Enabling Pressure Tolerant Power Electronics - …...1 Findings and interim conclusions from 10...
Transcript of Enabling Pressure Tolerant Power Electronics - …...1 Findings and interim conclusions from 10...
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Findings and interim conclusions from 10 years of research at
SINTEF Energy Research
Enabling Pressure Tolerant Power Electronics - PTPE
for Deep Water Applications
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Two Research projects at SINTEF Energy Research on
Pressure Tolerant Power Electronics
PTPEPressure TolerantPower Electronics
• 2006-2012: “Feasible power electronics for demanding subsea applications”– Financed by The Research Council of Norway
and 7 industry partner
• 2012-2016: "Pressure Tolerant Power Electronics for Subsea Oil and Gas Exploitation – PressPack– Financed by The Research Council of Norway
and 9 industry partner
• Main objective for both projects:– Provide fundamental material and packaging
knowledge for supporting realisation of reliable pressure tolerant power electronic components and circuits
– Reliable operation up to 500 bar ambient pressure, corresponding to 5000m sea depth
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This Presentation
Examples of subsea converter applications and power circuits
Converter circuitry and components
Potential advantages by PTPE
PT packaging challenges
Strategy for the research
Test objects, test facilities and test programs
Interim findings and conclusions
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Some subsea electric power converter applications
• Power supplies for control and monitoring
• Valve actuators
• Emergency power (UPS)
• Energy storage conversion
• Variable speed motor drives
• Pipeline heating systems (DEH)
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Q
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DC-link
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A general 3-phase AC/DC converter
• Bidirectional active power flow• Bidirectional reactive power flow• Very fast transition
Switching devicesDC-linkcapacitor bank
Filter reactors
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IGBT - Insulated Gate Bipolar Transistor
• Today the most common switching device
• Various encapsulations
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• A 750A/ 6500V IGBT module from Infineon
• A 1800A/ 4500V hockey puck type
• press-pack IGBT from Westcode
• 1000A/4500V StakPak
• press-pack IGBT from ABB
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Modular Multilevel Converter - MMC
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Converter topologies for higher voltage levels
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DC-link
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2L-VCS (one phase-leg)
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Series connectionof IGBTs
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Due to voltage limitation of single power semiconductors , high voltage converters need more complex topologies and/ or series connection of IGBTs
Single devices limited by voltage and current rating
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• Reduced weight and volume
Reduced container wall thickness
Full freedom for shape of container, e.g. flat constructions
Less filler material (liquid)
• Reliability and cost
Natural cooling possible
No moving parts (pumps, fans)
Reduced number of pressure penetrations
Reduced risk for leakage
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Potential advantages by pressure balanced solutions
Pressure balanced construction with direct conductive heating
through walls of vessel
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Pressurized converter power circuit
Dr.
Dr.
Driver Driver
SensorsV, I, T, P,H
Converter driver and sensor interface Aux. power
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One bar compartment forconverter central control
1-300 bar liquidenvironment
IGBT driverswith electric or optic interface
Pressure barrier
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• Identify the most critical components of a power electronic converter
Power semiconductors, DC-link capacitors, IGBT gate drivers
Auxiliary power supplies, I,V, P,T sensors etc. assumed to be located in pressure compartment
• Provide roadmap for the experimental work
Involving component and material manufactures
Provide custom made test objects
Provide the required special equipment for the experimental work
• Component material experiments
Electric insulation properties
Chemical compatibility
• Single components experiments
Passive tests and live tests
• Converter power modules
Live operation up to rated power for the components
With the most critical power components
Insulation tests, Pulse testing and Continuous operation
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Focusing the assumed most critical power components
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Summary of pressure tolerant packaging challenges
• Mechanical stress to encapsulations caused by the high pressure environment, and also possibly due to vacuuming processes in connection with filling.
– Dedicated experiments in pressure vessel with high pressure slew rates
• Possible change of functionality and characteristics of semiconductors due to pressure
– Such as changes in switching performance due to impact on driver electronics and/or directly on IGBT parameters.
– Live experiments with high voltage converter modules in pressure vessels
– Including IGBTs, driver electronics auxiliary supply, sensors etc.
• Impact from the pressurized environment on the "self-healing" performances of PP-film capacitors.
– Live testing of components according to established procedures for industrial applications
• Possible reduced performance of the electric insulating materials.
– Such as existing IGBT silicon gel facing various external insulation liquids.
– Systematical studies on silicon gel in contact with insulation liquid candidates.
• Impact from humidity on the power semiconductor insulation
– Giving requirements to the surrounding filling liquid, or to barriers between the most critical locations and external less critical filling liquid.
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Base plate / Heat sink
E1 C1 E2 Diode D2 Transistor T1
Plastic housing / Hard cover
Gel
E1 C1 E2 Diode D2 Transistor T1
Coating for chip protection (orange)
Base plate / Heat sink
Base plate / Heat sink
E1 C1 E2 Diode D2 Transistor T1
Gel
New top coating (blue)
Options for enabling PT planar/ bonded IGBT modules
Requirements:
• Provide 100% filling of solids or liquids
• Electrical insulation properties as good as or better than existing/replacement materials
• The required long term chemical compatibility between the new materials and with the existing component interface materials (e.g. with existing gel of IGBT modules, or with chip surface if gel is not used).
• Sealing properties (particles, ions, humidity) as good as or better than existing/replacement materials.
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Investigering the most critical locations of the semiconductor chips
Guard rings for controlling E- field
Vce
1200V,400m
• Dedicated insulation material experiments
– On IGBT & diode chips
– On substrates
– Complete modules
– Long term insulation stress
– Controlled humidity
– Material compatibility
• Live experiments with converter modules
– Alternative insulation schemes
– In switch mode operation
– Up to rated component voltage of 6.5 kV
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Some PP-film capacitor challenges
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Assumed interior weak points of metallized film capacitor
Risk for unsuccessful self-healing under high pressure
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• Planar bonded IGBT modules
• Highest voltage available (6.5kV)
• Press-pack IGBT
• Highest voltage available (4.5kV)
• Need 100% filling of dielectric liquid
• Good electric insulator
• Free from contaminants
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Power semiconductor test objects
GateEmitter
Collector
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IGBT driver electronics test object
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SINTEF driver interface board
Signal (Opt)
Power
Concept1SC0450V driver
Pressure vessel
External signalling
External power
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Capacitor test objects
• PP-film capacitor elements for live testing
• PP- films 4µm, 5.8µm, 8.5µm, 9.8µm
– for self-healing experiments
– for liquid compatibility experiments
• Ceramic capacitor test samples for live testing
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Test cell for experiments with live converter module in liquid pressurized environment
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Major HSE concerns:• High voltage• High current• High pressureSolved by:• Custom test circuits• Certified pressure vessels• Multiple safety barriers
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Test circuit for experiments with live converter modules in liquid pressurized environment 0-300 bar
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Solving HSE concerns:• Separate voltage supplies for continuous operation and
insulation testing High impedance line supply Very high impedance insulation tester
• Circulating power• Limiting external DC buffer capacitor• Limiting capacitor test object in pressure vessel• Pressure vessel certified to 500 bar• 100% liquid filling• Multiple safety barriers
• Pulse testing
• Continuous switching
• Voltage withstand ability testing
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IGBT
driver
IGBT
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IGBT
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supply
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driverRS
Pressure vessel
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Live experiments of capacitors in pressurized environment
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C1 C2
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• Characterization: IEC 61071:2007
• Voltage: Up to 1.5x rated DC
• Current: Up to rated AC
• Test liquid: Midel@7131
• Pressure: 0-300 bar
Solving HSE concerns:• Separate voltage and current control• High impedance voltage source• Resonant mode current control• Pressure vessel certified to 500 bar• 100% liquid filling• Multiple safety barriers
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Insulation material experiments
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Materials – Liquids1. Midel – Synthetic ester2. FR3 – Organic ester3. Fluorinert FC-77(3M)4. Perfluorpolyether – Galden (Solvay)5. Monobenzyltoluene - Jarylec
Test objects• Custom made PCB• 6.5 kV DBC substrate• 4.5 kV diode chips• 6.5kV IGBT modules
Materials – surface cover1. Parylene2. Silicone Gels3. Polyimide
Conditions
• Influence of water
• Influence of temperature
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Chip termination area is vulnerable for particles
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4.5kV diodeTest object
Microscopy analysis after insulation breakdown
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Findings from live experiment with converter module 0-300bar
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Pressuretest
program
VIGBT
IIGBT
VFWD
IFWD
Measuring Turn ON/OFF
time
time
time
time
1 sec
max ~160 usec
1 sec
"Double pulsing" waveforms
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Some findings from live experiments of PP film capacitors
• 0-300 bar in synthetic ester Midel 7131
• Failures have been experienced
– When subject to 1.5 times rated DC voltage
– Own post investigations and by the manufacturers gives reason to suspect unsuccessful "self-healing"
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Close to failure(several layerspenetrated)
Complete failure
Several successfulevents
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Interim conclusions capacitors
• PP-film capacitors and ceramic capacitors
– All electrical characteristics, such as capacitance and tan δ are well maintained in high pressure liquid environment up to 300 bar.
– The mechanical durability such as the film interconnection to the termination layers is maintained.
• PP-film capacitors
– Even though traces from the surrounding liquid are found inside the film roll, there are no indications of deterioration of the film metallization like erosion.
– The major concern is that the important self-healing mechanism of the metalized PP-film seems to be negatively affected by the high pressure.
– Continuing experiments applying reduced DC-voltage has been in operation for a significant longer period compared to those resulting in failure.
– This is taken as an indication that high pressure operability of PP-film capacitors could be feasible provided significant derating of operating voltage
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Interim conclusions IGBT and IGBT driver packaging
• All electrical characteristics as well as mechanical ruggedness are maintained at least up to 300 bar– IGBT voltage and current waveforms close to unaffected by pressure
– Indicating that IGBT and IGBT driver electrical functionality have the sufficient pressure ruggedness
• Chip termination area is vulnerable for fibers and other particles.– The chip and substrate interface need to be protected from direct contact with liquids by a
material with the sufficient mechanical and electrical properties.
– One option is to maintain the generally used silicon gel, however the long-term compatibility with adjacent liquids need to be further investigated
– Experiments with 30-50µm Parylene covering the silicon die surface look promising
– Long-term compatibility between liquids and adjacent IGBT materials to be further investigated
• Humidity control is important– By time humidity will penetrate the complete converter environment, including critical
locations
– Then either hermetically sealed components encapsulations are required
– Otherwise the complete converter filling liquid need to have humidity control
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Interim conclusions other components in 0-300 bar
• Magnetic core materials
– Iron wound cores, Amorphous wound cores, Ferrite cores, Nanoperm, Arnold powder cores
– Mapping coercive force, saturation flux density, relative permeability
– More or less affected by pressure
– All test objects seem to be possible candidates, provided proper design considerations
• Temperature and humidity sensors
– All have maintained their specified functionalities
• Current transducers
– Close to no influence from pressure on functionality, accuracy, characteristics
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-250 -200 -150 -100 -50 0 50 100 150 200 250-1.5
-1
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Ampere-turns N*I [At]
Magnetic f
lux B
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1: pressurized LEM2: Amorphous core (operated at 500 Hz)3: Nanocrystalline core(operated at 5000 Hz)4: Cable connectors(connected to penetrator)5: Close-up of LEM6: LEM capsule
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Thank you for your attention!