Automatic Control of Freeboard and Turbine Operation
Contents
1. 7 4 GENERATOR CONTROBLE decise eu Ee E O 10 OPERATION EXPERIBNGES 2 eU E TD M Dm D E Ue DE D 10 TURBINE PERFORMANCE a a A 12 INSTALLATION OF CYLINDER GATE TURBINES sccccscoscecccscescscccscesescecescucescsseecscescscscscsescesescesescucescesesceseccecess 14 S LITTERA PURE ss ccccasatasccesseausesesdinsusqerccsssanesodswenasevesnacens svausanessansspeswonascsesancens sveusavessenaspeswendcpsansnoepesvousavessencemessenss 16 1 Introduction This report deals with the modules for automatic control of freeboard and turbine operation on board the Wave Dragon Nissum Bredning WD NB prototype and covers what has been going on up to ultimo 2003 The modules have been implemented on board WD NB by means of a Siemens PLC The control and monitoring of the PLC 1s achieved through a SCADA software package SIMATIC WinCC V6 running on a Windows 2000 PC situated on board preliminary Users manual 1s available Nimskov 2003 The two modules for automatic control of freeboard and turbine operation are denoted Buoyancy and Generators respectively in the SCADA system The Buoyancy part controls the freeboard by blowing air into or letting air out of air chambers underneath the structure and thereby raise or lower it The generator part controls2. Aalborg Universitet AALBORG UNIVERSITY DENMARK Automatic Control of Freeboard and Turbine Operation Kofoed Jens Peter Frigaard Peter Bak Friis Madsen Erik Nimskov Morten Publication date 2004 Document Version Publisher s PDF also known as Version of record Link to publication from Aalborg University Citation for published version APA Kofoed J P Frigaard P B Friis Madsen E amp Nimskov M 2004 Automatic Control of Freeboard and Turbine Operation Wave Dragon Nissum Bredning Aalborg Department of Civil Engineering Aalborg University Hydraulics and Coastal Engineering No 1 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights Users may download and print one copy of any publication from the public portal for the purpose of private study or research You may not further distribute the material or use it for any profit making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us at von aub aau dk providing details and we will remove access to the work immediately and investigate your claim Downloaded from vbn a
3. 31 03 03 and severe erosion of dummy turbine gate 11 08 03 11 As a result of this erosion two of the three dummy turbines jammed In addition the hydraulic cylinder in one of the turbines was damaged bent in the process of attempting to move it The cylinder was removed and has since been repaired at the workshop In light of theses operational problems dummy turbine re conditioning work was carried out AII three turbine shells were extracted individually using the hoist shown in Fig 4 6 left before rust removal and treatment was carried out Galvafroid and greased The result is shown in Fig 4 6 right Fig 4 6 Hoist used for dummy turbine removal and dummy turbines following maintenance This allowed the shells to open and close effectively In addition the re conditioned hydraulic cylinder was installed in the appropriate turbine three turbines now operate satisfactorily Doubts remain however as to the long term operating ability of same Efforts need to be concentrated on improving the vertical guidance of the shells with a self centering system preferred Another point of note involves the operation of the siphon turbine It was reported 11 08 03 that the hydraulic cylinder for operating the aeration valve on the siphon turbine did not work Without any corrective action in the interim this valve was found to function on the visit dating 15 09 03 Despite this it 15 planned to carry out inspection tests on a
4. 10 Preliminary overtopping data from WD NB prototype As it is seen from Fig 4 10 some scatter is present in the preliminary overtopping data Though the main impression 15 that the measured overtopping rates are in the expected range based on the findings from the laboratory However more data will soon be available and more solid conclusions can then be drawn Installation of cylinder gate turbines On 12 09 03 the six cylinder gate turbines were installed Below are some of the pictures from the process 14 Fig 4 13 Installation of draft tube and installed turbines Installation of generators is currently ongoing Testing of the WCU has been done and running in of the system is also ongoing 15 5 Literature Hald T and Frigaard P 2001 Forces and overtopping on 2 generation Wave Dragon for Nissum Bredning Phase 3 project Danish Energy Agency Project no ENS 51191 00 0067 Hydraulics amp Coastal Engineering Laboratory Aalborg University Hald T and Friis Madsen E 2001 Strategy for regulating the crest freeboard of a floating wave energy converter Int Conf on Marine Renewable Energies MAREC 2001 Newcastle Kofoed J P and O Donovan E 2003 Status report First offshore experiences Wave Dragon Nissum Bredning The Hydraulics and Engineering Group Aalborg University Nov 2003 Knapp W and Riemann S 2003 Measurements on Wave Dragon Nissum Bredning on 24 of May 2003 Dummy turbine cal
5. Fig 3 6 Buoyancy test sequence in calm waves no overtopping First reservoir is filled by use of Flygt pump Then TFL was changed from 44 to 88 cm However the water is lost before TFL is reached see figure below 18 2004 1202 01 Current user jen peter Significant wave height 10 5 Basin work span Basin relative level N T HUHN mme o 001101 frend nthe tore ona Pes Fig 3 7 Basin level during increase of floating level going from 44 to 88 cm As it can be seen the water is lost A significant experience has been that the system for measuring actual floating level heel and trim initially installed on board WD NB has not performed well The system was based on 4 pressure transducers place underneath the floating platform in the front of the ramp under the turbine area and one in each of the rear corners It has turned out that these transducers can not produce reliable outputs over long time months because of what seems to be a drift in the offset probably caused be the harsh conditions they are working under marine growth etc It should be noted that the pressure transducers are not accessible for other but a diver Initially this was initially worked around by frequently re adjusting the offsets but this is not a sustainable solution Therefore two inclinometers have been installed for the measurement of heel and trim and retracta
6. WD NB is responsible of achieving the wanted floating level heel and trim Generally the target for the heel and trim regulation 15 to keep the platform level heel and trim at 0 However the SCADA configuration page allows for specifying another constant target value for heel and trim The target floating level TFL can be specified using 4 parameters A and B in the expression TFL A H B where is the significant wave height and a min and max TFL value Thus the TFL can be set to a constant value or to be a linear function of the wave height with an upper and lower boundary As described by Hald amp Friis Madsen 2001 the regulation of the freeboard can also be done without measuring the directly In this case 15 estimated based on the current overtopping rate for the current crest freeboard and an assumption on the relation between the peak period and H Then from the optimal crest freeboard can be determined From this it can also be seen than the H is merely an intermediate link which actually is not necessary In principle the optimal crest freeboard can be determined based on the current overtopping rate and the current crest freeboard alone However problems can arise as the measurement of especially the current overtopping rate might be influenced by errors due spilling the overtopping rate 15 measured by adding up the outflow through the turbines Therefore at the current state of the project t
7. au dk on december 16 2015 AALBORG UNIVERSITY Automatic Control of Freeboard and Turbine Operation Wave Dragon Nissum Bredning Project Sea Testing and Optimization of Power Production on a Scale 1 4 5 Test Rig of the Offshore Wave Energy Converter Wave Dragon according to EU ENERGIE contract no ENK5 CT 2002 00603 Jens Peter Kofoed amp Peter Frigaard Aalborg University Erik Friis Madsen Wave Dragon Aps Morten Nimskov Balslev February 2004 Department of Civil Engineering Aalborg University Sohngaardsholmsvej 57 DK 9000 Aalborg Telephone 45 9635 8080 ave Dragon EL AUTOMATION INFORMATIK UN e l re DEPARTMENT OF CIVIL ENGINEERING 1 AALBORG UNIVERSITY SOHNGAARDSHOLMSVEJ 57 DK 9000 AALBORG DENMARK TELEPHONE 45 96 35 80 80 TELEFAX 4598 14 25 55 e Lx p Hydraulics and Coastal Engineering No 1 Automatic Control of Freeboard and Turbine Operation Wave Dragon Nissum Bredning by Jens Peter Kofoed amp Peter Frigaard Aalborg University Erik Friis Madsen Wave Dragon Aps Morten Nimskov Balslev Februar 2004 Table of contents Me INEFERODUC TION rc o t 3 PLCSCADA SYSTEM TETTE 4 A BUOYANCY CONTROL hd dieses 6 BIO AIC PIS sa eed cle a 6 OPERATING EP BRI IN NEIN
8. ble pressure transducer is under installation for measuring the floating level 4 Generator control The generator control module consists of a PLC part and a frequency converter and controller unit delivered by West Control WCU The different parts play different roles in the control of the generators and thereby the turbines e Based on the relative basin level a percentage of the basin level work span in which the turbines are active the PLC decides which turbines should be on Based on the pressure head over the turbines calculated from the floating level and basin level and the turbine characteristics the optimal turbine speed 15 set by the PLC for each turbine The status and the wanted turbine speed for each turbine is send to the WCU This is applicable for real turbines the siphon and cylinder gate turbines The PLC also controls the activation of the siphon on the siphon turbine and the cylinder gates on the cylinder gate and dummy turbines Based on the wanted speeds sent to the WCU from the PLC the PLC operates the frequency converters and thereby the generators in each turbine to obtain the wanted turbine speed The actual speeds are then reported back to the PLC along with information about the power voltage current and cos phi for each turbine generator Initial operation experiences Initial operation of the turbines highlighted the need for some adjustments including Water level switch
9. es required for identifying water in aeration tube and lubricating water siphon turbine see Fig 4 1 e Large diameter pipe in aeration tube to avoid water in the vacuum pump see Fig 4 2 e Debris collecting at the dummy turbines in cases of heavy overtopping preventing operation of same This problem will be eliminated with the planned inclusion of mesh fence to be placed all around the turbine area prior to the start of operation of the cylinder gate turbines see Fig 4 3 e Intrusion of saltwater in solenoids controlling the hydraulic pistons in the turbines This has on more than one occasion lead to malfunction of the pistons Shielding of these units has been installed see Fig 4 4 e Corrosion of black steel dummy turbines More on that below Fig 4 1 Aeration tube water level switch installation and siphon turbine water level switch 10 Fig 4 4 Saltwater corrosion of solenoid 23 06 03 The adverse effects of sea conditions on the operational integrity of WD have nowhere been more noticeable than in the functioning of the dummy turbines It 15 interesting to compare the depreciation of the turbine gate material black steel over the five month period at sea Fig 4 5 shows the dummy turbine shell after deployment in late March In contrast the severe erosion of the annular ring of the turbine gate through which the shell slides is clearly evident four 2 months later Fig 4 5 Dummy turbine condition
10. his approach has not been utilized The buoyancy control adjusts the floating level heel and trim by regulating the air pressure and thereby also the water level in the air chambers underneath the reservoir These chambers are divided into 5 zones and air can be blown into or lead out of each of them individually by means of valves and a blower controlled by the PLC Initial buoyancy testing Much of the preliminary testing was carried out without the reflectors in place An obvious initial test was to examine the floating ability of the main body This involved evacuating the air chambers Fig 3 1 Complete flooding of reservoir with no pressure in air chambers It was also of interest to examine the behavior of the main body in cases of significant heel to the front and rear In the case of extreme heel to the rear it is obvious from Fig 3 1 that there 1s no flooding of the container Indeed there is an allowance of approx 20 cm from water level to container base In contrast Fig 3 2 shows WD with a heel of approx 10 in the forward direction A useful feature of forward heel 1s the ability to walk along the rear base plate to carry out maintenance work see Fig 3 2 Fig 3 2 Heel of 10 to the front This leaves the base plate uncovered Operating experience The first layout of the buoyancy control module was able to achieve and maintain the wanted floating level and also to control heel and trim reasonably for lower float
11. ibration Laboratorium f r Hydraulische Maschinen Technische Universit t M nchen Germany Nimskov M 2003 Wave Dragon SCADA interface User manual Balslev December 2003 16
12. ing levels However for higher floating levels and thus typically higher wave states and filled reservoir the heel and trim regulation becomes quite unstable men Boyance step Significant wave height cm ts ARRA TETTE MEM EM M re 601922703 1352 0 16 17 00 224200 2 07 00 CF VW 1 57 00 162320 20 99 00 01 1220 63300 100220 14 2300 185220 231360 034200 02 09 00 12 3 00 15 59 00 21240 01 1300 14 00 102300 Tine Trend in the Foreqrcuns Rost Jove Fig 3 3 Floating conditions in harsh wave climate using initial control module layout The control strategy have been tested and optimized and the optimization is still in progress In order enable detailed adjustments of the buoyancy regulation a number of additional control parameters have been included for configuration in the SCADA system nad 1 yit op a n EE seco F nad i eel LL ILILIL IE JE JH PMR x T Fig 3 4 Configurable control parameters buoyancy regulation on the left The current situation is that the performance of the buoyancy regulation has been improved significantly see the figures below However adjustments and optimization of the regulation will continue Fig 3 5 Buoyancy test sequence in calm waves no overtopping no water in reservoir First TFL was changed from 50 to 88 cm then from 88 to 44 cm
13. ll turbines dummy and otherwise A good opportunity to carry out this work may be to correspond with the installation of the systems on the six new K ssler turbines Danfoss Turbine performance data The specific speed as obtained from turbine calibration data Kofoed amp O Donovan 2003 was used in the evaluation of actual overtopping power production data see Fig 4 7 A similar approach to that used in the evaluation of the turbine calibration plot was adopted with time intervals of 10 seconds being used on this occasion to yield Flow V s Time performance series for WD as shown in Fig 4 8 12 Fig 4 7 Power production plot 0 04 0 035 0 03 0 025 0 02 q m 3 s 0 015 0 01 0 005 0 100 200 300 400 500 t s Fig 4 8 Flow V s Time series Furthermore the discharge due to overtopping was evaluated from established relationships based on the doubly curved overtopping ramp Hald amp Frigaard 2001 and compared with experimental results from the second Generation WD model Laboratory and calculated overtopping discharge rates where found as Calculated 0 063 m sec Measured 0 034 m sec See also Fig 4 10 The power production as depicted by the SCADA system does not agree with the hydraulic power 1 e mass flow rate x acceleration due to gravity x head Figures for average power production have been found to be 150 W from the SCADA system based on data fro
14. m the WCU while the available hydraulic power is found to be only 10 W The reason for this discrepancy has been found to be some problems in the communication between the PLC and the WCU which currently is being solved Preliminary analyses have also been performed on overtopping events as the one given in Fig 4 9 where the dummy turbines and the calibrations hereof by Knapp amp Riemann 2003 have been utilized The results hereof are given in Fig 4 10 13 17207004 1 28 FM Current user jang pater Basin work span cm Turbine step 4 Basin level cm as Basin relative bowed Significant wave height cm i dH i 1 J BI i ll all HT EUR 10 ill Ur il i ui T i i itai 1 1 A i 7 CI H LT US 7 OU 216 FH 230 Fe 235 PM Zag Pe 7 ferred artes Ew Fig 4 9 Example of basic data from the SCADA system used for calculation of the overtopping rates Prototype data 03 12 05 dummy turbines A Protype data siphon turbine Prototype data 04 02 04 dummy turbines Prototype data 04 02 05 dummy turbines Hald amp Frigaard 2001 0 003 0 0025 I 0 002 a amp 0 0015 8 0 001 9 0 0005 0 0 0 02 0 04 0 06 0 08 0 1 0 12 0 14 0 16 R R Hs sqrt Sop 27 Fig 4
15. stics 060104 B 14332005 21478 FM jens paiar Basin work span cm Turbine step 9 Basin tever form Pham nh 1 la ell Dd Se 11 1 m NS mne e mf m rr n me ram ms S BRE tooo PEF E WI ums 0C WC oy vnm 200FM 203 PN 23 210FMw Tow Inthe foreground DWS 222223 Pu aestu UH Fig 2 3 Graphs of turbine step and water level in reservoir left and Example of alarms right from the SCADA system Generally the SCADA system 15 used for control and configuration of the PLC and for data presentation The two main modules Buoyancy and Generator can be set to run in either manual or automatic mode When set to manual mode valves blowers etc can be operated manually while when in automatic mode the PLC controls the Buoyancy and Generator modules as set in the configuration part of the SCADA system Furthermore using the SCADA system it 1s possible to control the Flygt pump and the external lights on board Fig 2 4 The Flygt pump in operation Fig 2 4 shows the Flygt pump running which is used for pumping water to the reservoir for testing purposes in the case of no incoming waves For further information on the PLC SCADA system please refer to Nimskov 2003 3 Buoyancy control The buoyancy control of the
16. the generators and thereby the turbines by switching them on and of in order to maintain the water level in the reservoir within the specified work span Furthermore the generators are controlled by frequency converters so the rotational speed for each turbine 1s achieved corresponding to the optimal operation point In the following in introduction to the PLC and the SCADA system 15 given followed by descriptions of the Buoyancy and Generator modules 2 PLC SCADA System The running in of the PLC SCADA system has been on going over the period from system power up 07 04 2003 until 01 06 2003 when the reflectors were re mounted During this period the basic control modules for regulating the floating level and controlling the turbines were setup Fig 2 1 Connection of WD to the grid By the end of the period both the floating level and the turbine control systems were running in automatic mode However there were still items to solve as the automatic control systems were often stopped because alarm conditions were activated e g due to a stuck valve and the buoyancy control module has some instability problems especially for high floating levels Screen dumps from the SCADA system and pictures from the running in of the system are presented in Fig 2 2 and 2 3 Pent screen Fig 2 2 PC screen and supporting equipment for the SCADA system and the SCADA control system main page BALSLEV o AUTONATION Diagno
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