North East Pacific Time-series Underwater Networked Experiment (NEPTUNE): Power System Design, Modeling and Analysis

1. North East Pacific Time-series Underwater Networked Experiment (NEPTUNE):Power System Design, Modeling and Analysis Aditya Upadhye

2. Outline • NEPTUNE • Power system requirements • Two design alternatives • Version 1 • Version 2 • Cable analysis • Models • Simulation results • Conclusions and future work

3. NEPTUNE

4. Science requirements • Communication bandwidth - Gb/s • Power – 200kW • Reliability • Robustness of design • Thirty year lifetime • Maintenance and support

5. Power System Design • Basic tradeoffs • Frequency: ac versus dc • Network: radial versus interconnected • Loads: series versus parallel • Shore station supply at 10kV, 200kW • Max. current-carrying capacity = 10A • User voltage = 400V / 48V • Max. power at each node = 10kW

6. Power System Design • Protection • Sectionalizing circuit breaker • Breaker control • Monitoring and control • Current – voltage measurements • State estimation • Shore station control hardware / software

7. Power System Design: Version 1

8. Version 1 Circuit

9. DC Circuit Breaker Need • During initial energization • For fault isolation Required features • To force a current zero and minimize arcing • To prevent breaker restrikes

10. S2 S3 R1 R2 S4 S1 C DC Circuit Breaker Open Circuit

11. S2 S3 S4 R1 R2 S1 C DC Circuit Breaker Soft Closing

12. S2 S3 S1 S4 R1 R2 C DC Circuit Breaker Closed circuit

13. S3 S2 S4 R1 R2 S1 C DC Circuit Breaker Capacitor charging

14. S2 S3 S4 R1 R2 S1 C DC Circuit Breaker Capacitor discharging

15. DC Circuit Breaker Hardware prototype • 125V, 5A breaker circuit • Breaker control • MOSFETs drive the switch solenoids • Opto-isolator between logic circuit and driver circuit • Control logic has a counter, which continuously cycles through the breaker operations

16. DC Circuit Breaker Hardware prototype test results • Continuous Voltage: 125V • Continuous Current: 4.5A • Total Breaker Cycles: 125,000 • Normal cycle switching frequency: 20Hz • Maximum cycle switching frequency: 100Hz • Maximum tested voltage: 200V • Maximum tested current: 5A

17. Power System Design: Version 2

18. Version 2 Circuit

19. Branching Unit

20. Series Power Supply • Indigenous power supply for each BU • Less reliance on node converter • Use of zener diodes in reverse region • Back-to-back zener diodes

21. Modes of Operation • Normal • Fault • Fault-locating • Restoration Special case • System startup

23. Comparison of Version 1 and Version 2

24. Version 1 Version 2 Conventional approach to power system design Based on the philosophy that cable faults are rare but possible Response to a fault is at the system level by the shore station controls Response to a fault is at the local level by the nearest circuit breaker Circuit breaker is complicated with many components Complexity of circuit breaker is greatly reduced Fault current is interrupted; arcing and restrikes are possible Fault current is not interrupted; arcing and restrikes are not possible Single node failure can cause failure in a large section of the network Single node failure is not catastrophic for the system as that node only will be out of service Reliability is low Reliability is increased

25. Electromagnetic Transients Program (EMTP)

26. Alternate Transients Program

27. ATP Theory • ATP is a universal program system for digital simulation of transient phenomena of electromagnetic as well as electromechanical nature • With this digital program, complex networks and control systems of arbitrary structure can be simulated • Trapezoidal rule of integration

28. Cable Parameters

29. ALCATEL OALC4 Cable

30. Inductance Calculations • The generalized formulae were applied to the OALC4 cable • The core (steel) current caused flux linkages within a) the core b) the sheath c) the insulation • The sheath (copper) current caused magnetic flux linkages within: a) the sheath b) the insulation

31. Inductance Calculations Where T is the total flux linkage associated with the conductor, i is the flux linkage internal to the conductor, and e is the flux linkage external to the conductor Where icable is the total current in the cable

32. Results

33. Simulation Models

34. t = topen t = (topen-t) t =( topen +t) Switch closed Switch open: initial arcing Capacitor charging Version 1: Opening of Circuit Breaker

35. RESTRIKE!!! Vmax Initial Arcing Period topen Simulation of Restrikes

36. Restrikes: Simulation Circuit

37. Capacitor Current Restrike No Restrike

38. Capacitor Voltage Restrike No Restrike

39. Simulation Results

40. Current Limiting Operation • The shore station power supplies are rated at 200kW, 10kV • The steady-state system current = 10A • Under certain conditions, the system current may increase due to • Cable faults • Topology changes • Load fluctuations

41. Current Limiting Operation • The system current is limited to a value below 10A using the control circuitry in the shore station • This is done by dropping the shore voltage which in turn reduces the current • The control action is initiated only for steady-state overcurrents and not transient overcurrents.

42. Fault Analysis

43. Version1: Simulation Circuit

44. Results of Current Limiting: Shore Output voltage and Current Voltage Current

45. Voltage and Current at Node 2: No Current Limiting Voltage Current

46. Capacitor Current of Node 2

47. Version 2: Fault Studies • A pre-insertion resistance may be placed at the shore station to limit the fault current • This resistance will limit the fault current before the shore controls take the appropriate mode-dependant control action • Three controllable parameters in simulations: • Value of pre-insertion resistance • Response time of control circuitry • Distance of fault from the shore station

48. Simulation Circuit X=100km/1200km

49. Results: Vary Response Time

50. Results: Vary Fault Distance