Keywords

1 Introduction

The VPP concept is rapidly transforming the way we think, design and plan the development of future energy grids. This is because VPPs have the capability of increasing the chances of integrating renewable energy sources into the conventional power grid. The advantage of this development is the enhancement of sustainable energy generation and its subsequent decline in the use of fossil-based energy sources. It also enhances decentralization of the energy grid from a single supply system to a more liberal and diverse supply, based on multiple sources [1]. The VPP concept will also enable small-scale energy producers to participate in the electricity market and will eventually help to overcome the stochastic nature of distributed energy resources (DERs), resulting in a more stable power grid [2].

The VPP concept is supported by a merge of different technological and managerial concepts, principles and ideas from diverse domains and fields of study. One of such fields is the domain of Collaborative Networks (CN) which embodies knowledge about collaboration amongst heterogenous organizations, systems, and entities which are autonomous in nature and are geographically dispersed. These CNs usually collaborate to achieve common and compatible goals [3].

The objective of this work is to perform a panoramic review of the area of VPPs to primarily identify common grounds where both domains converge. This is necessary because VPPs are constituted of integration of heterogenous systems, organizations, and entities which collaborate to ensure optimal generation, distribution, storage, and sale of renewable energy in the energy market. The main contribution of this paper is the extraction of the underlying collaborative mechanisms, organizational forms, motivation for collaborations, key collaboration agents/players as well as related technologies within the VPP area, using foreknowledge in CNs.

2 Relationship to Resilient Systems

VPPs are anticipated to help in overcoming the stochastic nature of DERs which will result in a more stable and smart power grid. However, with the current level of system integration which includes: high levels of artificial intelligence, smart cyber components, cloud computing, IoT, etc., incorporated in the power grid, coupled with frequent disruptive events around the globe which include: natural disasters, globalization, climate change, economic crisis, demographic shifts, fast technological evolution, terrorism and cyber-attacks, the power grid is becoming more and more susceptible to many forms of attacks which will eventually endanger the sustainability of the grid.

The collaborative and decentralized nature of VPPs however presents a good opportunity to incorporate resilience into the power grid. For instance in [4] a collaborative observation network consisting of multiple DERs within the power system which monitor the behaviors of all its neighbors, and collectively decide to isolate DERs suspected to be under attack is proposed. Again, Egbue et al. [5], concluded in a survey work that micro-grids, which also function collaboratively like VPPs have high potential to increase the reliability and resilience of the smart grid during a blackout or cyber-attack. This is because the decentralized nature of micro-grids/VPPs can provide direct cyber-security benefits if structured properly.

In relation to resilient systems, or towards a resilient power grid, the VPPs concept is hereby perceived as essential components of the grid which cannot simply be overlooked.

3 Survey Approach

To establish a credible correlation of the application of CN principles in the domain of VPPs, the systematic literature review (SLR) method was used. The motivation for this approach is that it provides a balanced and objective summary of research evidence, by evaluating and interpreting available research work, relevant to a particular research question, topic area or phenomenon of interest [6]. SLR is evidence based and has been used extensively by many researchers in other domains.

Systematic Mapping (SM) [7] is a variant of SLR which provides a well-defined structure for any area of research, by categorizing articles in that domain in a way that gives a visual summary or pictorial map of the area. According to [8] the main goals of SM are to provide an overview of a research area and also identify the quantity, type of research and results available within it. A secondary goal can be to identify the forums in which research in the area has been published.

Research Questions.

The concept of VPP is found to be relatively new, therefore publications in this area are highly dispersed in terms content and organization. To establish a good synergy and a better synthesis of the area, five guiding research questions are developed to help define the scope of the survey. The research questions are as follow:

  • Research question 1: What are the key drivers or motivation for collaboration in the domain of VPPs? [Seeking to identify motivation for collaborations]

  • Research question 2: Which collaborative organizations are emerging in the domain of VPPs? [Seeking to identify organizational forms]

  • Research question 3: Which collaborative principles are being applied in the emerging collaboration forms? [Seeking to identify CN principles]

  • Research question 4: Which technological elements support collaboration in VPPs? [Seeking to identify collaborative technological]

  • Research question 5: Who are the key players, agents or systems that participate in these collaborations? [Seeking to identity key players in the collaborations]

4 Focus Areas

4.1 VPP Aggregation

VPP aggregation is the process of collecting and merging capacities of diverse dispatchable and non-dispatchable DERs, energy storage systems, which may include electric vehicles, controllable loads and demand response programs, etc., to create a composite VPP, which capacity, characteristics and functions are equivalent to a physical power plant. The aggregation method is expected to ultimately impact on the performance and operation of the VPP, hence various approaches proposed by different researchers. Table 1 below summarizes the findings under VPP aggregation with emphasis on motivation for collaboration, collaborative principles that were observed, collaborative forms that were seen, and key players involved in the collaboration.

Table 1. Summary of VPP aggregation
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4.2 VPP Architecture and Infrastructure

VPP architecture and infrastructure covers articles that make contributions to VPP architecture and associated infrastructural support. General software and hardware architecture of power systems and related ICT infrastructure are also considered. In Table 2, a summary of VPP architecture and infrastructure in the context of collaborative technology, collaborative infrastructure, motivation for collaborations and key collaborative players are also analyzed and presented.

Table 2. Summary of VPP architecture and infrastructure
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4.3 VPP Management

VPP management is the process of organizing and coordinating all resources and activities within the VPP to optimize generation, transmission, and distribution of energy. VPP management results in cost and loss minimization and ultimately maximizes profit. In this work, the authors considered publications that made contributions to various aspects of VPP management. In this focus area, VPP managerial techniques as well as collaborative principles were analyzed. Additionally, motivation for collaborations and key collaborative players/systems were also reviewed. Table 3 present the findings under this focus area.

Table 3. Summary of VPP management
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4.4 VPP Market

The core objective of VPPs is to enable DERs participation in the energy market. The energy market is a trading system that enables purchases, through bids for buying or selling, or through offers and short-term trades, generally in the form of financial or obligation swaps. Bids and offers use supply and demand principles to set the prices. In this work, the authors considered publications that covered tariffs, remunerations and negotiations within the VPP market. The focus here was to identify collaborative technology and collaborative principles within the VPP market.

Table 4. Summary of VPP market
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4.5 VPP Security

VPP networks are supported extensively by ICT infrastructure which are deployed to enable wide area monitoring, protection, and control of the grid. With this kind of integration, the traditional power system is gradually evolving into a cyber-physical entity that is constituted of distributed smart devices which will eventually subject the power grid to cyber related attacks. VPP security therefore a very critical components future grid. Under this section (Table 5), the authors considered collaborative technologies, motivation for collaboration and key collaborative players under VPP security.

Table 5. Summary of VPP security
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4.6 VPP Policy and Roadmaps

Under this section, the authors considered short-term and long-term policy documents that support plans intended to guide the development of technologies that will enhance communication and collaborative technologies in the smart grid (SG).

Table 6. Summary of VPP policy and roadmaps
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5 Conclusions

The following general remarks can be made based on the outcome of the survey

  1. (a)

    Various CN organizational forms, principles, concepts and technology have significant level of penetration within the VPP concept.

  2. (b)

    VPPs are found to form various strategic and dynamic collaborative alliances which are similar to various CN organizational forms.

  3. (c)

    Prospects for new and hybrid collaborative forms and mechanisms are very high within VPP energy ecosystem.

  4. (d)

    The two communities were found to use different languages or terminologies although referring to similar concepts. For instance, in the VPP domain, the process of accumulating DERs is called “aggregation”. However, a similar process in the domain of CNs is referred to as a “VO creation”. Another process in CNs called “partner search and selection process” occurs in the VPP domain, however, this process is named differently and adopts different functional approach. Some examples include the Common Active Registry [9] and Virtual DER Clustering Aggregator [10, 11]. This suggests the need for the two communities to engage in further interactions to develop inter-disciplinary knowledge-base.

  5. (e)

    The discipline of CN constitutes a matured, well defined and clearly structured body of knowledge in various aspects of collaborations across diverse disciplines. By adopting CN body of knowledge within the VPP collaborative environment, the VPP concept and its associated technologies can greatly be enhanced. A merge between these two disciplines could forge a clear niche for a collaborative VPP ecosystem which is agile and highly resilient.