Abstract-The supply of electrical power is usually achieved by a generator, driven from a prime mover, by some form of mechanical drivetrain. Such an electro-mechanical system will have natural resonant modes in both the electrical and mechanical subsystems. The electrical generator provides a coupling between the subsystems, transferring not only useful power but also disturbances between electrical and mechanical domains: these disturbances may excite resonances resulting in cross-domain (electro-mechanical) interaction. This can lead to lifetime reduction in the mechanical components and instability in the electrical network, resulting in poor reliability for the wider system, and potentially catastrophic component failure. Electro-mechanical interaction is particularly critical in power generation systems onboard aircraft, because the generator is driven by a gas turbine via an inherently low-stiffness drive train. It is then critical to identify electro-mechanical interaction at the design stage so that these issues can be avoided. However, predicting the occurrence of interaction, through simulation, is challenging, requiring multi-domain models, operating with different time scales. This paper analyses an aircraft auxiliary power offtake to produce a reduced-order mechanical drivetrain model, allowing the modal frequencies to be predicted and crossdomain interactions to be modelled. A purpose-built electromechanical test platform is used to validate the model and demonstrate how electrical disturbances are passed through the generator to the mechanical system and affect the electrical network. Future research will use the test bed to demonstrate strategies for avoiding or suppressing unwanted interactions.

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.

Modern aircraft require a robust and reliable supply of electrical power to drive a growing number of high power electrical loads. Generators are driven by a mechanical offtake from the variable speed gas turbine, while a constant frequency AC network is preferred. Here doubly-fed induction machines are advantageous since they can be controlled, through a fractionally rated converter, to decouple electrical frequency from the mechanical drive speed, making control of the network frequency possible. However, the converter must be suitably rated, according to drive speed range, electrical voltage and frequency regulation, and power requirements. This paper develops and validates a simulation model of the doubly-fed induction generator system, which is applied to find the power flow through the machine's stator and rotor connections over a wide mechanical speed range in order to size the converter. A field orientated control scheme is implemented, to provide standalone voltage and frequency regulation across a drive range of ±40% synchronous speed, on a purpose-built 6.6kW hardware test platform. Based on the mechanical speed range of an aero gas turbine and the identified converter sizing, the suitability of a doubly-fed induction generator for aero applications is appraised. It is shown that a converter rated at 18% of full system rating can be used to meet the aircraft electrical specifications, and offer a potential improvement in aircraft performance, with no additional mechanical components.

I. INTRODUCTIONLECTRICAL machines are essentially wound components for modern industrial systems. During operation, the insulation materials in electrical machines are exposed to thermal stresses. These thermal stresses initiate progressive degradation of the insulation materials, which lead to the deterioration of the insulation characteristics and consequently to insulation breakdown [1]. Therefore, knowledge relating to the condition of the insulation systems and an estimation of the remaining life has become an important concern to manufacturers and users of electrical systems [2]. Real-Time lifetime prediction of insulation materials is of interest in this work. Severe winding insulation breakdown due to thermal stresses have been reported as contributing to as much as 30-40% of all stator winding failures in conventional induction machines [3]. It was also reported in [4][5][6] that thermal ageing is the dominant ageing factor and can contribute up to ≈31% of the deterioration of the insulation materials.The lifespan of the insulation is usually predicted using accelerated ageing tests. An accelerated ageing test is used in the effort to obtain failure statistics in shorter timescales. In [2,7], the lifetime of the insulation material was estimated using an electro-thermal ageing model that takes into account the combined electrical and thermal stresses in the lifetime prediction. Real-time insulation lifetime predictions during steady-state and transient operating conditions of wound components have received less attention in the available literature.The thermal ageing model based on the classical Arrhenius relationship can be adapted for real-time steadystate and transient thermal ageing predictions of the insulation materials for wound components. The key input to the insulation lifetime model is the measured temperature distribution around the winding insulation.Winding temperatures are conventionally sensed using thermocouples or resistance temperature detectors embedded on the exposed external surfaces of the electrical machine and/or windings [8]. These techniques commonly provide single-point temperature measurements that are often unreliable [8]. Moreover, these sensors come with significant challenges imposed by the location of the sensors close to or within the stator windings for example due to use of electrically conductive materials in the sensor packages as well as susceptibility to electromagnetic interference [8]. The key objective in this work is to access the capability of predicting real-time remaining life of wound components insulation materials using Fibre Bragg Grating (FBG) sensors embedded directly into the stator coils during fabrication. The FBG sensors are fibre-optic sensors that have been used in other applications, ranging from frame vibration sensing of the stator core and coil surface thermal monitoring [9][10][11][12]. The FBG sensors are small and can be laid into the middle of the coils during the wind process and can provide real-time temperature information at several...

The purpose of this study was to investigate the effects of prolonged high-intensity running on impact accelerations in trained runners. Thirteen male distance runners completed two 20-minute treadmill runs at speeds corresponding to 95% of onset of blood lactate accumulation. Leg and head accelerations were collected for 20 s every fourth minute. Rating of perceived exertion (RPE) scores were recorded during the third and last minute of each run. RPE responses increased (P < .001) from the start (11.8 ± 0.9, moderate intensity) of the first run to the end (17.7 ± 1.5, very hard) of the second run. Runners maintained their leg impact acceleration, impact attenuation, stride length, and stride frequency characteristics with prolonged run duration. However, a small (0.11–0.14g) but significant increase (P < .001) in head impact accelerations were observed at the end of both first and second runs. It was concluded that trained runners are able to control leg impact accelerations during sustained high-intensity running. Alongside the substantial increases in perceived exertion levels, running mechanics and frequency domain impact attenuation levels remained constant. This suggests that the present trained runners are able to cope from a mechanical perspective despite an increased physiological demand.

Modern aircraft require a robust and reliable supply of electrical power to drive a growing number of high power electrical loads. Generators are driven by a mechanical offtake from the variable speed gas turbine, while a constant frequency AC network is preferred. Here doubly-fed induction machines are advantageous since they can be controlled, through a fractionally rated converter, to decouple electrical frequency from the mechanical drive speed, making control of the network frequency possible. However, the converter must be suitably rated, according to drive speed range, electrical voltage and frequency regulation, and power requirements. This paper develops and validates a simulation model of the doubly-fed induction generator system, which is applied to find the power flow through the machine's stator and rotor connections over a wide mechanical speed range in order to size the converter. A field orientated control scheme is implemented, to provide standalone voltage and frequency regulation across a drive range of ±40% synchronous speed, on a purpose-built 6.6kW hardware test platform. Based on the mechanical speed range of an aero gas turbine and the identified converter sizing, the suitability of a doubly-fed induction generator for aero applications is appraised. It is shown that a converter rated at 18% of full system rating can be used to meet the aircraft electrical specifications, and offer a potential improvement in aircraft performance, with no additional mechanical components.

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