ONR SUPPORTED RESEARCH EFFORTS AT DREXEL'S CENTER FOR ELECTRIC POWER ENGINEERING

1. ONR SUPPORTED RESEARCH EFFORTS AT DREXEL'S CENTER FOR ELECTRIC POWER ENGINEERING Contribution to the Panel on ONR Research Opportunities D. Niebur, Member, IEEE, C.O. Nwankpa, Member, IEEE, K. Miu, Member, IEEE, H. Kwatny, Fellow, IEEECenter for Electric Power Engineering Drexel University Philadelphia, PA 19104 [niebur,miu,nwankpa]@ece.drexel.edu kwatny@coe.drexel.edu Center for Electric Power Engineering Drexel University

2. NAVY OBJECTIVES Supply Navigation Executive Medical Medical Operations Engineering Air Combat Systems

3. ONR SPONSORED PROJECTS Project 1: Power System Monitoring And Control For Autonomous Naval Shipboard Electric Power Distribution Systems (ANSEPD) PIs: D. Niebur, C. Nwankpa and H. Kwatny, R Fischl, F&H Applied Science Assoc., Inc, Program: Response to a Broad Area Announcement, 1997-2001 Students: Supported partially 3 MS and 1 PhD student Project 2: Application of the Interconnected Power System Laboratory Towards the Definition of a Simulation-Stimulation Interface (SIM-STIM) PIs: R Fischl, F&H Applied Science Assoc., Inc, K. Miu and C. Nwankpa Program: Response to a Broad Area Announcement, 1999-2000 Students: Supported partially 2 PhD students Project 3: Multi-frequency Analysis of Large-scale Systems (MFALSS) PI: K. Miu Program: ONR-Young Investigators Program, 2001-2004 Students: Supports partially 1 MS and 1 PhD student Project 4: Non-linear Observability Analysis for Shipboards Systems (NLOASS) PIs: C. Nwankpa, C. Dafis Program: In-House Laboratory Independent Research Program at NAVSEA, 2002-2005 Students: Supported 1 PhD student

4. 1. POWER SYSTEM MONITORING AND CONTROL FOR AUTONOMOUS NAVAL SHIPBOARD ELECTRIC POWER DISTRIBUTION SYSTEMS Objectives of ANSEPD:Development of an Analysis, Simulation and Test environment for an Electric Power Management System(EPM) as part of shipboard power distribution monitoring and control for future autonomous shipboard management Tasks: • Component modeling of the Ship Service Power Block, particularly single-phase and 3-phase power converters. • System modeling of the IPS system including power converters. • Development of symbolic software (IPSST) for investigating the non-linear dynamic behavior of the IPS system. • Identifying the security indicators including voltage stability indicators. • Development of a framework for AC/DC Security and Survivability. • Test environment in Drexel’s Power System Laboratory. • Simulation and experimental validation of the non-linear dynamic behavior of the IPS system under different operating scenarios.

5. ONR SPONSORED WORKSHOPS • Organizers and Proceedings Editors: • Niebur D., Drexel University and C. Whitcomb C., ONR ONR-DREXEL-NSWC Workshop onElectric Shipboard System Modeling, Simulation and Control, Drexel University, Philadelphia, PA 19104, USA, June 22-23, 1998. 130 participants from industry, government and academia

6. ANSEPD - CONFIGURATION OF INTEGRATED POWER SYSTEM BLOCKS

7. ANSEPD IPS STABILITY TOOLBOX

8. ANSEPD-AC/DC-DYNAMIC SYSTEM MODEL Bus 1: Slack bus (Modeling AC System1 as Generator) Bus 2: PI Bus (Modeling Rectifier AC Terminal) Bus 3: Slack Bus (Modeling Voltage Controlled Inverter Terminal Bus 4: PQ Bus (Modeling AC System 2 as Constant Power Load)

9. ANSEPD-CONVERTER CONTROL MODE TRANSFERS BETWEEN MODES BI BI Firing angle = 0 AI BII AII BIII BIV

10. ANSEPD-DECISION FUSION OF VOLTAGE STABILITY INDICATORS FOR IPS **The objective of this work is to look at static voltage collapse using a probabilistic approach. **An optimal indicator is obtained from static voltage collapse indicators using Bayesian decision strategy with hypotheses based on existence of load flow solution using continuation method. Data fusion technique is used. **In this work load fluctuations are modeled as zero mean Gaussian distribution. **Three static voltage collapse indicators are used as input to system.

11. Decision1 PI1 PI2 Decision2 Fusion center Global Decision PIk Decisionk ANSEPD BAYESIAN DECISION FUSION • Scheme below is used to design a better indicator out of the individual indicators with lower probability of error.

12. ANSEPD - DECISION FUSION METHODOLOGY Monte Carlo simulation N (10000) to generate random Gaussian noise different realizations of load Calculate a solution for every load realization. Obtain a priori probabilities: P {H0} and P {H1}. Is the set tolerance level met in calculations? YES NO Assign to this realization the largest PI value in the set. Calculate PIs based on solution A Using N=10,000 we obtain for  = 0.1, P{(|Sn-|) }<0.005 where Sn is the sample mean (weak law of Large Numbers)

13. ANSEPD-OPERATING CHARACTERISTICS OF PIS Of THE AC\DC SYSTEM Prior probabilities of the hypotheses:

14. 2. TOWARDS THE DEFINITION OF A SIMULATION-STIMULATION INTERFACE Rest of System (ROS) Hardware under Test (HUT) U S C Advanced Electric Power System - AEPS Hardware under Test (HUT) Sim/Stim Interface Virtual ROS Interconnectsthe virtual ROS with the HUT, translating the virtual output into POWER and control Signals to the HUT 14

15. SIM-STIM FRAMEWORK Hardware Stability Regions U S C • Software • Stability • Regions* Hybrid Sim/Stim Realization Stability Region • Each system exhibits stable regions of operation • “Overlap” between each region suggests valid operating regions * includes: theoretical, numerical and computational stability 15

16. SIM-STIM: IDENTIFYING STABLE REGIONS U S C Defining a SimStim Interface - (Power Regions) (1) Hardware exhibits maximum power transfer characteristics (2) A system with a S/SI Interface will have a different maximum power transfer limit Goal: Establish a relationship between (1) & (2). • Identifying regions of valid operation - Hardware • Experimental setups with RL loads • Provide trajectories which lead to maximum power transfer points • Identifying regions of valid operation - Hybrid SimStim 16

17. 3. MULTI-FREQUENCY ANALYSIS FOR LARGE SCALE POWER DISTRIBUTION SYSTEMS • END GOAL: • PERFORMANCE INDICES FOR LARGE-SCALE SYSTEMS WITH SUBSYSTEMS NORMALLY OPERATING AT DIFFERENT FREQUENCIES • MODELING: • FOR POWER SYSTEMS WITH POWER CONVERTERS AND MULTIPLE GENERATORS • MODELS WHICH SPECIFY SYSTEM ANALYSIS TECHNIQUES • ADAPTING EXISTING COMPONENT MODELS INTO SYSTEM MODELING APPROACHES • ANALYSIS: • ANALYSIS AND ESTIMATION SCHEMES INCLUDING • MODIFIED NODAL ANALYSIS, DECOMPOSITION APPROACHES • LOAD AND STATE ESTIMATION

18. MFALSS: OVERVIEW • Hardware: • a three-phase variable frequency converter • 120Vac, 60Hz input • 10kVA throughput • for use in the Reconfigurable Distribution Automation and Control Laboratory (RDAC) [NSF] • 36-bus, 3f distribution system, 7.5kW • the design and development of experiments concerning multi-frequency, power distribution systems.

19. ANSEPD/MFALSS AC/DC - DC/AC POWER SYSTEM The converter consists of • Rectifier • DC Link • Inverter ac side of the rectifier ac side of the inverter [1]

20. ANSEPD/MFALSS EXPERIMENTAL RESULTS Test Network Bus Voltage Profile Center for Electric Power Engineering Drexel University http://power.ece.drexel.edu

21. 4. A NONLINEAR POWER SYSTEM OBSERVABILITY FORMULATION (NLPSO) Sponsored by NAVSEA-ILIR (In-House Laboratory Independent Research) Program • Targeted towards NAVSEA employees who are pursuing advanced degrees • Funded by the Office of Naval Research • Types of projects funded are considered basic research projects –High Risk/High Payoff “Behold the turtle, he makes progress only when he sticks his neck out” James B. Conant • Opportunity for students to leverage research topics towards shipboard applications • Program introduces various student advisors to the Navy community and the shipboard perspective of various technology problems • Provide a source for new and innovative ideas into Applied Research and other higher level programs • Maintain and grow the NAVSEA’s Science and Technology capabilities • Individual project funding typically lasts for 3 years

22. (NLPSO) ISSUES IN POWER SYSTEM MODELING AND ANALYSIS Trend to Focus on Nonlinear Dynamics of the System in Modeling and Analysis –Impact on System Performance • Controllability – Many current controllers are designed around a desired operating point, using a linearized system model. When the system operating point deviates significantly from this desired point, the controller becomes ineffective. • Stability – Traditional methods are based on linearized models of system dynamics, and cannot account for nonlinear interactions between system components. • Observability– Existing approaches either use topological analysis, based on Graph Theory, or numerical approaches derived from the state-estimation problem. These approaches focus on providing a fast analysis of large systems, and do not incorporate the dynamics of the system. • In General – Linearized power system models can be analyzed in parts –this does not account for component interference, cooperation/competition. The move is towards dynamic system analysis

23. EXPERIENCES • Learned a small fraction of the Jargon (DD21, -ilities etc.) • Worked closely with our sponsor • Navy interest is very heavy and enthusiastic • Obtaining data is very difficult • If you are a US citizen, you may go on NAVY ships • If you are a US citizen, you may obtain summer fellowships to work at NRL or other NAVY labs

24. SELECTED REFERENCES • Stoicescu, R., Miu, K., Nwankpa, C. and Niebur, D., Yang, X.., “3-Phase Converter Models for Power Flow Studies of Small Integrated AC/DC Power Systems,” IEEE Transactions on Power Systems, Nov 2002. • Fan, Y.K., Niebur, D., Nwankpa, C.O., Kwatny, H. and Fischl, R, “Voltage Dynamics of Small Integrated AC/DC Power Systems,” Proceedings of American Control Conference, ACC 2001, Arlington, VA, June 24-27, 2001, 829-830. • Sam, D., Nwankpa, C. and Niebur, D., “Decision Fusion of Voltage Indicators for Small-sized Power Systems,” Proceedings of theIEEE Summer Meeting, Vancouver, B. C., Canada, July 15-19, 2001. • Buzilow, Randy, Falls, Michael, Iaccio, Kevin and Worley, Charles., “Small Scale Integrated Power System (SSIPS)” Drexel University Senior Design Team Report ECE-005, May 5, 2001. • Bah , Chernor A., Jacobucci , Jefferson J., Michel, Joseph S., Needham, Benjamin, Santoni, Charles M., “Shipboard Island Power Energy Management System,” Drexel University Senior Design Team Report ECE-030, May 5, 2001. • Fan, Y.K., Niebur, D., Nwankpa, C.O., Kwatny, H. and Fischl, R, “Saddle-Node Bifurcations of Voltage Profiles of Small Integrated AC/DC Power Systems,” IEEE Summer Meeting, Seattle, July 16-21, 2000. • Fan, Y.K., Niebur, D., Nwankpa, C.O., Kwatny, H. and Fischl, R, “Multiple Power Flow Solutions of Small Integrated AC/DC Power Systems,” International Conference on Circuits and Systems, ISACS’2000, Geneva, Switzerland, May 28-31, 2000.