Enabling Pressure Tolerant Power Electronics - PTPE for Deep Water Applications

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Anissa Chambers
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1 Enabling Pressure Tolerant Power Electronics - PTPE for eep Water Applications Findings and interim conclusions from 10 years of research at SINTEF Energy Research Magnar.Hernes@sintef.no 1

Two Research projects at SINTEF Energy Research on Pressure Tolerant Power Electronics

The Research Council of Norway and 7 industry partner 2012-2016: "Pressure Tolerant

Council of Norway and 9 industry partner Main objective for both projects: Provide

pressure tolerant power electronic components and circuits Reliable operation up to

2 Two Research projects at SINTEF Energy Research on Pressure Tolerant Power Electronics : Feasible power electronics for demanding subsea applications Financed by The Research Council of Norway and 7 industry partner : "Pressure Tolerant Power Electronics for sea 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 PTPE Pressure Tolerant Power Electronics 2

3 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 3

4 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 (EH) 4

5 A general 3-phase AC/C converter P 2 Q V C-link U V V,I,f W 1 Filter reactors Bidirectional active power flow Bidirectional reactive power flow Very fast transition C-link capacitor bank Switching devices 5

6 IGBT - Insulated Gate Bipolar ansistor Today the most common switching device Various encapsulations A 750A/ 6500V IGBT module from Infineon 1000A/4500V StakPak press-pack IGBT from ABB A 1800A/ 4500V hockey puck type press-pack IGBT from Westcode 6

7 Converter topologies for higher voltage levels 2 2 Modular Multilevel Converter - MMC module #1 module #1 module #1 C-link U Vdc U phase V W 1 IGBT_1 Vdc_ module # module # module # L-VCS (one phase-leg) IGBT_2 module #n module #n module #n 2 Vdc/2 Neutral point U phase Vdc Single devices limited by voltage and current rating [H] [H] module #1 module #2 [H] [H] module #1 module #2 [H] [H] module #1 module #2 Vdc/2 1 Series connection of IGBTs module #n module #n module #n 3L-VCS (one phase-leg) ue to voltage limitation of single power semiconductors, high voltage converters need more complex topologies and/ or series connection of IGBTs 7

flat constructions Less filler material (liquid) Reliability and cost Natural cooling possible No moving

8 Potential advantages by pressure balanced solutions 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 Pressure balanced construction with direct conductive heating through walls of vessel 8

9 Pressurized converter power circuit One bar compartment for converter central control Converter driver and sensor interface Aux. power Pressure barrier bar liquid environment river river IGBT drivers with electric or optic interface r. r. r. Sensors V, I, T, P,H r. r. r. 9

10 Focusing the assumed most critical power components Identify the most critical components of a power electronic converter Power semiconductors, C-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 10

11 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. edicated 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. 11

12 Options for enabling PT planar/ bonded IGBT modules Plastic housing / Hard cover 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. Gel E2 iode 2 E1 ansistor T1 Base plate / Heat sink New top coating (blue) Gel E2 iode 2 E1 ansistor T1 Base plate / Heat sink Coating for chip protection (orange) E2 iode 2 E1 ansistor T1 Base plate / Heat sink C1 C1 C1 12

humidity Material compatibility Vce Guard rings for controlling E- field 1200V, 400 m Live experiments

13 Investigering the most critical locations of the semiconductor chips edicated insulation material experiments On IGBT & diode chips On substrates Complete modules Long term insulation stress Controlled humidity Material compatibility Vce Guard rings for controlling E- field 1200V, 400 m Live experiments with converter modules Alternative insulation schemes In switch mode operation Up to rated component voltage of 6.5 kv 13

14 Some PP-film capacitor challenges Assumed interior weak points of metallized film capacitor Risk for unsuccessful selfhealing under high pressure 14

15 Power semiconductor test objects 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 Gate Emitter Collector 15

16 IGBT driver electronics test object Pressure vessel External signalling External power Signal (Opt) SINTEF driver interface board Power Concept 1SC0450V driver 16

17 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 17

18 Test cell for experiments with live converter module in liquid pressurized environment Major HSE concerns: High voltage High current High pressure Solved by: Custom test circuits Certified pressure vessels Multiple safety barriers 18

Test circuit for experiments with live converter modules in liquid pressurized environment 0-300 bar Solving

supply Very high impedance insulation tester Circulating power Limiting external C buffer capacitor Limiting

safety barriers 400 V supply Variac 3 3 3 3 IGBT driver R S IGBT driver IGBT driver High voltage High

19 Test circuit for experiments with live converter modules in liquid pressurized environment bar 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 C buffer capacitor Limiting capacitor test object in pressure vessel Pressure vessel certified to 500 bar 100% liquid filling Multiple safety barriers 400 V supply Variac IGBT driver R S IGBT driver IGBT driver High voltage High impedance source + - IGBT driver Pulse testing Continuous switching Voltage withstand ability testing Pressure vessel 19

impedance voltage source Resonant mode current control Pressure vessel certified to 500 bar 100% liquid filling Multiple safety

20 Live experiments of capacitors in pressurized environment p tank P Pressure vessel U C + H T T liquid V V C,cap - C1 C2 U C T T cap A A 10:6 I cap T A C L filt T tank V C,inv V AC V T T room 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 Characterization: IEC 61071:2007 Voltage: Up to 1.5x rated C Current: Up to rated AC Test liquid: Midel@7131 Pressure: bar 20

21 Insulation material experiments Materials Liquids Conditions 1. Midel Synthetic ester Influence of water 2. FR3 Organic ester Influence of temperature 3. Fluorinert FC-77(3M) 4. Perfluorpolyether Galden (Solvay) 5. Monobenzyltoluene - Jarylec Test objects Custom made PCB 6.5 kv BC substrate 4.5 kv diode chips 6.5kV IGBT modules Materials surface cover 1. Parylene 2. Silicone Gels 3. Polyimide 21

22 Chip termination area is vulnerable for particles 4.5kV diode Test object Microscopy analysis after insulation breakdown 22

23 Findings from live experiment with converter module 0-300bar Pressure test program max ~160 usec VIGBT 1 sec 1 sec IIGBT time time VFW Measuring Turn ON/OFF IFW time time "ouble pulsing" waveforms 23

Some findings from live experiments of PP film capacitors

manufacturers gives reason to suspect unsuccessful

24 Some findings from live experiments of PP film capacitors bar in synthetic ester Midel 7131 Failures have been experienced When subject to 1.5 times rated C voltage Own post investigations and by the manufacturers gives reason to suspect unsuccessful "self-healing" Several successful events Close to failure (several layers penetrated) Complete failure 24

25 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 C-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 25

26 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 26

Interim conclusions other components in 0-300 bar Magnetic

Ferrite cores, Nanoperm, Arnold powder cores Mapping coercive

or less affected by pressure All test objects seem to be

Temperature and humidity sensors All have maintained their

influence from 4pressure on functionality, accuracy,

(operated at 500 Hz) 3: Nanocrystalline core (operated at

5 to penetrator) 5: Close-up of LEM1 bar UP 6: LEM capsule

27 Interim conclusions other components in bar Magnetic core materials Iron wound cores, Amorphous wound cores, Ferrite cores, Nanoperm, Arnold powder cores Mapping coercive force, saturation 2 flux density, relative permeability More or less affected by pressure All test objects seem to be possible candidates, provided proper design 3 considerations Temperature and humidity sensors All have maintained their specified functionalities Current transducers Close to no influence from 4pressure on functionality, accuracy, characteristics 1 1: pressurized LEM 2: Amorphous core (operated at 500 Hz) 3: Nanocrystalline core (operated at 5000 Hz) 4: Cable connectors (connected 1.5 to penetrator) 5: Close-up of LEM1 bar UP 6: LEM capsule 300 bar 1 1 bar OWN Magnetic flux B [T] Ampere-turns N*I [At] 6 27

28 Thank you for your attention! 28

Power Electronics Roadmap. Updated by the Advanced Propulsion Centre in collaboration with and on behalf of the Automotive Council

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