This thesis investigates techniques for prototyping and evaluation of medium voltage (MV) power module packages. Specific focus will be given to the utilization of silver sintering as a bonding method for high temperature, high density power modules. Nano-silver paste and preform will be examined in detail as enabling technologies for a new generation of power electronics. To accomplish this task, analysis and characterization of the metal-ceramic substrate and its structure is performed. First, finite element models are created to evaluate the fatigue behavior of the large area bonds in the substrate structure. Prototypes of these multi-layer substrates have also been fabricated and will be subjected to thermal cycling tests for experimental verification of the efficacy of their sintered silver bonds. Stacked direct-bonded aluminum (DBA) substrates have been found to withstand up to 1000 thermal cycles of –40 °C to 200 °C when attached with low pressure-assisted silver sintering. The thermal performance of 10 kV SiC power module utilizing multi-layer DBA substrates bonded with a large-area, low pressure-assisted sintered silver bond will also be examined to ensure the sintered bond is viable for the harsh operating conditions of MV modules. A junction-to-case thermal resistance of 0.142 °C/W is measured on a module prototype utilizing stacked DBA substrates. Finally, analysis of a double-sided cooling scheme enabled by large area sintering is simulated and prototyped to demonstrate a 6.5 kV package for a MV power device. Residual stress failures induced by a highly rigid structure have been examined and mitigated through implementation of a 5 MPa pressure-assisted, double-sided silver sintering approach. / Master of Science / Power modules are the building blocks of the electrical grid of the future. As society transitions to renewable energy to fight the crisis presented by climate change, the structure of the energy grid will have to change to accommodate the increase in solar, wind, geothermal, and other renewable sources of energy generation. A clean energy grid structure will contain ubiquitous opportunities to use power modules for medium-voltage (MV) applications, like managing the flow of electricity from solar panels and wind turbines to neighborhoods and office buildings. However, these MV power modules will need to be resilient to extreme temperature and electrical stresses inherent to these applications. Current technology must be improved in both performance and reliability to match the needs of this future grid. This thesis investigates, through both experiment and computer simulation, techniques for improving the reliability of MV power modules without sacrificing thermal or electrical performance. Techniques presented in this work have the potential to transform power modules, so they may operate at higher temperatures and efficiencies for a longer lifetime than the current state-of-the-art.

THE CRITICAL FLASHOVER (CFO) VOLTAGE OF AN INSULATION STRUCTURE IS COMMONLY USED TO DESCRIBE THE INSULATION STRUCTURE¡¯S LIGHTNING IMPULSE STRENGTH. THE FIBERGLASS DISTRIBUTION POLE WAS RECENTLY INTRODUCED TO POWER DISTRIBUTION SYSTEMS. HOWEVER, VERY LITTLE WORK HAS BEEN DONE ON EITHER THE LIGHTNING IMPULSE CHARACTERISTICS OF DISTRIBUTION LINE STRUCTURES WITH FIBERGLASS POLES OR THE ELECTRICAL DEGRADATION OF FIBERGLASS. THE WORK IN THIS THESIS REPRESENTS THE RESULTS OF A LABORATORY STUDY ON LIGHTNING IMPULSE CHARACTERISTICS OF DISTRIBUTION LINE STRUCTURES WITH FIBERGLASS POLES AND THE ELECTRICAL DEGRADATION OF FIBERGLASS. THE CRITICAL FLASHOVER (CFO) VOLTAGES OF THE FIBERGLASS DISTRIBUTION POLE AS AN INSULATION STRUCTURE ALONE AND ITS COMBINATION WITH VARIOUS INSULATORS WERE EVALUATED. THE ADDED CFO VOLTAGES FROM FIBERGLASS DISTRIBUTION POLES TO BASIC INSULATION COMPONENTS WERE CALCULATED BASED ON THE TEST RESULTS. THE ACCELERATED AGING TESTS AND CORRESPONDING ELECTRICAL EVALUATION TESTS WERE ALSO CONDUCTED TO INVESTIGATE THE ELECTRICAL DEGRADATION OF FIBERGLASS.

With distributed generation being introduced in the meshed distribution networks under increased loading conditions, maintaining the system voltage stability will become one of the major concerns. The conventional approach of repetitive power flow solutions fails to obtain the critical loading point as Jacobian becomes singular before maximum loading point. Continuation power flow methods, based on the predictor-corrector scheme, overcome this difficulty with the use of parameterization techniques. Continuation power flow tools, already developed for transmission systems, need to be extended to handle three phase unbalanced distribution systems. This research work contributes towards development of a robust and efficient three phase unbalanced continuation power flow tool for voltage stability assessment of shipboard power systems and terrestrial distribution systems. The developed continuation power flow method is based on adaptive step length control and pseudo arc length/local parameterization technique, which have been tested on several I test systems and a shipboard power system.

Electrical power systems are vulnerable to contingencies due to the possibility of fault or damage. When a serious fault (which cannot be removed immediately) occurs in the power system, the fault needs to be isolated, and the remaining system should be reconfigured to make efficient use of available energy. Reconfiguring the system by making an island can be one of the strategies to continue the energy supply using the remaining generation capacity. By analyzing the effect of contingencies on power systems in terms of voltage support, reliability and stability, survivability of the system can be predicted. A survivability index of the system can be developed based on voltage support, reliability and the stability index with predefined weight given to each performance criterion. These weights may vary for different system conditions. The purpose of this research work is to develop a survivability index for shipboard power system and rank reconfiguration choices based on the developed index.

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