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Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Generator Requirements and Functionality for Ocean Energy
ConvertersDr. Dara O’Sullivan
Hydraulics & Maritime Research Centre, UCC
21st Oct 2010
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Overview
Evolution of generator technology Common requirements of OE generators Device specific requirements of OE
generators Generator functionality within OE devices
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Traditional Generators
Synchronous Fixed speed Fault current – 3-4 pu Field regulated reactive power
Turbine
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Technology Migration
Asynchronous
Two-speed
Variable Speed
Variable SpeedGearless
Driven by Wind Turbine Development
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Technology Drivers
Energy Capture – MPPT Mechanical Robustness – drive-train torque
loads Grid Connect Codes Reliability
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
What about OE Generators?
Are the issues the same as wind? What are the differences?
= ?
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Generator Requirements
Common Device Specific
Environmental
Grid Connect
Speed Range
Torque Rating
Custom or OTS
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Operation and Maintenance
High cost – minimise requirement!Tidal – Expensive to perform at bestWave – weather windows
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Brushed Generators
Typical brush life – 3-8k hrs Twice yearly maintenance/replacement –
corresponds with wind industry best practice Brushes are considerably more inaccessible
in many OE devices Brush film formation disrupted in oscillatory
current flows – significantly enhanced wear
Brushed generators may be unsuitable for OE devices
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Corrosion
Saline air exposure Not air conditioned generator enclosures PMGs sensitive Special coatings available e.g. VACCOAT
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Mechanical Design
Significant heave and pitch accelerations in many devices e.g. OWC:Pitch: 7deg/s2
Pitch: 4 m/s2
2x bearing rating due to gyroscopic loads
Robustness important
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Grid Connection
Voltage Limits Voltage Distortion Flicker Reactive Power Control Requirements Active Power Control Requirements Fault Ride-Through
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Voltage Distortion
HVMV
LV
t
Pelec
t
Local Voltage
10s
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Generator Grid Connect OptionsFully variable speedReactive power controlControlled fault ride-through
‘Fixed’ speedNo reactive power controlNo fault ride-through
Fixed speedReactive power control Controlled fault ride-through
Limited variable speedLimited reactive power controlControlled fault ride-through
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Device Specific Requirements
Oscillating Water Column Hydraulic Point Absorber Overtopping Device with Hydro PTO Direct Drive Point Absorber Tidal Turbine Tidal Oscillating Hydrofoil
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Oscillating Water Column
Air turbine with limited range of efficient operation
Variable speed OTS design High peak-to-average
torque ratio
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Hydraulic Point Absorber Generator design
strongly linked to hydraulic circuit design
Fixed speed possible OTS possible Hydraulics can absorb
torque pulsationsWavebob Prototype
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Overtopper Conventional hydro
turbines High pole or gearbox
coupled Rating equals maximum
mean power Fixed speed possible Wave Dragon prototype
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Direct Drive Point Absorber
Direct drive linear or rotary generator Custom design Must have power electronics conversion Low speed and high torque High part load efficiency very important
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Tidal Devices
Tidal turbinesMarine equivalent of wind turbinesHigher gear ratios
Oscillating hydrofoilsSimilar to hydraulic point absorbers
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
Functionality
Determines how the generator sits within the power conversion chain1. Power conversion
2. Prime mover efficiency optimisation
3. Power smoothing
4. Damping control
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
SummaryOEC Prime Mover Speed
Range Generator Peak Torque
RangeGenerator Type
OWC 600-1500 rpm 2-4 pu; reduces with added inertia
VS SCIG/SG/PMG
PA - hydraulic
1000-3000 rpm Close to 1 pu with high accumulator storage, up to 4 pu as storage reduces
FS SG/SCIG-SVC for high storage designs
VS SG/PMG/SCIG for low storage designs
Overtop 100-250 rpm Close to 1 pu GBC: FS SG/SCIG-SVC or VS PMG/SCIG
Low speed VS PMG
PA - direct
0-3m/s 0-400 rpm
2-5 pu; reduces with added inertia
Linear: PMG (custom) Rotary: GBC VS SG/PMG
Tidal turbine
0-10 rpm Close to 1 pu GBC, FS SG/SCIG-SVC or VS SG/PMG/SCIG
Tidal hydrofoil
1000-3000 rpm Close to 1 pu FS SG/SCIG-SVC for high storage designs or VS SG/PMG/SCIG for low storage designs
Hydraulics & MaritimeResearch Centre
hmrc.ucc.ie
Charles Parsons Energy ResearchNUIM Ocean Energy Seminar, October 21st 2010
National Ocean Test Facility
THANK YOU
QUESTIONS?