说明：  Production of energy in centralized power plants and transmitted via transmission lines to the customers is always with high power losses. Distributed generation (DG) especially renewable energy resources (RES) and energy storage systems (ESS) through distributed system are very cost saving and sometimes inevitable. If these small DGs want to connect to power system and participate in energy market directly, both distribution and energy market would have many problems with control such a high amount of information and small supplies of DGs. Application of virtual power plant (VPP) as an aggregation of some DGs with own local energy management system and some fix and variable loads is a suitable solution for DGs and networks problems.