a virtual power plant is a system that integrates several types of power sources to give a reliable overall power supply. the sources often form a cluster of different types of dispatchable and non-dispatchable, controllable or flexible load (cl or fl) distributed generation (dg) systems that are controlled by a central authority and can include microchps, natural gas-fired reciprocating engines, small-scale wind power plants (wpp)s, photovoltaics (pvs), run-of-river hydroelectricity plants, small hydro, biomass, backup generators, and energy storage systems (ess).