CWD NewsCWD – Center for Wind Power Drives of RWTH Aachen University | www.cwd.rwth-aachen.de April 2016, No. 1

Dear Partners and Friends of CWD,Dear Readers,

today I am pleased to present thefirst issue of our CWD News to you.Our new publication will be distributed on a quarterly basis. It is our way to keepyou updated regarding current activities atthe Center for Wind Power Drives (CWD)of the RWTH Aachen. At the same time,we would like to invite you to participate inour many research projects and to visitthe upcoming events we hold. We wouldbe pleased to incorporate your ideasand suggestions.

In the current issue, we will be reportingabout how CWD researchers include the rapidly progressing technologicaladvancements of fast-rotating electricalmachines through the design of morecost-effective and efficient wind turbinegenerators. Furthermore, we will beshowing you how cost effective „FaultRide Through“ testing is possible thanksto the enhancement of the system testbench. Last, but not least, we would liketo draw your attention to our CWDWorkshops. This is the place whereintense discussions amongst industryexperts and esteemed researchersfrequently lead to new joint researchprojects.

We hope you enjoy reading this issue and remain,

Yours

Georg Jacobs

PS: In case you no longer wish to receive our newsletter, please send an email with„unsubscribe“ to news@cwd.rwth-aachen.de. If you are not a subscriber yet and would like to receive this newsletter, kindly send amessage with your own contact information to this email address.

� Editorial� In this Issue

� Snap-Shot

RapidWind: A 6 MW multi generator drive train concept with fast-rotating electrical machines

lowers costs and increases efficiency (see section ‘From the Research Department – RapidWind’,

on page 2).

From the Research Department 2

RapidWind: Efficient Six Pack 2

News from the Test Bench 2

Enhanced System Test Bench for ‘Fault Ride Through’ Testing 2

Workshops 3

Successful 5th CWD Workshop 3

White Etching Cracks Workshop 3

Spotlight 3

Visit from China 3

Brian Feeny from Michigan State University holds Workshop at CWD 3

New Research Projects at CWD 3

Best Paper Award for Nurhan Rizqy Averous 3

Events 3

CWD 2017/Call for Papers 3

CWD NewsCWD – Center for Wind Power Drives of RWTH Aachen University | www.cwd.rwth-aachen.de Page 2

� From the Research Department

� News from the Test Bench

RapidWind: Efficient Six Pack

Fast-rotating electrical machines offerbenefits in many applications. In compari-son to commonly used generators, theyoccupy less space, are lighter and theirconstruction requires significantly lessmagnetic material. This results in conside-rable cost reductions. However, this tech-nology has not been used in the windpower industry – at least not yet. In thecurrently ongoing research projectRapidWind, funded by the Bundes-ministerium für Wirtschaft und Energie(Federal Ministry for Economic Affairs andEnergy), researchers at the CWD areinvestigating the possible uses of fast-rotating generators in high-performancewind turbine generators.

For this purpose, a 6 MW multi generatordrive train concept has been developedcomprising six identical generators (seethe figures on pages 1 and 2), capable ofgenerating power in the high speed rangewith up to 5,000 revolutions per minute.In addition to the named benefits of high-speed generators, the use of sixindependently operating generatorsincreases the availability of the wind turbinegenerator. Depending on the wind con-ditions, each generator and its affiliatedgear train can be selectively activated ordeactivated via couplings. The respectivecontrol strategy is also provided. This leadsto considerable improvements in efficiency,especially when operating in the partialload range.

Whithin the project RapidWind, the drivetrain concept with six sub gear trains andaffiliated generators is already developed intheory and tested by simulations. In afollow-up project, a prototype is plannedwhich will thoroughly be tested on thesystem test bench at the CWD. One ofthe project targets will be the functiontesting of the switchable couplings inthe drive train. Furthermore, it shoulddemonstrate that the simulated dynamicbehaviour of the 6 MW multi generator

drive train lives up to its expectedefficiency improvement on the testbench.

The funding for this follow-up projecthas not yet finally been granted. However,there have been encouraging signals fromthe funding side, provided that this inno-vative technology meets the interest of theindustry. Potential project partners areasked to contact us at news@cwd.rwth-aachen.de.

Enhanced System Test Benchfor ‘Fault Ride Through’ Testing

Power generation systems connected tothe medium-voltage power grid have tocontribute towards dynamic grid support.In the event of a short-circuit they are notallowed to disconnect from the grid,regardless of the short-circuit nature.Thanks to an enhancement of the systemtest bench, fault ride through (FRT) test cannow be conducted at the CWD. The aim ofthese tests is to check whether the exa-mined wind turbine generator recognisesvoltage drops and is able to ride throughwithout damages.

A converter-based grid emulator is usedfor the FRT tests at the CWD nacelle testbench. This emulator generates voltagedrops with specific amplitudes withoutrepercussion to the real grid. To perform theFRT tests, the present electric load emulatoris enhanced in order to increase both thedynamic and the load capacity of thesystem.

In contrast to corresponding forms offield-tests, the FRT testing on the CWD

test bench can be carried out indepen-dently from changing external circum-stances, such as weather conditions orgrid status. If needed, FRT tests at thetest bench are repeatable under identicalconditions on demand. Furthermore,time expenditure is considerably low,compared to field tests. All these factorsreduce costs associated with FRTtesting at the test bench.

The key component of the testinfrastructure is the Real Time DigitalSimulator (RTDS) from the Institute forAutomation of Complex Power Systems(ACS). The RTDS provides the grid emulatorwith the voltage characteristics. The valuesmeasured at the grid connection pointinfluence the grid calculation of the RTDSand the voltage characteristics specified bythe grid emulator. This „Power Hardware inThe Loop“ system is a relatively simple andcost effective method to investigate theinfluences of various grid states and thereaction of the wind turbine generator in a “virtual matter”.

CWD NewsCWD – Center for Wind Power Drives of RWTH Aachen University | www.cwd.rwth-aachen.de Page 3

� Workshops � Events

5th CWD Workshop

The first of two annual CWD Workshops(the fifth overall) took place in the end of February. Experts from leading companiesin the wind power industry as well as CWDengineers addressed current and futuretechnical developments and identified opportunities for potential research acti-

vities. This time, technical questions about condition monitoring systems, caststructure components and adjustable systems were addressed and discussed.We expect that this workshop will again result in joint, industry-related research projects. The 6th CWD Workshop is plannedfor the fourth quarter of 2016 and again,experts from the entire wind industry areexpected to attend it.

White Etching Cracks Workshop

Representatives from the industry (Schaeffler Technologies and Qass) andscientists from Southampton, Erlangen and Aachen all came together in mid January at the CWD’s White Etching Cracks (WEC) Workshop to discuss the state-of-the-art technology and current research developments.

CWD 2017/Call for Papers

The Conference for Wind Power Drives(CWD 2017) will take place on the 7th and8th of March 2017 at Eurogress in Aachen.The focus is going to be on the latest deve-lopments and innovations in drive trains as

well as pitch and yaw systems of wind tur-bine generators. Interested parties are invi-ted to register their talk until the 23rd of May2016 by submitting a short abstract.Further information about the conferenceand the Call for Papers are available atwww.cwd.rwth-aachen.de/conference.

Visit from China

Professors Yonggang Meng, Jianbin Luoand Wei Sun from the Tsinghua University inPeking visited the 4 MW system test benchof the CWD after participating in an inter-national congress. Opportunities for research collaboration were discussed within the framework of this visit.

Brian Feeny from Michigan StateUniversity holds Workshop at CWD

In February, Brian Feeny, professor of theDepartment of Mechanical Engineering atMichigan State University, reported on thesubject of modelling and analysis of rotorblade vibrations within an intriguing work-shop at the CWD.

New Research Projects at CWD

� HydroLa: Hydrodynamic Main Bearingfor a 6 MW Offshore-Wind Turbine

� Torque Measurement in the MNmRange

� BCMS: Observer-Based Condition Monitoring System for Main Gears inWind Power Plants

� WEA-GLiTS: Thermally Injected Hydro-dynamic Bearing Coatings for Main Bearings in Wind Power Systems

Best Paper Award for Nurhan Rizqy Averous

For his presentation on „Development of a4 MW Full-Size Wind-Turbine Test Bench“,Nurhan Rizqy Averous M.Sc. received the‘Best Paper Award’ at the „PEDG 2015 6th

International Symposium on Power Electro-nics for Distributed Generation Systems“.

� Spotlight

� DisclaimerCWD I Center for Wind Power Drives

ACS I Institute for Automation of Complex Power SystemsProf. Dr.-Ing. Antonello Monti

AIA I Institute of AerodynamicsProf. Dr.-Ing. Wolfgang Schröder

CWD I Chair for Wind Power DrivesProf. Dr.-Ing. Georg Jacobs

IEM I Institute of Electrical MachinesProf. Dr.-Ing. habil. Dr. h. c. Kay Hameyer

IRT I Institute of Automatic ControlProf. Dr.-Ing. Dirk Abel

PGS I Institute for Power Generation and Storage Systems Prof. Dr. ir. Dr. h. c. Rik W. De Doncker

WZL I Laboratory for Machine Tools and Production EngineeringProf. Dr.-Ing Christian Brecher

Editorial and Contact:Freia Harzendorf, M.Sc.Center for Wind Power DrivesRWTH Aachen University Campus-Boulevard 61 | D-52074 Aachen

Tel.: +49 241 80 90245Fax: +49 241 80 92885E-mail: news@cwd.rwth-aachen.deURL: www.cwd.rwth-aachen.de