Maximal stability region of a perturbed nonnegative matrix

For a class of positive matrices A + K with a stable positive nominal part A and a structured positive perturbation part K, we address the problem of finding the largest set of admissible perturbations such that the global matrix remains stable. Theoretical bounds are derived and an algorithm for constructing this set is presented. As an example, this algorithm is applied to the regulation of water flow in open channels

Hybrid power solution modelling based on artificial intelligence

peer reviewedPower electronics become increasingly resourceful as the use of renewable energies increases. Microgrids and active distribution networks include various controllable devices that interact and may create instabilities. This underlines the necessity of modeling complex systems to conduct system-level analyses. As a first step toward tools for modeling inverter-based electrical systems, this paper introduces a model of the HyPoSol system, put in perspective with measurements on the real system. The HyPoSol system consists of a photovoltaic (PV) inverter, a battery, and a three-port converter designed by CE+T Power. To develop a model of the PV inverter, we employed an enhanced polytopic model which uses neural networks as weighting functions. The PV inverter model is combined with a Tremblay’s battery model and a simplified model of the three-port converter. We conduct system-level analyses on the overall representation of the HyPoSol system and compare the results with measurements

North Sea Wind Power Hub: System Configurations, Grid Implementation and Techno-economic Assessment

In 2017, Energinet and TenneT, the Danish and Dutch Transmission System Operators (TSOs), have announced the North Sea Wind Power Hub (NSWPH) project. The project aims at increasing by 36 GW the North Sea offshore wind capacity, with an artificial island collecting all the power produced by wind turbines and several HVDC links transmitting this power to the onshore grids. This project brings together new opportunities and new challenges, both from a technical and economic point of view. In this regard, this paper presents three analyses regarding the design and operation of such an offshore system. First, we perform a techno-economic assessment of different grid configurations for the collection of the power produced by wind farms and its transmission to the hub. In this analysis, two frequencies and two voltage levels for the operation of the offshore grid are investigated. Our findings show that the nominal-frequency high-voltage option is the more suitable, as low-frequency does not bring any advantage and low-voltage would results in higher costs. The second analysis is related to the differences in operating the system with low- or zero-inertia; different dynamic studies are performed for each configuration to identify proper control actions and their stability properties. Comparing the outcomes of the simulations, we observed that voltage and frequency oscillations are better damped in the zero-inertia system; however, the risk of propagating offshore faults in the connected onshore grids is mitigated with the inclusion of the synchronous condensers. Lastly, a comparison of ElectroMagnetic Transient (EMT) and phasor-mode (also known as RMS) models is presented, in order to understand their appropriateness of simulating low- and zero- inertia systems. The results show that phasor approximation modelling can be used, as long as eigen-frequencies in power network are well damped.Comment: Submitted to "CIGRE Technical Exhibition 2020 - Session 48" on January 3, 2020 - Revised on February 15, 2020 - Accepted on June 4, 202

Contribution of the subthalamic nucleus to motor, cognitive and limbic processes: an electrophysiological and stimulation study in monkeys

Deep brain stimulation of the subthalamic nucleus (STN) has become the gold standard surgical treatment for Parkinson’s disease and is being investigated for obsessive compulsive disorders. Even if the role of the STN in the behavior is well documented, its organization and especially its division into several functional territories is still debated. A better characterization of these territories and a better knowledge of the impact of stimulation would address this issue. We aimed to find specific electrophysiological markers of motor, cognitive and limbic functions within the STN and to specifically modulate these components. Two healthy non-human primates (Macaca fascicularis) performed a behavioral task allowing the assessment of motor, cognitive and limbic reward-related behavioral components. During the task, four contacts in the STN allowed recordings and stimulations, using low frequency stimulation (LFS) and high frequency stimulation (HFS). Specific electrophysiological functional markers were found in the STN with beta band activity for the motor component of behavior, theta band activity for the cognitive component, and, gamma and theta activity bands for the limbic component. For both monkeys, dorsolateral HFS and LFS of the STN significantly modulated motor performances, whereas only ventromedial HFS modulated cognitive performances. Our results validated the functional overlap of dorsal motor and ventral cognitive subthalamic territories, and, provide information that tends toward a diffuse limbic territory sensitive to the reward within the STN

A second order model of road junctions in fluid models of traffic networks

This article deals with the modeling of junctions in a road network from a macroscopic point of view. After reviewing the Aw & Rascle second order model, a compatible junction model is proposed. The properties of this model and particularly the stability are analyzed. It turns out that this model presents physically acceptable solutions, is able to represent the capacity drop phenomenon and can be used to simulate the traffic evolution on a network

Lyapunov stability analysis of networks of scalar conservation laws

It is shown how an entropy-based Lyapunov function can be used for the stability analysis of equilibria in networks of scalar conservation laws. The analysis gives a sufficient stability condition which is weaker than the condition which was previously known in the literature. Various extensions and generalisations are briefly discussed. The approach is illustrated with an application to ramp-metering control of road traffic networks