Search

A hierarchical control architecture is proposed for the optimal day-ahead commitment of multiple grid support services within a virtual power plant (VPP). The day-ahead optimization considers pricing and cost data to determine the commitment schedule, and a robust Model Predictive Control (MPC) approach is included to minimize the unbalance fees during real-time operations. The multi-level control has been demonstrated experimentally using a hybrid test system, where the VPP is formed of a commercial 240 kW, 180 kWh battery energy storage system (BESS), while the additional assets are modelled in a real-time digital simulator (RTDS). Two case studies are analyzed: the first assumes a purely-electrical VPP, with a single connection to the public network; the second involves a multi-energy approach, with the introduction of a gas-supplied Combined Heat and Power unit (CHP). Both winter and summer price scenarios are tested. The results show the superiority of the multiple-service operation compared to providing a single grid support service. For example, the net revenue is increased by 30% (winter) and 7% (summer) when compared to just frequency regulation, and by +99% (winter) and 30% (summer) when compared to only energy arbitrage.

The high temperature performance of water-in-salt electrolytes was investigated using a carbon-based electrode with commercial cell components. Supercapacitors using 21 m Li bis(trifluoromethylsulphonyl)imide (TFSI) and 21 m LiTFSI + 7 m Li trifluoromethanesulphonyl electrolytes are shown to operate at a voltage of 2 V at 100 °C and 120 °C, respectively, with gravimetric capacitances exceeding 100 F g−1.

A new criterion and potentiostatic method is demonstrated to determine the electrochemically stable potential window (ESPW) of supercapacitors, enabling the calculation of the optimal electrode mass ratio for two different electrode-electrolyte pairings. The criterion uses the decay of electrode current in a three-electrode test cell during potentiostatic ageing at progressively higher voltages to determine the ESPW. To perform these measurements a quasi-reference electrode (QRE) was incorporated within a CR2032 coin cell with a small and simple modification. This enabled three-electrode measurements to be performed inside the coin cell using organic electrolytes whilst outside a glovebox. The voltage-optimised mass ratio (m+/m−) for activated carbon electrodes in 1 M tetraethylammonium tetrafluoroborate (TEABF4) in acetonitrile (ACN) and propylene carbonate (PC) electrolytes was shown to be 2.38 and 0.61 respectively. The validity of the technique was verified by full-cell potentiostatic ageing experiments on mass-balanced and mass-symmetric supercapacitors. For both electrolytes the maximum operating voltage, energy storage capacity and cycle lifetime were improved significantly with mass balancing. The maximum voltage increased from 2.0 V to 2.9 V for ACN and from 2.3 V to 2.7 V for PC, whilst the energy density increased by ∼90% for ACN and by ∼40% for PC.

This work presents the comparison of the variations in the electrical performance of two lithium-ion batteries during a cycling experiment. The experiment consists of a sequence of full charge/full discharge cycles, with constant current and constant voltage phases for the charge and the discharge. The main difference between the tests conducted over the two batteries is the rest time after charge in each cycle. For one battery, this time is, one hour, while for the other one is one minute. The analysis is performed in terms of capacity, charge-discharge times, voltage evolution during the rest period and internal resistance. The results show that, in terms of the characteristics analyzed, there is not a considerable difference in the degradation behavior of the two batteries, which may mainly be due to the relatively short length of the rest periods with respect the time constants related to phenomena, such as the capacity recovery.

Three pulse-width-modulation (PWM) digital control approaches are evaluated to provide the current sharing between phases in high-power dual-interleaved DC-DC converters. The implementation of a digital peak current, multi-sample averaged current and an enhanced single-sample averaged current control in a TMS320F28377D is described. A summary of stability requirements is provided for designing the controllers and experimental results from a 60 kW, 75 kHz silicon carbide DC-DC converter are used to evaluate the steady-state and dynamic performance of the three control methods. Overall the best performance in terms of tracking and speed of response was achieved by the enhanced single-sample method. The multi-sampled technique provided the highest tracking accuracy, but at the expense of the slowest dynamic response. The fastest dynamic response was achieved by the digital peak current control, but this method is limited by poor noise immunity and instability for duty ratios in the region of 0.5.

Background: Systemic mastocytosis (SM) is a disorder of neoplastic mast cells ranging from indolent to aggressive multi-system disease. We previously reported our large single centre experience managing SM. Since 2019 patients have had access to new treatments within trials. Prognostic scoring systems developed in SM to improve outcome predictions and guide treatment have been a focus of recent studies, although are yet to be validated in real-world setting. We sought to apply these scoring systems within our UK cohort, with a particular focus on the international prognostic score (IPSM) and the mutation-adjusted risk score (MARS). Methods: We performed a retrospective study of 192 adult patients diagnosed with SM between 2009 and 2021 including demographics, clinical data, as well as next generation sequencing (NGS) based myeloid gene panels carried out in advanced SM patients (AdvSM) where available. Prognosis for all patients was calculated based on IPSM (Sperr et al. [2019]) in all our SM patients and MARS scores in those with AdvSM (Jawhar et al. [2019]). Results: There was no gender bias in our cohort with 87 (46%) males and 105 (54%) females. Median age at diagnosis was 52 years (range 5-84) and majority of patients had indolent SM (ISM; 129/192 [67%]), 8/192 (4%) smouldering SM (SSM) and 55/192 (29%) advanced SM (AdvSM). In those with AdvSM, 43/55 (78%) had an associated haematological neoplasm (SM-AHN); 9/55 (17%) aggressive SM (ASM) and 3/55 (5%) mast cell leukaemia. As expected, AHN sub-types were myeloid with majority being CMML (16/55; 29%) [Table 1]. Median tryptase at diagnosis in ISM patients was 41ug/L (range 3-351ug/L), while in SSM it was 494ug/L (range 174-682ug/L) and in AdvSM it was 155ug/L (range 10-1551). Most patients were positive for the KIT D816V mutation (131/192; 68%). As expected, ISM and SSM (non-AdvSM) patients had better prognosis compared to those with AdvSM [Figure 1a], with median overall survival (OS) not reached in the former and 12 months in the latter with 11-year follow-up. We next applied the IPSM score to the AdvSM cohort, with the largest proportion categorised as AdvSM-3 (25/55; 45%) while 10/55 (18%) were AdvSM-4 [Table 1]. Survival outcome was notably higher in the AdvSM-1 group (4/55; 7%) with no deaths recorded, while 6/25 (24%) and 4/10 (40%) deaths were reported in AdvSM-3 and AdvSM-4 groups respectively [Figure 1b]. SM patients are known to carry somatic mutations in addition to KIT, in particular SRSF2, ASXL1 and RUNX1 (S/A/R) which are associated with adverse outcome. In our AdvSM cohort, 10/55 (18%) of patients were positive for one of these mutations on NGS-based myeloid gene panel and 8/55 (15%) carried ≥2. Additional clinically significant mutations are summarised in Table 1. We next examined the MARS score; most of our AdvSM patients categorised as low-risk (28/55, 51%), 21/55 (38%) were intermediate-risk and 6/55 (13%) high-risk [Table 1]. Survival outcome as expected in the low-risk group was higher compared to the intermediate- and high-risk groups, with 10-year OS of 87% versus 35% and 30% respectively [Figure 1c]. On reviewing our AdvSM cohort, 6/55 (11%) had progressive disease: 5 transforming to acute myeloid leukaemia (AML) and 1 to mast cell leukaemia (MCL). Interestingly, when reviewing cause of death, the highest proportion were due to AHN progression (6/16; 38%) while 2/16 (13%) were from transformation to AML [Table 1]. As expected within our cohort, there was a discrepancy between the IPSM and MARS scores as the latter includes the presence of S/A/R mutations. 2 patients diagnosed with MCL in 2016 and 2019 respectively, were categorised high risk based on both scores. Both are alive to date having received the KIT inhibitor avapritinib, with one continuing on this treatment. The other progressed to AML and underwent allogeneic stem cell transplant, with ongoing complete remission. Other treatments received by our AdvSM patients are summarised in Table 1. Conclusion: Application of the IPSM and MARS prognostic scores to our data reflects findings of other groups with better outcomes seen in non-AdvSM compared to AdvSM patients. Furthermore, although our AdvSM cohort is small, the presence of adverse risk factors could be overcome through recent advances in treatments and consolidation with stem cell transplant. Hence, identification of high-risk patients using these prognostic scores can direct targeted first-line therapy and improve outcomes. Figure 1 Figure 1. Disclosures Sriskandarajah: Celgene: Speakers Bureau; Novartis: Other: Education. Green: Novartis: Other: Education. Ong: Novartis: Other: Education. Harrison: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte Corporation: Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Constellation Pharmaceuticals: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Geron: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Keros: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Galacteo: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sierra Oncology: Honoraria; AOP Orphan Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Promedior: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Grattan: Novartis: Speakers Bureau. Radia: Blueprint Medicines Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Study steering group member, Research Funding; Cogent Biosciences Incorporated: Other: Study Steering Committee; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Education events; EXPLORER and PATHFINDER studies: Other: Member of the Response Adjudication Committee.

A detailed system-level Model Predictive Control (MPC) framework is developed for use with sustainable technology systems which have either electrical or thermal load flexibility. Differently from the majority of relevant works in the literature, the proposed MPC framework includes non-ideal conversion efficiencies, flexibility in electrical/thermal loads and a detailed battery degradation model. A hybrid PV estimator based on clear-sky models and actual measurements is exploited for the photovoltaic production prediction within the MPC optimization problem. The formulated MPC problem is multi-objective, which aims to maximize the profit from energy arbitrage and minimise carbon emissions via a sustainable technology weighting factor ( λ C I ). A key novelty of the proposed approach is associated with the real-time experimental testing of the MPC framework using a microgrid consisting of an actual energy storage asset, a PV system and two buildings with electrically powered thermal loads. The experimental setup comprises a Hardware-in-the-loop (HIL) system together with a physical 240 kW 180 kWh battery energy storage system and a Real Time Digital Simulator (RTDS). Three scenarios with differing levels of flexibility in the electrical and thermal loads are considered, so as to derive consistent comparisons. When flexibility in both the electrical and thermal loads is utilised, a C O 2 reduction of up to 75 kg/day ( λ C I = 0.01) and an energy saving of up to 50 £/day ( λ C I = 0) is observed, yielding a reduction of around 10% in carbon emissions or energy consumption with respect to the base case.

Mycobacterium marinum is typically seen in patients who have a history of exposure to aquariums. We report a unique case of M. marinum that developed on the right knee following participation in a Hurricane Katrina reconstruction project. We are hopeful that this report will alert providers to elicit a thorough history and include cultures for less commonly encountered infectious agents along with routine bacterial and fungal stains and cultures when seeing patients with particular exposure histories such as this.

This paper investigates the impact of energy storage systems (ESSs) response speed on its ability to perform fast frequency support services such as the UK’s enhanced frequency response (EFR) services. The response time of a commercial Siemens SieStorage 240kVA/180kWh grid-linked battery energy storage system (BESS) is characterized and the results are used to model an emulated BESS in a representative micro-grid system using a real-time digital simulator (RTDS). The SieStorage system is also linked to the RTDS micro-grid through an Ethernet connection, forming a hardware-in-the-loop (HIL) system. Simulations and then HIL tests of the emulated BESS providing EFR to the micro-grid are conducted to investigate the impact of the communication latency, the physical power delivery time, and also the installed capacity of the BESS. The study shows that the communication latency has a much more significant impact than the physical power delivery time; for better EFR support, reducing the communication latency of a BESS could be even more effective than increasing the power capacity, which is costly.

This paper presents a method for the forecasting of the voltage and the frequency at the point of connection between a battery energy storage system installed at The University of Manchester and the local low-voltage distribution grid. The techniques are to be used in a real-time controller for optimal management of the storage system. The forecasters developed in this study use an artificial neural network (ANN)-based technique and can predict the grid quantities with two different time windows: one second and one minute ahead. The developed ANNs have been implemented in a dSPACE-based real-time controller and all forecasters show very good performance, with correlations coefficients >0.85, and mean absolute percentage errors of

Hybridizing aircraft propulsion systems through the addition of electrically driven fans and on-board battery storage has been shown in several studies to have the potential to significantly reduce aircraft fuel burn and emissions. This paper investigates how different hybrid electric aircraft (HEA) operation regimes may affect the lifetime of the battery electric storage system (ESS). Battery cycling tests emulating three widely proposed electric operation regimes -a constant power regime, a stepped power regime, and a ramped power regime- are conducted. The capacity degradation and internal dc resistance change of the cells under test are investigated. The tests show that the stepped power operation regime is better for retaining the capacity of ESS batteries; whereas the ramped power operation regime designed for maximum fuel saving tends to accelerate battery degradation most severely.

Transmission System Operators (TSOs) are obliged to maintain the system’s frequency within statutory limits. In the UK these limits are 49.5-50.5 Hz. There are two categories of frequency response services; dynamic or non-dynamic. The main dynamic frequency response services procured by National Grid plc, the UK’s TSO, are enhanced frequency response (EFR) and dynamic firm frequency response (DFR). Historical frequency data has been analysed to demonstrate that a battery energy storage system (BESS) providing either EFR narrow (±0.015 Hz deadband), or DFR low will operate for 64.7% of the time at less than 40% of its rated power, and that only 0.24 pu energy is needed to respond to all single event frequency deviations; this 0.24 pu energy suggests the battery cells must be capable of operating at approximately 4C. An algorithm has been developed to estimate the energy and power for a BESS. The inclusion of losses in the algorithm improved the accuracy of the absorbed energy from 82.54% to 98.41% when compared to data from a commercial BESS. The enhanced algorithm has then been used to show that the BESS availability during the most energy demanding day in terms of low frequency events can be maximised by starting with a state of charge (SoC) which targets the upper SoC limit, and by providing the DFR low service. When the frequency data for all of March 2018 is considered, then if the BESS is continuously operated it achieves 100% availability if the BESS provides the DFR low service, whereas the most unavailable days occur if EFR narrow is used.

We present a new strategy to optimise the energy density of supercapacitor cells, by systematically varying the amount of graphene-related additive, while mass balancing the positive and negative electrodes. The capacitance and the electrochemically stable potential window of the electrodes have been determined for several electrodes with different additive loadings by using a recently reported electrode optimisation technique. These key factors for calculating the mass balance were obtained based on the constant current charge/discharge cycling with a coin-cell-incorporated quasi-reference electrode. Then, multi-pairing of electrodes is proposed based on the maximum theoretical energy density, and optimised supercapacitor cells have been assembled. Using this strategy, these cells are shown to reach a voltage of 3.2 V within stability conditions, providing an energy density of 37.9 W h kg−1 (double the value for a symmetric non-graphene cell) and a power density of 149 kW kg−1 at 2 A g−1, using 1 M tetraethylammonium tetrafluoroborate (TEABF4) in acetonitrile as the electrolyte, placing these cells in between traditional and hybrid supercapacitors.

Circuit-level analytical models for hard-switching, soft-switching, and $dv/ dt$ -induced false turn on of SiC MOSFETs and their experimental validation are described. The models include the high-frequency parasitic components in the circuit and enable fast, accurate simulation of the switching behavior using only datasheet parameters. To increase the accuracy of models, nonlinearities in the junction capacitances of the devices are incorporated by fitting their nonlinear curves to a simple equation. The numerical solutions of the analytical models provide more accurate prediction than an LTspice simulation with a threefold reduction in the simulation time. The analytical models are evaluated at 25 °C and 125 °C. The effect of snubber capacitors on the soft-switching waveforms is explained analytically and validated experimentally, which enables the techniques to be used to evaluate future soft-switching solutions. Finally, the $dv/ dt$ -induced false turn-on conditions are predicted analytically and validated experimentally. It was observed that consideration of nonlinearities in the junction capacitances ensures accurate prediction of false turn on, and that the small shoot-through current due to false turn on can increase the switching loss by 8% for an off-state gate bias of −2 V.

To extend the operating range of the snubber assisted zero-voltage and zero-current transition dual-interleaved boost converter beyond its inherent soft-switching limit of D = 0.5, a resonant pulse transformer is proposed instead of the resonant inductor. The 1 : 2 turns ratio of the transformer ensures full discharge of the snubber capacitor at all duty ratio values to facilitate zero-voltage zero-current switching at turn on of the main switching devices. The effectiveness of the topology has been confirmed by SPICE simulation and demonstrated by a 20 kW SiC metal–oxide–semiconductor field-effect transistor converter. The prototype operated at 20 kW, 112 kHz, 320–600 V achieving 98.7% efficiency and achieved 98.2% efficiency at 6 kW. Taking the additional losses in the auxiliary circuit into account, the switching losses at 20 kW are reduced by 74% compared with hard-switching operation, representing a 54% reduction in overall losses.

Grid-connected battery energy storage systems with fast acting control are a key technology for improving power network stability and increasing the penetration of renewable generation. This paper describes two battery energy storage research facilities connected to the UK electricity grid. Their performance is detailed, along with hardware results, and a number of grid support services are demonstrated, again with results presented. The facility operated by The University of Manchester is rated at 236kVA, 180kWh, and connected to the 400V campus power network, The University of Sheffield operates a 2MVA, 1MWh facility connected to an 11kV distribution network.

A design study for a 2 MW commercial wind turbine is presented to illustrate two connection methods for a standard doubly-fed induction machine which can extend the low speed range down to 80% slip without an increase in the rating of the power electronic converter. This far exceeds the normal 30% lower limit. The low speed connection is known as induction generator mode and the machine is operated with a short circuited stator winding with all power flow being through the rotor circuit. A two loop cascaded PI control scheme has been designed and tuned for each mode. The purpose of this paper is to present simulation results which illustrate the dynamic performance of the controller for both doubly-fed induction generator connection methods for a 2 MW wind turbine. A simple analysis of the rotor voltage for the doubly-fed connection method is included as this demonstrates the dominant components that need to be considered when designing such advanced control strategies.

Analytical models for hard-switching and soft-switching SiC MOSFETs and their experimental validation are described in this paper. The models include the high frequency parasitic components in the circuit and enable very fast, accurate simulation of the switching behaviour of SiC MOSFET using only datasheet parameters. The much higher switching speed of SiC devices over Si counterparts necessitates a clear detailed analysis. Each switching transient was divided into four distinct sub-periods and their respective equivalent circuits were solved to approximate the circuit state variables. Nonlinearities in the junction capacitances of SiC devices were considered in the model. Analytical modelling results were close to the LTspice simulation results with a threefold reduction in the simulation time. The effect of snubber capacitors on the soft-switching waveforms is also explained analytically and validated experimentally, which enables the analytical model to be used to evaluate future soft-switching solutions. It was found that the snubber branch can significantly reduce the turn off ringing of the SiC MOSFET in addition to the reduction of switching losses.

An adaptive energy management control with an integrated variable rate-limit function is described for an energy storage system (ESS). The proposed control protects the primary power source(s) in the system as effectively as possible from sudden load transients within the constraints of the available stored energy. The control can be designed to use the available energy more aggressively during load changes in the low or high power regions while offering the lowest possible rate-of-change of main source power, or offer a fixed minimum rate-of-change in power for a given total load and amount of energy. The control design is described in detail and demonstrated experimentally when applied to a super-capacitor energy storage system within an aircraft test facility.

A DC-DC converter topology is presented combining the soft switching effects of the Snubber Assisted Zero Voltage and Zero Current Transition (SAZZ) topology and the increased inductor frequency of the dual interleaved boost converter with interphase transformer. The snubber capacitors and output capacitances of the main devices are discharged prior to turn on using a single auxiliary inductor, eliminating turn on losses. Furthermore, the turn off losses are significantly reduced since the energy stored in the device output capacitance at turn off is recovered at turn on. The effectiveness of the topology is demonstrated on a SiC prototype operating at 12.5 kW, 112 kHz, reducing the switching losses by 50%.

A system compensator is designed to cancel the mechanical characteristics of a power electronics-controlled induction motor drive with a coupled electrical generator system. The emulation scheme using the compensator enables accurate emulation of high-speed and high-power mechanical system dynamics. The compensator is developed based on the system transient response of the test rig, considering the full operating range of the test system. The design process of the compensator is described, and it is validated in both the time and frequency domains. Finally, the effectiveness of the compensator is demonstrated by simulation and experimental emulation of aero gas engine dynamics.

A system-level modelling technique for a switched reluctance generator (SRG) is described for aerospace applications. Unlike existing techniques, this model is very simple and only reproduces the average behaviour of the input-output variables that are required for system-level analysis of the aircraft power distribution system. The model is parameterised from the measured generator response, avoiding the need for a detailed knowledge of the equipment structure, which may be unavailable. The modelling procedure is described in detail and validated by measurements on a switched reluctance generator within an aircraft test facility.

High-voltage DC-bus power quality is examined when the power network is supplied by a PWM rectifier controlled using different DC-bus voltage regulation schemes. Three controllers are compared, a voltage oriented control and two model predictive control schemes, predictive current fixed frequency and predictive direct power control. A set of PWM rectifier simulation models illustrate the performance of the controllers; a switched model, an ideal averaged-value model and an enhanced averaged-value model which contains the key loss mechanisms. The DC-bus transients are within the limits defined in MIL-STD-704F only when a predictive direct power control is employed.

A system-level behavioural modelling technique is described for a switched reluctance motor drive (SRMD). The model enables simple and efficient analysis or simulation of multiple drive systems such as pumps, actuators and engine starters within a more-electric network for example on-board an aircraft. The behavioural model is based on a power balance analysis. The transfer functions in the model are parameterised from experimental tests on the drive system, resulting in a simple model that only reproduces the average behaviour of the input-output variables necessary for system-level analysis. No data from the manufacturer is required to develop the model. The technique is discussed and validated using an engine starter in an aircraft test facility.

An intelligent agents based platform is presented which offers an instantaneous, automatic decision-making capability, enabling the execution of complex system level power management and mission planning/re-planning tasks on board a UAV. The agents platform is integrated with a 100 kW, aircraft power systems experimental test facility to demonstrate the response of the entire system to vignette- based mission events which are triggered both by the test hardware, such as electrical drive faults, and emulated events, such as a fuel shortage. (6 pages)

Higher-voltage, 540V, aircraft DC-bus power quality is examined experimentally and by computer simulation during a short-circuit fault across the phase terminals of a 70kW, 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. © 2011 The Institution of Engineering and Technology.

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 70kW generator and 30kW programmable load emulation devices.

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.

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.

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. © 2011 © The Institution of Engineering and Technology.

Future transportation systems for aircraft, vehicles or marine vessels are all candidates for redesigned propulsion systems as a result of the more-electric revolution. Accurately emulating these new propulsion system designs to assess the dynamic engine-generator-electrical system interactions will be an invaluable design tool. A HIL mechanical emulation system is presented which utilises a novel compensator design to extend the emulation capability of a physical hardware system without the need for any hardware changes. A 30 kW test system is used to emulate variable inertia mechanical systems and drivetrain models to show the capability of a single test system to be used to emulate a wide range of systems. The compensator is not restricted to transport applications and will also improve the emulation of smart grid sources and advanced renewable sources.

An energy management controller based on multiple charge/discharge profiles is proposed and analysed for an energy storage system. Each profile is designed to use the available energy more aggressively in different power regions, including the low or the high power regions, or both regions to minimise the rate-of-change of power source output. The performance of the energy storage system with the profiles is examined by simulation when connected to an aircraft 540V DC bus with a fault-tolerant starter/generator and high power, pulsed loads.

There is a growing need for highly efficient, power dense DC-AC converters to support a number of future more electric aircraft technologies. SiC has been identified as a potential technology to improve the efficiency of these converters. To analyse the semiconductor losses, this paper presents the semiconductor loss equations for the two-level converter (2LC), three-level neutral point clamped converter (3LNPCC) and the three-level T-Type converter (3LTTC). Based on the equations and current datasheet information, it is identified that SiC technology offers significant reductions in losses compared with traditional Si devices. The paper also discusses a number of hybrid device combinations to achieve the benefits of high efficiency in SiC technology and low cost of Si technology. Based on the semiconductor losses the converter efficiencies in the SiC 2LC and the 3LTTCs are about 3-4 % higher than in the Si 2LC for a 42 kW three phase converter operating at a 25 kHz switching frequency.