Ship Electric Power Systems: Research Activities at USC Dr. Yong-June Shin ESRDC Annual Workshop, Austin, TX May 19-21, 2008

2 Objectives NGIPS ship power architecture –Modeling and simulation –Pulsed power load –Harmonics/ transient problems –Protection of DC architecture Electric wiring/ cable integrity –Diagnostics/ prognostics methodology –Wireless sensors for non-intrusive monitoring

3 Acknowledgement Mr. Blake Langland –Modeling and Simulation with VTBPro Dr. Mohammad Ali –Cable Diagnostics/ Wireless Sensors Drs. Roger Dougal and Enrico Santi –Ship power architecture and stability Graduate Students in Power IT Group –Mr. Philip Crapse, Mr. Jingjiang Wang

4 Prop Motor InverterRectifier Main Gen Aux Gen TransformerRectifier Ship Service Load Centers DC/DC Inverter Low Voltage Baseline 4160 V, 60 Hz 36 MW 4 MW

5 High Voltage Allows for lower current and increased power levels Prop Motor InverterRectifierTransformer Main Gen Aux Gen TransformerRectifier Ship Service Load Centers DC/DC Inverter 13.8 kV, 60 Hz 36 MW 4 MW

6 HV, High Frequency Size and weight reduction of generators and transformers Prop Motor InverterRectifier Transformer Main Gen Aux Gen Rectifier Ship Service Load Centers DC/DC Inverter Transformer 13.8 kV, 240 Hz 36 MW 4 MW

7 Factors for Comparison of Architectures Accommodating power level Size / Weight of components Inherent disturbance invulnerability –Level of natural disturbance Switching rectifiers Adjustable speed drives Pulse loads –Isolation of vital motors / loads –Robust power quality

8 AC VTB Pro AC Electric Ship IPS Power Loop

9 AC VTB Pro AC Electric Ship IPS Ship Service Load Center 3 4 5

10 Disturbance Simulation ArchitectureBaselineHVHV, HF Frequency60 Hz 240 Hz Voltage4160 V13.8 kV Disturbance Energy 1.5 MJ / 0.1 s 150 MJ / 1 s

11 LV – HV Comparison Load 3 Load 4 Load 5 THD = 7.27% LV THD = 1.01% HV 1.5 MJ over 0.1 s Disturbance THD = 1.72% THD = 0.42% THD = 9.56% THD = 4.36% The high voltage architecture inherently better maintains the quality of power delivered to the vital loads than the low voltage architecture

12 Harmonic Distance and Similarity LV – HV LVHV

13 Transient THD HV – HV,HF Comparison 150 MJ over 1 s Disturbance HV, HF THD = 9.76% HV Transient THD THD = 16.99%THD = 4.06% THD = 24.86%THD = 57.13% THD = 16.44% 345

14 Harmonic Distance and Similarity HV – HV, HF HV HV, HF

15 Protection for DC System Inserted inductance limits the rising rate of fault current Semiconductor instantly and momentarily turns off to limit fault current, then permanently turns off fault is identified as real. Freewheeling diode limits voltage Capacitor supports the bus voltage so that other loads are not interrupted. Circuit topology of protection circuit module (PCM) Power Distribution Module Protection Module Branch circuit Protection Modules Multiple loads per circuit

16 Protection Simulation by VTB Protection circuit reacts to any over-current situations (including load inrush current, disturbance, or short-circuit fault) Fault current limiting begins immediately at (e.g.) 1.2X rated, and restricts fault current to less than twice rated current. Protection circuit limits fault current quickly (e.g. 60μs), and isolates fault within ms. Protection circuit stops current- limiting and returns to normal operation immediately and automatically if the fault is self- extinguished, or the start-up of capacitive load is completed.

17 Conclusion Proposed AC electric ship integrated power systems can be modeled and simulated using VTB Pro Combining traditional and innovative metrics –the invulnerability of an IPS may be quantified –the effects of particular disturbances may be tracked Each architecture has unique advantages, but in terms of harmonic power quality, the 13.8 kV, 60 Hz architecture is most robust

18 Future Work Investigate the various effects of changing the location and number of transient disturbance Develop a method for analyzing the proposed medium-voltage DC architecture Stability investigation with multiple converters

19 Wiring/ Cable Integrity Constant vibration Routine maintenance Water and Heat Age-related disturbances Problems Endanger the integrity of the wiring system in IPS What is needed: Diagnostic/ Prognostics technique: –Detect and locate hard defects before they lead to serious damage –Monitor the status and predict the remaining life of a cable –Detect incipient defects before they evolve into hard defect In-situ /non-intrusive wireless sensor development:

20 Experimental Setup for Cable Test Bed JTFDR System Functional Diagram: Experimental Setup: AWG Circulator Reference Signal Cable Oscilloscope Reflected Signal Accelerated Aging Thermal Chamber

21 Results A: Diagnostics JTFDR Classical TDR M17/95-RG180, with PTFE insulation Cable

22 Results B: Prognostics Aging Temperature: 250 °C (50°C higher than the maximum operating temperature) 5 hours 15 hours 20 simulated years 60 simulated years

23 Interdigitated Non-Intrusive Electric-Field Sensor Sensor is proximity coupled –Injects a low frequency signal into a cable –Measures the capacitance –Identifies voids in insulation –Identifies presence of water within insulation Capacitance Measurement

24 Detection of Water-related Damage GRA: Rashed BhuiyanFaculty Advisor: Dr. Mohammod Ali Water-filled holes Conductor Insulation Damage Type Measured Capacitance (pF) 123Avg. No damage Water in hole PUR cable PVC cable

25 Future Work: Sensor Network for Cable Diagnostics in IPS Sensor cable interface (Reflection coefficient Γ 1 and Γ 3 ) Sensor Conductor Insulation 60 Hz Fault Forward wave Return wave Γ2Γ2 Proximity sensor for cable fault monitoring Faculty Advisor: Dr. Mohammod Ali Preliminary open circuit test Develop an advanced wireless sensor network for cable diagnostics and prognostics 1.Reference signal design 2.Detection and localization of defects 3.Sensor Management 4.Prognostics

26 Conclusion and Future Work Diagnostics/Prognostics Wireless Senor Network Provide information about the state of a cable under test To predict the remaining life of the cable Robust, accurate, sensitive Nondestructive, nonintrusive Configurable incident signal to suit application JTFDR

27 Backup Viewgraphs

28 Harmonic Distance Metric PQI = Power Quality Index –Total Harmonic Distortion (THD), Distortion Index (DIN), etc.

29 Harmonic Similarity Metric Cross-Power Spectral Density Harmonic Similarity in Magnitude Harmonic Similarity in Phase Harmonic Similarity

30 Notional AC Electric Ship IPS One-Line Diagram – Ring Bus

31 Notional AC Electric Ship IPS One-Line Diagram – Ship Service Load Center