TSO/DSO Coordination for RES Integration: A Systematic Literature Review

Data Availability Statement: Not applicable.Copyright: © 2022 by the authors. The increasing penetration of large-scale Renewable Energy Sources (RESs) has raised several challenges for power grid operation. Power management solutions supporting the integration of RESs, such as those based on energy storage technologies, are generally costly. Alternatively, promoting a more proactive role of the Distribution System Operator (DSO) to successfully manage RESs’ uncertainty, and take advantage of their flexible resources for the provision of ancillary services, can avoid installing expensive devices in the network and reduce costs. In this line, improved coordination between Transmission System Operators (TSOs) and DSOs is highly desirable. In this paper, the feasibility of solving different aspects of the integration of RESs through an improved TSO/DSO coordination is evaluated. In particular, a Systematic Literature Review (SLR) is conducted to study the most relevant TSO/DSO coordination approaches, exclusively focused on integrating distributed RESs, currently available in the literature. Their main operational, managerial, economic, and computational challenges, advantages, and disadvantages are discussed in detail to identify the most promising research trends and the most concerning research gaps to pave the way for future research toward developing a solid TSO/DSO coordination mechanism for integrating RESs efficiently. The main results of the SLR show a clear trend in implementing decentralized TSO/DSO coordination models since they provide efficient facilitation of RESs’ services, while reducing computational burden and communication complexity and, consequently, reducing operative costs. In addition, while different aspects of the TSO/DSO coordination implementation, such as reactive power and voltage regulation, operational cost minimization, operational planning, and congestion management, have been thoroughly addressed in the literature, further research is needed regarding data exchange mechanisms and RESs’ uncertainty modeling and prediction. In this line, the development of standardized communication solutions, based on the Common Grid Model Exchange Standard (CGMES) of the International Electrotechnical Commission (IEC), has shown promising interoperability results, whereas the use of learning-based approaches to predict RESs’ uncertain behavior and distribution networks’ responses, using only historical data, which relieves the need for access to commercially sensitive and proprietary network data, has also shown itself to be a promising research directionThis research received no external funding

Market integration and TSO-DSO coordination for viable Market-based congestion management in power systems

The article presents the findings on market-based congestion management (CM) in power systems. The main idea is to unlock flexibility from both small and large-scale resources by creating a platform so that flexibility can enter the markets through the platform and be used by system operators (DSOs and TSOs) for CM. The article recognizes two pressing issues in market-based CM: low liquidity and adverse impacts of flexibility activation. The article proposes leveraging market integration and TSO-DSO coordination to address the pressing problems and incorporate them into the platform. Bids from the intraday market at Nord Pool as well as the balancing market bids, were used for CM to show the possibility of addressing the low liquidity issue by receiving bids from well-established markets. In TSO-DSO coordination, an algorithm-agnostic process is proposed and implemented to involve SOs' network limitations before flexibility is traded to mitigate the adverse impacts of flexibility activation. As the market integration and TSO-DSO coordination functionalities rely on flexibility-related data that are often in huge quantities, a metadata register is also implemented to gather, process, and store data to be smoothly accessed by different stakeholders depending on their needs and access rights.Peer reviewe

Learning the price response of active distribution networks for TSO-DSO coordination

The increase in distributed energy resources and flexible electricity consumers has turned TSO-DSO coordination strategies into a challenging problem. Existing decomposition/decentralized methods apply divide-and-conquer strategies to trim down the computational burden of this complex problem, but rely on access to proprietary information or fail-safe real-time communication infrastructures. To overcome these drawbacks, we propose in this paper a TSO-DSO coordination strategy that only needs a series of observations of the nodal price and the power intake at the substations connecting the transmission and distribution networks. Using this information, we learn the price response of active distribution networks (DN) using a decreasing step-wise function that can also adapt to some contextual information. The learning task can be carried out in a computationally efficient manner and the curve it produces can be interpreted as a market bid, thus averting the need to revise the current operational procedures for the transmission network. Inaccuracies derived from the learning task may lead to suboptimal decisions. However, results from a realistic case study show that the proposed methodology yields operating decisions very close to those obtained by a fully centralized coordination of transmission and distribution

Optimised TSO-DSO Coordination to Integrate Renewables in Flexibility Markets

The necessary energy transition to decarbonize power systems is leading to increasingly important challenges for the operation of power systems. On the one hand, the intermittent nature of renewable generation requires system operators to procure ancillary services in larger volumes than in the past. On the other, the growing penetration of medium- and small-scale, flexible demand and storage systems in distribution networks could potentially offer network services, if they are aggregated effectively and there is an appropriate coordination between transmission system operators (TSOs), distribution system operators (DSOs) and aggregators. Therefore, an important topic to be analysed is whether distributed energy resources (DER) can replace traditional generation in the provision of ancillary services (AS), how this replacement will affect the system operators’ roles and how to improve the coordination between TSOs and DSOs. This paper shows the results of the cost-benefit analysis (CBA) performed within the project SmartNet to assess the advantages or disadvantages of different TSO-DSO coordination schemes, as well as the follow-up activities to be carried out in the project CoordiNet.These projects have received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements No 691405 & No 824414

Use of radio base stations to provide ancillary services to the DSO through local flexibility markets

The changes in the energy sector require an appropriate coordination between transmission systems operators (TSOs), distribution systems operators (DSOs) and aggregators. The project SmartNet aims at defining and comparing different TSO-DSO coordination schemes, by implementing dedicated analyses in Italy, Denmark and Spain. This paper describes the pilot project implemented in Spain and presents its main outcomes.The research leading to this article has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691405

Cost-Benefit Analysis of TSO-DSO coordination to operate flexibility markets

This paper presents the outcome of the cost-benefit analysis (CBA) for the different alternatives defined in the project SmartNet for the coordination between transmission system operators (TSOs) and distribution system operators (DSOs). The CBA compares five coordination schemes in three countries (Italy, Denmark and Spain) on the basis of several economic indicators. On top of them, it also calculates some non-economic indicators to enrich the analysis. The main results for the Italian and the Spanish cases are presented in this paper.The research leading to this article has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691405

ICT architectures for TSO-DSO coordination and data exchange: a European perspective

The coordination between system operators is a key element for the decarbonization of the power system. Over the past few years, many EU-funded research projects have addressed the challenges of Transmission System Operators (TSO) and Distribution System Operators (DSO) coordination by implementing different data exchange architectures. This paper presents a review of the ICT architectures implemented for the main coordination schemes demonstrated in such projects. The main used technologies are analyzed, considering the type of data exchanged and the communication link. Finally, the paper presents the different gaps and challenges on TSO-DSO coordination related to ICT architectures that must still be faced, paying especial attention to the expected contribution of the EU-funded OneNet project on this topic. IEEECoordiNet H202

TSO-DSO-Customer coordination for purchasing flexibility system services: Challenges and lessons learned from a demonstration in Sweden

This paper presents a real-word implementation of a TSO-DSO-customer coordination framework for the use of flexibility to support system operation. First, we describe the general requirements for TSO-DSO-customer coordination, including potential coordination schemes, actors and roles and the required architecture. Then, we particularise those general requirements for a real-world demonstration in Sweden, aiming to avoid congestions in the grid during the high-demand winter season. In the light of current congestion management rules and existing markets in Sweden, we describe an integration path to newly defined flexibility markets in support of new tools that we developed for this application. The results show that the use of flexibility can reduce the congestion costs while enhancing the secure operation of the system. Additionally, we discuss challenges and lessons learned from the demonstration, including the importance of the engagement between stakeholders, the role of availability remuneration, and the paramount importance of defining appropriate technical requirements and market timings.This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 824414

TSO-DSO Coordination Schemes to Facilitate Distributed Resources Integration

The incorporation of renewable energy into power systems poses serious challenges to the transmission and distribution power system operators (TSOs and DSOs). To fully leverage these resources there is a need for a new market design with improved coordination between TSOs and DSOs. In This paper we propose two coordination schemes between TSOs and DSOs: one centralised and another decentralised that facilitate the integration of distributed based generation; minimise operational cost; relieve congestion; and promote a sustainable system. In order to achieve this, we approximate the power equations with linearised equations so that the resulting optimal power flows (OPFs) in both the TSO and DSO become convex optimisation problems. In the resulting decentralised scheme, the TSO and DSO collaborate to optimally allocate all resources in the system. In particular, we propose an iterative bi-level optimisation technique where the upper level is the TSO that solves its own OPF and determines the locational marginal prices at substations. We demonstrate numerically that the algorithm converges to a near optimal solution. We study the interaction of TSOs and DSOs and the existence of any conflicting objectives with the centralised scheme. More specifically, we approximate the Pareto front of the multi-objective optimal power flow problem where the entire system, i.e., transmission and distribution systems, is modelled. The proposed ideas are illustrated through a five bus transmission system connected with distribution systems, represented by the IEEE 33 and 69 bus feeders