Methods for Advanced Wind Turbine Condition Monitoring and Early Diagnosis: A Literature Review

Condition monitoring and early fault diagnosis for wind turbines have become essential industry practice as they help improve wind farm reliability, overall performance and productivity. If not detected and rectified at early stages, some faults can be catastrophic with significant loss or revenue along with interruption to the business relying mainly on wind energy. The failure of Wind turbine results in system downtime and repairing or replacement expenses that significantly reduce the annual income. Such failures call for more systematized operation and maintenance schemes to ensure the reliability of wind energy conversion systems. Condition monitoring and fault diagnosis systems of wind turbine play an important role in reducing maintenance and operational costs and increase system reliability. This paper is aimed at providing the reader with the overall feature for wind turbine condition monitoring and fault diagnosis which includes various potential fault types and locations along with the signals to be analyzed with different signal processing methods

An Assessment of PIER Electric Grid Research 2003-2014 White Paper

This white paper describes the circumstances in California around the turn of the 21st century that led the California Energy Commission (CEC) to direct additional Public Interest Energy Research funds to address critical electric grid issues, especially those arising from integrating high penetrations of variable renewable generation with the electric grid. It contains an assessment of the beneficial science and technology advances of the resultant portfolio of electric grid research projects administered under the direction of the CEC by a competitively selected contractor, the University of California’s California Institute for Energy and the Environment, from 2003-2014

Assessment of a PLL-ASMO position/speed estimator for sensor-less control of rotor-tied DFIG (RDFIG)

DATA AVAILABILITY STATEMENT : Data is contained within the article.In this paper, an adaptive sliding mode observer (ASMO) associated with a phase locked loop (PLL) is assessed for the sensor-less control of a rotor-tied doubly-fed induction generator (RDFIG). In the proposed PLL-ASMO estimator, the ASMO utilizes the stator current, the stator voltage, and the back electromotive force (EMF) as state variables. The proposed ASMO is used in order to estimate the back-EMF from which the slip position/speed is extracted using a PLL. The design of the ASMO gains is based on the Lyapunov stability criteria to ensure the convergence of the proposed observer in a finite time. Therefore, the main contribution of this paper is to propose a PLL-based ASMO estimator that aims to improve the estimation by reducing the chattering effect. A comparative study between the standard PLL-SMO estimator and the PLL-ASMO estimator is presented. Also, For the first time, an adaptive sliding mode observer is used for the sensor-less control of a RDFIG. The performance of the proposed sensor-less control strategy is validated through simulation and experimental measurements under various operating conditions. Furthermore, the estimator is shown to be robust to machine parameter variation.National Research Foundation of South Africa.http://wileyonlinelibrary.com/iet-joehj2024Electrical, Electronic and Computer EngineeringSDG-09: Industry, innovation and infrastructur

Offline Parameter Estimation of a 18.5 kW Doubly fed induction generator

Thesis (MEng)--Stellenbosch University, 2018.ENGLISH ABSTRACT: In the past years, technology advancements have allowed the wind energy to become one of the most economical forms of power generation in the field of renewable energies. Nowadays, wind turbines that produce electricity make use of the advance and mature technologies and generate sustainable sources of energy. In the areas where the wind is plentiful, it is a major rival to the conventional sources of energy. Many countries worldwide have vast resources of it but still, haven’t used its capacity to the fullest. The upsides of wind energy are: . Omitting the emission of greenhouse gases. . The energy supplies can be increased and diversified using wind energy. . In comparison to the other power sources, a shorter time is required for planning, design, and construction. The flexibility of such projects so that the current wind farms can host more turbines in case of higher demand for energy. . Finally, a significant saving in terms of materials, labor and investment. The extracted energy from the wind, is in the form of kinetic energy and is harnessed by the rotor blades and turned into mechanical energy. Then, this mechanical energy is transformed into the electrical energy by a wind turbine generator. The nominal power extracted from the wind varies based on the size of the rotor and the wind speed, regardless of the losses. The power ratings for wind generators varies from some hundred watts to multi-megawatt generators depending on the utilization and where they are stationed. Nowadays, a vast percentage of the larger scale wind generators employ the geared topologies, AC outputs connected to the power grid through power electronic converters, while it seems that the dynamic in the market is gradually changing towards employing the permanent magnet, gearless topologies by using the fully-rated power electronic converters. On the other hand, the small-scale turbines usually employ the direct drive generators with DC outputs and aeroelastic blades. However, the use of wind generators in a direct drive topology accompanied by the aeroelastic blades and DC outputs is rarely used and still under development. It is impossible to have the exact same power generation from the wind each year due to its variable nature. Furthermore, the wind generators can only be used in areas where a minimum speed of 4.5 m/s or higher is available. The suitable sites are chosen based on the measurements on the site and the data from a wind atlas. There are several methods for analyzing the dynamic behavior of the wind turbines. Employing the parameters of such systems is a suitable way to analysis the machine dynamic behavior and reduces complexities regarding the use of higher order models. The problem is that these parameters are subject to change in different operating conditions and need to be estimated accurately by some methods. This study concentrates on estimating the parameters of a doubly fed induction generator by employing the previously proposed Mathlab c-code and s-function codes and investigates the practical application of that method on a 18.5 kW doubly fed induction generator.AFRIKAANSE OPSOMMING: In die afgelope jaar het tegnologie vooruitgang die windenergie toegelaat om een van die mees ekonomiese vorme van kragopwekking op die gebied van hernubare energie te word. Vandag maak windturbines wat elektrisiteit produseer, gebruik van die voor- en volwasse tegnologie en volhoubare energiebronne. In die gebiede waar die wind oorvloed is, is dit 'n groot mededinger in die konvensionele energiebronne. Baie lande wêreldwyd het groot middele, maar het nog steeds nie sy vermoë tot die uiterste gebruik nie. Die opwaartse windenergie is: . Om die uitstoot van kWeekhuisgasse uit te skakel. . Die energiebronne kan verhoog en gediversifiseer word met behulp van windenergie. . In vergelyking met die ander kragbronne word 'n korter tyd benodig vir beplanning, ontwerp en konstruksie. . Die buigsaamheid van sulke projekte, sodat die huidige windplase meer turbines in die geval van hoër vraag na energie kan gasheer. . Ten slotte, 'n beduidende besparing in terme van materiale, arbeid en belegging. Die energie wat uit die wind onttrek word, is in die vorm van kinetiese energie en word deur die rotorblades aangewend en omskep in meganiese energie. Dan word hierdie meganiese energie omgeskakel na die elektriese energie deur 'n windturbine generator. Die nominale krag wat uit die wind onttrek word, hang af van die grootte van die rotor en die windspoed, ongeag die verliese. Die kraggraderings vir windopwekkers wissel van sowat honderd watt na multi-megawatt kragopwekkers, afhangende van die gebruik en waar hulle gestasioneer is. Deesdae gebruik 'n groot persentasie van die grootskaalse windopwekkers die toegepaste topologieë, AC-uitsette wat via die elektriese elektroniese omsetters aan die rooster verbind word, terwyl dit blyk dat die dinamiek in die mark geleidelik verander na die gebruik van die permanente magneet, ratlose topologieë deur die volwaardige krag elektroniese omsetters. Aan die ander kant gebruik die kleinschalige turbines gewoonlik die direkte dryfgenerators met gelykstroomuitsette en aeroelastiese lemme. Die gebruik van windgenerators in 'n direkte dryf topologie, vergesel van die aeroelastiese lemme en GS-uitsette word egter selde gebruik en steeds onder ontwikkeling. Dit is onmoontlik om elke jaar dieselfde kragopwekking uit die wind te kry as gevolg van die veranderlike aard daarvan. Verder kan die windgenerators slegs gebruik word in gebiede waar 'n minimum spoed van 4,5 m / s of hoër beskikbaar is. Die geskikte plekke word gekies op grond van die metings op die terrein en die data van 'n windatlas. Daar is verskeie metodes om die dinamiese gedrag van die windturbines te ontleed. Die gebruik van die parameters van sulke stelsels is 'n geskikte manier om die masjien dinamiese gedrag te ontleed en kompleksiteite te verminder rakende die gebruik van hoë-orde modelle. Die probleem is dat hierdie parameters onderworpe is aan verandering in verskillende bedryfsomstandighede en deur sommige metodes akkuraat beraam moet word. Hierdie studie fokus op die raming van die parameters van 'n dubbel gevoed induksie generator deur gebruik te maak van die voorheen voorgestelde Mathlab c-kode en s-funksie kodes en ondersoek die praktiese toepassing van die metode op 'n 18.5 kW dubbel gevoed induksie generator

European White Book on Real-Time Power Hardware in the Loop Testing : DERlab Report No. R- 005.0

The European White Book on Real-Time-Powerhardware-in-the-Loop testing is intended to serve as a reference document on the future of testing of electrical power equipment, with specifi c focus on the emerging hardware-in-the-loop activities and application thereof within testing facilities and procedures. It will provide an outlook of how this powerful tool can be utilised to support the development, testing and validation of specifi cally DER equipment. It aims to report on international experience gained thus far and provides case studies on developments and specifi c technical issues, such as the hardware/software interface. This white book compliments the already existing series of DERlab European white books, covering topics such as grid-inverters and grid-connected storag

Novel sensorless generator control and grid fault ride-through strategies for variable-speed wind turbines and implementation on a new real-time simulation platform

The usage of MW-size variable-speed wind turbines as sources of energy has increased significantly during the last decade. Advantages over fixed-speed wind turbines include more efficient wind power extraction, reduced grid power fluctuation, and improved grid reactive power support. Two types of typical generation systems for large-size variable-speed wind turbines exist. One is the doubly-fed induction generator (DFIG) with a partial-scale power electronic converter. The other is the permanent-magnet synchronous generator (PMSG) with a full-scale power electronic converter. This research is to develop the model of these two wind turbine systems for real-time simulation, including the complete aerodynamic and mechanical and electrical components. The special focus of this dissertation addresses the mechanical sensorless control of wind generators and grid fault ride-through strategies. In the electrical controller of a DFIG, A mechanical speed sensor is normally required to provide accurate information of the machine speed and rotor position. However, sensorless operation is desirable because the use of a mechanical speed sensor coupled with the machine shaft has several drawbacks in terms of degraded robustness, extra cost and cabling, and difficult maintenance. In this dissertation, design and analysis of a novel sensorless vector controller using a reduced-order state observer is addressed in detail. Results have revealed that the proposed sensorless observer is more robust against parameter variations than other speed estimation schemes. Nowadays, almost all the grid code specifications over the world have included fault ride-through requirements for grid-connected wind turbines. In US, as mandated by the Federal Energy Regulatory Commission (FERC) Order 661-A, wind farms are required to remain online in the presence of severe voltage disturbances as low as 0.0 pu, as measured at the high voltage side of the wind generator step-up transformer, for up to 9 cycles (150 ms). These strict requirements present a significant challenge to the existing wind turbine technologies. In this dissertation, an improved technique combining the traditional crowbar protection circuit and the demagnetizing current injection to ride-through symmetrical grid voltage dips is analyzed and verified for a DFIG-based wind turbine. Also, an improved fault ride-through control strategy without using any extra protection hardware for a PMSG-based wind turbine to mitigate the dc-link overvoltage is developed. In this dissertation, a new real-time simulation platform is developed based on industry standard simulation tools, RTDS and dSPACE. The aforementioned wind turbine models and proposed sensorless controller as well as fault ride-through strategies are all implemented in real-time on this hardware-in-the-loop type of simulation platform. The necessary measures in hardware and software aspects to enable the collaborative simulation of these two industry standard simulators are addressed. Results have shown this integrated real-time simulation platform has broad application prospects in wind turbine controller design and grid interconnection studies

Wind energy harvester interface for sensor nodes

The research topic is developping a power converting interface for the novel FLEHAP wind energy harvester allowing the produced energy to be used for powering small wireless nodes. The harvester\u2019s electrical characteristics were studied and a strategy was developped to control and mainting a maximum power transfer. The electronic power converter interface was designed, containing an AC/DC Buck-Boost converter and controlled with a low power microcontroller. Different prototypes were developped that evolved by reducing the sources of power loss and rendering the system more efficient. The validation of the system was done through simulations in the COSMIC/DITEN lab using generated signals, and then follow-up experiments were conducted with a controllable wind tunnel in the DIFI department University of Genoa. The experiment results proved the functionality of the control algorithm as well as the efficiency that was ramped up by the hardware solutions that were implemented, and generally met the requirement to provide a power source for low-power sensor nodes

Power Management Strategies for a Wind Energy Source in an Isolated Microgrid and Grid Connected System

This thesis focuses on the development of power management control strategies for a direct drive permanent magnet synchronous generator (PMSG) based variable speed wind turbine (VSWT). Two modes of operation have been considered: (1) isolated/islanded mode, and (2) grid-connected mode. In the isolated/islanded mode, the system requires additional energy sources and sinks to counterbalance the intermittent nature of the wind. Thus, battery energy storage and photovoltaic (PV) systems have been integrated with the wind turbine to form a microgrid with hybrid energy sources. For the wind/battery hybrid system, several energy management and control issues have been addressed, such as DC link voltage stability, imbalanced power flow, and constraints of the battery state of charge (SOC). To ensure the integrity of the microgrid, and to increase its flexibility, dump loads and an emergency back-up AC source (can be a diesel generator set) have been used to protect the system against the excessive power production from the wind and PV systems, as well as the intermittent nature of wind source. A coordinated control strategy is proposed for the dump loads and back up AC source. An alternative control strategy is also proposed for a hybrid wind/battery system by eliminating the dedicated battery converter and the dump loads. To protect the battery against overcharging, an integrated control strategy is proposed. In addition, the dual vector voltage control (DVVC) is also developed to tackle the issues associated with unbalanced AC loads. To improve the performance of a DC microgrid consisting wind, battery, and PV, a distributed control strategy using DC link voltage (DLV) based control law is developed. This strategy provides simpler structure, less frequent mode transitions, and effective coordination among different sources without relying on real-time communication. In a grid-connected mode, this DC microgrid is connected to the grid through a single inverter at the point of common coupling (PCC). The generated wind power is only treated as a source at the DC side for the study of both unbalanced and balanced voltage sag issues at a distribution grid network. The proposed strategy consists of: (i) a vector current control with a feed-forward of the negative-sequence voltage (VCCF) to compensate for the negative sequence currents; and (ii) a power compensation factor (PCF) control for the VCCF to maintain the balanced power flow between the system and the grid. A sliding mode control strategy has also been developed to enhance the overall system performance. Appropriate grid code has been considered in this case. All the developed control strategies have been validated via extensive computer simulation with realistic system parameters. Furthermore, to valid developed control strategies in a realistic environment in real-time, a microgrid has been constructed using physical components: a wind turbine simulator (WTS), power electronic converters, simulated grid, sensors, real-time controllers and protection devices. All the control strategies developed in this system have been validated experimentally on this facility. In conclusion, several power management strategies and real-time control issues have been investigated for direct drive permanent magnet synchronous generator (PMSG) based variable speed wind turbine system in an islanded and grid-connected mode. For the islanded mode, the focuses have been on microgrid control. While for the grid-connected mode, main consideration has been on the mitigation of voltage sags at the point of common coupling (PCC)