Electromagnetic Interference (EMI), primarily common mode (CM), is problematic in a wide range of electronic circuits due to its propensity to radiate, particularly in high power applications. It is routine for much effort and resources to be dedicated to its characterization and reduction as EMI compliance is a requirement for most electronic systems and devices, including power electronics. Many well-known factors contribute to a system’s EMI performance including intentional coupling from system components as well as unintentional coupling from parasitics. Sources of intentional coupling may include Y-capacitors intended to mitigate EMI as part of a filter. Unintentional coupling is more elusive and can exist throughout the system in PCB layout, cabling, load construction, and internal to components such as inverter bridges. Lesser-known contributions to EMI performance irregularities can be EMI filter asymmetries, switching asymmetries, line impedance variances, and galvanic coupling from the metrology intended to measure EMI. It is critical to understand these contributors to facilitate designs with optimal EMI performance. EMI filters are often added to designs with no consideration to asymmetries in construction and component tolerances. This proposal evaluates the impact to CM currents in cases of coupling or leakage inductance imbalances of a CM choke. Similarly, CM currents are also evaluated for cases when EMI filter Y-capacitor imbalances span the components tolerance band. Also analyzed are switching asymmetries in a typical converter topology to understand EMI impact and evaluate potential benefits if intentional asymmetric switching is applied. A practical method is introduced to measure line impedance upstream of devices under test as line impedance variation can impact the performance of EMI filter design. However, few documented practices exist to measure line impedance without specialized instrumentation. Finally, this work proposes a streamlined method for conducted emissions evaluation employing an oscilloscope, differential voltage probes, and post-processing software implemented in MATLAB. This method eliminates unintended metrology ground coupling that can significantly impact EMI measurements and minimizes risk of instrumentation damage particularly in high power systems.

Wide bandgap (WBG) semiconductor devices are becoming increasing popular in power electronics applications. However, WBG semiconductor devices generate a substantial amount of conducted electromagnetic interference (EMI) compared to silicon (Si) devices due to their ability to operate at higher switching frequencies, higher operating voltages and faster slew rates. This thesis explores and analyzes EMI mitigation techniques that can be applied to a power module architecture at the packaging level. In this thesis, the EMI footprint of four different module architectures is measured experimentally. A time domain LTspice simulation model of the experimental test setup is then built. The common mode (CM) EMI emissions that escape the baseplate of the module into the converter is then examined through the simulation. The simulation is used to explore the CM noise footprint of eight additional module architectures that were found in literature. The EMI trends and the underlying mitigation principle for the twelve modules is explained by highlighting key differences in the architectures using common mode equivalent modelling and substitution and superposition theorem. The work aims to help future module designers by not only comparing the EMI performance of the majority of module architectures available in literature but by also providing an analysis methodology that can be used to understand the EMI behavior of any new module architecture that has not been discussed. Although silicon carbide (SiC) modules are used for this study, the results are applicable for any WBG device. / M.S. / As society moves towards the electric grid of the future, there have been increasing calls for high efficiency, high power density, and low electromagnetic interference (EMI) power electronic converters. EMI is a big problem when using wide-bandgap (WBG) devices as these devices can switch very quickly and handle higher voltages when compared to silicon devices. In this study, ways to reduce EMI in a WBG power module through twelve different types of packaging are explored. Four WBG power modules are designed and fabricated in the lab, whereas a simulation model was created to study the EMI behavior of the remaining eight power module. The EMI behavior of these modules is explained using common mode (CM) equivalent modeling and substitution and superposition theorem. This study is important because WBG devices are becoming more and more popular in power electronic applications. The author hopes the findings and analysis presented in this paper can help future module designers reduce the EMI footprint of modules they design.