1. Pareto Optimization to enable set-based Designs of ship systemsBy
Researchers Rounak Siddaiah, Marzieh Karami, Graduate Students-University of Wisconsin-Milwaukee Dr. Rob Cuzner, Assistant Professor-University of Wisconsin-Milwaukee

2. As a result of the ongoing improvements in the area of power electronics, the penetration of power electronic converter systems into numerous traditional and modern applications has continuously been increasing.
An example is the growing utilization of electric propulsion in automobiles, ships and aircraft. These above examples are driven by the increased environmental awareness and the demand for higher functionality of the modern society.
Based on the observed trends in state-of-the-art applications, it can be expected that the need for enhanced power electronic converter systems with a higher efficiency, reliability and functionality at concurrently lower costs, weight, volume and development time will further increase in the near future.
The analysis of the relevant literature shows that the dimensioning and optimization of converter systems is often carried out with a limited scope and focusing on only one or a few performance criteria.
This is often a consequence of a missing systematic approach which enables a comprehensive consideration of the inherent trade-offs between different performance measures (e.g. converter volume vs. losses).

3. Abstractions, measurements and empirical research
Abstractions, measurements and empirical research. The primary aim of the proposed design method is the precise prediction of the converter characteristics which enables an effective and efficient system optimization with fewer hardware prototype iterations and a shorter time to market.
The proposed methodology is applied to the multi-objective optimization and comparison of various DC/DC and DC/AC converter systems under consideration of the latest available SiC semiconductors.
The case studies on the one hand highlight the capability of the employed methodology to handle complex optimization problems and to find the corresponding solutions with a comparably low computational effort and time need.
Experimental measurements on an implemented DC/DC hardware prototype on the other hand verify the high accuracy of the employed models.
The results of the two case studies reveal that the employment of SiC semiconductors in the considered applications is attractive despite the higher costs of SiC semiconductors in contrast to conventional Si components.
In both examples, the superior performance of SiC enables considerable improvements regarding efficiency, power density and functionality of the converter systems at comparable overall system costs.

4. Pareto Optimization Objective Function Constraints Design Variables
Size
Weight
Losses
Reliability
Constraints
Ripple current in the capacitors
Maximum voltage on the capacitors
Losses and thermal constraints
Design Variables
PEBB types
Electrical frequency
Output DC voltage level
Ambient temperature
Output Variables
Arm inductor current
Submodule capacitor
Arm inductor

5. Accepted design variables
Accepted Vaules
Module Types
PEBB 1000, PEBB 6000
DC Voltage Values (kV)
12, 18, 24, 30, 36
Generator Frequency (Hz)
60, 120, 240, 360
Inlet Cooling Water Temperature (°C)
5-35
The possibility of using diesel generators with flexibility in the nominal electric frequency and voltage levels provide an opportunity to decrease the size of the conversion topology. Therefore, selecting the generator frequency and also the rated voltage of the generator are two other input arguments to make the MMLC design optimal. The other design variable is DC rated voltage. This variable will affect the other aspects of microgrid as well so it can be set as an input value or a variable

6. Algorithm for designing an optimal MMCs

7. Different controllers
Controller with the goal to keep the DC voltage of submodule capacitors constant: Suitable for Inverters
Closed loop scheme that needs measuring capacitor voltage
Generate the control signal with nominal average voltage of capacitor

8. Virtual Prototyping Routine

9. Modular multilevel convertor

10. PEBB layout

11. Conclusion
Besides innovation and the employment of MMC technologies, system optimization is a main enabler of improved performance. In this context, the methodology of virtual prototyping is identified to be a powerful tool for systematic optimizations of the converter systems’ primary performance measures, i.e. the efficiency, volume, weight, component costs and the reliability.