Special Issue "Electrical Power and Energy Systems"
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A special issue of Energies (ISSN 1996-1073).
Deadline for manuscript submissions: closed (30 April 2012)
Special Issue Editors
Guest Editor
Prof. Dr. Paul Stewart
School of Engineering, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
Website: http://www.lincoln.ac.uk/engineering
E-Mail: pstewart@lincoln.ac.uk
Phone: +44 1522 668896
Interests: power and energy; systems modeling and optimisation; electrical machines and drives; advanced fuels and combustion; control and simulation; electric and hybrid vehicles; more electric aircraft; gas turbines; internal combustion engine; advanced powertrains; electrical systems; artificial intelligence; low carbon operation; CFD
Guest Editor
Prof. Dr. Chris Bingham
School of Engineering, University of Lincoln, Brayford Pool Lincoln, LN6 7TS, UK
Website: http://www.kenan-flagler.unc.edu/faculty/directory/strategy-and-entrepreneurship/christopher-bingham
E-Mail: cbingham@lincoln.ac.uk
Phone: +44 1522 668896
Interests: aircraft dynamics and advanced control; impact of driver behavior on energy efficiency of EVs/HEVs, electrical power distribution for deep-sea ROVs; power electronic servo-drive systems; real-time prognostics and diagnostics for industrial systems; sensor validation and fault detection; high-efficiency power supplies for domestic products; active magnetic bearings for high-speed energy storage
Special Issue Information
Dear Colleagues,
Electrical power and energy systems are at the forefront of application developments in renewable energy, smart grid, more electric aircraft, electric and hybrid vehicles and much more. The associated technologies and control methods are crucial to achieving global targets in energy efficiency and low-carbon operations, and will also contribute to key areas such as energy security. The greatest challenges occur when we combine new technologies at large-scale and often complex system level. The Special Edition will cover theoretical developments with special emphasis on applications in electrical power and energy systems. Topics of interest for publication include, but are not limited to:
- Renewable Energy Systems - Energy management; hybrid systems; distributed systems; renewable sources and integration; transient energy storage, charging networks.
- Electrical Machines, Drives and Applications - AC and DC machines and drives; multiscale systems modeling; remote monitoring and diagnosis; electric and hybrid vehicles; energy conversion, vehicle to grid interaction.
- Power Electronic Systems - Converters and emerging technologies; modeling simulation and control; power factor correction; power supplies; active filters; reliability and fault tolerance.
- Electrical Power Generation Systems - Modeling and simulation of electrical power systems; load management; power quality; distribution reliability; distributed and islanded power systems, sensor networks, communication and control.
- Electrical Power Systems Modeling and Control - Modeling and control methodologies and applications; intelligent systems; optimization and advanced heuristics; adaptive systems; robust control.
Prof. Dr. Paul Stewart
Prof. Dr. Chris Bingham
Guest Editors
Submission
Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.
Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed Open Access monthly journal published by MDPI.
Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs).
Keywords
- power systems
- energy systems
- energy management
- electrical power systems
- renewable energy
- electrical machines
- electrical drives
- power electronics
- energy conversion
- power generation
- distributed power systems
- electric vehicles
Published Papers (14 papers)
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Received: 1 February 2012; in revised form: 26 March 2012 / Accepted: 11 April 2012 / Published: 19 April 2012
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Abstract: Dissolved gas analysis (DGA) has been widely applied to diagnose internal faults in transformer insulation systems. However, the accuracy of DGA technique is limited because of the lack of positive correlation of the fault-identifying gases with faults found in power transformers. This paper presents a laboratory study on the correlation between oil dissolved gas formation and partial discharge (PD) statistical parameters. Canonical correlation analysis (CCA) is employed to explore the underlying correlation and to extract principal feature parameters and gases in the development of different PD defects. This study is aimed to provide more information in assisting the separation, classification and identification of PD defects, which might improve the existing transformer dissolved gas analysis (DGA) schemes. An application of a novel ratio method for discharge diagnosis is proposed. The evaluation of DGA data both in laboratory and actual transformers proves the effectiveness of the method and the correlation investigation.
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Received: 19 March 2012; in revised form: 15 May 2012 / Accepted: 21 May 2012 / Published: 4 June 2012
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Abstract: This paper presents a high performance real-time simulator for power electronic systems applications and primarily intended for controller hardware-in-the-loop (CHIL) testing. The novelty of the proposed simulator resides in the massively parallel hardware architecture that efficiently exploits fine-grained parallelism without imposing severe communication overhead time that can limit the performance. The simulator enables the use of a nanosecond range simulation timestep to simulate power electronic systems. Through the use of this nanosecond range simulation timestep, the simulator minimizes the error arising from the intersimulation timestep switching phenomenon associated with CHIL. The proposed hardware architecture is realized based on the FPGA technology. The simulator is tested and its CHIL capability verified based on the closed-loop testing of a robust multivariable servomechanism controller for autonomous operation of a distributed generation unit.
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Received: 26 April 2012; in revised form: 5 June 2012 / Accepted: 7 June 2012 / Published: 13 June 2012
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Abstract: Because of its strong inherent safety features and high outlet temperature, the modular high temperature gas-cooled nuclear reactor (MHTGR) is already seen as the central part of the next generation of nuclear plants. Such power plants are being considered for industrial applications with a wide range of power levels, and thus power-level control is an important technique for their efficient and stable operation. Stimulated by the high regulation performance provided by nonlinear controllers, a novel dynamic output-feedback nonlinear power-level regulator is developed in this paper based on the technique of iterative damping assignment (IDA). This control strategy can provide the L2 disturbance attenuation performance under modeling uncertainty or exterior disturbance, and can also guarantee the globally asymptotic closed-loop stability without uncertainty and disturbance. This newly built control strategy is then applied to the power-level regulation of the HTR-PM plant, and numerical simulation results show both the feasibility and high performance of this newly-built control strategy. Furthermore, the relationship between the values of the parameters and the performance of this controller is not only illustrated numerically but also analyzed theoretically.
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Received: 27 April 2012; in revised form: 9 June 2012 / Accepted: 19 June 2012 / Published: 21 June 2012
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Abstract: Electric vehicles (EVs) and the related infrastructure are being developed rapidly. In order to evaluate the impact of factors on the aggregated EV load and to coordinate charging, a model is established to capture the relationship between the charging load and important factors based on data mining. The factors can be categorized as internal and external. The internal factors include the EV battery size, charging rate at different places, penetration of the charging infrastructure, and charging habits. The external factor is the time-of-use pricing (TOU) policy. As a massive input data is necessary for data mining, an algorithm is implemented to generate a massive sample as input data which considers real-world travel patterns based on a historical travel dataset. With the input data, linear regression was used to build a linear model whose inputs were the internal factors. The impact of the internal factors on the EV load can be quantified by analyzing the sign, value, and temporal distribution of the model coefficients. The results showed that when no TOU policy is implemented, the rate of charging at home and range anxiety exerts the greatest influence on EV load. For the external factor, a support vector regression technique was used to build a relationship between the TOU policy and EV load. Then, an optimization model based on the relationship was proposed to devise a TOU policy that levels the load. The results suggest that implementing a TOU policy reduces the difference between the peak and valley loads remarkably.
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Received: 3 May 2012; in revised form: 8 June 2012 / Accepted: 22 June 2012 / Published: 26 June 2012
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Abstract: The dispatching properties of power packets in indoor power line channel were investigated. A power packet is physically composed of a power payload and information signals. For evaluation, the arrival power ratio and the bit error rate were calculated by numerical simulation. The results are important for the development and design of power packet transfer, based on the transmission frequency and bit energy parameters.
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Received: 25 May 2012; in revised form: 18 June 2012 / Accepted: 29 June 2012 / Published: 5 July 2012
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Abstract: Switching overvoltages (SOV) are considered a possible source of component failures experienced in existing offshore wind farms (OWFs). The inclusion of sufficiently accurate and validated models of the main electrical components in the OWF in the simulation tool is therefore an important issue in order to ensure reliable switching operations. Transient measurement results in an OWF are compared with simulation results in PSCAD EMTDC and DigSILENT Power Factory. A user-defined model of the vacuum circuit breaker (VCB) is included in both tools, capable of simulating multiple prestrikes during the closing operation. An analysis of the switching transients that might occur in OWFs will be made on the basis of the validated model, and the importance of the inclusion of a sufficiently accurate representation of the VCB in the simulation tool will be described. The inclusion of the VCB model in PSCAD greatly improves the simulation results, whereas little improvement is found in DigSILENT. Based on the transient study it is found that the simulated SOV can be up to 60% higher at the sending end when using the detailed VCB representation compared to the built-in switch, which emphasises the need for accurate representation of the VCB for energisation studies.
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Received: 26 March 2012; in revised form: 7 June 2012 / Accepted: 29 June 2012 / Published: 6 July 2012
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Abstract: Distributed generation with a combustion engine prime mover is still widely used to supply electric power in a variety of applications. These applications range from backup power supply systems and combined wind-diesel generation to providing power in places where grid connection is either technically impractical or financially uneconomic. Modelling of such systems as a whole is extremely difficult due to the long-time load profiles needed and the computational difficulty of including small time-constant electrical dynamics with large time-constant mechanical dynamics. This paper presents the development of accelerated, reduced-order models of a distributed internal combustions engine generator unit. Overall these models are shown to achieve a massive improvement in the computational time required for long-time simulations while also achieving an extremely high level of dynamic accuracy. It is demonstrated how these models are derived, used and verified against benchmark models created using established techniques. Throughout the paper the modelling set as a whole, including multi level detail, is presented, detailed and finally summarised into a crucial tool for general system investigation and multiple target optimisation.
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Received: 23 May 2012; in revised form: 25 June 2012 / Accepted: 9 July 2012 / Published: 17 July 2012
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Abstract: Power semiconductor switching devices play an important role in the performance of high power wind energy generation systems. The state-of-the-art device choices in the wind power application as reported in the industry include IGBT modules, IGBT press-pack and IGCT press-pack. Because of significant deviation in the packaging structure, electrical characteristics, as well as thermal impedance, these available power switching devices may have various thermal cycling behaviors, which will lead to converter solutions with very different cost, size and reliability performance. As a result, this paper aimed to investigate the thermal related characteristics of some important power switching devices. Their impact on the thermal cycling of a 10 MW three-level Neutral-Point-Clamped wind power converter is then evaluated under various operating conditions; the main focus will be on the grid connected inverter. It is concluded that the thermal performances of the 3L-NPC wind power converter can be significantly changed by the power device technology as well as their parallel configurations.
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Received: 15 June 2012; in revised form: 24 July 2012 / Accepted: 26 July 2012 / Published: 31 July 2012
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Abstract: Single-phase positive sequence modelling is often used in power systems when power flows and short circuit analysis are assessed. Of course, the use of single-phase positive sequence modelling assumes purely three-phase configurations and perfectly symmetrical ones so that single-phase modelling considers that all the phase conductors behave in the same way. When considering the physical reality of power networks, this assumption can be questionable and the behaviors of all the system conductors including the passive ones (earth wires for overhead lines, metallic screens and armours for cables and enclosures for gas insulated lines) is completely unknown. Therefore, the present multiconductor cell analysis (MCA) becomes necessary, since it allows one to achieve great precision results on the regimes of both phase conductors and passive conductors. MCA offers a powerful tool in order to validate (or less) approximated and simplified computation methods. In particular, for single and double circuit overhead lines (OHLs), the current phasors induced in the earth wires and the ground return current alongside the line can be directly computed by MCA in steady state and faulty regimes. It is worth noting that, for faulty regimes, MCA allows also evaluating the approximation degree and validity field of screening factors k.
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Received: 13 June 2012; in revised form: 20 July 2012 / Accepted: 26 July 2012 / Published: 2 August 2012
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Abstract: This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 × 10−8 ± 3.5 × 10−9. Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.
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Received: 16 June 2012; in revised form: 15 August 2012 / Accepted: 30 August 2012 / Published: 5 September 2012
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Abstract: A microgrid is an eco-friendly power system because renewable sources such as solar and wind power are used as the main power sources. For this reason, much research, development, and demonstration projects have recently taken place in many countries. Operation is one of the important research topics for microgrids. For efficient and economical microgrid operation, a human operator is required as in other power systems, but it is difficult because there are some restrictions related to operation costs and privacy issues. To overcome the restriction, autonomous operation for microgrids is required. Recently, an intelligent agent system for autonomous microgrid operation has been studied as a potential solution. This paper proposes a multiagent system for autonomous microgrid operation. To build the multiagent system, the functionalities of agents, interactions among agents, and an effective agent protocol have been designed. The proposed system has been implemented by using an ADIPS/DASH framework as an agent platform. The intelligent multiagent system for microgrid operation based on the proposed scheme is tested to show the functionality and feasibility on a distributed environment through the Internet.
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Received: 18 May 2012; in revised form: 23 August 2012 / Accepted: 10 September 2012 / Published: 13 September 2012
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Abstract: When a three-phase induction generator (IG) supplies unbalanced loads, its terminal voltages and line currents are also unbalanced, which may cause the IG to overheat and need to be derated. A single-phase loaded self-excited induction generator (SEIG) works under most unfavorable load unbalance conditions. This paper proposes a three-capacitor circuit scheme and a method to find the values of the self-excitation capacitors that allow the SEIG to be balanced. The SEIG is modeled by a two-port network equivalent circuit that resolves the SEIG into its positive- and negative-sequence circuits associated with the self-excitation capacitors and the load. The network can then be analyzed by common AC circuit analysis techniques. Successful results for balancing the SEIG supplying a single-phase load have been achieved by properly choosing the values of the excitation capacitors. The proposed method has also been validated by experiments on a 0.37 kW SEIG.
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Received: 19 April 2012; in revised form: 23 July 2012 / Accepted: 30 August 2012 / Published: 27 September 2012
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Abstract: Automatic Generation Control (AGC) and Automatic Voltage Control (AVC) are key approaches to frequency and voltage regulation in power systems. However, based on the assumption of decoupling of active and reactive power control, the existing AGC and AVC systems work independently without any coordination. In this paper, a concept and method of hybrid control is introduced to set up an Integrated Coordinated Optimization Control (ICOC) system for AGC and AVC. Concerning the diversity of control devices and the characteristics of discrete control interaction with a continuously operating power system, the ICOC system is designed in a hierarchical structure and driven by security, quality and economic events, consequently reducing optimization complexity and realizing multi-target quasi-optimization. In addition, an innovative model of Loss Minimization Control (LMC) taking into consideration active and reactive power regulation is proposed to achieve a substantial reduction in network losses and a cross iterative method for AGC and AVC instructions is also presented to decrease negative interference between control systems. The ICOC system has already been put into practice in some provincial regional power grids in China. Open-looping operation tests have proved the validity of the presented control strategies.
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Received: 15 September 2012; in revised form: 31 October 2012 / Accepted: 31 October 2012 / Published: 8 November 2012
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Abstract: This paper presents a new coherency identification method for dynamic reduction of a power system. To achieve dynamic reduction, coherency-based equivalence techniques divide generators into groups according to coherency, and then aggregate them. In order to minimize the changes in the dynamic response of the reduced equivalent system, coherency identification of the generators should be clearly defined. The objective of the proposed coherency identification method is to determine the optimal coherent groups of generators with respect to the dynamic response, using the Partitioning Around Medoids (PAM) algorithm. For this purpose, the coherency between generators is first evaluated from the dynamic simulation time response, and in the proposed method this result is then used to define a dissimilarity index. Based on the PAM algorithm, the coherent generator groups are then determined so that the sum of the index in each group is minimized. This approach ensures that the dynamic characteristics of the original system are preserved, by providing the optimized coherency identification. To validate the effectiveness of the technique, simulated cases with an IEEE 39-bus test system are evaluated using PSS/E. The proposed method is compared with an existing coherency identification method, which uses the K-means algorithm, and is found to provide a better estimate of the original system.
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Last update: 5 October 2012
