.