Electric Power Delivery Research Articles

Calculation of the Thermal Regime of Gas-Insulated Electrical Transmission Lines

Gas-insulated transmission lines (GIL) are used for high-power extraction from electric power plants and high power delivery to large cities and industrial centers. A large part of a GIL lies above the earth’s surface. In an overhead configuration GIL are subject to climatic factors that affect their transmission, which is determined by the thermal regime. A method for calculating the thermal regime of overhead GIL is developed which takes the influence of climatic factors into account. Calculations for a specific GIL design are presented and analyzed.

Covalently functionalized graphene as a supercapacitor electrode material

The need for efficient, lightweight, flexible, stable and eco-friendly portable electric power delivery has placed research on supercapacitor electrode materials at the forefront of endeavors to provide future energy storage. Graphene-based materials and composites have been shown to be promising materials toward this goal. In this review, we describe recent progress in the development of electrode materials by the covalent functionalization of graphene. Covalent graphene derivatives are an emerging and potentially large class of very efficient materials, whose structural and physicochemical properties can be tailored according to the specific needs of capacitive charge storage. They also open doors to new composites and hybrids, which may further advance the field-encoding properties and other features as yet unexplored.

A novel voltage regulation strategy for the electric power delivery system of a 6000-m ROV

Owing to the increasing demand for deep sea exploration, remotely operated vehicles (ROVs) that can conduct scientific tasks up to a depth of 6000 m are essential for exploring unknown areas. For electrically propelled ROVs, a voltage regulation system is used to maintain the load-side voltage within a limited range during power load variation. The load-side voltage fluctuated frequently during load variation, thus challenging the design of the voltage regulation system. Hence, we propose a novel voltage regulation strategy in the ship-side of a 6000-m-deep ROV system. In this strategy, the nonlinear relationship of the compensated voltage in the ship-side and the active current in the umbilical cable are solved by piecewise linear fitting using the least-squares method. Subsequently, a feedback PID controller is designed to achieve a faster dynamic response and maintain a stable load-side voltage. The real applications of the ROV system for oceanographic surveys demonstrated that the fast response and high accuracy of the voltage regulation system for intense fluctuations of the load-side voltage could be achieved.

Electrical power to run ventricular assist devices using the Free-range Resonant Electrical Energy Delivery system.

Models of power delivery within an intact organism have been limited to ionizing radiation and, to some extent, sound and magnetic waves for diagnostic purposes. Traditional electrical power delivery within the intact human body relies on implanted batteries that limit the amount and duration of delivered power. The efficiency of current battery technology limits the substantial demands required, such as continuous operation of an implantable artificial heart pump within a human body. The fully implantable, miniaturized, Free-range Resonant Electrical Energy Delivery (FREE-D) system, compatible with any type of ventricular assist device (VAD), has been tested in a swine model (HVAD) for up to 3 hours. Key features of the system, the use of high-quality factor (Q) resonators together with an automatic tuning scheme, were tested over an extended operating range. Temperature changes of implanted components were measured to address safety and regulatory concerns of the FREE-D system in terms of specific absorption rate (SAR). Dynamic power delivery using the adaptive tuning technique kept the system operating at maximum efficiency, dramatically increasing the wireless power transfer within a 1-meter diameter. Temperature rise in the FREE-D system never exceeded the maximum allowable temperature deviation of 2°C (but remained below body temperature) for an implanted device within the trunk of the body at 10 cm (25% efficiency) and 50 cm (20% efficiency), with no failure episodes. The large operating range of FREE-D system extends the use of VAD for nearly all patients without being affected by the depth of the implanted pump. Our in-vivo results with the FREE-D system may offer a new perspective on quality of life for patients supported by implanted device.

Bidirectional DC-DC Converter Systems: Sustaining Power Component Design Methodology to Achieve Critical Power Conditioning

Converting interchangeable loads and sources on committed power interconnect is becoming more commonplace in the art of switch-mode power design. Simple, robust schemes have ended up serving in strategically important applications such as those in the dc bus system of NASA's International Space Station and in the more familiar world of automotive hybrid electric vehicles [1], [2]. As more diverse sources of energy lend themselves to economical and efficient conversion into electricity, the need to streamline the delivery of electrical power from one dc potential to another becomes more apparent. Switched-mode power conversion is a well-established means of achieving high-efficiency dc regulation. It has been found that making adaptations to a proprietary switched-mode resonant topology results in the achievement of a reliable, high-performance bidirectional converter (BDC). The flexibility BDCs offer in numerous applications brings significant economic and operational outcomes.

Decentralised electric power delivery for rural electrification in Pakistan

The paper evaluates solar powered microgrids as a candidate solution for rural electrification in Pakistan where over 51 million people still live off-grid. Microgrids can significantly reduce the cost of providing basic electrification and may also be scaled up to provide higher levels of services efficiently through energy and cost sharing. A census of 6 off-grid villages highlights the demand for electrification. On average household report a willingness to pay of USD 1.78 per month for the provision of high quality lighting and USD 3.24 per month for the addition of a fan. Furthermore, households are willing to pay an additional USD 0.89 per month for a communal load. First order cost calculations show that this demand can be met through the use of various solar topologies, in particular decentralised microgrids by local entrepreneurs with suitable public sector subsidies. Recommendations to modify the current legal framework are also presented, so as to provide an enabling environment for rural electrification through solar microgrids.

Enabling remote-control for the power sub-stations over LTE-A networks

In recent years, smart grid (SG) applications have been proven a sophisticated technology of immense aptitude, comfort and efficiency not only for the power generation sectors but also for other industrial purposes. The term SG is used to describe a set of systems customized to rapidly and automatically monitor user demand, restore power, isolate faults and maintain stability for more efficient transmission, generation and delivery of electric power. Nevertheless, the quality of service (QoS) guarantee is essential to maintain the networking technology used in different stages and communication of the SG for efficient distribution, which may be drastically obstructed as the sensors of the application increases. Undoubtedly, receiving and transmitting of this information requires two-way, high speed, reliable and secure communication infrastructure. In this paper, we have proposed a scheduling approach guarantees the efficient utilization of existing network resources that satisfy the sensors’ demands sufficiently. The proposed approach is based on hierarchical adaptive weighting method, which helps to overcome the issues of studied scheduling approach and intended to aid SG sensors applications, based on its QoS demands. We have employed four enabler SG applications for remote power control, namely demand response, advanced metering infrastructure, video surveillance and wide area situational awareness applications for the implementation of the remote-power substation controlling. Moreover, the cooperative game theory technique has been incorporated into a solution for the optimal estimation and allocation of bandwidth among different sensors. The results have been evaluated in terms of throughput, fairness index and spectral efficiency and results have been compared with the well-known scheduling approaches such as exponential/proportional fairness (EXP/PF), best channel quality indicator (Best-CQI) and exponential rules (EXP-Rule). The results demonstrated that the proposed approach is providing a better performance in terms fairness index by 25, 66 and 68% compared to EXP/PF, EXP/RULE and Best-CQI, respectively.

Multichannel Data Signals and Power Transmission by Power-Over-Fiber Using a Double-Clad Fiber

This letter presents multichannel data signals and feed light transmission based on power-over-fiber using a double-clad fiber (DCF). To demonstrate the feasibility of this technique, we experimentally demonstrate simultaneous data signals and feed light transmission using a DCF link. The data signals consist of a single-channel analog signal and four-channel digital signals with each having a channel spacing of 100 GHz. The feed light has a maximum power of 60 W and delivers the feed light to a remote unit where it is converted into electrical power using multiple high-power photovoltaic converters. In this letter, we successfully achieve good transmission performance of the DCF for all the analog and digital signals and over 7-Watt electrical power delivery, for the first time.

Retracted: Placement of combined photovoltaic and shunt capacitor to minimize power loss using heuristic quadratic curve fitting technique

Power loss minimization is crucial for reliable electrical power transmission and delivery. Numerous ways have been implemented to reduce power loss including photovoltaic and shunt capacitor installation. Nonetheless, improper allocation of these devices cause unstable voltages and increase power losses. Therefore, this research highlights placement of combined photovoltaic and shunt capacitor to minimize power losses using quadrature curve fitting rule. First, Fast voltage stability index (FVSI) is employed to determine the location of PV and shunt capacitor. Next, quadratic curve fitting rule is used to compute the size of the devices. The correct sizing of PV also influenced by Tenaga Nasional Berhad (TNB), Malaysian energy company guideline. Simulation results indicates the effectiveness of the techniques in minimizing power loss.

High Temperature Polymer Electrolyte Membrane Fuel Cells for Integrated Fuel Cell – Methanol Reformer Power Systems: A Critical Review

AbstractThe development of reliable power sources is important for the continuous operation of various electric equipment in unmanned aircraft and the field environment. Currently electric power delivery to such systems is mainly by battery packs. An alternative is to use fuel cells (FCs). FCs are electrochemical devices that are used to convert chemical energy of fuels such as hydrogen and methanol to electricity. Methanol is an attractive fuel because it is liquid at ambient temperature, has a much higher energy density than hydrogen and low reforming temperature (220–300 °C). Thus, integration of methanol steam reformers (MSRs) with FCs makes it possible to continuously produce electricity. The key challenge in such power system is the development of fuel cells which can be effectively operated at compatible temperature range of MSR, i.e., 220–300 °C in order to increase synergetic heat integration and system reliability. Herein, the latest development of high temperature polymer electrolyte membrane fuel cells (HT‐PEMFCs) is critically reviewed. The prospect of the integrated HT‐PEMFCs‐MSR as a reliable and compact power source is discussed. The results indicate that phosphoric acid doped polybenzimidazole (PA/PBI) membranes with in situ formed phosphosilicate nanocluster proton carriers show the technical feasibility of the development of HT‐PEMFCs at temperatures of 200–300 °C.

Optimal Stochastic Operation of Integrated Low-Carbon Electric Power, Natural Gas, and Heat Delivery System

Integrated energy system is important for the high-efficient utilization of multitype energy systems. In this paper, the stochastic optimal operation is investigated for the micro integrated electric power, natural gas, and heat delivery system (IPGHS). First, a low-carbon micro-IPGHS is proposed with the comprehensive consideration of renewable generation, carbon-capture-based power-to-gas technology, and the combined power and heat units. Second, a scenario-based optimal operation model for micro-IPGHS is proposed to handle uncertainties in energy demand and renewable generation. In the proposed model, energy transactions between micro-IPGHS and upstream energy systems as well as constraints for battery storage, natural gas storage, and heat storage systems are considered. Finally, a case study is used for the proposed low-carbon micro-IPGHS to validate the optimal stochastic operation approach. The proposed integrated system can effectively utilize the variable clean energy for optimizing the delivery of the green operation in micro-IPGHS.

Locomotive dynamic performance under traction/braking conditions considering effect of gear transmissions

ABSTRACTTraction or braking operations are usually applied to trains or locomotives for acceleration, speed adjustment, and stopping. During these operations, gear transmission equipment plays a very significant role in the delivery of traction or electrical braking power. Failures of the gear transmissions are likely to cause power loses and even threaten the operation safety of the train. Its dynamic performance is closely related to the normal operation and service safety of the entire train, especially under some emergency braking conditions. In this paper, a locomotive–track coupled vertical–longitudinal dynamics model is employed with considering the dynamic action from the gear transmissions. This dynamics model enables the detailed analysis and more practical simulation on the characteristics of power transmission path, namely motor–gear transmission–wheelset–longitudinal motion of locomotive, especially for traction or braking conditions. Multi-excitation sources, such as time-varying mesh stiffness and nonlinear wheel–rail contact excitations, are considered in this study. This dynamics model is then validated by comparing the simulated results with the experimental test results under braking conditions. The calculated results indicate that involvement of gear transmission could reveal the load reduction of the wheelset due to transmitted forces. Vibrations of the wheelset and the motor are dominated by variation of the gear dynamic mesh forces in the low speed range and by rail geometric irregularity in the higher speed range. Rail vertical geometric irregularity could also cause wheelset longitudinal vibrations, and do modulations to the gear dynamic mesh forces. Besides, the hauling weight has little effect on the locomotive vibrations and the dynamic mesh forces of the gear transmissions for both traction and braking conditions under the same running speed.

An intelligent hybrid model for power flow optimization in the cloud-IOT electrical distribution network

Power quality is an essential parameter in delivery of electrical power through the distributions networks in real time. Power transmission quality is affected by several factors which include frequently occurring voltage variations in the form of swells and sags, harmonic distortions, voltage and noise spikes. They severely degrade the quality of power delivered if unattended and directly have a consequence on the energy consumption which in turn increases the system cost and efficiency. The proposed research paper proposes and investigates an intelligent hybrid implementation of electrical network driven by a five layer ANFIS module driven by a set of FIS rule base. The proposed model has been tested after an elaborate mathematical modeling to arrive at the design electrical equations which are exported on to the ANFIS for training and validation. The proposed technique has been compared against existing ANN and Fuzzy algorithms and superior performance with respect to stability, settling time, reduction in noise have been observed in the experimentation. Faster convergence towards optimal power flow is achieved using the ANFIS model.

Vulnerability and Robustness of Civil Infrastructure Systems to Hurricanes

Civil infrastructure systems play an important role in community resilience. Without proper functioning of the infrastructure, especially power delivery, society will not recover quickly from disruptive events such as hurricanes. In this paper, the vulnerability, response and recovery of selected infrastructure at the system level for several hurricanes in the USA are modeled using geo-statistical methods and employing post-event data. Inoperability is the main variable modeled for each infrastructure system. In this paper, robustness is a property considered to be the opposite of vulnerability and it plays an important role in the resiliency modeling. The infrastructure systems examined in this paper are electric power delivery and telecommunications. Connections among the systems are briefly explored.

Collapse simulations of a long span transmission tower-line system subjected to near-fault ground motions

Observations from past strong earthquakes revealed that near-fault ground motions could lead to the failure, or even collapse of electricity transmission towers which are vital components of an overhead electric power delivery system. For assessing the performance and robustness, a high-fidelity three-dimension finite element model of a long span transmission tower-line system is established with the consideration of geometric nonlinearity and material nonlinearity. In the numerical model, the Tian-Ma-Qu material model is utilized to capture the nonlinear behaviours of structural members, and the cumulative damage D is defined as an index to identify the failure of members. Consequently, incremental dynamic analyses (IDAs) are conducted to study the collapse fragility, damage positions, collapse margin ratio (CMR) and dynamic robustness of the transmission towers by using twenty near-fault ground motions selected from PEER. Based on the bending and shear deformation of structures, the collapse mechanism of electricity transmission towers subjected to Chi-Chi earthquake is investigated. This research can serve as a reference for the performance of large span transmission tower line system subjected to near-fault ground motions.

Electrochemical performances of Na2MnSiO4 as an energy storage material in sodium-ion capacitors

In this work, we report the synthesis of Na2MnSiO4 via high-temperature solid-state chemical reaction method. The crystal structure and morphology of the synthesized Na2MnSiO4 material prepared at different temperatures (600, 700, 800, and 900 °C) were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy. The XRD patterns indicate that high-purity Na2MnSiO4 was obtained at the annealing temperature above 700 °C. The morphology observed by SEM shows that the particle size of the material increased with the increase of annealing temperature. Electrochemical energy storage performance of the material measured by galvanostatic charge–discharge reveals that the material prepared at 800 °C demonstrated the best energy storage capability with a specific capacitance of 123.8 F g− 1 at 0.5 Ag− 1. In addition, the material shows relatively good stability and 82% of initial capacitance was retained after 1000 charge–discharge cycles. Further testing by electrochemical impedance spectroscopy shows that the synthesized Na2MnSiO4 electrode has low series resistance (1.3 Ω) and charge transfer resistance (7.4 Ω), favoring the delivery of electrical power at a fast rate. These results suggest that the synthesized Na2MnSiO4 material has great potential for application in sodium-ion capacitors.

Steady State Control Enhancement and Power Flow Analysis of Longitudinal Power Systems Incorporating Interline Power Flow Controller

Transmission lines operating in steady state are prone to several challenges such as; poor steady-state power flow control, active and reactive power loss and voltage limit violations. These challenges can be solved either by the use of Flexible Alternating Current Transmission System (FACTS) controllers such as Interline Power Flow Controller (IPFC) and Generalized Unified Power Flow Controller (GUPFC) or other non-economical means such as building additional generation and transmission facilities. Previous works have incorporated IPFC to solve the challenges in meshed transmission system but has not been applied to solve the inherent challenges of the longitudinal Nigerian transmission system operating in steady state. This work performs power flow analysis with the incorporation of IPFC into the Nigerian 330-kV, 28-bus transmission system to solve its steady state challenges. Steady state power system component model produces a set of algebraic equations while the steady state IPFC model in rectangular form produces another set of algebraic equations for power flow analysis. The sets of equations were solved simultaneously using Newton-Raphson numerical iteration method, due to its fast quadratic convergence and high efficiency. Newton-Raphson power flow algorithm was implemented using MATLAB 8.1.0.604 (version R2013b) and the analysis was performed without and with the incorporation of IPFC data into the Institute of Electrical and Electronic Engineers (IEEE) 14-bus and the Transmission Company of Nigeria (TCN) 330-kV, 28-bus system. The performance evaluation of IPFC was investigated using active and reactive power as performance variables. The incorporation of IPFC rectangular model into the Nigerian 330-kV, 28-Bus TCN and IEEE 14-bus system demonstrated the capability of IPFC to control active and reactive power flow. IPFC typifies effective enhancement and the maximum use of Nigerian 330-kV, 28-Bus TCN and IEEE 14-bus transmission infrastructure for better delivery of electrical power to the end users.

ITO nanoparticles break optical transparency/high-areal capacitance trade-off for advanced aqueous supercapacitors

Indium tin oxide nanoparticles break optical transparency/high-areal capacitance trade-off for advanced aqueous supercapacitors.

Diagnosis and location of faults in submarine power cables

Nowadays, when compared with overhead lines, power cables are becoming increasingly attractive for the delivery of electrical power. Their reduced environmental impact complies with the public concern on the compatibility of electrical infrastructures in residential areas. The lower fault rate of high voltage DC (HVDC) cables matches the need of transmission and distribution system operators for high reliability in power delivery [1], [2], and sometimes they are the only solution, e.g., submarine links. In general, the growing demand and dependency on offshore produced renewable energy makes submarine cables essential, and they have become critical infrastructures for the reliable delivery of electrical power [1]-[3].

Multi-hazard system-level logit fragility functions

Fragility functions are used to represent the probability of failure of a structure or lifeline system conditional upon a hazard or set of hazards and are essential in the performance-based design process. Continuous lognormal damage fragilities are traditional, but recent formulations have implemented logit transformations from the family of generalized linear models for categorical data with a binary outcome (e.g., failure, no failure). In wind engineering, single hazard parameters derived from correlated variables (e.g., integrated kinetic energy, IKE) have been employed to indirectly include the effect of more than one hazard variable; however, even with more general hazard metrics, the lognormal formulation is still unduly restrictive for realistic fragility modeling. Using a statistical approach based on a logit formulation, a shift towards more robust fragility functions can be achieved. Because of its simplicity and ability to represent multiple predictor variables to improve the fitted model, this paper proposes use of the logit formulation of the fragility function at the system level for two or more simultaneous weather hazards. Successful applications of the model to characterize lifeline system-level fragility functions for electric power delivery during Hurricane Isaac in Louisiana and Hurricane Sandy in New York City using in-situ damage and hazard data are shown. While the results here are empirically derived, the modeling approach may be expanded for other structural systems subject to multiple loadings or demand variables.