References of "Ernst, Damien"
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See detailA biased random key genetic algorithm applied to the electric distribution network reconfiguration problem
de Faria Jr., Haroldo; Resende, Mauricio; Ernst, Damien ULg

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 ▲]

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See detailPulse-Based Control Using Koopman Operator Under Parametric Uncertainty
Sootla, Aivar; Ernst, Damien ULg

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 ▲]

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See detailAn Optimal Control Formulation of Pulse-Based Control Using Koopman Operator
Sootla, Aivar; Mauroy, Alexandre; Ernst, Damien ULg

E-print/Working paper (2018)

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 ▲]

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See detailForeseeing New Control Challenges in Electricity Prosumer Communities
Olivier, Frédéric ULg; Marulli, Daniele; Ernst, Damien ULg 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 ▲]

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See detailReinforcement Learning for Electric Power System Decision and Control: Past Considerations and Perspectives
Glavic, Mevludin ULg; Fonteneau, Raphaël ULg; Ernst, Damien ULg

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 ▲]

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See detailThe state of play in cross-border electricity trade and the challenges towards a global electricity market environment
Chatzivasileiadis, Spyros; Ernst, Damien ULg

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

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See detailResilience of the DSO network near to 50.2Hz
Vangulick, David ULg; Ernst, Damien ULg; Van Cutsem, Thierry ULg

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 ▲]

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See detailE-CLOUD, the open microgrid in existing network infrastructure
Vangulick, David ULg; Cornélusse, Bertrand ULg; 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 ▲]

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See detailEfficient management of a connected microgrid in Belgium
Cornélusse, Bertrand ULg; Ernst, Damien ULg; Warichet, Luc et al

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

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See detailSimple connectome inference from partial correlation statistics in calcium imaging
Sutera, Antonio ULg; Joly, Arnaud ULg; 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 ▲]

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See detailAutomatic phase identification of smart meter measurement data
Olivier, Frédéric ULg; Ernst, Damien ULg; Fonteneau, Raphaël ULg

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 ▲]

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See detailEnergy: the clash of nations
Ernst, Damien ULg

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 ▲]

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See detailQuestions d'argent - Damien Ernst
Sury, Caroline; Ernst, Damien ULg

Article for general public (2017)

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See detailApproximate Bayes Optimal Policy Search using Neural Networks
Castronovo, Michaël ULg; François-Lavet, Vincent ULg; Fonteneau, Raphaël ULg et al

in Proceedings of the 9th International Conference on Agents and Artificial Intelligence (ICAART 2017) (2017, February)

Bayesian Reinforcement Learning (BRL) agents aim to maximise the expected collected rewards obtained when interacting with an unknown Markov Decision Process (MDP) while using some prior knowledge. State ... [more ▼]

Bayesian Reinforcement Learning (BRL) agents aim to maximise the expected collected rewards obtained when interacting with an unknown Markov Decision Process (MDP) while using some prior knowledge. State-of-the-art BRL agents rely on frequent updates of the belief on the MDP, as new observations of the environment are made. This offers theoretical guarantees to converge to an optimum, but is computationally intractable, even on small-scale problems. In this paper, we present a method that circumvents this issue by training a parametric policy able to recommend an action directly from raw observations. Artificial Neural Networks (ANNs) are used to represent this policy, and are trained on the trajectories sampled from the prior. The trained model is then used online, and is able to act on the real MDP at a very low computational cost. Our new algorithm shows strong empirical performance, on a wide range of test problems, and is robust to inaccuracies of the prior distribution. [less ▲]

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See detailResidential heat pump as flexible load for direct control service with parametrized duration and rebound effect
Georges, Emeline ULg; Cornélusse, Bertrand ULg; Ernst, Damien ULg et al

in Applied Energy (2017), 187

This paper addresses the problem of an aggregator controlling residential heat pumps to offer a direct control flexibility service. The service consists of a power modulation, upward or downward, that is ... [more ▼]

This paper addresses the problem of an aggregator controlling residential heat pumps to offer a direct control flexibility service. The service consists of a power modulation, upward or downward, that is activated at a given time period over a fixed number of periods. The service modulation is relative to an optimized baseline that minimizes the energy costs. The load modulation is directly followed by a constrained rebound effect, consisting of a delay time with no deviations from the baseline consumption and a payback time to return to the baseline state. The potential amount of modulation and the constrained rebound effect are computed by solving mixed integer linear problems. Within these problems, the thermal behavior of the building is modeled by an equivalent thermal network made of resistances and lumped capacitances. Simulations are performed for different sets of buildings typical of the Belgian residential building stock and are presented in terms of achievable modulation amplitude, deviations from the baseline and associated costs. A cluster of one hundred ideal buildings, corresponding to retrofitted freestanding houses, is then chosen to investigate the influence of each parameter defined within the service. Results show that with a set of one hundred heat pumps, a load aggregator could expect to harvest mean modulation amplitudes of up to 138 kW for an upward modulation and up to 51 kW for a downward modulation. The obtained values strongly depend on the proposed flexibility service. For example, they can decrease down to 2.6 kW and 0.4 kW, respectively, if no rebound effect is allowed. [less ▲]

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See detailAn App-based Algorithmic Approach for Harvesting Local and Renewable Energy Using Electric Vehicles
Dubois, Antoine; Wehenkel, Antoine; Fonteneau, Raphaël ULg et al

in Proceedings of the 9th International Conference on Agents and Artificial Intelligence (ICAART 2017) (2017, February)

The emergence of electric vehicles (EVs), combined with the rise of renewable energy production capacities, will strongly impact the way electricity is produced, distributed and consumed in the very near ... [more ▼]

The emergence of electric vehicles (EVs), combined with the rise of renewable energy production capacities, will strongly impact the way electricity is produced, distributed and consumed in the very near future. This position paper focuses on the problem of optimizing charging strategies for a fleet of EVs in the context where a significant amount of electricity is generated by (distributed) renewable energy. It exposes how a mobile application may offer an efficient solution for addressing this problem. This app can play two main roles. Firstly, it would incite and help people to play a more active role in the energy sector by allowing photovoltaic (PV) panel owners to sell their electrical production directly to consumers, here the EVs’ agents. Secondly, it would help distribution system operators (DSOs) or transmission system operators (TSOs) to modulate more efficiently the load by allowing them to influence EV charging behaviour in real time. Finally, the present paper advocates for the introduction of a two-sided market-type model between EV drivers and electricity producers. [less ▲]

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See detailUber-like Models for the Electrical Industry
Ernst, Damien ULg

Speech/Talk (2017)

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See detailLes batteries vont bouleverser notre quotidien
Scharff, Christine; Ernst, Damien ULg

Article for general public (2017)

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See detailGREDOR. Outcomes and recommendations
Cornélusse, Bertrand ULg; Ernst, Damien ULg

Report (2017)

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See detailAgent-based analysis of dynamic access ranges to the distribution network
Mathieu, Sébastien ULg; Ernst, Damien ULg; Cornélusse, Bertrand ULg

in Proceedings of the 6th European Innovative Smart Grid Technologies (ISGT) (2017)

There is a need to clearly state an interaction model that formalizes interactions between actors of the distribution system exchanging flexibility. In previous works we quantitatively evaluated the ... [more ▼]

There is a need to clearly state an interaction model that formalizes interactions between actors of the distribution system exchanging flexibility. In previous works we quantitatively evaluated the performance of five interaction models devised with industrial partners using the agent-based testbed DSIMA. Simulation results showed that these interaction models relying on active network management suffer from a lack of coordination between the distribution and the transmission system operator, activating flexibility simultaneously in opposite directions. This paper introduces a new interaction model fixing this issue based on dynamic access bounds to the network changing throughout the day and preventing the activation of flexibility leading to congestions. This new interaction model is implemented in DSIMA and compared to a model restricting the grid users to a very restrictive but safe access range. Results show that this new model allows to safely increase by 55% the amount of distributed generation in the network. [less ▲]

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