# Virtual Power Plant Optimization in Smart Grids: A Narrative Review
## 4 VPP Applications in Smart Grids
### Energy Services Delivery
The sustainability concerns increased the adoption of medium-small renewable VPPs distributed in the grid. However, the lack of central monitoring generated a whole new set of challenges for power system operations. With the implementation of the VPP for energy management concept comes the growth of the power system benefits, as well as the increase in the efficiency of the distributed generation units, which can become more visible and maximize the opportunities regarding incomes when it comes to selling the energy [22]. A VPP is used as a tool to integrate distributed renewable and storage with the needs of consumers in demand response programs [73]. In [61], blockchain and self-enforcing smart contracts are used to allow VPP construction out of prosumers' pools with the main objective of providing energy services. The prosumer level constraints (energy profiles and requirements) have been modeled and encoded in smart contracts to enable their aggregation in VPPs. The VPP is managed using blockchain offering decentralized energy trading and financial settlement. In [54], a probabilistic model is defined for optimal scheduling of a VPP considering electrical and thermal energy flexibility. It is able to participate as a service provider in different markets, contributing to the demand balancing and efficient distribution of the energy. The uncertainties in VPP optimization generated by energy prices and renewable production [77] are addressed using scenario-based decision-making. The VPP acts as a participant in the market, selling energy, and is can be seen as a controllable demand unit by the main grid. The VPP can not only enable participation in the market of small generation resources but also can provide additional services such as reactive power control. In [58], the authors depict a VPP model consisting of distributed generation and controllable resources. It will handle the management of the energy market of the VPP, helping to reduce transmission losses and electricity scarcity. The distributed renewables deployment leads to increasing generation variability and uncertainty. A solution to this issue is a VPP that offers services and aggregates a hybrid resources. In this way, [56] proposes a modeling framework that allows a VPP to participate in energy markets. It is divided into three stages (the high, mid, and low level) that allow the optimization of resource scheduling and dispatch. A real case study with electricity and hydrogen is being conducted in South Australia and shows that the VPP can coordinate the resources with promising results. In [59] is depicted a model approach to determine the optimization and coordination of a VPP participation in energy markets for energy services delivery. The authors propose a mixed-integer linear programming optimization model for day-ahead optimal energy and reserve dispatch and optimal real-time energy re-dispatch. A VPP that provides software as services for the community or cross-sector services represents a new direction for the future, and the studies on this topic and possible implementations started in the past decade [78]. There are still a lot of unknowns because renewable energy is influenced by the weather, but this topic can help solve the energy demand problems. The studied approaches focused on possible implementation for these services but also on solutions on how to make them function optimally and securely for all types of renewable energy. Table 3 summarizes the categories of energy services proposed in the research literature for VPP energy management.