Large Scale Simulation of a Ship Power System with Energy Storage and Multiple Directed Energy Loads

R. E. Hebner, J. D. Herbst, A. L. GattozziCenter for ElectromechanicsUniversity of Texas, Austin

July 13, 2010

Presentation Overview

• Ship Design Challenges & Power System Studies• CEM Ship Power System Model• Modeling Issues & Simulation Alternatives• Path Forward

Challenges to Naval Power System Designers

• Wide variety of loads on board – Continuous duty to pulsed– Loads with different requirements

(low freq. ac, high freq. ac, dc)

• Generated power capacity minimally larger than averagetotal load and smaller than peak load– Reliance on energy storage to supply intermittent loads

• Increased use of power electronics• Need to maintain power quality and stability margins• Need flexible architecture suitable for fault

management and reconfiguration

Ship Power System Studies

• Modeling and Simulation play a crucial role– Experimental data not easy to generate– Difficult to reproduce the complexity of system

interactions in subscale physical models– Scarcity of accumulated experience with non-

traditional energy resources and loads• Models provide a common base to evaluate

alternatives and study component interactions• Key concerns:

– Scale of the model– Modeling technique– Software and Hardware PlatformsNeed a flexible tool for the ship designer, not application specific codes

CEM’s Notional Ship Power System

• Two turbo-generators with cross-connect option• Two flywheel energy storage systems• System designed around common 6 kVdc bus• Subsystems modeled :

– Propulsion– Hotel Loads– Free Electron Laser (FEL)– AN/SQQ-90 Sonar System– Electromagnetic Rail Gun– Active Denial System– Advanced Radar– Laser Weapon System– Electromagnetic Aircraft Launch System

Conceptual Diagram of CEM’s Ship Model

Interactive ModelOperator can change in real time,as the simulation is running,the status of allanalog gains,pushbuttons,switches.

FEL Operational Modes

Pier Side FEL in minimal power state; necessary maintenance performed (425 kW)

Underway Ship is crossing open waters; no imminent threat (625 kW)

Hot Standby Ship is in combat theater; threat could appear at any time (1 MW)

Engagement FEL is firing upon incoming threat (17 MW)

Collaboration with NAVSEA, NPS, Stanford, AES, JLab

FEL Component Overview

Linac10 kW filaments

16 MW RF

Current

Power:Active – yellowReactive-pink

Voltage

ACTIVE DENIAL EM GUN

Voltage

Current

Heat

ControlSignals

Modeling Issues

• Modeling some very unusual loads, many still experimental or in the R&D stage

• Complex model results in long simulation times

• Typical values are σ ≈ 100,000 (real time is σ = 1)– 6 seconds simulated time = 1 week running time on a

64-bit, 3.16 GHz, 3.93 GB, dual core desktop.

,

simulation time

simulated time

• Segmentation of the simulation model – Run one section at a time– Creates interface issues similar to parallel processing– Makes interpretation of results more difficult

• Compression of operating scenarios– Not reflective of realistic operating scenarios– Affects component interactions– Prevents real time operator engagement

• Eliminated GUI due to impact on simulation times

– Makes interpretation of results more difficult

Simulation Alternatives & Issues

Multi-Rate / Multi-Core Options• Expanded use of multi-rate techniques

– Models run now on dual rates– Expansion to further levels is possible

• Multi-core calculations:– MATLAB/Simulink version for parallel computations (Parallel Computing

Toolbox) run on quad core computer resulting in speed gains of ~2-3:1– Third-party supported parallel MATLAB not being pursued now but

remains an option• MATLAB/Simulink run on computer cluster (Distributed

Computing Server) in cooperation with the Texas Advanced Computing Center (TACC)– Work is ongoing– Goal is 10:1 speed gain

• Develop custom code to fully exploit parallel processing– Kept as a last option due to cost and specificity of resulting code

Heterogeneous ComputationFPGA assisted processing:

FPGAs outperform CPUs by >1 order of magnitude in speed

Potential solution should: 1. Retain broad utility of programs developed 2. High degree of generality

Pursue COTS suppliers e.g.National Instruments (NI),Xilinx, etc.

Heterogeneous Computation

• NI offers a hybrid architecture that can be exploited by their LabView software

• LabView is an intrinsically parallel language – Simulink is sequential

• Our model can be transferred to LabView and executed on NI’s RT-HPC system

The University of Texas has a Long Term Working Relationship with National Instruments

Path Forward• Heterogeneous computation appears to be a

promising path to significant reductions in simulation times– Capabilities of FPGA’s and GPU’s are increasing

• UT-CEM is seeking opportunities to apply these techniques to simulation of Naval power systems– Exploring collaborations with National Instruments

and Xilinx

Questions?