Methodology for Tuning MTDC Supervisory and Frequency-Response Control Systems at Terminal Level under Over-Frequency Events

This paper proposes a methodology for tuning a supervisory and frequency-response outer loop control system of a multi-terminal direct current (MTDC) grid designed to transmit o_shore wind energy to an onshore AC grid, and to provide frequency support during over-frequency events. The control structure is based on a master–slave scheme and ensures the achievement of frequency response, with specific implementation of the UK national grid code limited-frequency sensitive (LFSM) and frequency-sensitive (FSM) modes. The onshore AC grid is modelled with an equivalent frequency-response model to simulate the onshore AC grid dynamics under frequency deviations. The main innovation of this paper is the development of a methodology for tuning simultaneously two hierarchical levels of a MTDC coordinated control structure, i.e., the MTDC supervisor, given by the active power set point for slave terminal, and the slope of frequency-response functions at onshore terminals. Based on these two hierarchical levels, di_erent strategies are evaluated in terms of frequency peak reductions and change of the frequency order type. Moreover, tuning guidance is given when a di_erent MTDC control structure or di_erent synchronous generator characteristics of the onshore AC grid are considered.This research was funded by the Spanish Ministry of Economy, Industry and Competitiveness (project ENE2016-79145-R AEI/FEDER, UE) and the Basque Government (project KK-2017/00083, and research group GISEL, grant number IT1083-16

On the tuning of fractional order resonant controllers for a voltage source converter in a weak AC grid context

This paper proposes a method for tuning the fractional exponent of different types of fractional order resonant controllers for a voltage source converter in a weak AC grid context. The main objective is to ensure the stability of the controlled system in a weak AC grid environment and to achieve an adequate dynamic response under disturbances. Therefore, six commonly used integer order proportional resonant (PR) control structures are selected from the literature and compared with each other according to their frequency behaviour. Afterwards, a rational approximation for the fractional order term is selected based on continuous fraction expansion technique. The inclusion of a fractional exponent in each integer order PR structure generates the fractional order proportional resonant (FPR) control transfer functions. Once the FPR controllers have been obtained, their closed-loop responses are tested via eigenvalue trajectory analysis. For each FPR control structure, a range of the fractional exponent that ensures stability is obtained. The conclusions of eigenvalue trajectory analysis are tested by implementing the FPR control structures in an specific application consisting in a modular multi-level converter (MMC) connected to a weak AC grid with adjustable short-circuit ratio. By means of time-domain simulations, not only the previous eigenvalue analyses are validated, but also new tuning criteria are given for the fractional exponent in combination with other control parameters, such as the damping frequency and the inductance of the complementary feedback branch. Moreover, a sensitivity analysis of the tuning criteria is carried out for other sizes of the AC filter inductance.This work was supported by the Basque Government through the Project of Research Group GISEL under Grant IT1083-16. Besides, TECNALIA is a ‘‘CERVERA Technology Centre of Excellence’’ recognised by the Ministry of Science and Innovation

Energy and Cost Analysis of an Integrated Photovoltaic and Heat Pump Domestic System Considering Heating and Cooling Demands

The integration of photovoltaic panels and heat pumps in domestic environments is a topic that has been studied extensively. Due to their electrical nature and the presence of elements that add thermal inertia to the system (water tanks and the building itself), the functioning of compression heat pumps can be manipulated to try to fulfill a certain objective. In this paper, following a rule-based control concept that has been identified in commercial solutions and whose objective is to improve the self-consumption of the system by actively modulating the heat pump compressor, a parametric analysis is presented. By making use of a lab-tested model, the performance of the implemented control algorithm is analyzed. The main objective of this analysis is to identify and quantify the effects of the main parameters in the performance of the system, namely the climate (conditioning both heating and cooling demands), the photovoltaic installation size, the thermal insulation of the building and the control activation criteria. A total of 168 yearly simulations have been carried out. The results show that the average improvement in self-consumption is around 13%, while the cost is reduced by 2.5%. On the other hand, the heat from the heat pump and the power consumed increase by 3.7% and 5.2%, respectively. Finally, a linear equation to estimate the performance of the controller is proposed.This publication is part of the R+D+i project PID2021-126739OB-C22, financed by MCIN/AEI/10.13039/501100011033/ and “ERDF A way of making Europe”. Also, it has been financed by the Basque Business Development Agency (SPRI) in the 2020–2022 period in the projects ZL-2020-00379, ZL-2021-00225 and ZL-2022-00644 (BEROGRID); and by the Basque Government under the BIKAINTEK 2019 program

Value of green hydrogen when curtailed to provide grid balancing services

This paper evaluates the potential of grid services in France, Italy, Norway and Spain to provide an alternative income for electrolysers producing hydrogen from wind power. Grid services are simulated with each country's data for 2017 for energy prices, grid services and wind power profiles from relevant wind parks. A novel metric is presented, the value of curtailed hydrogen, which is independent from several highly uncertain parameters such as electrolyser cost or hydrogen market price. Results indicate that grid services can monetise the unused spare capacity of electrolyser plants, improving their economy in the critical deployment phase. For most countries, up-regulation yields a value of curtailed hydrogen above 6 €/kg, over 3 times higher than the EU's 2030 price target (without incentives). However, countries with large hydro power resources such as Norway yield far lower results, below 2 €/kg. The value of curtailed hydrogen also decreases with hydrogen production, corresponding to the cases of symmetric and down-regulation.This publication has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under the European Union's Horizon 2020 research and innovation programme under grant agreement No. 779469. Any contents herein reflect solely the authors' view. The FCH 2JU and the European Commission are not responsible for any use that may be made of the information herein contained. TECNALIA is a “CERVERA Technology Centre of Excellence” recognised by the Spanish Ministry of Science and Innovation. The authors wish to thanks Stefano Rossi of ARERA for his advices on the Italian energy market and regulation aspects

A Straightforward Methodology to Obtain the Power Coefficients Matrices for Unbalanced Distribution Networks to be Used in Flexibility Markets

The objective of the paper is to address the congestion problem in a specific distribution line by means of sensitivity coefficients seeking an intelligent a ctivation of t he available flexibility, based not only on economic a spects but also on the efficient use of flexibility. This paper proposes a straightforward methodology to obtain the sensitivity coefficient matrices for the unbalanced distribution networks, employing the perturb-and-observe (P & O) approach to assure an efficient usage of flexible resources. This means that a small change in the active power value of a particular flexibility provider, either load or generator, is applied to evaluate the power variation, therefore the loading variation, in every line of the system. The paper shows how these coefficients can be implemented in at heoretical energy market by the market operators by validating its application in an unbalanced network case and then compared with a real balanced distribution network. The simulations have been carried out in DIgSILENT PowerFactory through its API in Python.H2020, 824414, CoordiNe

Flexibility markets to procure system services. CoordiNet project

The article describes the objectives of the CoordiNet project, the proposed coordination schemes and architecture to allow TSOs and DSOs to procure systems services in a coordinated manner, and the platforms being developed in the three demonstrators of the project (Spain, Sweden, Greece).The efficiency and reliability of electricity systems depend, among other aspects, on an efficient collaboration between the different market participants, which require updating the roles of all agents involved. The CoordiNet project, co-funded by the EU, intends to demonstrate how TSOs and DSOs can act in a coordinated manner, to purchase and activate system services, promote the cooperation of all actors and eliminate barriers for the active participation of DERs in the market. The results of the project will help to design scalable tools and methodologies for system operators and third parties to safely connect, manage and coordinate flexibility providers. This paper describes the developments in CoordiNet to ensure the interoperability of the different markets and platforms developed by TSOs and DSOs across Europe.European Commissions' H2020 under grant agreement No 824414

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

Markets and platforms to coordinate the procurement of system services from large-scale and small-scale assets connected to the electricity network

The efficiency and the reliability of the electricity system depend on an efficient collaboration between the different market participants. New challenges for the power sector, which require updating the roles of all agents involved, have emerged due to the growing importance of renewable energy sources, the advance of distributed generation, the development of self-consumption, the storage of energy and the mass integration of the electric vehicles. In this context, the safe and efficient functioning of the electricity system is linked to exploiting the untapped flexibility potential in both generation and demand. Therefore, the coordination of distribution system operators (DSOs) and transmission system operators (TSOs) in the procurement of system services provided by units located in both distribution and transmission grids become one of the current challenges.The CoordiNet project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 824414

Value of green hydrogen when curtailed to provide grid balancing services

International audienceThis paper evaluates the potential of grid services in France,Italy, Norway and Spain to provide an alternative income for<a href="https://www.sciencedirect.com/topics/engineering/electrolyser"title="Learn more about electrolysers from ScienceDirect's AI-generated Topic Pages"class="topic-link"&gtelectrolysers</a&gt <a href="https://www.sciencedirect.com/topics/engineering/producing-hydrogen"title="Learn more about producing hydrogen from ScienceDirect's AI-generated Topic Pages"class="topic-link"&gtproducing hydrogen</a&gt from wind power. Gridservices are simulated with each country's data for 2017 for energyprices, grid services and wind power profiles from relevant windparks. A novel metric is presented, the value of curtailedhydrogen, which is independent from several highly uncertainparameters such as electrolyser cost or hydrogen market price.Results indicate that grid services can monetise the unused sparecapacity of electrolyser plants, improving their economy in thecritical deployment phase. For most countries, up-regulation yieldsa value of curtailed hydrogen above 6 €/kg, over 3 times higherthan the EU's 2030 price target (without incentives). However,countries with large <a href="https://www.sciencedirect.com/topics/engineering/hydro-power"title="Learn more about hydro power from ScienceDirect's AI-generated Topic Pages"class="topic-link"&gthydro power</a&gt resources such as Norway yieldfar lower results, below 2 €/kg. The value of curtailed hydrogenalso decreases with <a href="https://www.sciencedirect.com/topics/engineering/hydrogen-production"title="Learn more about hydrogen production from ScienceDirect's AI-generated Topic Pages"class="topic-link"&gthydrogen production</a&gt, corresponding to thecases of symmetric and down-regulation