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As a typical big data representative, the information of global Cellular Signal Strength (CSS), defined as the signal power received by mobile phones, plays an important role in geographic flow analysis, because the density of such information can reflect the urbanization variables such as population, gross domestic product, built-up area, electric power consumption, and etc. Despite the importance, the real-time analysis of global CSS distribution remains a challenging problem due to the large data scale. In this paper, a Display-driven Computing (DisDC) technique is designed and applied to provide efficient large scale interactive CSS visualization, generating results by calculating the value of each pixel that directly for display that can dramatically improve system capacity in big data handling. Specifically, we present an efficient CSS measurement algorithm, which introduces spatial indexes and a corresponding query strategy; besides, an optimized parallel computing architecture is proposed to ensure the ability of real-time visualization. Experiments show that our approach obviously outperforms traditional methods and is capable of handling more than 40 million base stations in real-time. Moreover, an online demonstration is provided at https://github.com/MemoryMmy/CSSMap.

In this paper, an integrated drive converter of segmented-double-stator switched reluctance machine (SDS-SRM) with isolation and non-isolation charging capabilities for electric vehicle (EV) is presented. The proposed converter can not only reduce the number of the power switches, but also implement multiple operation modes. In non-isolation charging mode, the motor windings and existing power switches constitute a buck/boost converter to charge the battery. The appropriate rotor positions are obtained to achieve torque-free control, and the interleaved phase currents control method is introduced to reduce the charging current ripples. In isolation charging mode, the inner-stator is powered by the utility grid to drive the middle-rotor, and converts electrical energy into mechanical energy. While, the outer-stator is operated in generation mode to convert mechanical energy into electrical energy. The SDS-SRM is served as a rotating transformer to transfer the electric power to charge the battery with the galvanic isolation function. A low power proof-of-concept prototype platform is built and experiments are carried out to verify the effectiveness of the proposed integrated drive converter and the corresponding control schemes.

This paper presents a suite of analytics that are proposed to be embedded in next-generation smart sensors in electric power grids. The proposed analytics take the electrical signals as the input and unlock the full potential in signal processing and machine learning for real-time event detection and classification. Meanwhile, a robust synchrophasor estimation mechanism is housed within the proposed sensor technology that will be triggered following a detected event and guides on the adaptive selection of the best-fit (most accurate) synchrophasor estimation algorithms at all times. Embedding such analytics within the sensor and closer to where the waveforms are captured, the proposed distributed intelligence solution technology mitigates the potential risks to communication failures and latencies as well as malicious cyber threats. Our experiments demonstrate that the introduced scheme achieves improved quality of measurements with a promising event detection and classification accuracy, collectively resulting in enhanced online situational awareness in modern power grids.

This paper presents a comprehensive literature review with focus on the difficulties electric vehicles (EVs) face to charge the battery while on a trip, and proposes a solution without the need of an expensive change in infrastructure. The proposed method charges EVs while en route from another vehicle, which will be referred to as vehicle-to-vehicle recharging (VVR). The aim of this system is to bring an innovative way for EVs to charge their battery without getting off route on a highway. The electric vehicle can request such a service from a designated charger vehicle on demand and receive electric power wirelessly while en route. The vehicles that provide energy (charger vehicles) through wireless power transfer (WPT) only need to be semi-autonomous in order to engage/disengage during a trip. The state-of-the-art is divided into three subsections relevant to the proposed system and where most of the innovations to reduce the burden of charging EVs can be found: (1) infrastructure changes, (2) device level innovations, and (3) autonomous vehicles. The infrastructure changes highlight some of the proposed systems that aim to help EVs become a convenient solution to the public. Device level innovations covers some of the literature on technology that addresses EVs in terms of WPT. And finally, the autonomous vehicle subsection covers the importance of such technology in terms of safety and reliability, that could be implemented on the VVR system. Furthermore, modeling, analysis, and simulation is presented to validate the feasibility of the proposed system.

Integrated power systems (IPSs) are popular in the shipbuilding industry. DC shipboard microgrids (dc-SMGs) have many advantages compared with ac ones in terms of system efficiency, operation flexibility, component size, and fault protection performance. Being in the exploring stage, dc-SMGs have several potential configurations with different system architectures and voltage levels. In a dc-SMG, functional blocks integrated include power generation modules (PGMs), propulsion system, high power loads, and pulse loads specifically in naval ships. In modern ships, the PGMs include not only generators and fuel cells (FCs) but also energy storage systems (ESSs), which cooperate with generators to improve the overall efficiency and reliability. High power electric converters are vital interfaces between the functional blocks and the dc distribution system. Rectifiers for generators take the tasks of dc bus voltage regulation and power sharing. Inverters for propulsion motors are responsible for the motor drive in different operating conditions. Bidirectional dc/dc converters for ESSs are used to provide supply-demand balance and voltage fluctuation mitigation. This paper makes a comprehensive review of power architecture, functional blocks including electrical machines and energy storage, as well as power converters in dc shipboard power systems.

Probabilistic wind power forecasting is an important input in the decision-making process in future electric power grids with large penetrations of renewable generation. Traditional probabilistic wind power forecasting models are trained offline and are then used to make predictions online. However, this strategy cannot make full use of the most recent information during the prediction process. In addition, ensemble learning is recognized as an effective approach for further improving forecasting performance by combining multiple forecasting models. This paper studies an online ensemble approach for probabilistic wind power forecasting by taking full advantage of the most recent information and leveraging the strengths of multiple forecasting models. The online ensemble approach is first formulated as an online convex optimization model. On this basis, a quantile passive-aggressive regression model is proposed to solve the online convex optimization model. Case studies and comparisons with other online learning methods are conducted on an open wind power data set from Belgium. Results show that the proposed method outperforms competing methods in terms of pinball loss and Winkler score with high reliability.

Series-connected multi-pulse rectifiers (MPRs) are used to provide high quality electric power for high-voltage and high-power occasions. Due to conventional MPRs have limited harmonic reduction ability that cannot fulfill the related harmonic standard, some effective DC side harmonic reduction methods have been proposed to further improve power quality of the MPRs. This paper gives a comprehensive review on DC link harmonic reduction methods of series-connected MPRs. Passive and active harmonic reduction mechanisms are respectively analyzed based on two typical topologies, which are theoretical foundations for understanding and constructing novel harmonic reduction circuits (HRCs). Some useful DC side HRCs are presented and compared from aspects of their performances, complexity of overall structure, magnetic device capacity and power losses, etc. The necessary simulation results are given to verify and compare the effectiveness of some involved harmonic reduction methods. Based on these topologies, the advantages, drawbacks and future trends of the passive or active methods are concluded; besides, the hybrid harmonic reduction methods are also considered. This article aims to provide useful guidance for the researches of harmonic elimination and multi-pulse rectification technology.

CubeSats have been popular for space research due to lower cost, faster development, and easier deployment. The electrical power system (EPS) is one of the significant subsystem for the CubeSat since it handles power generation, energy storage, and power distribution to all other subsystems. Therefore, the design of EPS becomes crucial for successful CubeSat mission, wherein the first step is the selection of EPS architecture. The main objective of this paper is to present an extensive review of all the conventional and emerging EPS architectures of CubeSats. A total of seventeen categories of CubeSat EPS architectures have been identified, classified, and the operational aspects of these architectures are presented in addition to a qualitative comparison. This study is expected to provide a useful reference guide for all the researchers and developers working in the area of CubeSats EPS. Also, some of the potential research topics are provided to further exploration and innovation for the CubeSat EPS.

Hydrogen has shown great potential in the renewable power integration and urban mobility decarbonization like the hydrogen fuel cell vehicles (HFCVs). The HFCV refueling as an essential hydrogen load is of great flexibility. Considering the HFCV demand response, this paper studies the integrated electric power and hydrogen system (IPHS) operation. First, the HFCV refueling load model is formulated with its routing on the transportation network considered. Second, the optimal IPHS operation model is developed in which the electric power operation, tube-trailer based hydrogen delivery and HFCV refueling are coordinated. Third, a Lagrangian Relaxation (LR) based method is developed to solve the proposed model efficiently, which corresponds to a price-based demand response mechanism for HFCVs. Compared with existing works on IPHS, the influence of transportation networks is delicately analyzed on both HFCV refueling and hydrogen delivery. The case studies have proven the effectiveness of the proposed method and demonstrated that the overall operation cost is decreased via the proper guidance of HFCV refueling. The HFCV demand response shows great potential in exploring the synergy of energy and transportation systems.

Wind power producers have recently gained a significant penetration in the electric power network, which might cause some challenges for the system operation due to the uncertainties in the generated power. In this way, wind power owners may offer different services, such as providing reserve capacity besides their conventional role of delivering just energy. Currently, conventional generators are the main responsible for providing some reserve in case of uncertainty in renewable generation and demand changes. Therefore, this article introduces a novel approach that allows wind power producers to participate in both energy and reserve markets alongside conventional generators. A two-stage stochastic programming model is deployed for this purpose and the proposed approach is examined on the IEEE RTS 24-bus. The simulation results demonstrate that for ensuring a higher level of reliability by the suggested scheme, both conventional generators and wind power producers will receive more revenue in both markets, although the demands should pay more.

Due to the distributed structure of electric power networks (EPNs) and district heating networks (DHNs), distributed dispatch is favorable for coordination in an integrated electricity and heat system (IEHS). However, the feasibility issue of the dispatch solution remains unresolved. Without making this clear, critical threats may be posed to system operation, and there cannot be security guarantees. In this article, we propose a distributed method for real-time IEHS dispatch where feasibility is strictly ensured in each iteration. First, a network reduction method of DHNs retaining the temperature quasi-dynamics is derived. Based on that, a novel feasibility cut (FC) generation method is devised, which strictly maintains system security during the iterative process. Finally, modified Benders decomposition with guaranteed feasibility (MBD-GF) is proposed to tackle distributed IEHS dispatch. The case studies of two IEHSs validate the effectiveness and efficiency of the proposed method.

The motor in high power electric vehicle (EV) easily reached at voltage limit because of its large magnetic flux. Therefore, the motor should be designed so that the voltage is controlled at the limit. To achieve well voltage control condition, the interior permanent-magnet synchronous motor (IPMSM) is controlled by the field-weakening control method after the constant torque region. This is conducted by canceling the magnetic flux from the permanent magnet with the magnetic flux of the stator winding. However, this method generates many harmonics. In this paper, a design that effectively controls the voltage by reducing the harmonics generated in the field-weakening control is proposed. To reduce the harmonics in the field-weakening region, change stator and rotor design parameters, and the reason for using v-type permanent magnet arrangement for high-speed operation will be elucidated.

The space charge dynamic behavior and accumulation are important contributions to the formation of electrical trees, as recognized by crosslinked polyethylene (XLPE) cable insulation under alternating current electric stress. In this paper, in order to investigate the reasons for the charge accumulation phenomenon revealed by experiments under ac stress, a bipolar space charge transport model with symmetrical and asymmetrical parameters is built under AC stress. The charge accumulation mechanism is analyzed based on the variation of space charge density with different voltage application time and voltage phase. The effects of each major physical parameter are simulated and analyzed, respectively. The results show that there is no obvious space charge accumulation with the transport model under symmetrical physical parameters. However, asymmetrical parameters in the transport model result in different motions between positive and negative charges, which greatly enhances the charge accumulation. Each main parameter has an influence on charge accumulation in different perspectives and extents. The applicability of the simulation model with asymmetrical parameters is evaluated by comparing experiment and simulation results. This study contributes to the understanding of space charge generation mechanism under AC voltage and serves as a basis for improving the stability of XLPE electric power cables.

The current sampling errors in dual-motor group (DMG) cause more adverse effects on system performance than that in a single motor system. To solve this problem, in this article, a synergistic correction strategy for the abovementioned problems in DMG fed by double inverters is proposed. First, an orthogonal pulsewidth modulation carriers strategy is proposed to imitate the “shutdown” status of motor subsystems to obtain ascertainable current relations. Then, the current values with sampling errors in DMG at several “fixed” sampling points are derived, based on which the sampling errors in DMG are corrected. Meanwhile, the rules for the action time of active vectors and output voltage range in each inverter are analyzed for each “fixed” sampling point. Finally, the proposed strategy is verified by experimental results on a DMG system, which show that the sampling errors can be precisely estimated with the proposed strategy.

A Real-time electricity market transaction is an important method that is used to realize the interactive balance of source-network-load in a new generation power system. Based on the multi-camp economic choice and the needs of national conditions, the emergence of cluster operators is inevitable. Due to stability and development of photovoltaic users, it is important to evaluate the importance of users in a photovoltaic user group. In the existing model, users are too sensitive to the electricity price, which will lead to too high electricity adjustment rate. In order to make up for the lack of importance ranking research and the high adjustment rate of electricity consumption, this paper will introduce the electric power consumption satisfaction function and propose an optimal pricing model that is based on the master-slave game. The study analyzes the nature of operators’ revenue, and presents a method to calculate the contribution value using the cooperative game theory. The TOPSIS method is proposed to evaluate the ranking of the producers and sellers in the group. The developed illustration verifies the superiority of the cluster economic operation model.

In the subsequent decades, the increasing energy will demand renewable resources and intelligent solutions for managing consumption. In this sense, Non-Intrusive Load Monitoring (NILM) techniques detail consumption information for users, allowing better electric power management and avoiding energy losses. In high-frequency NILM methods, state-of-the-art approaches, mainly based on deep learning solutions, do not provide a complete NILM architecture, including all the required steps. To overcome this gap, this work presents an integrated method for detection, feature extraction, and classification of high-frequency NILM signals for the publicly available LIT-Dataset. In terms of detection, the results were above 90% for most cases, whilst the state-of-the-art methods were below 70% for eight loads. For classification, the final accuracies were comparable with other recent works (around 97%). We also include a multi-label procedure to avoid the disaggregation stage, indicating the loads connected at a given time, increasing the recognition of multiple loads. Finally, we present results in an embedded system, a subject also underexplored in the recent literature, demonstrating the proposal’s feasibility for real-time signal analysis and practical applications involving NILM.

The deterioration of cable insulation is a widely acknowledged problem, and detection lays the foundation for maintenance and overhaul. The measurement of Tangent delta (tan δ) at very low frequency (VLF) works well on cable insulation detection, nevertheless the conventional method could only be conducted offline, where the power outage is usually required, interrupting the normal operation. To break thus a limitation, an advanced online method is proposed, and tan δ would be calculated based on the measurement of an artificially injected VLF voltage and that of the VLF leakage current through cable insulation. To coordinate with this method, an injecting source, with the comprehensive self-protection and the by-pass channel for power-frequency signals, is developed to safely inject a VLF voltage to the power system, and a monitoring system, with an accuracy better than ±0.3 μA, is established to obtain the injected voltage’s and leakage current’s waveforms, which would be used to further calculate tan δ with the cross-correlation algorithm. In addition, this method, as well as developed devices, is applied on several cables in China Electric Power Research Institute, and the measuring results keep consistent with the actual conditions, which verifies the validity.

Use of far-field electric field sensors in an outdoor event detection is described. Electric field variations accompany broad variety of physical events, and field signature signals can be used in determination of activities in proximity of the sensor. Perimeter monitoring, moving objects recognition, electric power faults detection are only a few examples of such applications. This work presents development and signal processing for electric field sensor uses in human and animal motion detection and characterization.

With the standardization of 400ZR driving the focus on coherent pluggables for short-reach applications, cost-effective links must be deployed. A way to achieve this is by removing the optical amplification; however, this exacerbates the impact of a high peak-to-average power ratio (PAPR). We experimentally demonstrate the impact of pulse shaping and transmitted electrical power in an amplifier-less coherent link by analyzing the PAPR, transmitted optical power and power budget for short-reach applications. Through an extensive experimental campaign, we jointly optimize the spectral and energy efficiency of the system, demonstrating power budget gains of up to 7dB when compared to standard settings of coherent pluggables.

Wireless power transmission (WPT) using ultrasound is a promising way for wirelessly recharging implantable medical devices (IMDs). However, the transmitted power using ultrasound so far is insufficient for driving the existing IMDs. Moreover, the size of the receiving transducer is larger, which is not suitable for implantation. To increase the output power and reduce the size of the implantable receiver, this article presents a method of combining focused ultrasound with a miniaturized 1-3 piezoelectric composite receiving transducer to produce higher electrical power. An analytical fluid-structure interaction model is constructed to fully understand the operating mechanism of the receiving transducer under ultrasonic force. In our experiments, a miniaturized 1-3 piezoelectric composite receiving transducer with a diameter of 3.7 mm was used. The output power generated from the receiving transducer reached 60 mW at a distance of 150 mm. In vitro and in vivo animal experiments proved that the miniaturized transducer could successfully receive focused ultrasonic energy and convert it to electrical power. The method presented and the electrical power that we obtained can provide a valuable reference for wirelessly charging of IMDs.

The electricity demand of the fused magnesia smelting process (FMSP) is defined as the average electric power consumption over a fixed period of time, which is used to monitor the electricity cost in the FMSP. In this article, we develop a dynamic model of the electricity demand based on the closed-loop control system of the smelting current in the FMSP. The electricity demand prediction model combines an identifiable linear model with an unknown nonlinear dynamic system, which takes advantage of system identification. To predict the unknown nonlinear dynamic system, an adaptive deep learning prediction approach is proposed based on a multilayer long short-term memory. The real data in the FMSP is used to verify the effectiveness of the proposed electricity demand forecasting method.

Increased electrification of aircraft power systems has been widely presented as a route toward meeting environmental and emissions targets for aircraft performance, via more-electric aircraft and future hybrid-electric aircraft concepts. In parallel, the superior mechanical performance of carbon fiber reinforced polymer (CFRP) has resulted in its increasing use for aircraft structures. The relatively low electrical conductivity of CFRP compared to traditional aluminum structures and copper conductors limits the use of structural CFRP structures as electrical elements, so separate systems are needed. This adds structural mass and volume to a system, negating some of the benefits of using CFRP. Closer integration of the composite structure and electrical power system (EPS), with an ultimate goal of achieving components with multifunctionality (combined thermal, electrical, and structural functionality), offers a route toward the light-weighting of these systems, thus supporting improvements in aircraft performance. This article presents a roadmap to achieve this multifunctionality, supported by the combination of introducing definitions for different levels of multifunctionality, associated design thresholds, and trades between the EPS and CFRP materials/structures. Existing multifunctional (MF) electrical-thermal-structural CFRP-based solutions are contextualized within this roadmap. This enables the realization of viable routes for developing MF systems for the strategic focus of future research efforts.

Electrical power connectors are critical points of electrical networks. Failure in high-voltage connectors may result in major power outages, safety risks and important economic consequences. Therefore, there is an imperious need to tackle such issue by developing suitable on-line condition monitoring strategies to minimize the aforementioned problems and to ease the application of predictive maintenance tasks. This work develops an on-line condition monitoring method to predict early failures in power connectors from data acquired on-line (electric current and voltage drop across the connector, and temperature) to determine the instantaneous value of the connector resistance, since it is used as a signature or indicator of its health condition. The proposed approach combines a parametric degradation model of the resistance of the connector, whose parameters are identified by means of the Markov chain Monte Carlo stochastic method, which also provides the confidence intervals of the electrical resistance. This fast approach allows an on-line diagnosis of the health condition of the connector, anticipating its failure and thus, easing the application of predictive maintenance plans. Laboratory results emulating the ageing conditions of the connectors prove the suitability and feasibility of the proposed approach, which could be applied to other power products and apparatus.

Most loads of electrical power systems on a more electric aircraft (MEA) are regulated power converters. These loads behave as constant power loads (CPLs) that can significantly affect system stability. The system will become unstable and will be unable to operate at the rated power. In this article, a novel adaptive stabilization of a permanent magnet synchronous generator-based dc electrical power system in MEA is presented using a nonlinear feedback approach via loop-cancellation technique with a simple equation of feedback gain, which can be calculated from the power level of the CPL. The equation can be derived from a polynomial curve fitting based on the proposed mathematical model derived using the dq method. The adaptive stabilization results are validated by a small-signal stability analysis using the linearization technique, a large-signal stability analysis using the phase plane analysis, an intensive time-domain simulation using MATLAB, and experimentation. The results indicate that the proposed adaptive stabilization technique can provide the considered aircraft power system always stable for all operating conditions within the rated power, and the dc bus voltage can adhere to the MIL-STD-704F standard.

This work presents the steps for validating a new topology of magnetic coupling with direct application in automotive water pumps. Starting from analytical studies, a model in two dimensions for simulation by finite elements was created, whose effectiveness was proven with the performance measured by the construction of a prototype. Based on the eddy current coupling technology, the amount of power transferred can be adjusted according to the desired engine operating temperature. This technology consumes less electrical current in comparison with a motor-driven water pump since the primary pumping power source is the combustion engine. Another advantage is the residual torque operating mode that uses the magnetism generated by permanent magnets in the absence of electrical power, which is an important function to protect the engine against overheating in the case of an electrical failure. The results presented here validate the concept regarding the controllability of the device and highlight points to improve the machine’s performance, thus facilitating new developments and future work.

The increase in greenhouse gas emissions from the transportation sector together with the continued depletion of fossil fuels in general has encouraged an increase in the use of energy storage systems and renewable energy sources at seaports and also on short route yachts and ferries. At present, most seaports, particularly smaller ones, are not provided with cold-ironing facilities - shore-based power facilities, which provide electric power to ships from the national grid. Because of the lack of cold-ironing facilities at most ports, auxiliary diesel engines and diesel generators on ships must be kept operating and online while at berth to supply auxiliary loads of ship. To address these requirements, one possible solution would be to provide cold-ironing facilities at all ports. However, in many circumstances, this is not cost-efficient as a port might be far from the national grid. To overcome these limitations, a seaport microgrid can be formed through the integration of multiple shipboard microgrids (SMGs) with decentralized control together with a charging infrastructure that is located on-shore. This integration of multiple SMGs and port-based charging stations is termed a ship-based seaport microgrid. Typically, power is shared among different microgrids using data communication techniques, which adds to the cost and the complexity of the overall system. This article proposes a communication-less approach based on multimode, decentralized droop control that enables power sharing among several SMGs in both charging and discharging modes based on the state of charge of battery banks - electric power is either supplied or consumed. The proposed approach would be potentially useful for future autonomous ships and also for islands where port electrification is either not technically feasible or an economically viable solution. A simulation and hardware-in-the-loop results are provided to verify the control robustness of the proposed control strategy.

Electric vehicle users need access to recharging services within the all-electrical driving range of their vehicles. However, public charging stations to be located on remote highways are in many cases far from the power grid, where a connection to the power grid may be impossible, costly, or impractical. This article formulates a stochastic mixed integer linear programming (MILP) planning model for energy storage and renewable energy systems to cover the energy demand of stand-alone charging stations for plug-in electric vehicles (PEVs) entirely using green energy generated by renewable energy sources (RESs). The proposed model accounts for the stochastic behavior of PEVs and RESs as well as the technical, economic, and operational characteristics of a variety of energy storage technologies. A customer satisfaction criterion is introduced to allow for a tradeoff between performance and investment costs. The proposed model can also be used for designing fully green PEV charging stations in urban and rural settings to capitalize on PEV environmental benefits by avoiding the use of fossil-fuel-generated electric power in their charging or to reduce the main grid load. A set of numerical studies have been performed in General Algebraic Modeling System (GAMS) environment to demonstrate the feasibility and effectiveness of the proposed model.

In the electrical power and energy (EPE) area, the traditional concept in designing the synchronization system of power converters is using the phase-locked loop (PLL) concept. An alternative way is using the frequency-locked loop (FLL) concept, which is also known as the adaptive notch filter, adaptive noise cancelation technique, gradient descent estimator, adaptive observer, D-estimation method, and transformation angle detector, among others names. Along with the increased popularity and application of FLLs in EPE systems, the misconception about this design concept is growing. To be more exact, most EPE research communities introduce FLLs as synchronization systems of different properties compared to PLLs. This article aims to explain the main reasons behind this misconception and contribute to dispelling it.

The concept of microgrid (MG) empowers the application of renewable energy sources (RES) to meet the increasing demand of electrical power, which further inspires us to enable this technology under the study of inverter-based industrial loads (IL). The inclusion of inverter-based IL adds some noises in the MGs dynamics because of the non-linear characteristics of inverter and parametric uncertainty of loads. The above constraints impose extra-challenges to maintain reliable operation of the MGs. In this paper, integral based linear quadratic gaussian (ILQG) controller is proposed to maintain the tracking operation via the control of inverter used with ILs, which is further connected with the dc bus which is regulated by the inverter in grid side and dc-dc converter applied in utility grid, PV and battery, respectively. The proposed ILQG controller is designed based on the proper combination of linear quadratic gaussian (LQG) and integral controller and its performance is evaluated by changing the operating conditions, which includes the switching of supplying power from PV, and both PV and battery. Additionally, the investigation under the variation of the IL parameters and comparison with resonant controller is used to ensure the robust performance of the ILQG controller.

Electric power grids regularly experience uncertain fluctuations from load demands and renewables, which poses a risk of violating operational limits designed to safeguard the system. In this paper, we consider the robust AC OPF problem that minimizes the generation cost while requiring a certain level of system security in the presence of uncertainty. The robust AC OPF problem requires that the system satisfy operational limits for all uncertainty realizations within a specified uncertainty set. Guaranteeing robustness is particularly challenging due to the non-convex, nonlinear AC power flow equations, which may not always have a solution. In this work, we extend a previously developed convex restriction to a robust convex restriction , which is a convex inner approximation of the non-convex feasible region of the AC OPF problem that accounts for uncertainty in the power injections. We then use the robust convex restriction in an algorithm that obtains robust solutions to AC OPF problems by solving a sequence of convex optimization problems. We demonstrate our algorithm and its ability to control robustness versus operating cost trade-offs using PGLib test cases.

Passive integration technology is widely used in power electric converters since it can significantly reduce the volume of the passive components and improve the power density. This article highlights the flexible multilayer foil (FMLF) integration technology since it can meet the future requirements than other integration technologies. The realization, structures, and applications of the FMLF integration technology are summarized. The magnetic materials, dielectric materials, and conductive materials used in FMLF are investigated. Then, the approaches of the analysis and design for FMLF integrated units are introduced. Finally, it is compared with the planar printed circuit board integration technology to highlight the advantages of its characteristics and expounds its future research fields. Eventually, the power electronics engineers and researchers can comprehend the intrinsic properties of the FMLF integration technology.

Generally accepted industry standards, such as National Fire Protection Association (NFPA) 70E-2018, require arc-flash incident energy analysis to be updated when changes occur in the electrical power distribution system, and the analysis shall be reviewed for accuracy at least every five years. NFPA 70E also requires the data used for creating equipment labels, which contain arc-flash energy information, to be reviewed at least every five years, and, if the review identifies a change that renders the arc-flash energy label inaccurate, the equipment label must be updated.

The possibility of exploiting electrical energy scavenged from bicycle mechanical vibrations by piezoelectric harvesters is investigated. The bicycle vibrations on a typical city track are characterized through road tests and the power spectral densities (PSDs) of measured vibrations are presented. Both analytical and experimental methods are adopted to estimate the average electric power that can be harvested by a standard piezoelectric harvester with tip mass mounted on the bicycle. The possibility of tuning the harvester by means of liquid tip masses, resulting in a better trade-off between generated power and stress inside the piezoelectric layer, is investigated as well.

The Technology development and rising standards of living are increasing the demand for electricity in city centres. In addition, the density of electric power in different areas of a city changes with the construction of new residential areas. Variation in load density can be managed by adjusting the voltage on distribution lines, installing new lines and transformer centres, and reconfiguring existing lines and transformer centres. In this study, the Istanbul Uskudar District of Kanlica-Cubuklu Region was examined and coverage areas were modified depending on the load density and power of the existing transformers. A novel systematic approach to determine the coverage area of transformers is presented. In this approach, the coverage area and overlap of each transformer with its neighbours were determined. Subsequently, transformers that are under-used or have significant overlap with neighbouring transformers were removed from the network. The transformers were placed into an optimal structure in the network by distributing the load of an excluded transformer to its nearest neighbours. This approach further allows the minimum route for the high voltage distribution wiring between transformers and cost to be determined.

This article presents an investigation on the optimal design of a transmit coil for a wireless power transfer system (WPTS) for biomedical implants with the goal of maximizing the magnetic flux density (B-field) at the location of the implant while not violating magnetic field exposure limits. Maximizing the B-field correlates to higher transferable electric power for certain WPTSs, such as those that use magnetoelectric receivers. While previous works have optimized the thermal efficiency, or system efficiency, to our knowledge no one yet has developed the procedure to optimize the transmitter to maximize the B-field subject to an imposed safety limit constraint for magnetic field exposure. In addition to this safety constraint, the optimal design of the transmitter is considered when the system geometry or the input current is constrained. Equations for determining the design parameters of an optimal solenoid transmitter are derived subject to constraints on either transmitter size or electric current. If a certain magnetic field strength is required, solutions to the size and current of the transmitter are presented, which allow the desired fields without violating the safety constraint. The mathematical model is experimentally validated, and a case study is described that illustrates the optimal design rules.

In this article, we discuss how energy storage (behind the meter or otherwise) improves the performance of industrial and public distribution systems in various ways. We focus on large industrial or commercial electricity consumers and the corresponding supplying utility. Note that this article does not represent any guidance, policy, or preference from any specific electric utility [i.e., American Electric Power (AEP)].

The renewable energy-based hydrogen production can lead to the integrated electric power and hydrogen system (IPHS) and offer a pathway to a sustainable energy utilization. Hydrogen is mainly transported via hydrogen tube trailers (HTs), making the hydrogen energy system (HES) operation quite different from those of other energy technologies. This paper proposes an optimal IPHS operation strategy which utilizes HT for transportation. The proposed strategy coordinates hydrogen generation, transportation, and storage stages considering constrained operations of electric power system (EPS), transportation system, and variable renewable energy. The proposed solution method is based on the alternating direction method of multipliers (ADMM) in which HES and EPS constraints are managed individually and the respective solutions are coordinated accordingly. The case studies using the modified IEEE-RTS79 have verified the validity of the proposed IPHS model and its solution method and confirmed the necessity of considering HES in enhancing the EPS operation. The synergies between EPS and HES are studied via numerical examples and the impact of the flexibilities in hydrogen generation, transportation and demand are highlighted.

International audience; This paper proposes a new framework for the operational reliability evaluation of integrated electric power-gas networks (IEPGNs). First, a novel approach for modeling the failure modes of natural gas pipelines is presented. This approach utilizes the concept of virtual nodes and employs a gas release rate model to consider the pinhole, hole, and rupture failure modes of pipelines. Thereafter, a four-state Markov model for natural gas-fired generators (NGFGs) with dual-fuel capabilities is proposed. The area risk method is extended to include the proposed reliability models, and the partial reliability indices of the area risk method are evaluated using a non-sequential Monte Carlo simulation (NSMCS). A nonlinear optimization model is also proposed to calculate electric and gas load curtailments for each system state in NSMCS. This model is linearized to obtain a mixed-integer linear programming (MILP) model for reducing the computational burden. The computational performance of NSMCS is further improved by adopting cross entropy (CE)-based importance sampling (IS). Finally, the efficacy of the proposed framework is demonstrated on three test systems. Case studies validate the importance of considering the proposed reliability models of IEPGNs for operational reliability evaluation. The impacts of operational strategies on the operational reliability indices are also demonstrated.

Induction generators (IG) are widely used in renewable energy systems, such as wind power, and micro/mini hydro-turbines. In applications, such as urban wind-energy systems, electric vehicles and more electric aircrafts, induction machines can be used to supply electrical power to auxiliary loads, deriving power from main engines. In this article, an IG system with open-end stator windings is proposed for simultaneous supply of regulated power to frequency insensitive ac-loads and dc-link loads for the first time. One end of the stator winding is connected to auxiliary loads while the other end is connected to a capacitor-fed voltage source inverter (VSI). In the proposed system, VSI is controlled to supply reactive power required by the IG while simultaneously regulating the dc-link voltage and ac load voltage at required level. The proposed method is based on scalar-control of the induction machine, thus making it a simple and robust system to supply active power demanded by ac and dc loads. The proposed control scheme has been simulated in MATLAB-Simulink and experimentally verified for steady state and transients with various ac loads including linear, nonlinear, and unbalanced loads.

This paper provides an overview of hyperloop technologies, including a brief discussion of key components of a hyperloop system that determine the electric power requirements as a function of time. At-scale hyperloop systems do not yet exist, so a model was used to generate a set of load profiles for conceptual hyperloop realizations at four locations in the United States: two systems in California and one each in Colorado and Ohio. In all four cases, the modeled hyperloop load profiles included pulses in both active and reactive power. Grid modeling was performed to estimate the grid impacts and for discussing grid integration challenges. The paper discusses how energy storage systems might be used to eliminate the pulsating load characteristics or significantly reduce it to accommodate current grid planning guidelines.

With the increased demand for electrical power, it is required to increase the number of power transformers in power systems. One of the main challenges facing protection engineers is the protection and isolation of power transformers in the shortest time possible, during internal faults. One of the alternative solutions to reduce the fault current in the power system is the application of a superconductor fault current limiter (SFCL). In this article, the ratios-based transformer differential protection algorithm is evaluated in the presence of resistive SFCL during internal fault conditions. A model of the system under study, including SFCL, is simulated and studies are performed in MATLAB/Simulink environment. The results demonstrate the capability of the ratios-based differential protection scheme to detect internal faults in the presence of SFCL.

The use of high temperature superconducting (HTS) power cables is viable solution to address the growing demand for electric power, while ensuring low loss and high electric power transmission. Usually, HTS power cables and circular connection of substations reduce grid impedance, and the fault current is increased over the capacity of the circuit breaker. To protect the electric power grid, the fault current should be reduced below the allowable level. Of late, research on HTS power cables having fault current limiting (FCL) functions has increased. An inductive FCL HTS power cable uses the increased inductive impedance caused by magnetic flux leakage to a neighboring iron yoke when a quench occurs at the shielding layer of the cable core due to electromagnetic coupling with the conducting layer. Therefore, there is less heat generation, and the temperature rise is suppressed. In this study, we describe the increased inductive impedance and reduced fault current using a FCL model coil. To demonstrate the electromagnetic coupling between the conducting and shielding layers of the cable core, two concentrically wound REBCO coils were fabricated. The iron yoke inside the coil increases the inductive impedance when a fault current flows through the conducting layer, and quench occurs at the shielding layer. The results are used to develop an FCL HTS power cable with 154 kV, 600 MVA class.

A wireless power transmission (WPT) system using the high temperature superconducting (HTS) coil for a railway vehicle is required to transmit the electric power of several hundred kW in a short time (60 s). In order to design the WPT system using HTS coil with the thermal stability, and it is necessary to clarify the thermal characteristics of the HTS coil at the operating current in kHz band and the operating conditions considering thermal stability in the WPT system. We analyzed the frequency characteristics of the critical current in the HTS coil above 1 kHz and investigated the operating conditions considering thermal stability in the WPT system for the railway vehicle using HTS coil in liquid nitrogen. As a result, the critical current of the HTS coil in the kHz band decreased with the frequency. This is because the AC loss in the HTS coil increased with the frequency, and the critical current density of the HTS coil decreased with increasing the surface temperature. In order to design the HTS coil with thermal stability in the kHz band, and it is necessary to operate the HTS coil on alternating current less than about 50% of the critical current measured by direct current. We found that the thermally stable WPT system capable of fast charging for 60 seconds can be realized by operating current at the frequency of about 2 kHz.

This paper investigates the small-signal power oscillations in a VSC-based multi-terminal DC (MTDC) power transmission system. Regarding the DC power oscillation modes (DPOMs), this paper demonstrates that when the master–slave control is adopted for the MTDC power system, there is only one DPOM. In contrast, when the DC voltage droop control is adopted, the DC electric power oscillations (DEPOs) may be multi-modal oscillations as there are multiple DPOMs. Furthermore, a better understanding of DEPOs, which is analogous to low-frequency electric power oscillations (LEPOs) in conventional AC power systems, is obtained, unveiling how the DPOMs determine the power oscillations in AC and MTDC power systems. Moreover, this paper theoretically verifies that the DPOMs determine the behaviors of both DEPOs in MTDC systems and power oscillations between the VSCs (which adopt the DC voltage control or DC voltage droop control) and external AC systems. By analogy to LEPOs, damping torque analysis is applied to examine the stability risk of the MTDC power system. The results indicate that even if VSCs are self-stable, there is a potential risk of growing DEPOs occurring in MTDC power systems under heavy DC loads.

Over the past year, the PES society has battled a pandemic that raised uncertainty, confusion, and fear about the future of many companies and industries. The electric industry rose to the challenges and ensured that the one thing society did not have to worry about was its electric power. Reliability of the electric grid became more important than ever to ensure that people stayed connected and safe as we all moved out of the office and into our isolated home environments. Our customers could depend on a stable electric grid.

With the rapid development of electric power grid, the application of Metal Oxide Surge Arrester (MOSA) in electrical power system network has been enhanced. MOSA has been used as protective device in electrical power system (EPS) network. MOSA provides a basis of insulation coordination in EPS network. Premature failure of MOSA can affect the reliability of EPS network. Therefore, condition monitoring of MOSA on regular basis can enhance the reliability of EPS network. Currently various techniques are available of condition monitoring of MOSA. Out of them, leakage current signal-based monitoring is most popular and convenient way of MOSA monitoring as leakage current signal of MOSA can be acquired easily and it can give information of MOSA condition effectively. Therefore, most of the recent researches in the area of condition monitoring of MOSA are based on leakage current signal especially resistive leakage current analysis. This article presents a comprehensive review of leakage current signal employed methodologies used for condition monitoring of MOSA. The broad perspective of the review article is to provide various concepts used to extract resistive leakage current and find out suitable indicators, which are sensitive to MOSA condition. Advantages, limitations and challenges faced in the proposed methodologies are reported, which can be very useful for future research development in this field.

All-wheel-drive (AWD) multimotor electric powertrains offer greater potential for system performance, efficiency, and reliability improvements. In this article, a new AWD electric powertrain that can increase the overall powertrain efficiency and battery lifetime is introduced. The proposed powertrain is based on a compact and efficient flywheel-based kinetic energy recovery system (KERS) that overcomes most of the shortcomings of the conventional electric KERS. Here, a significant part of the mechanical power transfer takes place without conversion to electrical power. Therefore, a selectable fraction of the recoverable kinetic energy is processed by power electronics. Thus, no energy exchange is necessary between the battery and the powertrain during acceleration and deceleration, resulting in a reduced battery power rating. This article compares the proposed powertrain with a conventional AWD electric powertrain. Mathematical modeling and simulations based on the space vector method were used for both powertrains that show the advantage of the proposed powertrain over the conventional one. The experimental data are also presented from our proof of the concept laboratory setup.

Numerical simulation is the key technique for large-scale power system analysis. Redistribution of global renewable power via international interconnections requires new simulation tools to study the interconnected systems with different nominal frequencies as a whole. This paper introduces an open-source simulation toolkit for electrical power systems (STEPS) hosted at Github. Its kernel is coded in C++ with major functions of power flow and electro-mechanical dynamic simulation. Flexible options are provided and configurable to improve power flow solution and dynamic simulation. Common devices and models are supported in STEPS for AC/DC hybrid system studies. The study of interconnected systems with different nominal frequencies is supported in STEPS for research of international interconnection. Application program interfaces are provided and wrapped with Python to enable high-level interfaces for general applications. STEPS is thread-safe, and parallel computation is supported in both kernel-level and task-level parallelization to accelerate simulation. It is portable and works on Windows and GNU/Linux platforms. Cases from small to large-scale systems are thoroughly tested to validate the toolkit with commercial packages as benchmarks.

This paper presents the modeling and analysis of a novel priority valve controlled open-loop Cable Reeling Drum (CRD) drive of Load Haul Dump (LHD) vehicle. The LHD vehicle is basically a trackless loading machine having wide applications in underground mining operations. The CRD incorporated in the said machine performs the reeling/unreeling operation of the flexible trailing cables that supply electric power to the machine. In this respect, a novel hydraulic circuit is proposed that incorporates a priority valve for the operation of the hydro motor driving the CRD, unlike the existing LHD machines having a separate hydraulic arrangement for the CRD operation. In the present study, the flow through the bypass port of the priority flow divider (PFD) valve is utilized for driving the CRD. In analyzing the proposed hydraulic system, the detailed model is analytically solved in MATLAB/Simulink software, and the simulation results are validated experimentally. The effects of change of the critical parameters on the system's dynamic responses are analyzed using the validated simulation model. The investigations show that till the fluid flow metered to the PFD valve is higher than the priority flow demand, the machine's priority function is not affected by the operation of the CRD. However, with the actuation of the priority operation, the hydro-motor drive speed of the CRD decreases. The model proposed in this study may be considered as a basis for the re-design of the hydraulic arrangement of CRD drive incorporated in an LHD machine for its improved performance.