Post on 29-Jul-2020
transcript
HD MMC for platform-less HVDC offshore wind power collection system
Dr Chong Ng
Knowledge Area Lead, Electrical Infrastructure
20 Jan 2016
• ORE Catapult introduction
• Platform-less Offshore HVDC System
• Research History
• Current Status
• HD MMC
• State of the art
• HD Proposed Solution
Content
Catapults: A long-term vision for innovation & growth
• Established and overseen by the
Technology Strategy Board
• Bridging the gap between business,
academia, research and government to
create new products and services
• Open up global opportunities and generate
sustained economic growth for the future
• Delivering the ‘know-how’ economy
3
7Catapults
£1.4bnprivate and
public sector
investment
Offshore Renewable Energy (ORE) Catapult
Existing1. 50m blade test 2. Still water tank3. Wave flume4. Simulated seabed5. Wind turbine training tower6. Electrical and materials laboratories
New7. 3MW tidal turbine drive train 8. 100m Blade Test Facility9. Wind Turbine Nacelle Test Facility-201310. Offshore anemometry hub11. 7MW Wind Turbine
A Controlled and Independent Development Platform
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Electrical (HV & LV) Test Lab – Brief
• HV development laboratories – 600kVac, 1MVdc, 8kA, Rain drop simulator, Material lab
• Live environmental chamber – HV and current into chamber
• Flexible three phase LV network – generators & converters array (up to 100kW)
• Grid conformance testing – G59 test equipment in the facility
• 11kV 50Hz network available
• Vibration test rig – loads up to 500kg for endurance and accelerated ageing programmes
Project Example
HD MMC for Platform-less Offshore HVDC System
Project Example
Research History in here
Platform-less Offshore HVDC System
Features:
• HVDC power transmission from the very beginning• Reduce losses and components
• Decentralised multi-terminal HVDC system
• Increase availability – Offers flexibility and redundancy
• Reduce cost – Removal/minimise offshore substation
• Increase MMC voltage level without additional hardware
Objective: Develop a dedicated high fault tolerances, flexible and cost effective power collection technology for offshore wind industry
Converter topology analysis
Analysed across frequency range; 100Hz to 2kHz,
single phase
Findings:
Transformer core loss ≤ converter loss
Transformer core loss ≤ copper loss
HB-HB configuration:
+ Lower component count
+ Lower converter loss
- Less stable (power control) due to higher voltage
gradient
- Higher transformer loss (i.e. 1% higher than MMC)
MMC-MMC configuration:
+ Better control stability (<500Hz)
+ Lower transformer core loss
- Higher component count
- Higher converter loss
Results
• Optimum configuration found to
be HB-MMC at 1.4 kHz
• Majority of losses attributed to
converter conduction losses
• This can be decreased by
moving to 3-phase
• Different converter configurations modelled in Simulink
• HB-HB
• HB-MMC
• MMC-MMC
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
HB HB-MMC 7-11L MMC 11-11L MMC 11-25L MMC
50.5%55.1% 52.5% 50.4% 50.1%
26.4%23.1%
21.5%20.7% 20.8%
20.7% 19.8%23.9% 26.6% 26.8%
1.5% 1.4% 1.8% 1.9% 1.9%
0.8% 0.7% 0.3% 0.3% 0.3%
PL
oss
Core Loss
Secondary Winding Loss
Primary Winding Loss
Conveter Switching Loss
Converter Conduction Loss
• Based on input waveforms, the transformer
specifications are optimised and losses calculated
• Repeated for frequencies between 500 – 2,000 Hz
The Modular Multilevel Converter
• Its modular design make it ideal for
scaling up.
- Now used in a variety of
applications, including HVDC
• Very attractive for offshore wind
- Low THD on AC terminal
therefore no bulky filters
- High Efficiency
- High degree of controllability
L0 R0
iΔ_j Udc/2
Arm jp
Arm jn
ipj
ij
uarm_jn
Rdc idc
L0 R0
Rdc idc
inj
uarm_jp
Mpj1
Mpj1
Mpjm
Mnj1
Mnj1
Mnjm
Sb1
Sb2
SbnSwn
Sw1
Sw2 ucap
Vs
Vp Cmod
L0 R0
iΔ_j Udc/2
Arm jp
Arm jn
ipj
ij
uarm_jn
Rdc idc
L0 R0
Rdc idc
inj
uarm_jp
The Modular Multilevel Converter (MMC) Limitations
Mpj27
Mpj26
Mpj28
Mpj24
Mpj23
Mpj25
Mpj21
Mpj20
Mpj22
Mpj18
Mpj17
Mpj19
Mpj15
Mpj14
Mpj16
Mpj13
Mpj12
Mpj10
Mpj9
Mpj11
Mpj8
Mpj7
Mpj5
Mpj4
Mpj6
Mpj2
Mpj1
Mpj3
Mnj27
Mnj26
Mnj28
Mnj24
Mnj23
Mnj25
Mnj21
Mnj20
Mnj22
Mnj18
Mnj17
Mnj19
Mnj15
Mnj14
Mnj16
Mnj13
Mnj12
Mnj10
Mnj9
Mnj11
Mnj8
Mnj7
Mnj5
Mnj4
Mnj6
Mnj2
Mnj1
Mnj3
• Each module can only create 1 AC voltage
level Lconv:
𝐿𝑐𝑜𝑛𝑣 = 𝑛𝑚𝑜𝑑 + 1
• Therefore many modules required to reduce
THD < 3 % (≈ 30)
• Each module requires 2 valves and a large
capacitor
- Capacitor contributes to roughly 50 % of the
module volume
• Therefore low THD increases converter losses
but crucially converter size and weight
• A LARGE offshore platform required to support
it.
• Platform accounts for ≈ 70 % of substation
cost therefore significant savings possible by
reducing size
L0 R0
iΔ_j Udc/2
Arm jp
Arm jn
ipj
ij
uarm_jn
Rdc idc
L0 R0
Rdc idc
inj
uarm_jp
The High Definition Modular Multilevel Converter
• By using the novel HD-MMC control
algorithm 1 module corresponds to
multiple AC voltage levels
• Using the HD-MMC algorithm only 12
modules are required to create 29 L
• This is achieved by grouping modules into
sets, controlling each to provide additional
voltage levels such that LHD is given by:
• Therefore fewer capacitors and fewer
valves
• This results in a more compact converter
reducing platform size and cost
Mpj27
Mpj26
Mpj28
Mpj24
Mpj23
Mpj25
Mpj21
Mpj20
Mpj22
Mpj18
Mpj17
Mpj19
Mpj15
Mpj14
Mpj16
Mpj13
Mpj12
Mpj10
Mpj9
Mpj11
Mpj8
Mpj7
Mpj5
Mpj4
Mpj6
Mpj2
Mpj1
Mpj3
Mnj27
Mnj26
Mnj28
Mnj24
Mnj23
Mnj25
Mnj21
Mnj20
Mnj22
Mnj18
Mnj17
Mnj19
Mnj15
Mnj14
Mnj16
Mnj13
Mnj12
Mnj10
Mnj9
Mnj11
Mnj8
Mnj7
Mnj5
Mnj4
Mnj6
Mnj2
Mnj1
Mnj3
Reduce
modules
Reduce
modules
Group
into sets
Group
into sets
Proposed HD-MMC Control
• Non intrusive, the HD-MMC control algorithm (red) can be
inserted as an add on to the standard control methods
(blue) of the MMC.
• This simplifies implementation
HD-MMC Simulation Results
• On the left is a standard 28 level MMC and on the right is the HD-MMC concept.
• Capacitor voltages are maintained at set value throughout simulation
ORE Catapult
Inovo
121 George Street
Glasgow
G1 1RD
T +44 (0)333 004 1400
F +44 (0)333 004 1399
info@ore.catapult.org.uk
ore.catapult.org.uk
ORE Catapult
National Renewable Energy Centre
Offshore House, Albert Street
Blyth, Northumberland
NE24 1LZ
T +44 (0)1670 359 555
F +44 (0)1670 359 666
info@ore.catapult.org.uk
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