P.J. Tavner

Durham University | DU · Department of Engineering

This paper presents a method to estimate the BDFM equivalent circuit rotor current from rotor bar current measurements. Rotor currents are measured using a specially designed hardware that incorporates Rogowski coils and Bluetooth wireless transmission. The measurement of rotor currents enables the parameters in the BDFM's full equivalent circuit t...

Solder degradation is still a main failure mechanism for power semiconductor modules. This study proposes a monitoring method to detect the relative change in heat dissipation from a module in two opposing directions, affected by the degradation—upward via the silicone gel and downward via the solder layer to the heatsink. The method is based on ex...

Abstract A simple method is proposed here to improve the gap loss concentration problem of a nanocrystalline core in an LCL filter inductor for high switching frequency converters using SiC devices. This alloy‐gapped inductor design aims to reach two primary goals. First, to reduce the concentrated gap loss in a nanocrystalline core. Second, decrea...

Current climate change concerns accelerate interest in developing reliable renewable energy sources. Two of the most significant, in the wind and sea, are subject to turbulence, where its mathematics are at the forefront and the topic of this Conference.

Maintenance is essential in keeping wind energy assets operating efficiently. With the development of advanced condition monitoring, diagnostics and prognostics, condition‐based maintenance has attracted much attention in the offshore wind industry in recent years. This paper models various maintenance activities and their impacts on the degradatio...

Wind turbine technologies are evolving rapidly in terms of complexity and size and there is an urgent need for cost-effective Operations and Maintenance (O&M) strategies to increase the profitability of wind power assets. Component reliability as well as maintenance strategies have the greatest effect on O&M planning and costs, especially in offsho...

Power semiconductor chips are paralleled in modules to increase current rating. Under thermo-mechanical stresses in service, the die-attach solder layers will gradually develop into different levels of degradation. Early fault detection requires to monitor the occurrence of such an uneven degradation pattern. Internal temperature differences only s...

Virtual energy storage systems (VESS) are important new equipment for distribution networks, consisting of battery energy storage systems (BESS) or flexible loads (FL), that improve peak shaving, frequency regulation and energy management. This paper focuses on power management and real-time control for multiple virtual energy storage systems (MVES...

This paper proposes a review-based comparative study addressing the critical issue of tidal stream turbine drivetrain options. Indeed, tidal stream turbines are still in development stages with few industrial project deployments. Their technology is not as mature as wind turbine technology, while facing immersion constraints where have to withstand...

Tidal turbine technology is not as mature as wind turbine technology; in addition tidal turbines are submerged systems. Therefore, they have to withstand high loading and harsh submarine conditions. To make tidal energy competitive compared to the other renewable sources, many challenges need to be overcome. The drivetrain configuration choice is o...

This is an oral presentation for the 2018 IEEE PEC 2018.

In MW-sized wind turbines, the most widely-used generator is the wound rotor induction machine, with a partially-rated voltage source converter connected to the rotor. This generator is a significant cause of wind turbine fault modes. In this paper, a harmonic time-stepped generator model is applied to derive wound rotor induction generator electri...

The reliability of modern onshore wind turbines is at present at an acceptable level. This means that, assuming 100 % site accessibility and implementing a well-organised efficient maintenance strategy, most onshore wind turbines show availability levels of above 98 %. In other words the yearly downtime due to service and repair is less than 1 week...

The European Academy of Wind Energy (eawe), representing universities and institutes with a significant wind energy programme in 14 countries, has discussed the long-term research challenges in wind energy. In contrast to research agendas addressing short- to medium-term research activities, this eawe document takes a longer-term perspective, addre...

This chapter will outline the major power electronic architectures that have been used in WTs and then discuss the reliability of those innovations. This is particularly important for the growing number of offshore WTs, where early information is suggesting that the significant power electronic failure rates are causing increased downtimes because...

The time-varying operational conditions applied to wind turbines (WTs) not only challenge their operation but also make condition monitoring (CM) difficult. To achieve a reliable CM result, more advanced signal processing techniques, rather than the conventional spectral analyses, are urgently needed for interpreting the nonlinear and nonstationary...

This study investigates the probabilistic risk of gear tooth flank micro-pitting in wind turbine (WT) gearboxes and shows how relatively slow rate of supervisory control and data acquisition (SCADA) data, recorded during operation, can be used to analyse the onset of gear surface damage. Field measured time series of SCADA signals, including wind s...

Current wind turbine (WT) studies focus on improving their reliability and reducing the cost of energy, particularly when WTs are operated offshore. A supervisory control and data acquisition (SCADA) system is a standard installation on larger WTs, monitoring all major WT sub-assemblies and providing important information. Ideally, a WT's health co...

Abstract—The brushless doubly fed induction generator has been proposed for use in wind turbines as a more reliable alternative to the more commonly used doubly fed induction generator. To realize the commercial promises of the brushless doubly fed induction generator in this role, it must meet the existing grid connection codes, particularly with...

The brushless doubly fed machine (BDFM) is an alternative to the doubly fed induction generator, widely used in wind turbines without use of brush gear and slip ring. Rotor design is important for achieving an optimal multi-MW BDFM. To date, nested-loop rotors have been exclusively used in various BDFMs, although they may not be ideal for larger ma...

This study presents a new technique for detecting rotor electrical faults in wind turbine doubly-fed induction generators (DFIGs), controlled by a stator field-oriented vector control scheme. This is a novel method aimed at detecting and identifying rotor electrical asymmetry faults from within the rotor-side inverter control loop, using the error...

Improving the reliability of wind turbines (WT) is an essential component in the bid to minimize the cost of energy, especially for offshore wind because of the difficulties associated with access for maintenance. Numerous studies have shown that WT gearbox and generator failure rates are unacceptably high, particularly given the long downtime incu...

Deployment of larger scale wind turbine systems, particularly offshore, requires more organized operation and maintenance strategies to ensure systems are safe, profitable and cost-effective. Among existing maintenance strategies, reliability centred maintenance is regarded as best for offshore wind turbines, delivering corrective and proactive (i....

Improving the availability of wind turbines is critical for minimising the cost of wind energy, especially offshore. The development of reliable and cost-effective gearbox condition monitoring systems (CMSs) is of concern to the wind industry, because the gearbox downtime has a significant effect on the wind turbine availabilities. Timely detection...

Previous wind turbine condition monitoring work identified signals and methods for wind turbine fault detection. This paper concentrates on raising sensitivity so that high reliability is achieved. This is done by adopting techniques of earlier papers but aggregating them in Side Band and Harmonic Power Factor algorithms that can be applied remotel...

Increasing deployment of large wind turbines (WT) offshore and in remote areas requires reliable condition monitoring (CM) techniques to guarantee the high availability of these WTs and economic return. To meet this need, much effort has been expended to improve the capability of analysing the WT CM signals. However, a fully satisfactory technique...

Wind turbine condition monitoring is gaining in importance as operators and developers move towards larger, further offshore, less accessible wind farms. However, condition monitoring is made highly challenging by the variable speed, variable load nature of wind turbines. Electrical faults, in the form of brush gear or slip ring damage contribute s...

The fast growing wind industry has shown a need for more sophisticated fault prognosis analysis in the critical and high value components of a wind turbine (WT). Current WT studies focus on improving their reliability and reducing the cost of energy, particularly when WTs are operated offshore. WT Supervisory Control and Data Acquisition (SCADA) sy...

This study presents the performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator (DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and show the system's steady-state and dynamic performance and grid low-voltage ride-through capability. The medium-sp...

Increasing the availability of multi-megawatt wind turbines (WT) is necessary if the cost of energy generated by wind is to be reduced. It has been found that WT generator bearings have a surprisingly high failure rate, with failures happening too early to be due to classical rolling contact fatigue. One potentially important root cause of bearings...

The brushless doubly fed machine (BDFM) is a robust alternative to the doubly fed induction generator, currently widely used in wind turbines but prone to brush-gear and slip-ring failure. The rotor winding plays an important part in a BDFM, coupling the two stator windings. To date, nested-loop (NL) rotor windings have been exclusively used in pra...

Induction generators have been successfully applied to a variety of industries. However, their operation and maintenance in renewable wind and marine energy industries still face challenges due to harsh environments, limited access to site and relevant reliability issues. Hence, further enhancing their condition monitoring is regarded as one of the...

Concerns amongst wind turbine (WT) operators about gearbox reliability arise from complex repair procedures, high replacement costs and long downtimes leading to revenue losses. Therefore, reliable monitoring for the detection, diagnosis and prediction of such faults are of great concerns to the wind industry. Monitoring of WT gearboxes has gained...

Rapid wind power development in China has attracted worldwide attention. The huge market potential and fast development of wind turbine manufacturing capacity are making China a world leader in wind power development. In 2010, with the newly installed wind power capacity and the cumulative installed capacity, China was ranked first in the world. In...

The process of information systems development (ISD) has been studied before to enhance generated information systems. It has been recognised recently that the use of knowledge management (KM) methodologies in ISD, so-called knowledge-based information systems (KIS), supports the acquisition and representation of knowledge, both from application do...

In this study a steady-state equivalent circuit for a brushless doubly fed machine (BDFM), based upon earlier work, is introduced which takes account of core losses. Based upon some loss approximations, simple relationships have been derived, which show that the synchronous mode operation, in terms of core loss, of the BDFM is similar to the cascad...

This paper discusses the dynamic behavior of the brushless doubly fed induction generator during the grid faults which lead to a decrease in the generator's terminal voltage. The variation of the fluxes, back EMFs, and currents are analyzed during and after the voltage dip. Furthermore, two alternative approaches are proposed to improve the generat...

The paper presents the design and performance analysis of a 6 MW medium-speed Brushless Doubly-Fed Induction Generation (Brushless DFIG) for a wind turbine drivetrain. Two machines with different frame sizes have been designed to show the flexibility of the design procedure. The mediumspeed Brushless DFIG in combination with a two stage gearbox off...

Understanding the availability of wind turbines (WT) is vital to maximize WT energy production and minimize the capital payback period. Previous work on this subject concentrated on reliability and the location of WT failure modes rather than root causes. This paper concentrates on the influence of weather and WT location on failure rate and downti...

Previous research for detecting incipient wind turbine failures, using condition monitoring algorithms, concentrated on wind turbine Supervisory Control and Data Acquisition (SCADA) signals, such as power output, wind speed and bearing temperatures, using power-curve and temperature relationships. However, very little research effort has been made...

In this study, the steady-state operation of the brushless doubly-fed machine (BDFM) in various modes is physically elaborated and the active power flow and torque analysis are presented for each operating mode alongside confirmatory experimental results on a 4/8 pole D160 size machine. The machine behaviour in asynchronous operating modes is descr...

This study investigates the condition monitoring of wind turbine wound rotor and doubly fed induction generators with rotor electrical asymmetries by analysis of stator current and total power spectra. The research is verified using experimental data measured on two different test rigs and numerical predictions obtained from a time-stepping electro...

Nowadays, all new wind turbine generators have to meet strict grid codes, especially riding through certain grid faults, such as a low voltage caused by grid short circuits. The Low-Voltage Ride Through (LVRT) capability has become a key issue in assessing the performance of wind turbine generators. The mediumspeed Brushless DFIG in combination wit...

Condition monitoring power semiconductor devices can inform converter maintenance and reduce damage. This paper presents a method to monitor solder fatigue in a voltage source inverter insulated gate bipolar transistor power module by detecting the change of an inverter output harmonic. It is shown that low-order harmonics, caused by nonideal switc...

Tidal stream devices are a new technology for extracting renewable energy from the sea. Various tidal stream device models have been proposed and, if they are installed at chosen high tidal stream velocity sites, they may face extreme climatic, current, and wave load conditions. As they contain complex mechanical, electrical, control, and structura...

Condition monitoring is needed in power electronic systems as a cost-effective means of improving reliability. Packaging-related solder fatigue has been identified as one of the main root causes of power electronic module failures. This paper presents a method to monitor solder fatigue inside a module by identifying the increase of internal thermal...

THE DEVELOPMENT of offshore wind power has become a pressing modern energy issue and the UK is taking a major role, with a significant deployment of turbines in UK waters. Two rounds of UK deployment have resulted in about 1,800MW installed capacity.

This paper presents an advanced monitoring and diagnosis method for detecting of incipient electrical and mechanical faults in a wind-turbine-driven doubly-fed induction generator (DFIG). In this application, the stator windings are directly connected to the grid, whereas a converter controls the rotor currents by means of a Field Oriented Control...

The Brushless Double-Fed Machine (BDFM) is a type of variable speed generator or drive. Using theoretical analysis of simple BDFM rotors this paper establishes trends in how rotor structures determine the rotor's equivalent circuit resistance, leakage inductance and turns ratio. The variation in measured parameters of five prototype rotors is then...

This paper presents the design and testing of a 250 kW medium-speed Brushless Doubly-Fed Induction Generator (Brushless DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and show the system's steady-state and dynamic performance. The medium-speed Brushless DFIG in combination with a simplifi...

The Brushless Doubly-Fed Induction Generator (Brushless DFIG) shows commercial promise for wind power generation due to its lower cost and higher reliability when compared with the conventional Doubly-Fed Induction Generator (DFIG). In the most recent grid codes, wind generators are required to be able to ride through a low voltage fault and meet t...

This work presents a diagnostic technique for detecting rotor and stator electrical asymmetries in a wind turbine doubly fed induction generator (DFIG) controlled by a stator field oriented vector control (SFOVC) scheme. The aim of this paper is to introduce a new diagnostic method based on the analysis of the dq-rotor current error signals inside...

Increasing deployment of large wind turbines offshore and in remote areas urgently requires reliable and efficient condition monitoring techniques to achieve high turbine availability and the expected economic return. Much effort has been made in the past a few years to develop advanced signal processing technologies to improve wind turbine conditi...

As wind power is growing towards a major utility source of electricity, reducing the cost of energy becomes a critical issue in order to make wind power competitive to conventional sources. The current trend in wind turbine (WT) development is for larger, more complex machines located in remote offshore locations which present operation and mainten...

The development of offshore wind power has become a pressing modern energy issue in which the UK is taking a major part, driven by the need to find new electrical power sources, avoiding the use of fossil fuels, in the knowledge of the extensive wind resource available around our islands and the fact that the environmental impact of offshore wind f...

Abstract: Tidal stream devices are a new technology for extracting renewable energy from the sea. Various tidal stream device models have been proposed and, if they are installed at chosen high tidal stream velocity sites, they may face extreme climatic, current, and wave load conditions. As they contain complex mechanical, electrical, control, and...

In many power converter applications, particularly those with high variable loads, such as traction and wind power, condition monitoring of the power semiconductor devices in the converter is considered desirable. Monitoring the device junction temperature in such converters is an essential part of this process. In this paper, a method for measurin...

A questionnaire survey was carried out to determine the industrial requirements and expectations of reliability in power electronic converters. The survey was subjective and conducted with a number of high-profile semiconductor manufacturers, integrators, and users in the aerospace, automation, motor drive, utility power, and other industry sectors...

While the performance and the efficiency of wind turbines and their energy yields have been improved with time, their reliability still needs improvement, particularly when considering their deployment offshore. IWES has been gathering operational experience from wind turbines since 1989, being involved in different projects dealing with the topic...

This study describes the power conversion and control solution used in the electrical power take-off of a 35 kW test rig developed to investigate a linear, direct drive, air-cored, tubular, permanent magnet generator for an offshore wave energy device. The solution proposed is to collect the power extracted directly from individual coils of the gen...

Tidal Stream Devices (TSD) are relatively new and to date only a few prototypes have been op-erational in the water. Therefore, relatively little reliability data has been accumulated. However, increasing pressure to develop reliable sources of renewable electric power is encouraging investors to consider TSDs. There are a variety of tidal stream s...

Wind turbine condition monitoring is gaining importance as turbines increase in size and move further offshore. Monitoring signals from turbine drive trains are highly non-stationary as turbine load and speed vary with time. Manual analysis of signals from multiple turbines is challenging so an automated algorithm is required. Monitoring signals co...

Current wind turbine (WT) studies focus on improving their reliability and reducing the cost of energy, particularly when they are operated offshore. WT Supervisory Control and Data Acquisition (SCADA) systems contain alarm signals providing significant important information. Pattern recognition embodies a set of promising techniques for intelligen...

This paper has summarised the typical principal failure modes of WT gearbox and relevant SCADA & CMS measurements for health monitoring. Starting with the basics of heat and temperature, it derives the relationship between temperature, efficiency, and power output or rotational speed based on the first law of thermodynamics. This then leads to a ne...

Condition monitoring of doubly-fed induction generators (DFIGs) is growing in importance for modem wind turbines. This paper investigates the potential of the DFIG stator current and total instantaneous power signals to be used for condition monitoring of rotor faults, such as brush-gear faults or electrical unbalance, of differing severity. A purp...