NOVELTY - The system (110) has a grid side controller (140) controlling alternate current (AC) output power of a grid side converter (36). An energy storage converter (44) couples an electrical energy storage device (42) e.g. battery, to the direct current (DC) link i.e. split DC link. An energy storage controller (46) controls the storage converter to achieve desired power balance on the link, where a source side controller (138) and the grid side controller are operated independently when a state of charge (SOC) of the storage device is within an acceptable SOC operating range.    USE - Renewable power generation system e.g. wind power generation system and solar power generation system.    ADVANTAGE - The energy storage controller provides storage switching signals to the energy storage converter for achieving the desired power balance on the DC link, the SOC in the energy storage device is sufficient, thus allowing the source and grid side controllers to operate independently during achieving specific goals with out requiring assistance in achieving the desired power balance on the DC link and maintaining DC link voltage at a nominal value. The energy storage device is controlled as a primary DC link voltage regulator resulting in decoupling of generator torque from grid side output power over a wide dynamic range, so that generator torque is controlled independently of the grid side power, thus controlling the source side converter to provide desirable power extraction from wind with long mechanical life of the system. The grid side converter is controlled to provide grid-friendly features such as inertia, ramp rate control, fault ride through and power system stabilization. The grid side controller generates a DC link voltage reference signal comprising a value that is varied based on operating conditions so as to reduce losses in the system.    DETAILED DESCRIPTION - The system has a renewable power source (112) for producing source power. The renewable power source is selected from a group consisting of wind, solar and marine hydrokinetic energy power source.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a wind power generation system.    Grid side converter (36)    Electrical energy storage device (42)    Energy storage converter (44)    Energy storage controller (46)    Renewable power generation system (110)    Renewable power source (112)    Source side controller (138)    Grid side controller (140)