Thoughts on System Level Design of DC Microgrids

1. S.D. Sudhoff, H. Suryanarayana*School of Electrical and Computer EngineeringPurdue University*ABBPECI 2016 Thoughts on System Level Design of DC Microgrids • This work was supported by the Office of Naval Research (ONR) through Grant N00014-08-1-0080 and N00014-14-1-0160 • Harish Suryanarayana was partially funded by a fellowship provided by ABB Inc.

2. DC Microgrids Source: ESRDC - USC

3. Steady-State Power Flow • Multiple Generators (2 main, 2 aux) • Energy Storage (?) • Propulsion (2) • Radar (1) • Weapon Systems (?)

4. Transient Constraints • Transient specifications are based on MIL-STD-704F Start-up constraint Transient event constraint

5. Distortion Constraints • The rms voltage ripple at each bus is subject to a limit • The rms current ripple going into each component, when supplied by / supplying an ideal source / ideal load is subject to a limit

6. Stability

7. Generalized Immittance

8. Generalized Immittance

9. The Design Spiral

10. Optimization Based Design

11. Consider a Trivial System Minimize metrics (mass, loss, …) subject to all constraints (transient, distortion, stability, …) being met

12. Reducing Dimensionality • Vendor • Power Electronics Building Block (PEBB) • Fixed switching frequency • Fixed gate drive, snubber • Shock, vibration, thermal • Control platform • System Integrator • Programmable controls • Exterior passives

13. Generation System

14. Converter Module

15. Degrees of Freedom • Machine: 1 at 20 DOF • Inductors: 5 at 10 DOF • Capacitors: 4 at 4 DOF • Transformers: 1 at 15 DOF • Control gains: 10 DOF • Total: 109 DOF

16. Further Reducing Dimensionality • Target: Power Magnet Components • Approaches • Catalogs • Densities • Metamodels

17. Metamodeling • Consider an simple inductor …

18. Scaling • To scale • Dimensions, areas, volumes, mass: • Current, current density: • Power, energy, time: • Time, frequency: • Not scaled • Magnetic flux density • Voltage

19. Inductor Metamodel

20. Of Interest …

21. Scaled Machine Design • To scale • Dimensions, areas, volumes, mass: • Force, torque: • Current, current density: • Power, energy, time: • Frequency, speed • Not scaled • Magnetic Flux density • Voltage • Base

22. Challenge: Core Loss • MSE Model • Modification • Observation

23. Challenge: Poles • Stator backiron volume decreases • Stator end conductor volume decreases • Rotor backiron volume decreases • Increase in loss with frequency compensated for by decrease in volume

24. Challenge: Poles • The limiting factor - leakage

25. Metamodel Formulation

26. Degrees of Freedom • Machine: 1 at 1 DOF • Inductors: 5 at 2 DOF • Capacitors: 4 at 4 DOF • Transformers: 1 at 1 DOF • Control gains: 10 DOF • Total: 18 DOF - Piece of Cake Rubarb Pie!

27. Back to Our Test System… Minimize metrics (mass, loss, …) subject to all constraints (transient, distortion, stability, …) being met

28. Specifications - Transient

29. Specifications - Distortion

30. Specifications - Stability

31. Design Space Control Parameters Passive Components

32. Fitness Function • The fitness function is constructed as follows:

33. Results of Optimization • The optimization routines were evaluated using an initial population of 2000 individuals for 80 generations.

34. Sample Design

35. Transient Design Validation

36. Stability Design Validation