## 2 Smart Grids System
### Virtual Power Plants (VPPs)  
Electrical energy has a significant impact on people's lives all around the world. As the demand for electricity grew, the power infrastructure and the global environment were placed under additional strain [143; 144]. Buildings are a substantial producer of greenhouse gases (GHGs) [145; 146]. An effective EMS is required to address the fast increase in demand [147]. Furthermore, several nations have committed to submitting an annual GHG emission reduction plan under the Paris agreement, making the use of (RESs) essential [148; 149]. Due to the network's new topology RESs, traditional EMSs are no longer effective. In order to aggregate and accommodate RESs while considering geographic distribution and uncertainties, an optimal scheduling algorithm must be developed [150; 151]. The VPP concept is one of the most promising and practical energy management solutions, allowing for unique features by integrating embedded technology and communication networks into the energy system. Despite the fact that [PERSON] and [PERSON] proposed VPP in 1997, there is still no clear description for the VPP [152]. From a variety of perspectives, VPPs have been proposed in the literature. At the same time, the usual inclination is to aggregate DERs for energy management purposes [146]. Many research has concentrated on business and marketing factors [153]. Other publications, however, have emphasized technological viewpoints such as Internet of energy (IoE) [154], EMS [155], combination of RESs [156], an independent microgrid [110], or a data and connection system [117]. A trading platform used by DERs to make wholesale market contracts is known as VPP. VPP is a DER aggregator that considers the impact of the network on their output [157]. VPP is a control system for DERs, flexible loads, and storage that is defined as an information and communication system. According to the investigation, a VPP is a collection of DERs, controllable loads, and storage units combined to operate as a single power plant, with an  
Figure 6: Schematic illustrating concepts of distributed energy resources.  
EMS at its core [158]. VPP is defined as an aggregation of several DERs distributed at the distribution network's medium voltage (MV) level [159].  
In general, several solutions have been presented in recent years to overcome the aforementioned difficulties. The VPP concept is one of the most promising energy management concepts, allowing for unique features through the integration of embedded technologies and communication networks into the energy system. VPP uses a bidirectional energy flow to provide real-time monitoring and energy efficiency. As a result, they were able to exchange their excess electrical energy on the market without the involvement of a third party [160]. Prosumers, conversely, who install any small-scale RES, or storage (batteries) can trade because the scheduling algorithm maximizes their surplus energy. Customers without RES or storage can also contribute by moving loads, trimming peaks, and filling valleys, among other things. Lastly, through enhancing operating planning, VPP may conform with power administration rules [161, 162], as well as the five main areas that best illustrate the scope of the intelligent grids system, such as DR, PS, DER, MT and VPPs, as shown in Table 3.