Database management for high resolution condition monitoring of wind turbines

Wind turbine condition monitoring (CM) is an area of research which has been receiving a large amount of attention in the recent years. This has been influenced mainly by the recent uptake of wind farms being installed around the country. Operational and maintenance expertise in the area of wind turbine CM is therefore seen to be of growing importance but is yet to be well established in the industry due to its unverified economic benefits. The majority of the research which can be found in the literature has been based on simulation or test rig data, often due to the lack of availability of extensive historical data sets containing 'interesting' events, as well as the difficulties associated in gaining access to such data, due to its commercially sensitive nature. It can not be readily claimed, nor shown that laboratory based testing or simulations actually reflect real turbine operation, due to scaling, control and dynamic considerations. In order that different patterns of machine deterioration can be determined and detected in their incipient stages, precise high resolution data, of existing monitored parameters, should be sampled at frequencies higher than that is typically available in the integrated SCADA systems installed in most modern turbines today. This paper reports the design of a data acquisition platform which will be mounted on a 660 kW VESTAS V47 wind turbine. Details of the monitoring equipment used, the installation requirements as well as the system architecture will be presented and discussed

Fuel cells for power generation and organic waste treatment on the island of Mull

In-situ use of biomass and organic waste streams have the potential to provide the key to energy self sustainability for islands and remote communities. Traditionally biogas fuels have been used in combustion engines for electric power generation. However, fuel cells offer the prospect of achieving higher generating efficiencies, and additionally, important environmental benefits can be achieved by way of mitigating greenhouse gas emissions, whilst providing a carbon sink. This paper presents the design details of a biogas gas plant and fuel cell installation that will provide a practical solution on an island (and be applicable in other remote and rural areas) where connection to the grid can be expensive, and where biofuels can be produced on site at no significant extra cost

An investment led approach to analysing the hydrogen energy economy in the UK

The authors propose an alternative, investment-led approach to analysing the potential for the development of hydrogen energy in the UK

Dynamic model of a lead-acid battery for use in a domestic fuel cell system

This paper presents a review of existing dynamic electrical battery models and subsequently describes a new mathematical model of a lead acid battery, using a non-linear function for the maximum available energy related to the battery discharge rate. The battery state of charge (SOC) is expressed in a look-up table relative to the battery open circuit voltage (VOC). This look-up table has been developed through low discharge experiments of the battery modelled. Further, both the internal resistance and self-discharge resistance of the battery are subsequently expressed as functions of the open circuit voltage. By using an electrical model with these characteristics and a temperature compensation element to model different rates of charge and discharge, a relatively simple and accurate battery model has been developed. The new model takes into account battery storage capacity, internal resistance, self-discharge resistance, the electric losses and the temperature dependence of a lead acid battery. It is shown in this paper how the necessary parameters for the model were found. The battery modelled was a Hawker Genesis 42 Ah rated gelled lead acid battery. The simulation results of the new model are compared with test data recorded from battery discharge tests, which validate the accuracy of the new model

The effects of AC current on supercapacitor performance

Supercapacitor impedance spectra were found using AC currents for two types of supercapacitor: one containing a carbon aerogel and having a capacitance of 10 F and a maximum voltage of 2.5 V, and one containing activated carbon and an organic electrolyte and having a capacitance of 10 F and a maximum voltage of 2.3 V. Particular attention was paid to the region between 100 Hz and 100 kHz. This data was corrected by subtracting the impedance of the cables connecting the supercapacitor to the measurement hardware. The supercapacitor impedance was also measured using currents with both DC and AC components. The lowest impedance, and therefore the most efficient operating point, was found to be 10 kHz. This work has helped to identify an optimal working frequency for a power electronic converter to utilize a supercapacitor pack in an electric vehicle application

Electronic differential with sliding mode controller for a direct wheel drive electric vehicle

Traction drives used in electric vehicles can be divided into two categories, (i) single drive systems, and (ii) multi-drive systems. With multi-drive systems the motor controllers must additionally be configured to provide an electronic differential effect i.e. they must also perform a similar function as their mechanical differential counterpart. Thus the electronic differential must take account of the speed difference between the two wheels when cornering. This paper presents a design for an electronic differential utilising a sliding mode controller employing a 4-switch 3-phase inverter. This type of inverter is particularly suitable for this application as the supply batteries can be easily split into two separate battery strings. The system is evaluated on a test vehicle in which the rear wheels are directly driven by permanent magnet brushless motors. Results indicate that this arrangement can be successfully implemented into an electric vehicle drive train

Experimental testing and model validation of a small scale generator set for voltage and frequency stability analysis

The integration of numerous small-scale generators into existing power systems is anticipated to impact the operation, control and protection of such systems. In particular, maintaining voltage and frequency stability within defined limits is more onerous and requires investigation. The effect of protective limiters and characteristics such as the genuine inertia of the generation set must be taken into consideration in planning studies in order to accurately represent the overall dynamic characteristics of distributed generators. This paper focuses on the investigation of these issues by studying a small-scale reciprocating engine/generator set. The experimental procedures used to determine the genuine inertia of the test rig are described, and the influence and importance of considering the action of protective limiters such as voltage-per-hertz (V/Hz) in stability studies is demonstrated. This work is directly relevant to the review of current UK stability limits, and to the generation planning framework supported by the Scottish Executive

Development of a small-scale generator set model for local network voltage and frequency stability analysis

The integration of numerous small-scale generators into existing local networks (e.g., a microgrid) is anticipated to impact their operation, control, and protection. In particular, maintaining voltage and frequency stability within the defined limits is more onerous and requires investigation. The effect of protective limiters and characteristics such as the genuine inertia of the generation set must be taken into consideration in stability studies in order to accurately represent the overall dynamic characteristics of local distributed generators. This paper focuses on three fundamental aspects: 1) the development of a reciprocating engine/generator set model; 2) the laboratory testing of an experimental test rig; and 3) the influence of a volts-per-hertz ratio (volts-per-hertz ratio) limiter on the generator dynamic response. The experimental procedures used to determine the genuine inertia of the test rig are described and the system responses under different scenarios are used to validate the developed model. This emphasizes the significance of excitation protective limiters such as volts-per-hertz ratio, during the stability analysis

Control and mechanical component reduction in an EV direct wheel drive

This paper looks at control and mechanical component reduction in an EV direct wheel driv

The impact of energy storage devices used in conjunction with renewable embedded generators on the protection and control system

This paper has described the drivers and background to the development of renewable energy in the UK. Within this context the authors identified the New Electricity Trading Arrangements (NETA) as a potential risk to the continuing development of renewable generation and proposed the use of an energy storage system (ESS) as a mechanism to alleviate these concerns. An initial study has concluded that the use of a hybrid ESS/wind farm under the NETA conditions would result in an increase in operating revenue. However preliminary protection investigations have highlighted concerns over appropriate control and protection under the particular scenarios of a change in operating mode from load (i.e. as an electrolyser) to a generator (i.e. to a fuel cell) and vice versa. Work is continuing to produce more detailed modelling results of such a system. It is believed this work will have relevance to the wider spread study of the application of ESS devices in general, for example for use as large scale devices to ensure network security in a power system with high penetrations of local, small-scale embedded generatio