Model Identification of a Micro Air Vehicle

This paper is focused on the model identification of a Micro Air Vehicle （MAV） in straight steady flight condition. The identification is based on input-output data collected from flight tests using both frequency and time dorrtain techniques. The vehicle is an in-house 40 cm wingspan airplane. Because of the complex coupled, multivariable and nonlinear dynamics of the aircraft, linear SISO structures for both the lateral and longitudinal models around a reference state were derived. The aim of the identification is to provide models that can be used in future development of control techniques for the MAV.

Modelling Mechanical Properties in Native and Biomimetically Formed Vascular Grafts

The paper presents a detailed analysis of experimental data in order to characterize the elastic properties of arteries.Such analysis would provide a good basis for evaluation of biomimetic vascular grafts.Since the latter needs to exhibit similar properties of native tissue,it is important to accurately characterize the biomimetic sample in a large range of applied stresses. The stress-strain properties vary according to the specific pathology(e.g.arteriosclerosis,aneurism)and the tissue graft must be chosen correctly.Two models are proposed in this paper on the stress-strain characteristics.An extension for frequency-domain analysis is provided for one of the models.The comparison between vascular grafts and native tissue for carotid and thoracic arteries in pigs are in good agreement with results from literature.The proposed experimental method offers suitable parameters for identifying models which characterize both elasticity and stiffness properties of the analyzed tissues(stress-strain).The proposed models show good performance in characterizing the intrinsic material properties.

Design and testing of a centralized protection scheme for micro-grids

Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. This concept aims to move from "connect and forget" philosophy towards a full integration of DERs. Micro-grids can provide numerous economic and environmental benefits for end-customers, utilities and society. However, their implementation poses great technical challenges, such as a new philosophy in design of protection systems. In this work, a micro-grid protection scheme is presented based on positive-sequence component using phasor measurement units(PMUs) and a central protection unit(CPU). The salient feature of the proposed scheme in comparison with the previous works is that it has the ability to protect both radial and looped micro-grids against different types of faults with the capability of single-phase tripping. Furthermore, since the CPU is capable of updating its pickup values(upstream and downstream equivalent positive-sequence impedances of each line) after the first change in the micro-grid configuration(such as transferring from grid-connected to islanded mode and or disconnection of a line, bus, or DER either in grid-connected mode or in islanded mode), it can protect micro-grid against subsequent faults. Finally, in order to verify the effectiveness of the suggested scheme and the CPU, several simulations have been undertaken by using DIg SILENT Power Factory and MATLAB software packages.

电动汽车的建模与模拟——不同锂离子电池技术的实施(英文)

受限制的续航距离是锂离子电池电动汽车的缺点之一。特别是在低温下,由于低的电池容量、功率,以及辅助设备的附带能量需求,使得该续航距离又被减少。选用了一种基于模型的方法,来比较几种不同的电池技术的车内性能。设定了不同的试验情景,分析电池特性。模拟结果表明:由于电池容量的减少,限制了制动器能量的恢复,因此,在城市近郊及低温环境下,动力系的能量需求明显升高。此外,针对不同的温度、电池尺寸和驾驶周期,分析了电池和动力系的效率。最后,针对不同驾驶周期、温度和附加载荷,研究了电动续航距离。

Data Driven Modelling of Coronavirus Spread in Spain

During the late months of last year,a novel coronavirus was detected in Hubei,China.The virus,since then,has spread all across the globe forcing Word Health Organization(WHO)to declare COVID-19 outbreak a pandemic.In Spain,the virus started infecting the country slowly until rapid growth of infected people occurred in Madrid,Barcelona and other major cities.The government in an attempt to stop the rapssid spread of the virus and ensure that health system will not reach its capacity,implement strict measures by putting the entire country in quarantine.The duration of these measures,depends on the evolution of the virus in Spain.In this study,a Deep Neural Network approach using Monte Carlo is proposed for generating a database to train networks for estimating the optimal parameters of a SIR epidemiology model.The number of total infected people as of April 7 in Spain is considered as input to the Deep Neural Network.The adaptability of the model was evaluated using the latest data upon completion of this paper,i.e.,April 14.The date range for the peak of infected people(i.e.,active cases)based on the new information is estimated to be within 74 to 109 days after the first recorded case of COVID-19 in Spain.In addition,a curve fitting measure based on the squared Euclidean distance indicates that according to the current data the peak might occur before the 86th day.Collectively,Deep Neural Networks have proven accurate and useful tools in handling big epidemiological data and for peak prediction estimates.

Design of hybrid damping controller based on multi-target gravitational search optimization algorithm in a multi-machine power system with high penetration of PV park

A mathematical approach was proposed to investigate the impact of high penetration of large-scale photovoltaic park(LPP) on small-signal stability of a power network and design of hybrid controller for these units.A systematic procedure was performed to obtain the complete model of a multi-machine power network including LPP.For damping of oscillations focusing on inter-area oscillatory modes,a hybrid controller for LPP was proposed.The performance of the suggested controller was tested using a 16-machine 5-area network.The results indicate that the proposed hybrid controller for LPP provides sufficient damping to the low-frequency modes of power system for a wide range of operating conditions.The method presented in this work effectively indentifies the impact of increased PV penetration and its controller on dynamic performance of multi-machine power network containing LPP.Simulation results demonstrate that the model presented can be used in designing of essential controllers for LPP.

Notice of Post-Publication Acknowledgement

The research work in Ref.[1]received support from the Surgical Center Henri Mondor, University Paris 12,France.Therefore,we would like to publish the following acknowledgement:This work was within the framework of an Erasmus student mobility at the Higher Institute of Bio Science,University Paris 1 2,France,which enabled the international collaboration with Faculty of Medical Bioengineering,University ofIasi,Romania.The experimental measurements and partial processing ofthe data presented in this article

Observations on Arrhenius Degradation of Lithium-Ion Capacitors

Earlier research determined that lithium-ion capacitor (LIC) cycle life degradation can be accelerated by elevated temperature. LIC cycle life degradation can be described by an Arrhenius equation. This study performed cycle life testing at a constant temperature but varied cycle current. The results were described by an Arrhenius equation relying upon the number of cycles and a constant, which was determined by cycle current. Using mathematical derivations and experimental results, the researchers quantified the effects of activation energy and temperature upon this constant. Because cell temperature is nearly constant during cycles, it was deduced that elevated cycle current decreases activation energy. This lower activation energy then accelerates degradation. Thus this research demonstrates that cycle current ages LICs through its effects on their activation energies.

Improvements to Temperature, Warburg Impedance, and Voltage Computations for a Design-Based Predictive Model for Lithium-Ion Capacitors

An earlier study manipulated the Butler-Volmer equation to effectively model a lithium-ion capacitor’s (LIC) energy storage as a function of its constituent components and charge current. However, this model had several shortcomings: computed temperature values were too low, voltage was inaccurate, and the model required Warburg impedance values that were two orders of magnitude higher than experimental results. This study began by analyzing the model’s temperature and voltage computations in order to justify output values. Ultimately, these justifications failed. Therefore, in situ temperature rise was measured during charge cycles. Experimental results indicated that temperature increases minimally during a charge cycle (<1%). At high current densities (≥150 A·kg-1) temperature increase is negligible. After it was found that LIC temperature change is minimal during a charge cycle, the model accurately computed LIC voltage during the charge cycle and computed Warburg impedance that agreed with values derived from earlier experimental studies, even falling within the measurements’ precision error.

Time-domain Dynamic State Estimation for Unbalanced Three-phase Power Systems

In this paper,we present a time-domain dynamic state estimation for unbalanced three-phase power systems.The dynamic nature of the estimator stems from an explicit consideration of the electromagnetic dynamics of the network,i.e.,the dynamics of the electrical lines.This enables our approach to release the assumption of the network being in quasi-steady state.Initially,based on the line dynamics,we derive a graphbased dynamic system model.To handle the large number of interacting variables,we propose a port-Hamiltonian modeling approach.Based on the port-Hamiltonian model,we then follow an observer-based approach to develop a dynamic estimator.The estimator uses synchronized sampled value measurements to calculate asymptotic convergent estimates for the unknown bus voltages and currents.The design and implementation of the estimator are illustrated through the IEEE 33-bus system.Numerical simulations verify the estimator to produce asymptotic exact estimates,which are able to detect harmonic distortion and sub-second transients as arising from converterbased resources.

Additional Overloading Assessment for Future Low Voltage Networks Based on Smart Metering

The purpose of this article is to present an additional overloading assessment scheme to the current protection scheme, which can be applied in the low voltage distribution network to prevent overloading of network assets. As higher penetration of distributed generators is envisioned among distribution networks, the network operators will have an challenging task in the future to maintain the reliability and quality of supply. The distribution networks are going to be challenged simultaneously by increasing penetration of distributed generators and by increasing loading （inter alia heat pumps, air conditioners or electric vehicles）, which will change the operational perspective of the future distribution networks. Presented simulation results show that the increasing penetration of those appliances can jeopardize the functionality of current protection scheme in distribution networks. Therefore, an additional scheme for assessment of network overloading applicable at low voltage distribution networks is proposed and the application of this scheme, supported by smart metering infrastructure, is demonstrated in a case study. The proposed overloading assessment scheme should help the network operators to increase the flexibility of distribution networks, their hosting capacity, safety and reliability.

Marine Current Turbine Simulator Development Based on Hardware in the Loop Simulation Concept

This paper is a contribution to the development of real time simulators for energy conversion research with respects to the ＂hardware in the loop simulation＂ concept. The focus is on the study of marine current kinetics energy conversion from into electrical energy using a marine current turbine simulator, developed in three stages. In the first stage the marine current turbine is emulated with the help of an induction drive who reproduces at its shaft the characteristics of a real turbine. It is connected with a load break used to force the emulator to respect on its shaft the characteristics of the real turbine. In the second stage, the induction drive is connected on the shaft with a doubly feed induction generator, for the study of energy conversion. The emulator respects the working regime, developed in the previous step, of a real turbine due to the control of the drive. In the third stage the induction machine emulating the turbine is interconnected with the generator and the load break. This assembly is used for the dynamic study of the marine current turbine. The break is used to create extra loads on the shaft and a variable inertial moment.

A Mixed-integer Linear Programming Model for Defining Customer Export Limit in PV-rich Low-voltage Distribution Networks

A photovoltaic(PV)-rich low-voltage(LV)distribution network poses a limit on the export power of PVs due to the voltage magnitude constraints.By defining a customer export limit,switching off the PV inverters can be avoided,and thus reducing power curtailment.Based on this,this paper proposes a mixed-integer nonlinear programming(MINLP)model to define such optimal customer export.The MINLP model aims to minimize the total PV power curtailment while considering the technical operation of the distribution network.First,a nonlinear mathematical formulation is presented.Then,a new set of linearizations approximating the Euclidean norm is introduced to turn the MINLP model into an MILP formulation that can be solved with reasonable computational effort.An extension to consider multiple stochastic scenarios is also presented.The proposed model has been tested in a real LV distribution network using smart meter measurements and irradiance profiles from a case study in the Netherlands.To assess the quality of the solution provided by the proposed MILP model,Monte Carlo simulations are executed in OpenDSS,while an error assessment between the original MINLP and the approximated MILP model has been conducted.

The German Energiewende and its roll-out of renewableenergies： An economic perspective

This paper gives a short overview of the German Energiewende, i.e. the transition of a large and mostly thermal electricity system towards electricity generation from renewable energy source. It discusses both, the motivation of the transitions as future goals and current status. Furthermore, it gives an in-depth view into the changes in economic costs for society as well as electricity price effects, especially for average private households and industrial consumers. It also discusses the benefits of the promotion of renewable energies in Germany.

Transient voltage stresses in MMC-HVDC links-impulse analysis and novel proposals for synthetic laboratory generation

To evaluate and optimise insulation coordination concepts for state of the art high-voltage direct current(HVDC)transmission systems,appropriate test voltage shapes are required for laboratory imitation of occurring stresses.While especially transient voltages in the monopolar modular multilevel converter(MMC)-HVDC links show an extensive deviation from commonly applied switching impulse shapes,this study focusses on the analysis of over-voltages subsequent to direct current pole to ground faults.Additionally,novel methods for synthetic laboratory test voltage generation are proposed.Based on simulated transients occurring during fault scenarios in different symmetrical monopolar±320 kV MMC-HVDC schemes,curve fitting,and related analysis techniques are used in order to compare simulated over-voltages with standard test voltage shapes.Moreover,these techniques further allow the identification of novel relevant impulse characteristics.Subsequently,design considerations for the generation of non-standard impulses based on single-stage circuits are derived and discussed.Those synthetically generated voltages may,later on,provide the basis for future investigations on related dielectric effects caused by those non-normative over-voltages.