References of "Ernst, Damien"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailAn Optimal Control Formulation of Pulse-Based Control Using Koopman Operator
Sootla, Aivar; Mauroy, Alexandre; Ernst, Damien ULiege

in Automatica (in press)

In many applications, and in systems/synthetic biology in particular, it is desirable to compute control policies that force the trajectory of a bistable system from one equilibrium (the initial point) to ... [more ▼]

In many applications, and in systems/synthetic biology in particular, it is desirable to compute control policies that force the trajectory of a bistable system from one equilibrium (the initial point) to another equilibrium (the target point), or in other words to solve the switching problem. It was recently shown that, for monotone bistable systems, this problem admits easyto-implement open-loop solutions in terms of temporal pulses (i.e., step functions of fixed length and fixed magnitude). In this paper, we develop this idea further and formulate a problem of convergence to an equilibrium from an arbitrary initial point. We show that this problem can be solved using a static optimization problem in the case of monotone systems. Changing the initial point to an arbitrary state allows to build closed-loop, event-based or open-loop policies for the switching/convergence problems. In our derivations we exploit the Koopman operator, which offers a linear infinite-dimensional representation of an autonomous nonlinear system. One of the main advantages of using the Koopman operator is the powerful computational tools developed for this framework. Besides the presence of numerical solutions, the switching/convergence problem can also serve as a building block for solving more complicated control problems and can potentially be applied to non-monotone systems. We illustrate this argument on the problem of synchronizing cardiac cells by defibrillation. Potentially, our approach can be extended to problems with different parametrizations of control signals since the only fundamental limitation is the finite time application of the control signal. [less ▲]

Detailed reference viewed: 95 (15 ULiège)
Full Text
Peer Reviewed
See detailPulse-Based Control Using Koopman Operator Under Parametric Uncertainty
Sootla, Aivar; Ernst, Damien ULiege

in IEEE Transactions on Automatic Control (in press)

In applications, such as biomedicine and systems/synthetic biology, technical limitations in actuation complicate implementation of time-varying control signals. In order to alleviate some of these ... [more ▼]

In applications, such as biomedicine and systems/synthetic biology, technical limitations in actuation complicate implementation of time-varying control signals. In order to alleviate some of these limitations, it may be desirable to derive simple control policies, such as step functions with fixed magnitude and length (or temporal pulses). In this technical note, we further develop a recently proposed pulse-based solution to the convergence problem, i.e., minimizing the convergence time to the target exponentially stable equilibrium, for monotone systems. In particular, we extend this solution to monotone systems with parametric uncertainty. Our solutions also provide worst-case estimates on convergence times. Furthermore, we indicate how our tools can be used for a class of non-monotone systems, and more importantly how these tools can be extended to other control problems. We illustrate our approach on switching under parametric uncertainty and regulation around a saddle point problems in a genetic toggle switch system. [less ▲]

Detailed reference viewed: 43 (2 ULiège)
Full Text
Peer Reviewed
See detailEffect of Voltage Constraints on the Exchange of Flexibility Services in Distribution Networks
Mathieu, Sébastien ULiege; Olivier, Frédéric ULiege; Ernst, Damien ULiege et al

in Proceedings of the 9th Conference on Innovative Smart Grid Technology North America (ISGT 2018) (in press)

Detailed reference viewed: 301 (17 ULiège)
Full Text
Peer Reviewed
See detailA biased random key genetic algorithm applied to the electric distribution network reconfiguration problem
de Faria Jr., Haroldo; Resende, Mauricio; Ernst, Damien ULiege

in Journal of Heuristics (in press)

This work presents a biased random-key genetic algorithm (BRKGA) to solve the electric distribution network reconfiguration problem (DNR). The DNR is one of the most studied combinatorial optimization ... [more ▼]

This work presents a biased random-key genetic algorithm (BRKGA) to solve the electric distribution network reconfiguration problem (DNR). The DNR is one of the most studied combinatorial optimization problems in power system analysis. Given a set of switches of an electric network that can be opened or closed, the objective is to select the best configuration of the switches to optimize a given network objective while at the same time satisfying a set of operational constraints. The good performance of BRKGAs on many combinatorial optimization problems and the fact that it has never been applied to solve DNR problems are the main motivation for this research. A BRKGA is a variant of random-key genetic algorithms, where one of the parents used for mating is biased to be of higher fitness than the other parent. Solutions are encoded by using random keys, which are represented as vectors of real numbers in the interval (0,1), thus enabling an indirect search of the solution inside a proprietary search space. The genetic operators do not need to be modified to generate only feasible solutions, which is an exclusive task of the decoder of the problem. Tests were performed on standard distribution systems used in DNR studies found in the technical literature and the performance and robustness of the BRKGA were compared with other GA implementations. [less ▲]

Detailed reference viewed: 118 (0 ULiège)
Full Text
See detailTime to make a choice between a fully liberal or fully regulated model for the electrical industry
Ernst, Damien ULiege

Conference given outside the academic context (2017)

Detailed reference viewed: 46 (0 ULiège)
Full Text
See detailElectrification and DRC
Ernst, Damien ULiege

Conference given outside the academic context (2017)

Detailed reference viewed: 51 (1 ULiège)
Full Text
Peer Reviewed
See detailSiSTEM, a Model for the Simulation of Short-Term Electricity Markets
Mathieu, Sébastien; Petitet, Marie; Perrot, Marie et al

E-print/Working paper (2017)

The aim of this document is to present SiSTEM, a multi-level simulation model of European short-term electricity markets, covering day-ahead and intraday exchanges to balancing activations in real-time ... [more ▼]

The aim of this document is to present SiSTEM, a multi-level simulation model of European short-term electricity markets, covering day-ahead and intraday exchanges to balancing activations in real-time, and imbalance settlement. In this model, power companies interact by making offers, notifying their positions to the system operator and impacting the balance of the electric system. The system operator activates balancing energy to restore the balance of the system, using all balancing activation offers, including from balancing reserves. Imbalance settlement implies bidirectional transactions between the system operator and power companies depending on the direction of their imbalance. A simulation of the model is performed by sequentially considering each time step and simulating actors’ decisions. The objective of this model is to understand the problems behind decisions of the actors within the short-term electrical system operation, to provide insights on how these problems can be solved through market design and to see how the decisions are linked together to shape a coherent system. This paper presents different simulation cases of an illustrative system in order to portray main features of the model in a practical and effective manner. In particular, the results show the importance of considering steady-state constraints and notice delays of generation units when looking at short-term issues. Future works could use this model to provide quantitative assessments of short-term market designs. [less ▲]

Detailed reference viewed: 318 (1 ULiège)
Full Text
See detailA Simulator to Explore Tarification Designs for Distribution Networks
Manuel de Villena Millan, Miguel ULiege; Gautier, Axel ULiege; Fonteneau, Raphaël ULiege et al

E-print/Working paper (2017)

This paper introduces a computational tool to help assess the impact of regulation policies within distribution net- works in the deployment of distributed renewable electricity generation. This tool is a ... [more ▼]

This paper introduces a computational tool to help assess the impact of regulation policies within distribution net- works in the deployment of distributed renewable electricity generation. This tool is a comprehensive multi-agent simulator capable of handling the interaction between the users of a distribution network and their distribution system operator. With this simulator, it is possible to address the different regulatory constraints encountered by distribution system operators, for any regulation policy. In the simulator, we model individual electricity consumers as rational agents, who may invest in optimised distributed renewable energy installations, if they are cost-efficient compared to the network tariff. By modelling the cost recovery scheme of the distribution system operator, the simulator then computes the evolution of the network tariff in response to a change in the consumption and generation of the consumers in the distribution network, due to the deployment of distributed generation. The simulator is illustrated with various regulation policies. [less ▲]

Detailed reference viewed: 80 (9 ULiège)
Full Text
Peer Reviewed
See detailOn overfitting and asymptotic bias in batch reinforcement learning with partial observability
François-Lavet, Vincent ULiege; Ernst, Damien ULiege; Fonteneau, Raphaël ULiege

E-print/Working paper (2017)

This paper stands in the context of reinforcement learning with partial observability and limited data. In this setting, we focus on the tradeoff between asymptotic bias (suboptimality with unlimited data ... [more ▼]

This paper stands in the context of reinforcement learning with partial observability and limited data. In this setting, we focus on the tradeoff between asymptotic bias (suboptimality with unlimited data) and overfitting (additional suboptimality due to limited data), and theoretically show that while potentially increasing the asymptotic bias, a smaller state representation decreases the risk of overfitting. Our analysis relies on expressing the quality of a state representation by bounding L1 error terms of the associated belief states. Theoretical results are empirically illustrated when the state representation is a truncated history of observations. Finally, we also discuss and empirically illustrate how using function approximators and adapting the discount factor may enhance the tradeoff between asymptotic bias and overfitting. [less ▲]

Detailed reference viewed: 80 (4 ULiège)
Full Text
Peer Reviewed
See detailForeseeing New Control Challenges in Electricity Prosumer Communities
Olivier, Frédéric ULiege; Marulli, Daniele; Ernst, Damien ULiege et al

in Proc. of the 10th Bulk Power Systems Dynamics and Control Symposium – IREP’2017 (2017, August)

This paper is dedicated to electricity prosumer communities, which are groups of people producing, sharing and consuming electricity locally. This paper focuses on building a rigorous mathematical ... [more ▼]

This paper is dedicated to electricity prosumer communities, which are groups of people producing, sharing and consuming electricity locally. This paper focuses on building a rigorous mathematical framework in order to formalise sequen- tial decision making problems that may soon be encountered within electricity prosumer communities. After introducing our formalism, we propose a set of optimisation problems reflecting several types of theoretically optimal behaviours for energy exchanges between prosumers. We then discuss the advantages and disadvantages of centralised and decentralised schemes and provide illustrations of decision making strategies, allowing a prosumer community to generate more distributed electricity (compared to commonly applied strategies) by mitigating over- voltages over a low-voltage feeder. We finally investigate how to design distributed control schemes that may contribute reaching (at least partially) the objectives of the community, by resort in to machine learning techniques to extract, from centralised solution(s), decision making patterns to be applied locally. First empirical results show that, even after a post-processing phase so that it satisfies physical constraints, the learning approach still performs better than predetermined strategies targeting safety first, then cost minimisation. [less ▲]

Detailed reference viewed: 671 (10 ULiège)
Full Text
Peer Reviewed
See detailReinforcement Learning for Electric Power System Decision and Control: Past Considerations and Perspectives
Glavic, Mevludin ULiege; Fonteneau, Raphaël ULiege; Ernst, Damien ULiege

in The 20th World Congress of the International Federation of Automatic Control, Toulouse 9-14 July 2017 (2017, July)

In this paper, we review past (including very recent) research considerations in using reinforcement learning (RL) to solve electric power system decision and control problems. The RL considerations are ... [more ▼]

In this paper, we review past (including very recent) research considerations in using reinforcement learning (RL) to solve electric power system decision and control problems. The RL considerations are reviewed in terms of speci c electric power system problems, type of control and RL method used. We also provide observations about past considerations based on a comprehensive review of available publications. The review reveals the RL is considered as viable solutions to many decision and control problems across di erent time scales and electric power system states. Furthermore, we analyse the perspectives of RL approaches in light of the emergence of new-generation, communications, and instrumentation technologies currently in use, or available for future use, in power systems. The perspectives are also analysed in terms of recent breakthroughs in RL algorithms (Safe RL, Deep RL and path integral control for RL) and other, not previously considered, problems for RL considerations (most notably restorative, emergency controls together with so-called system integrity protection schemes, fusion with existing robust controls, and combining preventive and emergency control). [less ▲]

Detailed reference viewed: 762 (12 ULiège)
Full Text
Peer Reviewed
See detailThe state of play in cross-border electricity trade and the challenges towards a global electricity market environment
Chatzivasileiadis, Spyros; Ernst, Damien ULiege

in Ilaria, Espa; Cottier, Thomas (Eds.) International trade in sustainable electricity (2017)

Detailed reference viewed: 249 (3 ULiège)
Full Text
Peer Reviewed
See detailResilience of the DSO network near to 50.2Hz
Vangulick, David ULiege; Ernst, Damien ULiege; Van Cutsem, Thierry ULiege

in Proceedings of the 24th International Conference on Electricity Distribution (2017, June)

In an electrical system where decentralized and embedded productions are becoming more and more important, it is essential to ensure there is a good understanding of their behaviour at their operating ... [more ▼]

In an electrical system where decentralized and embedded productions are becoming more and more important, it is essential to ensure there is a good understanding of their behaviour at their operating limits. One the most important operating limits is when the system frequency approaches 50.2 Hz. At this frequency, following the old requirements, many existing European PV inverters have to be disconnected. In such situations, we will demonstrate that the variance of the frequency measurement taken at every PV inverter plays a key role. It will be demonstrated that this variance is actually a good thing from the system’s point of view as it allows for a gradual disconnection, leading to a controlled variation of the frequency. [less ▲]

Detailed reference viewed: 200 (2 ULiège)
Full Text
Peer Reviewed
See detailE-CLOUD, the open microgrid in existing network infrastructure
Vangulick, David ULiege; Cornélusse, Bertrand ULiege; Vanherck, Thierry et al

in Proceedings of the 24th International Conference on Electricity Distribution (2017, June)

The main goal of the E-Cloud, as with every microgrid, is to maximize the consumption of energy produced locally. To reach this goal, based on consumption profiles of customers willing to participate in ... [more ▼]

The main goal of the E-Cloud, as with every microgrid, is to maximize the consumption of energy produced locally. To reach this goal, based on consumption profiles of customers willing to participate in the E-cloud and given some local restrictions (e.g. wind turbines cannot be put everywhere), an optimal mix of green generation sources (in kW) and local storage (in kWh) needs to be computed. Then according to this computation, the required generating units and storage device are installed. A repartition mechanism grants the customer a share of the generated electricity and storage capacity. These shares are either computed offline, or dynamically adapted on line. The project will test two models: either the DSO or a producer owns and operates the storage device. Two flows of information (real-time for operation of the storage facility and ex-post for its settlement) are needed to correctly manage the E-Cloud and to ensure correct information exchange with the wholesale market. These information flows are completed thanks to a forecast that provides members of the E-Cloud the full capability to anticipate and obtain the maximum benefits of the local generation. The expected benefits for the customer are a reduction of their electricity bill by a minimum of 10%. Societal benefits should also arise: 1) easing the technical integration of renewables’ generation embedded in the distribution network, and 2) avoids extra investment on the DSO network. The E-Cloud may also ensure new revenue for the DSO thanks to new services provided to the E-Cloud community. [less ▲]

Detailed reference viewed: 268 (2 ULiège)
Full Text
Peer Reviewed
See detailEfficient management of a connected microgrid in Belgium
Cornélusse, Bertrand ULiege; Ernst, Damien ULiege; Warichet, Luc et al

in Proceedings of the 24th International Conference on Electricity Distribution, Glasgow, 12-15 June 2017 (2017, June)

Detailed reference viewed: 687 (12 ULiège)
Full Text
Peer Reviewed
See detailSimple connectome inference from partial correlation statistics in calcium imaging
Sutera, Antonio ULiege; Joly, Arnaud ULiege; François-Lavet, Vincent et al

in Soriano, Jordi; Battaglia, Demian; Guyon, Isabelle (Eds.) et al Neural Connectomics Challenge (2017)

In this work, we propose a simple yet effective solution to the problem of connectome inference in calcium imaging data. The proposed algorithm consists of two steps. First, processing the raw signals to ... [more ▼]

In this work, we propose a simple yet effective solution to the problem of connectome inference in calcium imaging data. The proposed algorithm consists of two steps. First, processing the raw signals to detect neural peak activities. Second, inferring the degree of association between neurons from partial correlation statistics. This paper summarises the methodology that led us to win the Connectomics Challenge, proposes a simplified version of our method, and finally compares our results with respect to other inference methods. [less ▲]

Detailed reference viewed: 134 (5 ULiège)
Full Text
Peer Reviewed
See detailAutomatic phase identification of smart meter measurement data
Olivier, Frédéric ULiege; Ernst, Damien ULiege; Fonteneau, Raphaël ULiege

in Proc. of CIRED 2017 (2017, June)

This paper highlights the importance of the knowledge of the phase identification for the different measurement points inside a low-voltage distribution network. Besides considering existing solutions, we ... [more ▼]

This paper highlights the importance of the knowledge of the phase identification for the different measurement points inside a low-voltage distribution network. Besides considering existing solutions, we propose a novel method for identifying the phases of the measurement devices, based exclusively on voltage measurement correlation. It relies on graph theory and the notion of maximum spanning tree. It has been tested on a real Belgian LV network, first with simulated unbalanced voltage for which it managed to correctly identify the phases of all measurement points, second, on preliminary data from a real measurement campaign for which it shows encouraging results. [less ▲]

Detailed reference viewed: 578 (22 ULiège)
Full Text
See detailEnergy: the clash of nations
Ernst, Damien ULiege

Speech/Talk (2017)

Le monde de l'énergie est en guerre. C'est une guerre qui est menée sur de nombreux fronts, du Texas à l'Arabie saoudite, des salons feutrés de l'ONU et de l'organisation mondiale du commerce aux conseils ... [more ▼]

Le monde de l'énergie est en guerre. C'est une guerre qui est menée sur de nombreux fronts, du Texas à l'Arabie saoudite, des salons feutrés de l'ONU et de l'organisation mondiale du commerce aux conseils d'administration des majors du pétrole, des laboratoires chinois en panneaux photovoltaïques aux champs éoliens de la mer du Nord. Dans ce tumulte guerrier, chaque nation essaie de défendre ses propres intérêts, d'avancer ses pions de la manière la plus intelligente possible, sachant très bien qu'une énergie abondante et bon marché est une des clés d'une économie puissante. Au cours de ce cours-conférence, le Prof. Ernst décodera cette guerre qui est en train de se passer sous nos yeux et que souvent, l'on ne comprend pas. Il expliquera à quel point la technologie pourrait changer la géopolitique de l'énergie et plonger certaines nations dans la tourmente. Il mettra aussi en garde contre tout espoir excessif en la technologie pour garantir un approvisionnement en énergie suffisant, tellement la soif d'énergie de nos sociétés est grande. Il discutera également des politiques énergétiques à mettre en place en Europe pour éviter que le vieux continent ne sorte perdant de cette nouvelle guerre des ressources. [less ▲]

Detailed reference viewed: 436 (9 ULiège)
Full Text
See detailQuestions d'argent - Damien Ernst
Sury, Caroline; Ernst, Damien ULiege

Article for general public (2017)

Detailed reference viewed: 82 (1 ULiège)