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ABSTRACT: Higher-voltage, 540 V, aircraft DC-bus power quality is examined experimentally and by computer simulation during a short-circuit fault across the phase terminals of a 70 kW, five-phase, permanent magnet fault-tolerant generator. The DC-bus transients caused by the short-circuiting of the generator phases are seen to exceed the limits in MIL-STD-704F and a control algorithm is proposed for a supercapacitor-based energy storage device that mitigates the transients. The controller performance is illustrated by computer simulations for a range of bus switching scenarios.
Electrical Systems in Transportation, IET. 10/2011;
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ABSTRACT: A second-harmonic direct current (DC) ripple compensation technique is presented for a multi-phase, fault-tolerant, permanent magnet machine. The analysis has been undertaken in a general manner for any pair of phases in operation with the remaining phases inactive. The compensation technique determines the required alternating currents in the machine to eliminate the second-harmonic DC-link current, while at the same time minimising the total rms current in the windings. An additional benefit of the compensation technique is a reduction in the magnitude of the electromagnetic torque ripple. Practical results are included from a 70 kW, five-phase generator system to validate the analysis and illustrate the performance of the compensation technique.
IET Electric Power Applications 02/2011; · 1.17 Impact Factor
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ABSTRACT: The design and simulation of a dual band, coaxial waveguide feedhorn structure for a satellite reflector dish is presented using CST's Microwave Studio™. The feedhorn operates on the satellite television frequencies, commonly referred to as the Direct Broadcast Satellite (DBS) frequencies of, 10.7-12.75, 19.7-20.2 and 29.5-30 GHz. The feedhorn structure consists of two separate waveguides that are placed inside one another and at the focal point of the reflector dish which will be illuminated with circular polarization from a geostationary satellite. The inner circular waveguide is filled with a dielectric material, Rexoilte™ that reduces the physical size of the waveguide but also serves to protect against moisture ingress and acts as a matching stub device. The outer circular waveguide is ridged in order to reduce the cut-off frequency for the first mode and to increase the bandwidth between the dominant TE<sub>11</sub> mode and the second mode of operation, TM<sub>01</sub>. A reduction in overall size is seen compared with previous work.
Antennas and Propagation Conference (LAPC), 2010 Loughborough; 12/2010
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ABSTRACT: The novel design of a circular waveguide feed structure for use with a Direct Broadcast Satellite (DBS) reflector dish that can operate in two frequency bands for HDTV, is presented. The dimensions of the waveguide are calculated from theory. The antenna is modelled and simulated in CST Microwave Studio™ with the addition of a dielectric to shrink one of the waveguides to reduce both size and cost. This antenna feed will have applications for those people in the UK and Ireland who do not receive a quality landline broadband service of at least 2 Mbps. The new DBS design will permit much greater bandwidth for multichannel HDTV and broadband duplex at greater than 2 Mbps via satellite to the home.
Antennas and Propagation Conference (LAPC), 2010 Loughborough; 12/2010
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ABSTRACT: Elpipes are polymer-insulated underground HVDC power lines that use relatively rigid extruded conductors designed for higher capacity and efficiency than is practical for overhead power lines. Elpipes can use far more conductor than cables, but also have more splices that an HVDC cable. The US Department of Energy showed early interest in massive underground transmission, but that faded until recently. The high efficiency of elpipes is motivated by the need to minimize heat dissipation while maintaining passive cooling. Minimizing waste heat production is critical since heat dissipation limits capacity. For a 325-800kV DC elpipe, we have selected a design basis of 1% loss per 1000 km, about three times better than an overhead 800kVDC line, and similar to “high temperature” superconducting (HTS) lines after accounting for the energy HTS lines consume for cryogenic cooling. This high efficiency enables continental scale power transfers with acceptable loss, and fully buried elpipes carrying up to 12 GW. Elpipes may one day enable continental scale HVDC grids, though there remain technological hurdles such as the need for HVDC breakers that must first be solved before that can occur.
High Voltage Engineering and Application (ICHVE), 2010 International Conference on; 11/2010
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ABSTRACT: Elpipes are polymer-insulated underground HVDC power lines that use relatively rigid extruded conductors designed for higher capacity and efficiency than is practical for overhead power lines. Elpipes can use far more conductor than cables, but also have more splices that an HVDC cable. The high efficiency of elpipes is motivated by the need to minimize heat dissipation while maintaining passive cooling. Minimizing waste heat production is critical since heat dissipation limits capacity. For a 325-800kV DC elpipe, we have selected a design basis of 1% loss per 1000 km, about three times better than an overhead 800kVDC line, and similar to “high temperature” superconducting (HTS) lines after accounting for the energy HTS lines consume for cryogenic cooling. This high efficiency could enable continental scale power transfers with acceptable loss, using fully buried aluminum elpipes carrying up to 12 GW. Surface mounted elpipes can deliver power up to at least 24 GW, whereas with internal cooling transfer capacities up to 200 GW are feasible.
Innovative Technologies for an Efficient and Reliable Electricity Supply (CITRES), 2010 IEEE Conference on; 10/2010
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ABSTRACT: High-voltage DC-bus power quality is examined experimentally and by computer simulation during a short-circuit fault across the phase terminals of a five-phase, permanent magnet fault-tolerant generator. The DC-bus transients are seen to exceed the limits in MIL-STD-704F [1] and a control algorithm is proposed for a supercapacitor-based energy storage device that mitigates the transients. The controller performance is illustrated by computer simulations.
Power Electronics, Machines and Drives (PEMD 2010), 5th IET International Conference on; 05/2010
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ABSTRACT: A power-based control method is proposed and analysed for a supercapacitor energy storage device. The performance of the energy storage device is examined by simulation and experimentally when operating on a high voltage DC bus with a multi-phase, fault-tolerant generator and a high power, pulsed load such as an actuation or avionic system. In the practical system the energy storage device is emulated using a bi-directional electronic load and a real-time simulation platform. The energy storage device is shown to minimise the DC bus transients and virtually eliminate the torque pulsation on the generator shaft. The system design and performance trade-offs are analysed. The experimental work uses a 70 kW generator and 30 kW programmable load emulation devices.
Applied Power Electronics Conference and Exposition (APEC), 2010 Twenty-Fifth Annual IEEE; 03/2010
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ABSTRACT: Hardware-in-the-loop (HIL) techniques are used to examine the start-up sequence for an all-electric UAV system powered by a two-spool gas engine with embedded electrical generators on both spools. Start-up begins with the auxiliary power unit charging the high voltage DC bus to enable the high pressure spool switched reluctance starter/generator (SRSG) to spin the gas engine to ground idle speed and ends with the SRSG and the low pressure spool fault-tolerant permanent magnet generator being connected in parallel. HIL methods are used to emulate the behaviour of the gas engine and the loads. The HIL elements compliment the `real' electrical generators and bus system. The start-up sequence is demonstrated on a purpose-built laboratory system to examine system interactions and the feasibility of the operating routine.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: This paper describes a new control strategy for an aircraft electrical systems evaluation platform. The 100 kVA, experimental facility includes multiple generators and power electronic loads interconnected by a high-voltage dc bus, centrally controlled by a real-time computer and data logging system. The Facility is to allow electrical power management techniques to be developed for future autonomous aircraft. The control of the facility presents important challenges as it has to be flexible, facilitating future expansion, robust, safe, and yet allow the development of advanced control strategies.
Industrial Electronics, 2008. IECON 2008. 34th Annual Conference of IEEE; 12/2008
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ABSTRACT: A simple, per-phase controller is described for a five-phase, fault-tolerant, permanent magnet generator. The power conditioning and control system for the generator comprises five independent H-bridge converters operating with sinusoidal PWM and supplying a common high-voltage DC bus. The separate controllers adjust the PWM pattern in each converter to regulate the DC bus voltage over the 3:1 machine speed range, which requires field weakening operation at high speed. Small-signal analysis is used to form a theoretical basis for the control loop design. Practical results are included from a 70 kW, five-phase prototype system to validate the analysis and illustrate the controller performance.
Vehicle Power and Propulsion Conference, 2008. VPPC '08. IEEE; 10/2008
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ABSTRACT: More-electric vehicle technology is becoming prevalent in a number of transportation systems because of its ability to improve efficiency and reduce costs. This paper examines the specific case of an Uninhabited Autonomous Vehicle (UAV), and the system topology and control elements required to achieve adequate dc distribution voltage bus regulation. Voltage control methods are investigated and a droop control scheme is implemented on the system. Simulation results are also presented.
Power Electronics, Machines and Drives, 2008. PEMD 2008. 4th IET Conference on; 05/2008
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ABSTRACT: With the increasing use of integrated full-electric propulsion systems in ships, some questions have been raised over the potential for interactions between electromechanical components and the need for integrated simulation tools. This paper focuses on the experimental validation of the propulsion drive models, as part of an integrated simulation of the power system. Load emulation of a hull-mounted propeller in variable sea conditions is complex. Hence a frequency domain approach has been used, in which a small- signal variable-frequency load disturbance was applied to a multiphase induction motor drive over a range of speed and load conditions using a dynamometer load. Experimental results have been compared with simulation predictions for different numbers of phases, giving confidence that the model will correctly represent the propulsion motor drive system when coupled to measured propeller performance characteristics.
Power Electronics, Machines and Drives, 2008. PEMD 2008. 4th IET Conference on; 05/2008
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I. Ben-Zvi,
J. Alduino,
D. Barton,
D. Beavis,
M. Blaskiewicz,
J. Brennan,
A. Burrill,
R. Calaga,
P. Cameron,
X. Chang, [......],
G. Bell,
D. Bruhwiler,
R. Busby,
J. Cary,
D. Dimitrov,
P. Messmer,
V. Ranjbar,
D. Smithe,
A. Sobol,
P. Stoltz
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ABSTRACT: The physics interest in a luminosity upgrade of RHIC requires the development of a cooling-frontier facility. Detailed calculations were made of electron cooling of the stored RHIC beams. This has been followed by beam dynamics simulations to establish the feasibility of creating the necessary electron beam. The electron beam accelerator will be a superconducting Energy Recovery Linac (ERL). An intensive experimental R&D program engages the various elements of the accelerator, as described by 24 contributions to the 2007 PAC.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: There is currently significant interest in offshore wind turbines up to 5 MW. One of the preferred options is doubly fed slip-ring generators. Turbine manufacturers have proposed an operating scheme for low speeds that is claimed to improve the overall energy extraction from the wind. This paper aims to examine the performance benefits for this new operational mode on a small experimental rig, confirmed by simulation, and to provide a fundamental understanding of the differences in the generator operation in both modes. This paper develops analytical steady-state models to provide this insight and correlates the operating performance with a dynamic real-time generator control scheme and experimental results obtained from a laboratory test machine. A theoretical study on a 2-MW commercial turbine is also undertaken
IEEE Transactions on Industry Applications 12/2006; · 1.66 Impact Factor
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ABSTRACT: There is currently significant interest in offshore wind turbines up to 5 MW. One of the preferred options is doubly-fed slip-ring generators. Turbine manufacturers have proposed an operating scheme for low speeds that is claimed to improve the overall energy extraction from the wind. The aim of this paper therefore is to examine the performance benefits for this new operational mode on a small experimental rig, confirmed by simulation, and to provide a fundamental understanding of the differences in the generator operation in both modes. The paper develops analytical steady-state models to provide this insight and correlates the operating performance with a dynamic real-time generator control scheme and experimental results obtained from a laboratory test machine. A theoretical study on a 2 MW commercial turbine is also undertaken.
Industry Applications Conference, 2005. Fourtieth IAS Annual Meeting. Conference Record of the 2005; 11/2005
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ABSTRACT: The inner surfaces of the 248 m Spallation Neutron Source (SNS) accumulator ring vacuum chambers are coated with ∼ 100nm of titanium nitride (TiN) to reduce the secondary electron yield (SEY) of the chamber walls. There are approximately 135 chambers and kicker modules, some up to 5m in length and 36cm in diameter, coated with TiN. The coating is deposited by means of reactive DC magnetron sputtering using a cylindrical cathode with internal permanent magnets. This cathode configuration generates a deposition rate sufficient to meet the required production schedule and produces stoichiometric films with good adhesion, low SEY and acceptable outgassing. Moreover, the cathode magnet configuration allows for simple changes in length and has been adapted to coat the wide variety of chambers and components contained within the arcs, injection, extraction, collimation and RF straight sections. Chamber types and quantities as well as the cathode configurations are presented herein. The unique coating requirements of the injection kicker ceramic chambers and the extraction kicker ferrite surface will be emphasized. A brief summary of the salient coating properties is given including the interdependence of SEY as a function of surface roughness and its effect on outgassing.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: The Spallation Neutron Source (SNS) ring is designed to accumulate high intensity protons. Ultrahigh vacuum of 10-9 Torr is required in the accumulator ring to minimize beam-residual gas ionization. To reduce the secondary electron yield (SEY) and the associated electron cloud instability, the ring vacuum chambers are coated with titanium nitride (TiN). This paper describes the design, fabrication, assembly and vacuum processing of the ring and beam transport line vacuum chambers as well as the associated instrumentation
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: As RHIC beam intensity increases beyond original scope, pressure rises have been observed in some regions. The luminosity limiting pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam induced desorption. Non-Evaporable Getter (NEG) coated beamtubes have been proven effective to suppress pressure rise in synchrotron radiation facilities. Standard beamtubes have been NEG coated by a vendor and added to many RHIC UHV regions. BNL is developing a cylindrical magnetron sputtering system to NEG coat special beryllium beamtubes installed in RHIC experimental regions. It features a hollow, liquid cooled cathode producing power density of 500W/m and deposition rate of 5000 Angstrom/hr on 7.5cm OD beamtube. The cathode, a titanium tube partially covered with zirconium and vanadium ribbons, is oriented for horizontal coating of 4m long chambers. Ribbons and magnets are arranged to provide uniform sputtering distribution and deposited NEG composition. Vacuum performance of NEG coated tubes was measured. Coating was analyzed with energy dispersion spectroscopy, auger electron spectroscopy and scanning electron microscopy. System design, development, and analysis results are presented.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: With increasing ion beam intensity during recent RHIC operations, rapid pressure rises of several decades were observed at most warm sections and at a few cold sections. The pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam ion induced desorption; and have been one of the major intensity and luminosity limiting factors for RHIC. Improvement of the warm sections has been carried out in the last few years. Extensive in-situ bakes, additional UHV pumping and anti-grazing ridges have been implemented. Several hundred meters of NEG coated beam pipes have been installed and activated. Vacuum monitoring and logging were enhanced. Preventive measures, such as pumping before cool down to reduce monolayer condensates, were also taken to suppress the pressure rises in the cold sections. The effectiveness of these measures in reducing the pressure rises during machine studies and during physics runs are discussed and summarized.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
