Showing papers by "Hydro-Québec published in 2018"

Sodium Vanadium Fluorophosphates (NVOPF) Array Cathode Designed for High-Rate Full Sodium Ion Storage Device

Abstract: Dongliang Chao, Chun‐Han (Matt) Lai, Pei Liang, Qiulong Wei, Yue‐Sheng Wang, Changrong (Rose) Zhu, Gang Deng ... et al.

A comprehensive review of lithium salts and beyond for rechargeable batteries: Progress and perspectives

Abstract: The increasing need for energy storage has been the motivation for intensive research in batteries with different chemistries in the recent past. Among the elements of the batteries, the salts and their solvent play an important role. In particular, the cathodic stability at low potential depends importantly on the choice of the cation, while the stability at high potentials is mainly due to oxidation of anions and the ion mobility and dissociation depend primarily on the delocalization of the anion, so that many attempts are made to find the optimum choice of both the cations and anions of the salts, and their solvents. Although lithium-based batteries are almost exclusively used today, efforts are currently made to explore batteries based on sodium, aluminum, magnesium, calcium, potassium. The purpose of the present work is to review the salts and solvents that have been proposed in these different batteries and discuss their properties and their ability to be used in the near future and in the next generation of batteries.

A photochemical diode artificial photosynthesis system for unassisted high efficiency overall pure water splitting.

Abstract: The conversion of solar energy into chemical fuels can potentially address many of the energy and environment related challenges we face today. In this study, we have demonstrated a photochemical diode artificial photosynthesis system that can enable efficient, unassisted overall pure water splitting without using any sacrificial reagent. By precisely controlling charge carrier flow at the nanoscale, the wafer-level photochemical diode arrays exhibited solar-to-hydrogen efficiency ~3.3% in neutral (pH ~ 7.0) overall water splitting reaction. In part of the visible spectrum (400–485 nm), the energy conversion efficiency and apparent quantum yield reaches ~8.75% and ~20%, respectively, which are the highest values ever reported for one-step visible-light driven photocatalytic overall pure water splitting. The effective manipulation and control of charge carrier flow in nanostructured photocatalysts provides critical insight in achieving high efficiency artificial photosynthesis, including the efficient and selective reduction of CO2 to hydrocarbon fuels. A major challenge facing solar-to-fuel technologies is the integration of light-absorbing and catalytic components into efficient water-splitting devices. Here, the authors construct a photochemical diode array to harvest visible light and split pure water at high solar-to-hydrogen efficiencies.

Fallback Control for Isochronous Energy Storage Systems in Autonomous Microgrids Under Denial-of-Service Cyber-Attacks

Abstract: This paper investigates and proposes a mitigation strategy for denial-of-service (DoS) cyber-attacks, targeting the most critical distributed energy resource (DER) in an islanded microgrid featuring a high penetration of renewables; the energy storage system (ESS) operating as the isochronous generator that forms and regulates the microgrid voltage and frequency. A rule-based fallback control strategy is proposed to enhance the resiliency of the microgrid to DoS cyber-attacks by managing the ESS state-of-charge in a decentralized manner, such that it can continue operating as the isochronous DER, while dispatching the remaining DERs in a centralized manner. Supplementary control loops are added to the ESS to manage and coordinate, using local frequency signals, with the remaining DERs, whose local controllers are specifically designed to provide frequency support in the event of DoS cyber-attacks. The proposed scheme is applied on a 25 kV islanded microgrid under two configurations, synchronous machine-based and 100% inverter-interfaced, and its effectiveness is validated on a real-time hardware-in-the loop testing platform.

Li4Ti5O12: A Visible-to-Infrared Broadband Electrochromic Material for Optical and Thermal Management

Abstract: Broadband electrochromism from visible to infrared wavelengths is attractive for applications like smart windows, thermal-camouflage, and temperature control. In this work, the broadband electrochromic properties of Li4Ti5O12 (LTO) and its suitability for infrared-camouflage and thermoregulation are investigated. Upon Li+ intercalation, LTO changes from a wide band-gap semiconductor to a metal, causing LTO nanoparticles on metal to transition from a super-broadband optical reflector to a solar absorber and thermal emitter. Large tunabilities of 0.74, 0.68 and 0.30 are observed for the solar reflectance, mid-wave infrared (MWIR) emittance and long-wave infrared (LWIR) emittance respectively. The values exceed, or are comparable to notable performances in the literature. A promising cycling stability is also observed. MWIR and LWIR thermography reveal that the emittance of LTO-based electrodes can be electrochemically tuned to conceal them amidst their environment. Moreover, under different sky conditions, LTO shows promising solar heating and sub-ambient radiative cooling capabilities depending on the degree of lithiation and device design. The demonstrated capabilities of LTO make LTO-based electrochromic devices highly promising for infrared-camouflage applications in the defense sector, and for thermoregulation in space and terrestrial environments.

Compressive strength and microstructure of assorted wastes incorporated geopolymer mortars: Effect of solution molarity

Abstract: This paper presents the solution molarity dependent microstructures and mechanical properties of multi-blend geopolymer mortars (GPMs). Geopolymer mortars were cured at ambient temperature under varying concentration (from 2 to 16 M) of sodium hydroxide (NH) solution. GPMs are by conducting mechanical tests such as compressive, split tensile and flexural strengths and characterised by microstructural studies, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray spectroscopy (EDS). The effect of Na2O, H2O content, solution modulus (SiO2:Na2O) and Na2O:Al2O3 on GPMs strength were determined. The flow ability and setting time of such GPMs found to decrease linearly with increasing alkali concentration. Conversely, the GPMs comprehensive, split tensile and flexural strengths and the density are enhanced with increasing alkali concentration. Samples activated with 12 M NH solution are most strongly affected by silica dissolution. Furthermore, the ratio of (Na2O:Al2O3) was demonstrated to influence the compressive strength significantly and the (Na2O:Al2O3 = 0.84) presented the optimum strength.

In Situ Scanning Electron Microscopy Detection of Carbide Nature of Dendrites in Li-Polymer Batteries.

Abstract: Li metal batteries suffer from dendrite formation which causes short circuit of the battery. Therefore, it is important to understand the chemical composition and growth mechanism of dendrites that limit battery efficiency and cycle life. In this study, in situ scanning electron microscopy was employed to monitor the cycling behavior of all-solid Li metal batteries with LiFePO4 cathodes. Chemical analyses of the dendrites were conducted using a windowless energy dispersive spectroscopy detector, which showed that the dendrites are not metallic lithium as universally recognized. Our results revealed the carbide nature of the dendrites with a hollow morphology and hardness greater than that of pure lithium. These carbide-based dendrites were able to perforate through the polymer, which was confirmed by milling the polymer using focused ion beam. It was also shown that applying pressure on the battery can suppress growth of the dendrites.

Application of μPMUs for adaptive protection of overcurrent relays in microgrids

Abstract: This study proposes a new application of micro-phasor measurement units (μPMUs) for adaptive coordination of overcurrent relays in microgrids. Mis-coordination of overcurrent relays usually arising from the variation of relays fault current and it can cause damage to equipment of network and raise operating costs. Fault current injection and direction to microgrid are highly dependent on network uncertainties; therefore, fault current is affected by line and power plant outages. This study proposes an algorithm to detect these uncertainties in online operation. Then, microgrid overcurrent relays coordination is optimised again. Uncertainties are line and power plant outages in transmission network and microgrid side and two distinct methods are used for each. For online detection of uncertainties in the transmission side, it is assumed that a μPMU is installed between transmission network and microgrid point of common coupling; so, the topology changes such as line outage is detected by monitoring of Thevenin impedance estimation that is obtained by μPMU measurements. Uncertainties detection in a microgrid is done by signals that are sent by μPMUs and installed all over the microgrid. All data are gathered and analysed in phasor data concentrators and then overcurrent relays coordination is updated with such changes.

The Role of Metal Disulfide Interlayer in Li–S Batteries

Abstract: Recently many observations related to the catalytic effects of layered metal disulfide versus polysulfide electrochemistry were documented. In this work, we investigated the reactivity of layered WS2 in a Li–S battery and observed a chemical reaction involving the removal of W ions by polysulfides. The presence of metallic tungsten nanoparticles in the sulfur cathode is the result of W ion oxidation reaction and subsequent recrystallization during cycling. In situ Raman spectroscopy and ex situ transmission electron microscopy were used in order to clarify the reaction mechanism.

Centralized Dynamic State Estimation Using a Federation of Extended Kalman Filters With Intermittent PMU Data From Generator Terminals

Abstract: An improved dynamic state estimation scheme that performs estimation for the full plant (states of a generator, exciter field voltage, and governor mechanical torque) using intermittent data from a phasor measurement unit (PMU) connected at generator terminal is presented. Overall fourth-order generator model is assumed in an extended Kalman filter (EKF), while first-order governors and excitation systems are assumed for simplicity of large-scale implementation. State estimation is performed using the EKF with random PMU data dropouts and known inputs, i.e., secondary reference signals P ref and V ref provided to a power plant by the network control center from economic dispatch. The state estimation scheme has been extended to all generators in network and DSE is performed using a computationally decentralized federation of EKFs at a centralized phasor data concentrator where PMU data are aggregated while dealing with a specified stochastic dropout rate. Required modifications have, thus, been made to standard EKF formulation to account for communication channel interruption and inherent delays. Simulation studies performed on the benchmark IEEE 9 and 39 bus system demonstrated performance and resilience of the proposed centralized EKF-based estimation technique. We also found that a centralized estimator can lead to improved wide-area instability indices derived from state estimates rather than PMU data directly.

Making of an Industry-Friendly Artificial Photosynthesis Device

Abstract: The distinct as well as the synergistic effect of the water oxidation co-catalyst (Co3O4), the proton reduction co-catalyst (Rh/Cr2O3), and the optimum surface properties of Ga(In)N nanowire arrays can significantly enhance the photocatalytic performance (STH ≈ 2.7%) and long-term stability (>580 h) of bias-free overall pure water splitting.

Time-Delay Analysis of Wide-Area Voltage Control Considering Smart Grid Contingences in a Real-Time Environment

Abstract: This paper addresses the time-delay effects of the wide-area monitoring and control systems (WAMCS) in smart power grids which may critically impact system stability The main purpose is to conduct a detailed delay analysis of the WAMCS in case of grid contingences This analysis is performed via an advanced WAMCS testbed where a flexible ac transmission system (FACTS) device is utilized and controlled via a wide-area controller (WAC) Phasor measurements units (PMUs) are adopted to collect the real-time measurements for the WAC The testbed results from an interface of four main segments known as the WAC; the actual FACTS device, the local area controller, and the power grid system along with the PMUs are simulated via a real-time digital simulator To mimic the real case scenario, both hardware-in-the-loop and software-in-the-loop schemes are adopted in the experimental testbed, considering time-delay effects The results obtained clarify the effect of delay in WAMCS in case of smart grid contingences

Improved Optimal Decentralized Load Modulation for Power System Primary Frequency Regulation

Abstract: Nowadays the interest in smart load technologies for primary frequency regulation is spurred due to the increasing penetration of renewable energy resources. In this paper, an improved optimal load control (improved OLC) is introduced by applying a multiobjective optimization-based gain-tuning method to the conventional OLC approach. The objective is to minimize the frequency nadir, time response, steady-state error, total load shed, and aggregated disutility of controllable loads subject to power balance over the network. Simulation results indicate that enabling a multiobjective optimization-based gain-tuning procedure in the OLC approach can provide better power system frequency regulation. Time-domain analysis confirms the superior performance of improved OLC in terms of frequency nadir (Hz), steady-state error (Hz), control effort, and NERC-based performance metrics (MW/0.1 Hz), with detailed load and wind farm models. Furthermore, small-signal analysis demonstrates that the improved OLC enhances the system closed-loop performance and stability margins by increasing the damping ratio of the system's critical modes.

Oscillatory stability assessment of microgrid in autonomous operation with uncertainties

Abstract: One of the main challenges of the microgrid (MG) operation in autonomous mode is the uncertain output due to the fluctuating nature of renewable energy resources (RES). This study investigates the effects of RES uncertainties to the oscillatory stability of a hybrid MG in islanded operation. A comprehensive model of Wind Energy Conversion System (WECS), a two-stage Photovoltaic (PV) and bio-diesel engine (BDE) based distributed generation (DG) units are considered to capture a complete dynamic response of the hybrid MG. Trajectories and distribution of damping ratios and oscillatory frequencies of the critical modes were thoroughly investigated through Monte Carlo simulation considering wind speed and solar irradiance uncertainties. From the probabilistic study, it was observed that the presence of RES variations results in a dynamic change of power-sharing strategies and introduce an adverse effect on small signal stability. Uncertain condition of wind speed brings more deterioration in system damping than solar irradiation variation. From time domain simulation, it was confirmed that at higher wind speed, damping on the critical modes reduced. As a consequence, the hybrid MG experienced more oscillatory conditions and even lead to unstable situation at high wind speed conditions. While with solar irradiance change, the investigated MG system can maintain its stable operation.

BINARM: Scalable and Efficient Detection of Vulnerabilities in Firmware Images of Intelligent Electronic Devices

Abstract: There is a widespread adoption of intelligent electronic devices (IEDs) in modern-day smart grid deployments. Consequently, any vulnerabilities in IED firmware might greatly affect the security and functionality of the smart grid. Although general-purpose techniques exist for vulnerability detection in firmware, they usually cannot meet the specific needs, e.g., they lack the domain knowledge specific to IED vulnerabilities, and they are often not efficient enough for handling larger firmware of IEDs. In this paper, we present BinArm, a scalable approach to detecting vulnerable functions in smart grid IED firmware mainly based on the ARM architecture. To this end, we build comprehensive databases of vulnerabilities and firmware that are both specific to smart grid IEDs. Then, we propose a multi-stage detection engine to minimize the computational cost of function matching and to address the scalability issue in handling large IED firmware. Specifically, the proposed engine takes a coarse-to-fine grained multi-stage function matching approach by (i) first filtering out dissimilar functions based on a group of heterogeneous features; (ii) further filtering out dissimilar functions based on their execution paths; and (iii) finally identifying candidate functions based on fuzzy graph matching. Our experiments show that BinArm accurately identifies vulnerable functions with an average accuracy of 0.92. The experimental results also show that our detection engine can speed up the existing fuzzy matching approach by three orders of magnitude. Finally, as a practical framework, BinArm successfully detects 93 real-world CVE vulnerability entries, the majority of which have been confirmed, and the detection takes as little as 0.09 s per function on average.

LineDrone Technology: Landing an Unmanned Aerial Vehicle on a Power Line

Abstract: This paper presents the design of a multirotor unmanned aerial vehicle (UAV) capable of landing semiautomatically on a power line while carrying a payload The vehicle then rolls along the line to perform an inspection Special attention is given to the vehicle's onboard vision system, which consists of a monocular camera and LiDAR used together to compute the pose of the vehicle relative to the power line Landing assistance is provided to the pilot by a position-based visual controller that aligns and keeps the vehicle centered along the power line The pilot remains in control of vertical and longitudinal movement during descent The proposed approach was tested on a full-scale test line and shows promise for future applications of high value to the electric industry such as non-destructive testing of power transmission lines

Safe Operation of DFIG-Based Wind Parks in Series-Compensated Systems

Abstract: Subsynchronous control interaction (SSCI) is the interaction between the power-electronics control and the series-compensated transmission system that occurs at frequencies below the system nominal frequency. SSCI may occur between the doubly-fed induction generator (DFIG) control system and the series-compensated transmission line, to which the wind park (WP) is connected. Not only do the DFIG control system parameters, but also the WP operating conditions have a significant impact on SSCI. In this paper, the impact of WP operating conditions and DFIG control system parameters on SSCI is analyzed in detail. Guidelines are presented for modifying the DFIG control system parameters to ensure safe operation and acceptable transient responses due to faults. This paper also examines the accuracies of various analytical tools used for SSCI problem identification and proposes a new frequency scan analysis approach for accurate prediction of potential SSCI problems.

Development of New Predictors Based on the Concept of Center of Power for Transient and Dynamic Instability Detection

Abstract: This paper proposes a novel approach based on the center of power (COP) applied on a sliding window for real-time instability prediction. Synchrophasor measurements are obtained from phasor measurements units connected at strategic locations of the network. In order to assess the instability, the new concept of COP from which two new indices are derived is defined. These new indices are used as predictors in a detection algorithm based on random forest of decision trees. Three study cases carried out on the IEEE 4 generators 10 buses, the Australian 14 generators, and the New England test system allowed validating successfully the performance of the proposed method.