1. Computational tools for early-stage ship design: UT Activities
University of Texas at Austin Activities
Presented by A. Ouroua
For PI’s: J. Beno, K. Davey, R. Hebner, and A. Ouroua
Center for Electromechanics

2. Computational tools for early-stage ship design: UT Activities
Tools for system performance assessment
Matlab/Simulink model of power system from generators to loads
Accessible with minimal training
Capability marginal for problem complexity
Generators
Breakers
Propulsion
Transformers
Rectifiers
Filter
Motor
Drive
Energy storage
Study Topics
Power routing
Motor shorts
Power restoration
to vital load
Harmonics
Efficiency
Pulse load
Energy storage
Matlab/Simulink is a useful, but limited, tool

3. Computational tools for early-stage ship design: UT Activities
Tools for system performance assessment: Typical results
Power routing to faulty propulsion power train
Motor ground faults
Power restoration to vital load
UPS Function of energy storage
Harmonics reduction
High pulse power load
Typical results obtained with the Matlab/Simulink tool are shown here.
Motor phase current during a 3-phase balanced ground-fault
Power restoration to a vital load
after a ship service 450 VAC bus is down power is drawn from a secondary bus
Power routing to supply a fault propulsion power train
Motor voltage during the power transfer is shown on this graph
Demonstration of harmonics reduction thru active filtering using available (pulse power energy storage) converters.
High power pulse loads
Analysis of UPS function of energy storage
Matlab/Simulink models can be used to study transient effects

4. Computational tools for early-stage ship design: UT Activities
Tools for system performance assessment: Beyond Matlab
Latin Hypercube in Optimization
Latin hypercube is a sampling technique for
probing an n dimensional space. It differs from
Monte Carlo methods in that it spreads out the
sample points while still maintaining stochastic
features.
The proper combination of a deterministic
algorithm (like Pattern Search) with Latin
Hypercube sampling can be shown to achieve the
benefits of a stochastic algorithm but with greater
speed and precision.
Original data
Latin Hypercube 15 point approximation
Other tools in the form of mathematical methods and approaches are being developed for system performance assessment such as the Latin hypercube sampling technique which improves computational speed and fidelity as compared to other techniques.
The example here shows a comparison between the Latin hypercube and Monte Carlo method. The Latin hypercube techniques gives better results.
Monte Carlo 15 point approximation
EMERGING MATHEMATICAL APPROACHES IMPROVE COMPUTATIONAL SPEED AND FIDELITY

5. Computational tools for early-stage ship design: UT Activities
Tools for system performance assessment
Addressing high frequency generation
HFAC
25 MVA PM Generators
Size reduction
Main Power
Distribution
Ship service
power
Mass
Volume
Design and analysis tools are used to assess high frequency generation
Generator size scales inversely with its output frequency. Size gets smaller as the frequency is increased.
We completed a study of 25 MVA PM generators operating at different frequency.
The results shown here give a realistic assessment of the gain in weight and volume but other considerations such are efficiency vs. frequency need to be considered as well.
Also needed
Efficiency vs. Freq …
HIGH FREQUENCY REDUCES COMPONENT SIZE BUT WORK NEEDED ON COST VS. BENEFITS

6. Computational tools for early-stage ship design: UT Activities
Tools for system performance assessment
Analysis of cross-connect concept(1)
Goal:
Save fuel at low speed on present-day ship
Concept:
Run 1 turbine only at low speed
Use motor/generator to transfer power to propulsion power trains
Analysis:
6 MW motor/generator size
~ 7 MVA converter size (COTS)
Design and analysis tools have been used to assess innovative concepts such as the x-connect concept shown here.
the idea here is to safe fuel by running only one gas turbine at low speed for present-day ships
This requires the addition of motor generators and power electronics
as well as clutches
the analysis shows that the volume of the equipment (mainly power electronics) is high
(1): D. Clayton and T. Doyle, “ Propulsion cross-connect on DDG51,” ASNE Advanced Naval Symposium 2006, Arlington, Virginia, USA, October 2006.
STUDY SHOWS LARGE VOLUME COST OF CONCEPT

7. Computational tools for early-stage ship design: UT Activities
Tools for system design
Design study of ITG topology
5 MW ~160”
Tools commonly CEM
SolidWorks
CosmosWorks
VF-Opera
Abaqus
Patran
Matlab/Simulink
Rectifier
PM Generator
Direct coupling
Gas turbine
Speed & Size
THD 5.5%
FEA model
Torque capability
Tools for system design are routinely used to assess new topologies before prototypes are built and tested such the Integrated-Turbine-Generator topology shown here.
Typical tools used in this analysis are shown here and some of the performance parameters are plotted here.
TOOLS ARE AVAILABLE FOR STUDIES FROM FUEL TO LOADS

8. Computational tools for early-stage ship design: UT Activities
Tools for component design
Power rectifiers
6.25 MVA 12-pulse rectifier
6.25 MVA 6-pulse rectifier
Thermal Analysis
Junction temperature ~ 55 0C
Cooling requirement ~ 0.7 gpm
24 diodes
175 kg
0.39 m3
+ Phase-shifting transformer
1.1 gpm
THDi = 5.5%
18 diodes
159 kg
0.24 m3
0.7 gpm
THDi = 19%
Water-cooled heat sinks
Similarly various tools are used for component design as illustrated here with 6- and 12-pulse passive rectifiers.
size, cooling requirement, and performance are obtained through modeling and simulation
12-Pulse Rectifier Circuit
Complete system modeling requires good performance, size, and thermal models of power electronics. These have been developed

9. Computational tools for early-stage ship design: UT Activities
Integration of design tools
Prime
Mover
Prop
Motor
Inverter
Rectifier
5 kVDC
Gen
Prime
Mover
Main Power
Distribution
Rectifier
Aux
Gen
DC/DC
40 MW
Various computational tools are being integrated into multi-disciplinary tools that allow the modeling and simulation process to be conducted within a single environment.
Power systems topologies are assessed through modeling and simulation using multi-disciplinary computational tools.
The MVDC topology shown here is a typical example showing the importance of integration of computational tools for rapid prototyping from concept to testing.
Loads
DC/AC
Ship Service
Power
5 MW
DESIGN TOOLS CAN CAPTURE BOTH SIZE AND FUNCTIONALITY

10. Computational tools for early-stage ship design: UT Activities
Limitations of existing computational tools and possible remedies
Encountered two main difficulties:
Very long computation time required to simulate realistic scenarios on PCs
Matlab/Simulink discrete solver fails to step-through large discontinuities
The solver problem was communicated to the software vendor
Very responsive initially, but no offer to work on improving it.
Suggested the use of variable-step continuous solvers (not practical)
To remedy these problems:
Discontinuities: Implement a numerical algorithm that can handle discontinuities (fast switching events and high power pulses) within reasonable times.
Long run time: Set-up model to run on PCs for simple analyses and on multi-processor machines, such as UT’s supercomputers or other multi-processor systems, for analyses that require large memory and long computation time.