Nicolas Retiere

• PhD
• Professor (Full) at Grenoble Alpes University

While electric power grids play a key role in the decarbonization of society, it remains unclear how recent trends, such as the strong integration of renewable energies, can affect their stability. Power oscillation modes, which are key to the stability of the grid, are traditionally studied numerically with the conventional view-point of two regim...

The ever increasing complexity of power systems mandates a further improvement of the numerical methods used for their simulation. We propose a new approach that is inspired by an exact analogy with quantum mechanics, but requires no specific knowledge of quantum physics. This approach allows in particular to use local methods commonly applied in q...

In this article, the transient stability conditions for an Electrical Vehicle (EV) charger power stage connected to the weak grid are investigated. An index based on a Lyapunov approach has been used to highlight possible stability issues. An EV charger generally includes Voltage Source Converters (VSCs), which may face difficulties in synchronizat...

Global energy transformation, urban growth and the increasing share of electricity in energy consumption stimulate the development of electrical distribution systems. In most cases, the structure of distribution networks has been the result of progressive decisions limited by technical, socio-economic and spatial constraints. These decisions are ta...

The load-flow equations are the main tool to operate and plan electrical networks. For transmission or distribution networks these equations can be simplified into a linear system involving the graph Laplacian and the power input vector. Decomposing the power input vector on the basis of the eigenvectors of the graph Laplacian, we solve this singul...

Power flows in transmission networks are driven by the structure of the network and the spatial distribution of generators and loads. Understanding the interplay between grid, generators, and loads is crucial for efficient and robust planning and management of electrical networks. Using the spectral properties of the graph Laplacian, we show that w...

Primary frequency control is the automatic mechanism implemented on power systems to regulate the power balance through frequency and hence, its action should be taken into account when modelling any contingency state leading to a modification of the active power balance (e.g. generator failures). This paper presents a fully distributed method to s...

We compare the fractal indices of the power grid of the city of Grenoble (France) to those computed on the spatial organization of the buildings and the road infrastructure. We assess the fractal dimensions and the curves of scaling behavior and conduct a concordance analysis. We study different districts within the city and compare the power and r...

We analyze the fractal properties of the distribution power grid of the city of Grenoble. We introduce the scaling behavior as a useful tool to compare the fractal behavior of multiple systems. We conduct a geographical concordance analysis between the power grid and both the road network and built-up areas of the city of Grenoble. We analyze the f...

We propose in this paper a distributed method to solve the security constrained optimal power flow problem (SCOPF) that considers not only contingencies on transmission lines but also on generators. With this aim, we extend the formulation of the SCOPF problem to consider the primary frequency response of generators as well as the short term constr...

The load-flow equations are the main tool to operate and plan electrical networks. For transmission or distribution networks these equations can be simplified into a linear system involving the graph Laplacian and the power input vector. We show, using spectral graph theory, how to solve this system efficiently. This spectral approach gives a new g...

We propose a fully distributed algorithm to solve the Chance Constrained Optimal Power Flow (CCOPF), with the advantages of ensuring the privacy and autonomy of the different operators and actors of the system. We present, in this paper, a two-step algorithm that, first, carries out a distributed sensitivity analysis to obtain the generalized gener...

This paper proposes an innovative method for optimizing the connectivity of meshed electrical pathways used to carry return current and provide grounding in more composite aircrafts. In normal operation, these networks should ensure a low voltage drop between power sources and electrical loads. The networks are modelled as graphs and spectral graph...

Purpose Static converters generate current harmonics in power grids. For numerous studies, analytical frequency modeling is preferred to carry out their harmonic modeling in the context of sizing by optimization. However, a design by optimization has to consider other constraints, e.g. modeling constraints and operating constraints. In this way, t...

The large-scale deployment of distributed generation including intermittent renewable energy sources introduces several challenges to power systems operation and planning. Although power systems often evolve in a fairly incremental way to meet these challenges, the ambitious objectives for RES development in the next decades (2030–2050), together w...

In the last two decades, electricity grids have faced many challenges that they were not designed to handle. These include integrating weather-dependent renewables, distributed generators, storage units and other advanced components, as well as taking into account active demand. These challenges, together with the ageing of infrastructures, make it...

The large-scale deployment of distributed generation including intermittent renewable energy sources introduces several challenges to power systems operation and planning. Although power systems often evolve in a fairly incremental way to meet these challenges, the ambitious objectives for RES development in the next decades (2030-2050), together w...

In the context of the incessant development of sustainable energy and ICT (Information and Communications technology) in power systems, power system becomes more and more intelligent, efficient and economic. However, using electrical infrastructure carrying information communication causes complexities in modeling and simulating. To overcome the pr...

The aircraft electric network is a complex system, consisting of many different elements integrated to form a unique entity, designed to perform a well-defined mission. In the current state, the network conceptual design is based on standards defined by the aircraft manufacturer. As a consequence, electric subsystem suppliers are doing local optimi...

Purpose – Due to the increase of the traffic, issues are appearing on DC-electrified railway feeding systems. One candidate solution to solve these issues and to improve their performances is to add storage systems in the railway DC electrical network. The purpose of this paper is to present a method based on an optimal power flow (OPF) for the an...

Electric aircraft network is a complex system containing high number of subsystems provided by different suppliers which must cooperate in safe and light weight operation. In the current state, the network conceptual design is based on standards defined by the aircraft manufacturer, each subsystem is designed separately according to standards only...

Power networks are complex systems composed of many heterogeneous and interacting components. Smart grids are even more complex systems due to the convergence of electrical and communication networks. In order to deal with this complexity, a mathematical model that is reduced-size, accurate, wide-band and knowledge based is required for dynamic stu...

Nowadays, embedded aircraft network contains electrical devices which must cooperate in safe and light weight operation. For designing such systems, different local strategies have been developed but no global optimization has been performed so far. In this paper, we present at first two approaches, a classical approach used at the moment and a uto...

Smart grids are new complex systems used for the optimal delivery of electricity. Their study and design require a better understanding of the interactions between their topological structure and performance. It is proved that the structure of power systems is self-similar and can be characterized by the spectral dimension. The effects of scale inv...

Non-integer-order systems are used to model diffusion in conductive parts of electrical machines as they lead to more compact knowledge models and also to improve their precision. In this paper, a linear half-order impedance model of a ferromagnetic sheet deduced from the diffusion of magnetic field is briefly introduced. Then, from physical consid...

After testing different existing design methods for complex problems, we have concluded that a good approach based on system decomposition must coordinate the design process of components to reach the system optimum. In this paper, we present a multilevel collaborative approach for designing complex systems based on several loops (here 2). A system...

Nowadays, embedded aircraft system contains electrical devices which must cooperate in safe and light weight network. For designing such systems, different local strategies have been developed but no global optimization has been performed so far. In this paper, we present and compare three strategies applied to the sizing of a whole network of more...

Purpose Static converters generate current harmonics in grids. Numerous studies on analytical frequency models of converters are often required to carry out their harmonic modeling in the context of sizing by optimization. Some formulations are proposed to solve such models. Each formulation has its own advantages and drawbacks. The paper mainly fo...

This paper aims at proving the application of the fault location method based on the Electromagnetic Time Reversal (EMTR) to multi-terminal HVDC (MTDC) networks. In particular, the paper integrates the EMTR fault location technique with the protection scheme recently proposed within the EU project TWENTIES. Further, in view of the peculiarity of th...

The recent evolution of aircraft power networks makes new design study necessary for solving key issues such as optimal efficiency, reliability, adaptability and performances. Indeed, DC power systems are subject to strong dynamic interactions between the source and the loads. In this paper, the need for a new design method of the power network is...

This paper presents a new wide-band frequency model based on scale invariance. Self-similarities observed in power systems are mathematically translated by power laws whose exponents are linked to spectral dimension. This parameter is an expression of the topological properties of the network. Power laws are used for obtaining a wide-band frequency...

The lmodern energy systems are in deep mutation, with electricity taking a bigger part every day. The integration of energetic systems is the ability to design these devices by assembling the most diverse and heterogeneous electrical equipments. To be successful, the integration process must lead to a performant, economical and easy-to-assemble sys...

Les systèmes énergétiques modernes sont en profonde mutation, l'électricité y prenant une part de plus en plus grande pour les transferts d'énergie. L'intégration est la capacité de construire ces systèmes par l'assemblage d'équipements électriques les plus divers. Pour être réussie, la démarche d'intégration doit conjuguer respect des impératifs d...

This paper presents a methodology which allows to obtain a time domain response of synchronous generator modelled by the half-order systems. The machine is connected to an electrical network composed of RL circuit. From the Park d-q axis equivalent circuit containing impedances modelled by the half-order transmittances, a state space equation syste...

A new modeling approach for electrical networks is introduced in this paper based on fractal geometry and self-similarity. A particular parameter called fractal dimension is computed using a box counting method. The resulting model, based on a scaling power law, gives an accurate mathematical representation of the frequency behaviour of the network...

This paper presents a half-order modelling approach applied to a saturated ferromagnetic sheet. Several analytical models are then developed and compared for one-dimensional formulation. In order to identify parameters and validate such models, the saturated ferromagnetic sheet has been simulated using Flux® finite element simulation software. The...

In this paper, a new HVDC power supply system for light rail systems is presented and compared to classical distribution networks based on AC/DC controlled converters. A simulation tool has been developed to simulate such a complex system, taking into account vehicle motion and HVDC electrical distribution. Then, an optimization of HVDC structure a...

The aim of this paper is to introduce a new approach for electrical power network modeling. It is based on fractal geometry. Over a wide range of frequency, power systems exhibit capacitive, inductive and resonant behaviors. In the resonant range, the authors show that it is possible to model the average behavior of the resonances by a power law. I...

The aim of this paper is to present a new international master curriculum in the field of information technologies (IT) focused on industrial processes automation (IPA), proposed by University Joseph Fourier (UJF) / University of Grenoble, France. The education objectives are set according to the latest concepts developed in IT for process automati...

Power electronics converters can generate a high level of harmonic perturbations on on-board electrical systems (planes, ships, road vehicles…). For the optimal sizing of these systems, harmonics must be known to select the best components (generator, filter…) that will limit their effects. In the paper, an analytical frequency domain modeling is p...

Purpose – The purpose of this paper is to describe an optimization methodology based on a mixed (analytical‐numerical) design model and evolutionary algorithms. Design/methodology/approach – In this paper, optimal sizing is used to design the new architecture of an embedded electrical system. An approach is presented for defining the specification...

This paper deals with the modeling and control of an electrical source for the future “All Electric” aircraft. It is constituted by a rotor wounded synchronous generator and a diode rectifier feeding the DC power system. Using H∞ control theory, this paper shows that usual disturbance rejection standards can not be met with such an electrical power...

Non integer order systems are used to model diffusion in conductive parts of electrical machines as they lead to more compact and knowledge models but also to improve their precision. Nevertheless, non integer order models have been established under linear conditions. It is than interesting to study the influence of saturation on such model parame...

A new methodology for aircraft HVDC power systems design is first proposed. The first goal is to design the network subsystems in order to obtain optimal devices from a weight point of view. The contribution of optimal linear multivariable control methods is shown to be major for this first design objective and H_infin synthesis is applie...

The recent evolution of aircraft power networks makes new design study necessary for solving key issues such as optimal efficiency, reliability, adaptability and performances. Indeed, DC power systems are subject to strong dynamic interactions between the source and the loads. In this paper, the need for a new design method of the power network is...

Non integer order systems have been used successfully to model in frequency domain the development of induced currents in electrical machines, especially in damper bars or massive parts of large synchronous machines. The objective of this article consists in extending the field of application of non integer order models for small signal stability s...

The fractional order systems have been used successfully to model the development of induced currents in synchronous generators. State-space theory can be generalized to give a dynamical representation of fractional order systems. In this paper, modal analysis of an electrical network modeled by fractional order systems is presented. For stability...

This paper presents a half-order modelling approach applied to a saturated ferromagnetic sheet. Several analytical models are then developed and compared for 1D formulation. In order to identify parameters and valid such models, the saturated ferromagnetic sheet has been simulated using Flux® finite element simulation software.

Improving the braking energy recovery efficiency in light rail systems can reduce their energy consumption. In order to compare and quantify contribution of different technologies with respect to traditional light rail systems, a quasi-static decoupled load flow modelling of a power supply network with AC-DC converters has been developed by the aut...

Ce travail s'inscrit dans un projet plus vaste de proposer un modèle dynamique de l'ensemble générateur électrochimique et stockage alliant une description fine des composants et une description de l'architecture du système (ensemble générateur, stockage et convertisseur). L'originalité des modèles dynamiques des composants porte sur l'utilisation...

In this article, the authors propose a new modelling of electrical networks based on fractional order systems, i.e. systems with non-integer derivative functions. The algorithm of identification of such systems has been applied on a particular network presenting a fractal behaviour on a restricted frequency range

Pareto borders are used to represent the best compromise, for a component or a system, between the objectives in multi-objective optimization. This paper presents also a method which will allow determining the global Pareto border of the system by integrating those of components in function of global parameters. Our approach uses the Pareto border...

The modeling of proton exchange membrane fuel cells (PEMFC) may work as a powerful tool in the development and widespread testing of alternative energy sources in the next decade. In order to obtain a suitable PEMFC model, which can be used in the analysis of fuel cell-based power generation systems, it is necessary to define the values of a specif...

La liberalisation du marche europeen de l'energie et l'arrivee a maturite de petits moyens de production ainsi que des directives europeennes et des contraintes ecologiques peuvent conduire a une arrivee massive de producteurs au niveau de la haute tension de niveau A (HTA, en France principalement 20 kV) et de la basse tension (BT, en France princ...

Vehicles of the future will store, transport and use large amounts of electrical energy. The main components of DC networks are power electronic converters. Combinations of such converters are known to be unstable in certain situations. By investigating the causes of instability and comparing current methods, a state space representation is chosen...

This paper is devoted to the design of a nonlinear controller well suited for the voltage regulation of embedded AC electrical networks, such as plane or ship power systems. The approach may also be applied without fundamental restriction to high voltage or distribution power networks. The here-proposed approach relies on the nonlinear differential...

The presented approach is a first view on how apply the fractal theory to the modelling of electrical power systems. The idea presented above can be illustrated by the ramifications of power networks which remind the structure of a fractal object. Using the example of an electrical circuit derived from the fractal of Cantor, the authors showed that...

En raison de la liberalisation du marche europeen de l'energie, de l'arrivee a maturite de petits moyens de production, des directives europeennes et des contraintes ecologiques, une arrivee massive deproducteurs au niveau de la Haute Tension de niveau A (HTA, en France principalement 20 kV) et de la Basse Tension (BT, en France principalement 400/...

Vehicles of the future stores, transports and use large amounts of electrical energy. The main components of DC networks are power electronic converters. Combinations of such converters are known to be unstable in certain situations. By investigating the causes of instability and comparing current methods, a state space representation is chosen for...

This work presents a new approach to model the dynamic behaviour of supercapacitors using half-order systems. The new model is determined in the frequency domain but a Matlab model can be use in simulating the voltage response and energy efficiency e,g. for automotive power.

The increasing number of power electronic converters connected to aircraft electrical supply networks increases the harmonic levels. Conventional filter design is not well adapted to many power converters, since their behaviour is strongly coupled with filter values. This paper proposes a methodology to optimize a passive input filter and to fulfil...

This paper presents an analytical frequency-domain method for harmonic estimation able to evaluate harmonics and interharmonics and to capture the coupling between frequencies. It is based on the linear time – periodic system theory as a result of the periodic behaviour of the state variables in steady state operation. It consists of describing the...

Les réseaux électriques ont profondément changé depuis leur apparition. Les petits réseaux locaux du début 20ème Siècle ont pendant longtemps été interconnectés pour former des réseaux plus vastes et fortement centralisés. Mais, les orientations politiques libérales des vingt dernières années ont inversé la tendance et les réseaux électriques sont...

Utility power systems are faced to an increasing number of small size producers requiring interconnection, particularly to the low voltage (LV) network. Since most distribution systems are not designed to accept large scale power injections, these small generation units may impact on their interconnected networks. The quality of the supplied energy...

The flowing of induced currents in electric machines, especially in the dampers or massive parts of large synchronous machines, implies an increase in the order of the equivalent circuits used to model their frequency response. But physical meanings of the circuit parameters are often lost. Thus, the authors propose to go back over the modeling of...

Utility power systems are faced to an increasing number of small size producers requiring interconnection particularly to the low voltage (LV) network. Since most distribution systems are not designed to "receive" large scale power injections, these small generation units may impact these networks specifically in terms of quality of the energy deli...

Modelling of skin effect in electrical machines requires considering frequency-dependent parameters in their equivalent circuits. The authors propose to model this frequency dependence with half-order systems. The resulting equivalent circuits are both accurate and physically representative over a wide range of the frequency.

This paper describes a new dynamic model of a turbo-charged diesel generator. The purpose of this model is to study the impact of dispersed generation on distribution systems. The model is based on the mean torque method which presents the advantages to be simple and representative and to have a modular structure. The developed model has been imple...

The flowing of induced currents in electric machines, especially in the dampers of synchronous machines, implies an increase in the order of the equivalent circuits used to model their frequency response. But physical meanings of the circuit parameters are often lost. Thus, the authors propose to come back over the modeling of skin effect and to de...

The flowing of induced currents in electric machines, especially in the dampers or massive parts of large synchronous machines, implies an increase in the order of the equivalent circuits used to model their frequency response. But, by this way, physical meanings of the circuit parameters are often lost. Thus, the authors propose to go back over th...

The flowing of induced currents in electric machines, especially in the deep-bars of induction machine cages and the dampers of synchronous machines, implies an increase in the order of the equivalent circuits used to model their frequency response. But, physical meanings of the circuit parameters are often lost. Thus, the authors propose to go bac...