Component and system design of a mild hybrid 48 V powertrain for a light vehicle
Doctoral thesis, 2020

This thesis presents contributions in three areas relevant for the development of 48 V mild hybrid electric powertrains for cars.

The first part comprises methodologies and extensive testing of lithium-ion battery cells in order to establish the electric and thermal performance using equivalent circuit models.  Empirical, lumped-parameter models are used to ensure fast simulation execution using only linear circuit elements. Both electrochemical impedance spectroscopy and high-current pulse discharge testing is used to extract model parameters. Plenty of parameter results are published for various cells, temperatures and SOC levels. Further on, the model accuracy in voltage response is also evaluated. It is found that an R+2RC equivalent circuit offers the lowest error, 11 mV RMSE in a 1.5 h drive cycle, which is among the lowest numbers found in the literature for similar models.

In the second part, electric machines with tooth-coil windings are explored as a viable candidate for mild hybrids. First, a method of analytically calculating the high-level electro-magnetic properties for all possible combinations of three-phase, dual layer tooth-coil winding machines is established and presented in a graphically appealing manner.  Then, a pair of pseudo-6-phase 50 kW PMSMs are designed, constructed and validated in a custom designed calorimetric dynamo test stand. These machines feature in-stator and in-slot forced oil cooling, enabling very high current densities of 25 A/mm² continuous and 35 A/mm² peak. A high net power density (19 kW/l) and a large area of high peak efficiency (95%) is shown numerically and validated by calorimetric measurements.

Finally, low-level design, construction and evaluation of 48 V inverter hardware is explored. By using high-performance, extra-low-voltage silicon-based MOSFETs with custom designed metal substrate printed circuit boards, custom made gate drivers, and water cooling, 3x220 A RMS is reached experimentally on a 154 cm² area and an efficiency of 95.6%.

MOSFET

48 V

Calorimetric measurement

Inverter

Li-ion battery

Permanent Magnet Synchronous Machine

Efficiency

Hybrid Electric Vehicle

Power Electronics

PWM

Multi-phase

Power density

Extra low voltage

Oil cooling

Online - please e-mail PhdAdm.e2@chalmers.se in advance to get the password
Opponent: Thomas M. Jahns, University of Wisconsin-Madison

Author

Stefan Skoog

Chalmers, Electrical Engineering, Electric Power Engineering, Electrical Machines and Power Electronics

Parameterization of Equivalent Circuit Models for High Power Lithium-Ion Batteries in HEV Applications

18th European Conference on Power Electronics and Applications, EPE 2016 ECCE Europe, Karlsruhe, Germany, 5-9 September 2016,; (2016)

Paper in proceedings

Pole-Slot Selection Considerations for Double Layer Three-phase Tooth-Coil Wound Electrical Machines

2018 XIII International Conference on Electrical Machines (ICEM),; (2018)p. 934-940

Paper in proceedings

Experimental and model based evaluation of mile hybrid fuel consumption gains and electric machine utilization for personal vehicle application

2017 IEEE Transportation Electrification Conference and Expo, Asia-Pacific, ITEC Asia-Pacific 2017,; (2017)

Paper in proceedings

Electro-thermal modeling of high-performance lithium-ion energy storage systems including reversible entropy heat

Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC,; (2017)p. 2369-2373

Paper in proceedings

Acquaviva, A. Stefan, S. Thiringer, T. Design and Verification of In-slot Oil-Cooled Tooth Coil Winding PM Machine for Traction Application

Acquaviva, A. Stefan, S. Grunditz, E. Thiringer, T. Electromagnetic and Calorimetric Validation of Direct Oil Cooled Tooth Coil Winding PM Machine for Traction Application

Acquaviva, A. Stefan, S. Thiringer, T. Manufacturing of in-slot cooled tooth coil winding PM machines

En stor andel av världens energiförbrukning används av bilar, vilka så gott som uteslutande drivs på fossila bränslen. Ett mycket kostnadseffektivt sätt att öka verkningsgraden och därmed minska utsläppen från nya fordon är att introducera elektriska stödfunktioner till förbränningsmotorn, så kallad elektrisk mildhybrid. I detta arbete undersöks ett elektriskt stödsystem som är begränsat till 48 V likspänning, vilket innebär att det kan klassas som ett relativt ofarligt system från elsäkerhetsperspektiv. Två av de elektriska huvud-komponenterna har studerats i detalj: högpresterande litium-jonbatterier och kompakta växelströmsmaskiner. För att kunna virtuellt representera batterierna under fordonens utvecklingsprocess har olika modeller och testmetoder utvärderats och tillämpats på många olika sorters litium-jonbatterityper. Det visar sig att pulsad urladdning med hög ström lämpar sig mycket väl för att extrahera en kraftfull elektrisk modell över batteriernas beteende som erbjuder mycket hög. Två växelströmsmaskiner har utvecklats från grunden, byggts och testats elektromekaniskt för att utvärdera deras prestanda. Två speciella egenskaper har byggts in i dessa maskiner: Direkt oljekylning och ett modulärt lindningskoncept. Tester av motorerna har gjorts upp till 24 kW kontinuerligt och det dubbla i toppeffekt. Verknings-graden är uppmätt till 95% och storleken på maskinens aktiva komponenter är väldigt kompakt; jämförbar effektdensitet med marknadsledande bilmärkens elmaskiner.

Utilize 48V system to gain CO2, safety & improved UX

VINNOVA, 2014-04-01 -- 2017-12-31.

Areas of Advance

Transport

Subject Categories

Aerospace Engineering

Other Materials Engineering

Other Electrical Engineering, Electronic Engineering, Information Engineering

ISBN

978-91-7905-323-9

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4790

Publisher

Chalmers University of Technology

Online - please e-mail PhdAdm.e2@chalmers.se in advance to get the password

Online

Opponent: Thomas M. Jahns, University of Wisconsin-Madison

More information

Latest update

5/29/2020