Burner liner thermal/structural load modelling

A serious problem exists interfacing the output temperatures and temperature gradients from either the heat transfer codes or engine tests with the input to stress analysis codes. A thermal load transfer code was developed and was used in conjunction with a three-dimensional model of a combustor liner for verification. The 3D heat transfer and stress analysis models of combustor liners and turbine blades were used to validate the mapped temperature produced by the transfer module. Verification cases were made for both finite element and finite difference heat transfer codes. A user manual for the code was written and is available

Dynamic Load Modelling Using Real Time Estimated States

Dynamic load models are necessary for accurate monitoring and control of the system during various events as well as for better understanding the behavior and the characteristics of the system. In this paper, a realistic approach of load modelling using real time estimated states is studied. Since Phasor Measurement Units (PMUs) are not installed yet at every bus, a linear state estimator is used to provide the state of the buses without PMUs. The overall impact of the real time estimated states and the inaccurate load model parameters are studied on the IEEE 39-bus dynamic test system. In addition, the realistic approach of load modelling is enhanced by using various load types while errors that affect the estimated states, such as line parameter errors and measurement gross errors are also considered. Furthermore, a sensitivity analysis with inaccurate load model parameters is performed to show their effect on the results of load modelling

Low-complexity energy disaggregation using appliance load modelling

Large-scale smart metering deployments and energy saving targets across the world have ignited renewed interest in residential non-intrusive appliance load monitoring (NALM), that is, disaggregating total household's energy consumption down to individual appliances, using purely analytical tools. Despite increased research efforts, NALM techniques that can disaggregate power loads at low sampling rates are still not accurate and/or practical enough, requiring substantial customer input and long training periods. In this paper, we address these challenges via a practical low-complexity low-rate NALM, by proposing two approaches based on a combination of the following machine learning techniques: k-means clustering and Support Vector Machine, exploiting their strengths and addressing their individual weaknesses. The first proposed supervised approach is a low-complexity method that requires very short training period and is {fairly accurate even in the presence of} labelling errors. The second approach relies on a database of appliance signatures that we designed using publicly available datasets. The database compactly represents over 200 appliances using statistical modelling of measured active power. Experimental results on three datasets from US, Italy, Austria and UK, demonstrate the reliability and practicality

Decomposition of aggregated load: finding induction motor fraction in real load

The main contribution of this paper is decomposition/separation of the compositie induction motors load from measurement at a system bus. In power system transmission buses load is represented by static and dynamic loads. The induction motor is considered as the main dynamic loads and in the practice for major transmission buses there will be many and various induction motors contributing. Particularly at an industrial bus most of the load is dynamic types. Rather than traing to extract models of many machines this paper seeks to identify three groups of induction motors to represent the dynamic loads. Three groups of induction motors used to characterize the load. These are the small groups (4kw to 11kw), the medium groups (15kw to 180kw) and the large groups (above 630kw). At first these groups with different percentage contribution of each group is composite. After that from the composite models, each motor percentage contribution is decomposed by using the least square algorithms. In power system commercial and the residential buses static loads percentage is higher than the dynamic loads percentage. To apply this theory to other types of buses such as residential and commerical it is good practice to represent the total load as a combination of composite motor loads, constant impedence loads and constant power loads. To validate the theory, the 24hrs of Sydney West data is decomposed according to the three groups of motor models

Internal load modelling of tapered-roller main bearings in wind turbines

The replacement of double-row spherical roller bearings with double-row tapered roller bearings as the main shaft support in wind turbines has been proposed as one of the solutions to the premature failures affecting the industry. In order to improve our scientific knowledge of tapered roller bearing loading in wind turbine main shafts, this thesis sets out to explore how these components may be modelled, how such models can be utilised to improve the understanding of their operational characteristics in relation to the inflow wind, and to compare their behaviour with that of spherical roller bearings. Novel drivetrain models with tapered roller main bearings are developed in this thesis with capabilities of evaluating internal component loading while accounting for variations in system sti↵ness at different operating points. The findings demonstrate that modelling the moment reaction behaviour of tapered-roller bearings is crucial for even simplistic representations, since moment loads at the wind turbine hub are key drivers of bearing displacement. The models developed here are used in an extensive analysis to determine characteristics and sensitivities regarding operational conditions experienced by double-row tapered roller bearings under realistic turbulent inflow conditions, while properly accounting for the system load-response behaviour, roller load distributions and impacts on bearing fatigue life ratings. The presence of “looped” loading structures and evidence of consistent roller edge-loading throughout normal operation is demonstrated, and load response was also found to be largely shared between the two roller rows, this contrasts strongly with the conditions known to hold for spherical-roller main bearings. High levels of fatigue life sensitivity to both operational and lubrication conditions are documented, and shear effects in the wind were found to have opposite effects depending on the bearing type in use, with increased shear exponents drastically reducing the fatigue life rating of the tapered roller bearing. Crucially, this work demonstrates the uniqueness of load conditions experienced by tapered roller bearings in wind turbines, indicating that experience developed in more conventional rolling bearing applications should not be reapplied blindly without first determining its validity in this application space.The replacement of double-row spherical roller bearings with double-row tapered roller bearings as the main shaft support in wind turbines has been proposed as one of the solutions to the premature failures affecting the industry. In order to improve our scientific knowledge of tapered roller bearing loading in wind turbine main shafts, this thesis sets out to explore how these components may be modelled, how such models can be utilised to improve the understanding of their operational characteristics in relation to the inflow wind, and to compare their behaviour with that of spherical roller bearings. Novel drivetrain models with tapered roller main bearings are developed in this thesis with capabilities of evaluating internal component loading while accounting for variations in system sti↵ness at different operating points. The findings demonstrate that modelling the moment reaction behaviour of tapered-roller bearings is crucial for even simplistic representations, since moment loads at the wind turbine hub are key drivers of bearing displacement. The models developed here are used in an extensive analysis to determine characteristics and sensitivities regarding operational conditions experienced by double-row tapered roller bearings under realistic turbulent inflow conditions, while properly accounting for the system load-response behaviour, roller load distributions and impacts on bearing fatigue life ratings. The presence of “looped” loading structures and evidence of consistent roller edge-loading throughout normal operation is demonstrated, and load response was also found to be largely shared between the two roller rows, this contrasts strongly with the conditions known to hold for spherical-roller main bearings. High levels of fatigue life sensitivity to both operational and lubrication conditions are documented, and shear effects in the wind were found to have opposite effects depending on the bearing type in use, with increased shear exponents drastically reducing the fatigue life rating of the tapered roller bearing. Crucially, this work demonstrates the uniqueness of load conditions experienced by tapered roller bearings in wind turbines, indicating that experience developed in more conventional rolling bearing applications should not be reapplied blindly without first determining its validity in this application space

Seasonal variation in household electricity demand: A comparison of monitored and synthetic daily load profiles

Abstract This paper examines seasonal variation in household electricity demand through analysis of two sets of half-hourly electricity demand data: a monitored dataset gathered from 58 English households between July and December 2011; and a synthetic dataset generated using a time-of-use-based load modelling tool. Analysis of variance (ANOVA) tests were used to identify statistically significant between-months differences in four metrics describing the shape of household-level daily load profiles: mean electrical load; peak load; load factor; and timing of peak load. For the monitored dataset, all four metrics exhibited significant monthly variation. With the exception of peak load time, significant between-months differences were also present for all metrics calculated for the synthetic dataset. However, monthly variability was generally under-represented in the synthetic data, and the predicted between-months differences in load factors and peak load timing were inconsistent with those exhibited by the monitored data. The study demonstrates that the shapes of household daily electrical load profiles can vary significantly between months, and that limited treatment of seasonal variation in load modelling can lead to inaccurate predictions of its effects

Modelling of 3-Phase p-q Theory-Based Dynamic Load for Real-Time Simulation

This article proposes a new method of modelling dynamic loads based on instantaneous p-q theory, to be employed in large powers system network simulations in a digital real-time environment. Due to the use of computationally heavy blocks such as phase-locked-loop (PLL), mean calculation,and coordinate transformation blocks (e.g., abc–dq0), real-time simulation of large networks with dynamic loads can be challenging. In order to decrease the computational burden associated to the dynamic load modelling, a p-q theory-based approach for load modelling is proposed in this paper. This approach is based on the well-known p-q instantaneous theory developed for power electronics converters, and it consists only of linear controllers and of a minimal usage of control loops, reducing the required computational power. This improves real-time performance and allows larger scale simulations. The introduced p-q theory-based load (PQL) model has been tested on standard networks implemented in a digital real time simulator, such as the SimBench semi-urban medium voltage network and the 118-bus Distribution System, showing significant improvement in terms of computational capability with respect to standard load models (e.g., MATLAB/Simulink dynamic load)