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

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

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

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

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

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, 30-31 October 2006. STUDY SHOWS LARGE VOLUME COST OF CONCEPT

Computational tools for early-stage ship design: UT Activities Tools for system design Design study of ITG topology 5 MW ~160” Tools commonly used @ 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

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

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

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.