# Virtual Power Plant Optimization in Smart Grids: A Narrative Review
## 1 Introduction  
Energy has been and will always be one of the resources without which the community, and society as a whole, could not be sustained and evolve. Nowadays, no industry is not dependent on the energy regime. The adoption of renewable and decentralized energy sources transforms the energy grid. The management processes become highly dependent on the metering and ICT technology to secure and optimize the power distribution. Renewable energy is generated intermittently and highly dependent on the weather, thus making the planning of energy resources usage complex and exposed to uncertainty [1]. The energy storage capabilities installed at the edge of the grid are insufficient and not able to mitigate the variations in energy production. The surplus or deficit in energy generation may threaten the security of consumers' energy supply, thus distribution system operators (DSO) must incorporate new techniques to avoidsystem overload and power outage situations. The distribution of the energy has to offer stability to the consumers, minimize the costs for the producer, and avoid CO\({}_{2}\) emissions, and all in a secure way. The economy and energy grid need to remain stable, but these goals are impacted by factors such as energy resources, policies, politics, markets, the number of customers, and the surface to cover [2]. In this context, the concept of virtual power plants (VPPs) has been proposed and used lately as a solution for assuring an affordable, secure, and steady supply of energy in the smart grid [3]. It aims at combining and coordinating energy production with storage and consumption resources featuring controllable loads in an optimal way to meet renewable integration or energy costs minimization objectives. The associated optimization problem is usually addressed in the literature using various heuristics [4]. VPPs consider the predicted energy demand and production values for different resources, the operational, power flow, and cost constraints. They virtually aggregate resources to participate in energy markets, plan their operation in advance to deliver energy services, aggregate energy profiles for a steady supply and provide demand response services. In the state-of-the-art literature, there are many works that that focus on creating such VPPs and optimally interacting them in various smart energy grid scenarios [5; 6]. At the same time there are multiple ways to create a VPP that offer solutions for the energy market such as energy service delivery, energy autonomy, energy community, energy management or energy optimization, each of them with different purposes and steps to achieve a balance in the markets [3]. In order to establish which is the best approach for different situations, a requirements engineering solution has to be used where the starting point is the scenarios that describe the issue, in this case the energy consumption, and how to ensure stability and balance in the energy market, and the solution for it, represented in this case by the energy that can be provided from renewable resources which can sustain the economy and the market if a VPP is created in the architecture. In this paper, we carry out a narrative review in the domain of VPP optimization for local energy grid sustainability. The objective is to identify and analyze the main grid scenarios that can be successfully addressed using virtual coordination of resources as well as the state-of-the-art solutions used in implementation. The motivation for conducting the present survey is to identify and describe the relevant literature approaches from the past six years that deal with VPP management and applications for smart grid sustainability. For our narrative review, we have defined a methodology that uses a couple of inclusion and exclusion criteria in the search strategy. We have focused on the reference interval 2015-2022 and we have created a list of keywords and phrases used often in the research literature.