A brief status on condition monitoring and fault diagnosis in wind energy conversion systems

There is a constant need for the reduction of operational and maintenance costs of Wind Energy Conversion Systems (WECSs). The most efficient way of reducing these costs would be to continuously monitor the condition of these systems. This allows for early detection of the degeneration of the generator health, facilitating a proactive response, minimizing downtime, and maximizing productivity. Wind generators are also inaccessible since they are situated on extremely high towers, which are normally 20 m or more in height. There are also plans to increase the number of offshore sites increasing the need for a remote means of WECS monitoring that eliminates some of the difficulties faced due to accessibility problems. Therefore and due to the importance of condition monitoring and fault diagnosis in WECS (blades, drive trains, and generators), and keeping in mind the need for future research, this paper is intended as a brief status describing different types of faults, their generated signatures, and their diagnostic schemes.     

Wind Energy Literature Survey No. 4

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from recent issues of the following periodicals: IEEE Transactions on Energy Conversion, IEEE Transactions on Power Electronics, IEEE Transactions on Control Systems Technology, International Journal of Energy Research, Journal of Wind Engineering and Industrial Aerodynamics, American Institute of Aeronautics and Astronautics Journal, Transactions of the ASME: Journal of Dynamic Systems Measurement and Control and Renewable Energy. This survey additionally contains articles relating to power system voltage restoration from selected journals. Compiled by Martin Hird, UMIST, PO Box 88, Manchester, M60 1QD, UK. Please e‐mail any suggestions to martin.hird@stud.umist.ac.uk . Copyright © 2003 John Wiley & Sons, Ltd.     

Wind Energy Literature Survey No. 6

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from recent issues of the following periodicals: Journal of Wind Engineering and Industrial Aerodynamics, IEEE Transactions on Energy Conversion, IEEE Transactions on Power Electronics, IEEE Transactions on Control Systems Technology, Transactions of the ASME : Journal of Dynamic Systems Measurement and Control, American Institute of Aeronautics and Astronautics Journal, International Journal of Energy Research and Renewable Energy. Compiled by Dave Rollinson, UMIST, PO Box 88, Manchester, M60 1QD, UK. Please e‐mail any suggestions to D.Rollinson@student.umist.ac.uk.     

Wind energy literature survey No. 5

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from recent issues of the following periodicals: IEEE Transactions on Energy Conversion, IEEE Transactions on Power Electronics, IEEE Transactions on Control Systems Technology, International Journal of Energy Research, Journal of Wind Engineering and Industrial Aerodynamics, American Institute of Aeronautics and Astronautics Journal, Transactions of the ASME: Journal of Dynamic Systems Measurement and Control and Renewable Energy. The list is arranged alphabetically by author. Compiled by Dave Rollinson, UMIST, PO Box 88, Manchester, M60 1QD, UK. Please e‐mail any suggestions to D.Rollinson@student.umist.ac.uk. Copyright © 2004 John Wiley & Sons, Ltd.     

Wind Energy Literature Survey No. 2

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from issues of the following periodicals: IEEE Transactions on Energy Conversion, IEEE Transactions on Power Electronics, IEEE Transactions on Control Systems Technology, International Journal of Energy Research, Journal of Wind Engineering and Industrial Aerodynamics, American Institute of Aeronautics and Astronautics Journal, Transactions of the ASME: Journal of Dynamic Systems Measurement and Control, and Renewable Energy. The list is arranged alphabetically by author. Compiled by Martin Hird, UMIST, PO Box 88, Manchester M60 1QD, UK. Please e‐mail any suggestions to martin.hird@stud.umist.ac.uk. Copyright © 2001 John Wiley & Sons, Ltd.     

Wind Energy literature survey no. 3

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from issues of the following periodicals: IEEE Transactions on Energy Conversion, IEEE Transactions on Power Electronics, IEEE Transactions on Control Systems Technology, International Journal of Energy Research, Journal of Wind Engineering and Industrial Aerodynamics, American Institute of Aeronautics and Astronautics Journal, Transactions of the ASME: Journal of Dynamic Systems Measurement and Control, and Renewable Energy. This survey additionally contains articles from a special wind energy issue of Transactions of the ASME: Journal of Solar Energy Engineering. The list is arranged alphabetically by author. Compiled by Martin Hird, UMIST, PO Box 88, Manchester, M60 1QD, UK. Please e‐mail any suggestions to martin.hird@stud.umist.ac.uk. Copyright © 2001 John Wiley & Sons, Ltd.     

Effects of the PWM carrier signals synchronization on the DC-link current in back-to-back converters

This paper presents a study about the synchronization effects of the PWM carrier signals of a back-to-back converter for grid connection of Wind Energy Conversion Systems based on Permanent Magnet Synchronous Generators. It is demonstrated by means of a spectral analysis that, with the proper synchronization of the carrier signals of both the rectifier and inverter stages, the rms value of the current through the DC-link capacitors is greatly reduced. As a result, the number of capacitors needed to build the back-to-back converter decreases, whereas its life cycle is expanded, so that the Wind Energy Conversion System becomes more cost effective. It is shown that the worst case occurs when the phase difference between both carrier signals is ±π/2, yielding the highest rms value of the DC-link capacitors current. In that case the harmonic with the highest rms value is located at twice the switching frequency. The theoretical analysis is compared with experimental results from a 10 kW back-to-back converter in order to validate the effects of the carrier signals phase shift on the DC-link capacitors current.     

Wind energy literature survey no. 7

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from recent issues of the following periodicals: Electric Power Components and Systems, Energy Sources, IEE Proceedings Control Theory and Applications, IEE Proceedings Electric Power Application, IEE Proceedings Generation, Transmission and Distribution, IEEE Control Systems Magazine, IEEE Journal of Oceanic Engineering, IEEE Power and Energy Magazine, IEEE Transactions on Applied Superconductivity, IEEE Transactions on Energy Conversion, IEEE Transactions on Industry Applications, IEEE Transactions on Industrial Electronics, IEEE Transactions on Instrumentation and Measurement, IEEE Transactions on Magnetics, IEEE Transactions on Power Electronics, IEEE Transactions on Power Delivery, IEEE Transactions on Power Systems, Journal of Solar Energy Engineering, Journal of Wind Engineering & Industrial Aerodynamics, and Renewable Energy. The survey is limited exclusively to journals not specifically devoted to wind energy and its applications. The survey contains just a portion of what is written on the subject in other journals, and is in no way exhaustive. More publications in these and other journals can be found by internet search machines like ‘Google Scholar’ or ‘Scirus’. The papers are categorized in Aerodynamics/Elastics/Acoustics, Structures/Loads/Fatigue, Performance, Wind, Control, Generators/Converters, Grid Connection, Miscellaneous. Each paper is mentioned only once, although many papers fit in more than one category. Compiled by Remko Gerbenzon and Gijs van Kuik, Duwind, Faculty of Aerospace Engineering, TU Delft, The Netherlands. Please email any suggestions to g.a.m.vankuik@tudelft.nl     

Wind Energy literature survey no.1

In order to help keep readers up‐to‐date in the field, Wind Energy contains a list of recently published articles drawn from issues of the following periodicals: IEEE Transactions on Energy Conversion, IEEE Transactions on Power Electronics, IEEE Transactions on Control Systems Technology, International Journal of Energy Research, Journal of Wind Engineering and Industrial Aerodynamics, American Institute of Aeronautics and Astronautics Journal and Transactions of the ASME: Journal of Dynamic Systems Measurement and Control. The list is arranged alphabetically by author. Compiled by Martin Hird, UMIST, PO Box 88, Manchester, M60 1QD, UK. Please e‐mail any suggestions to martin.hird@stud.umist.ac.uk martin.hird@stud.umist.ac.uk . Copyright © 2000 John Wiley & Sons, Ltd.     

FPGA-based reconfigurable control for switch fault tolerant operation of WECS with DFIG without redundancy

This paper deals with reconfigurable back-to-back converter topology and control orders in Wind Energy Conversion Systems (WECS). A typical WECS with Doubly Fed Induction Generator (DFIG) in balanced conditions is concerned. Based on the classical topology, a fault tolerant converter without any redundancy has been studied. The presented fault tolerant topology allows a “five-leg” structure with converters reconfiguration after switch failure detection. Furthermore, the control strategy for classical topology can no longer be applied after fault occurrence. Thus, a “five-leg” control strategy has also been proposed. The validation of the reconfigurable digital controller for the studied WECS with DFIG topology has been performed using a Hardware-in-the-Loop (HIL) reconfigurable platform including a Field Programmable Gate Array (FPGA) chip. HIL simulation results in both healthy and fault conditions have been presented to show simultaneously the viability of the studied converters topology and the reconfigurable control.     

On the energy output estimation of wind turbines

During the operation of the German test field for small Wind Energy Conversion Systems (WECS) on the island of Pellworm five wind turbines were tested following recommendations of the International Energy Agency (IEA) expert group. Possible errors in the estimation of a tested wind turbine's total energy output at a potential installation site are investigated. Different wind speed frequency distributions (the measured one, the Rayleigh and the two-parameter Weibull distribution) are used to calculate the total energy output. The differences between the various distributions are mostly below 10 per cent. An improvement of the energy output estimate by a Weibull-instead of a Rayleigh distribution was not found. It is also shown that the use of the recommended 10 min averages or any other average overestimates the WECS' efficiency, up to 14 per cent on average depending on turbulence intensity. Wind power instead of wind speed is the appropriate parameter for power performance testing. Spectra of wind power and electrical power output show three areas of different correlation. A resistance length for wind turbines is shown to be dependent on the WECS operation status.     

Five-leg converter topology for wind energy conversion system with doubly fed induction generator

In this paper, application of a five-leg converter in Doubly Fed Induction Generator (DFIG) for Wind Energy Conversion Systems (WECS) is investigated. The five-leg structure and its PWM control are studied and performances are compared with the classical six-leg topology. The main drawback of five-leg converter with respect to the six-leg back-to-back converter is the need to increase the dc-link voltage for the same operation point, i.e. the same powers in case of WECS. So, different methods for the reduction of the required dc-link voltage in the five-leg case are studied. The five-leg converter is used to replace the conventional six-leg one, with the same ability. For the performance evaluation of this structure and its fully digital controller in a more realistic and experimental manner, Hardware in the Loop experiments is carried out. It is shown that efficient control of active and reactive powers and dc-link voltage is performed. Hardware in the Loop results demonstrate the high performance of the proposed fully digital control which is implemented on an Altera FPGA target.     

Modeling of small wind turbines based on PMSG with diode bridge for sensorless maximum power tracking

The Permanent Magnet Synchronous Generator (PMSG) with diode bridge is frequently used in small Wind Energy Conversion Systems (WECS). This configuration is robust and cheap, and therefore suitable for small WECS. In order to achieve Maximum Power Point Tracking (MPPT) with no mechanical sensors, it is possible to impose the relationship between the DC voltage and the DC current on the optimum operating points. However, this relationship is difficult to calculate theoretically since the whole system is involved. In fact, as there is no model of the whole system in the literature, the optimum curve I_L¹(V_dc) is obtained with experimental tests or simulations. This paper develops an accurate model of the whole WECS, thereby making it possible to relate the electrical variables to the mechanical ones. With this model, it is possible to calculate the optimum curve I_L¹(V_dc) from commonly-known system parameters and to control the system from the DC side. Experimental results validate the theoretical analysis and show that maximum power is extracted for actual wind speed profiles.     

Fault detection of wind energy conversion systems using recurrent neural networks

Structure of wind energy conversion systems (WECSs) must be robust against faults. In order to accurately study WECSs during occurrence of faults and to explore the impact of faults on each component of the WECSs, a detailed model is required in which both mechanical and electrical parts of the WECSs are properly involved. In addition, a fault detection system (FDS) is required to diagnose the occurred faults at the appropriate time in order to ensure a safe system operation, avoid heavy economic losses, prevent damage to adjacent relevant systems and facilitate timely repair of failed components. This can be performed by subsequent actions through fast and accurate detection of faults. In this paper, by utilising a comprehensive dynamic model of the WECS, an FDS is presented using dynamic recurrent neural networks. In industrial processes, dynamic neural networks are known as a good mathematical tool for fault detection. The proposed FDS detects faults of the generator's angular velocity sensor, pitch angle sensors and pitch actuators. The presented FDS has high capability of fault detection in short time and it has much low false alarms rate. Simulation results verify validity and usefulness of the proposed fault detection scheme.     

PV–wind hybrid system performance: A new approach and a case study

Until now, there is no internationally accepted guideline for the measurement, data exchange and analysis of PV–Wind Hybrid Systems. As there is a need for such a tool, so as to overcome the barrier that the lack of confidence due to the absence of reliability means for the development of the market of Hybrid Systems, an effort has been made to suggest one tool for PV–Wind Hybrid Systems. The suggested guidelines presented in this work are based on the existing guidelines for PV Systems, as a PV–Wind Hybrid system can be roughly thought of as a PV System to which wind generation has been added. So, the guidelines for PV Systems are valid for the PV–Wind System, and only the part referred to wind generation should be included. This has been the process followed in this work. The proposed method is applied to a case study, the CICLOPS Project, a 5 kW PV, 7.5 kW Wind Hybrid system installed at the Isolated Wind Systems Test Site that CIEMAT owns in CEDER (Soria, Spain). This system has been fully monitored through a year and the results of the monitoring activity, characterizing the long-term performance of the system are shown in this work.     

An analysis of the potential of Wind Energy Conversion Systems

Wind Energy Conversion Systems (WECS) are solar systems because the sun drives the atmospheric circulation. About 20 TW of wind energy flows poleward annually, over land in temperate latitudes, in the 500 m deep atmospheric boundary layer. An average 500 GW of electricity could be generated by massive exploitation of the U.S. Great Plains wind field.There are, however, large fluctuations in available wind power. There are frequent 20% variations in annual supply; annual periodicity brings most wind power during the spring; there are storm cycles; and there is a diurnal cycle. Gusts and turbulence also require filtering to meet normal power requirements. Several schemes are evolving to tame this erratic wind power supply.Modern technology is refining horizontal-axis turbines of a wide size range. Progress is also being made toward producing an economical vertical-axis turbine. Standards for turbine performance evaluation and installation site selection are now being developed. Yet it will be a few years before proven systems can significantly affect national energy supplies.Eventually, mass-produced WECS may cost $1000 per installed, rated kW, but the wind does not often flow at turbine-rated speed. With some storage or filtering, problems with wind variability may be overcome. Then WECS electricity production may be as economical as other electric generators. No serious hazards or environmental impacts should slow WECS development.     

Adaptive back-stepping control for a permanent magnet synchronous generator wind energy conversion system

The maximize energy captured from the wind of a grid-connected variable speed Wind Energy Conversion System (WECS) based on a Permanent Magnet Synchronous Generator (PMSG) is investigated in this paper. An adaptive back-stepping control scheme is applied to achieve maximum power point tracking in the coefficient of maximum power. The features of the proposed control scheme are that it deals with the random nature of wind speed, the uncertainties and external perturbations the acting on WECS effectively, where the bounds of the perturbations are not known in advance. At the same time, a proof of the convergence of the closed-loop system under the proposed controller is derived using the Lyapunov stability theory. Finally, simulations are conducted to illustrate the effectiveness of the proposed approach.     

Economic feasibility and optimisation of an energy storage system for Portland Wind Farm (Victoria,Australia)

This paper presents the details of a theoretical study of the economic advantages of using large-scale energy storage to complement a wind farm in a base-load dominated electricity grid. A computer model is developed which simulates the operation of several energy storage systems when used with the 190-MW Portland Wind Farm (PWF) located in Portland, Victoria, Australia. A variety of operating strategies are compared with the results of a dynamic programming model which finds the maximum possible revenue which a given system can generate for a set of input conditions. Three energy storage systems are modelled and costed: Pumped Seawater Hydro Storage (PSHS), Compressed Air Energy Storage (CAES), and Thermal Energy Storage (TES). It is found that CAES is the most profitable storage medium, requiring a capital expenditure of A$140 M and generating a rate of return (ROR) of 15.4%. The ROR for PSHS was 9.6%, and for TES was 8.0%. Therefore, a significant investment opportunity exists for the installation of an energy storage system in this wind farm. It is therefore highly recommended that CAES is investigated further with the aim of introducing large-scale energy storage to PWF and other similar wind turbine installations.     

New strategy of pitch angle control for energy management of a wind farm

In this paper, we are interested in a Wind Energy Conversion System (WECS) based on a Permanent Magnetic Synchronous Generator (PMSG). The studied WECS is made by the association of three aerogenerators. The objective of this work is to investigate a new strategy of pitch angle control to ensure a balance between the produced energy and the demanded one by the loads. The control strategy of the wind farm is composed of two parts: a local control according to the characteristics of each wind turbine « Pitch control » to protect the turbines against mechanical failure in the event of wind gust and a global control according to the total power demand and the available wind power. This strategy leads to achieving power objectives (active and reactive power targets) and system constraints.     

A novel nonlinear observer‐based LQ control system design for wind energy conversion systems with single measurement

The issue of tracking the optimal power for wind energy conversion systems (WECSs) via regulating the rotor speed of the generator is taken into account in this study. Additionally, a novel polynomial observer is proposed for estimating not only aerodynamic torque in WECSs but also d‐axis and electromagnetic torque. Therefore, in this new approach, only the rotor speed of the generator is required to be measured instead of measuring all state variables. With the new observer form, the aerodynamic torque does not need to satisfy any constraints, which are mandatory in the previous methods. It should be noted that this methodology has not been investigated for the WECSs in any previous papers. To design a complete control system, a linear optimal control method cooperated with the polynomial observer is employed to track the optimal trajectory of a generator. Moreover, in this paper, the permanent magnet synchronous generator is used. In addition, on the basis of the Lyapunov theory and sum‐of‐square (SOS) technique, the conditions for observer synthesis are derived in the main theorems. Finally, the simulation results are provided to prove the effectiveness and merit of the proposed method.