In this paper, a selective harmonic current mitigation pulsewidth modulation (SHCM-PWM) technique with low switching frequencies is proposed for grid-connected cascaded H-bridge multilevel rectifiers to fully meet harmonic requirements within extended harmonic spectrum. In the proposed technique, instead of using the voltage references to calculate switching angles for the rectifier as in conventional selective harmonic elimination-PWM (SHE-PWM) or selective harmonic mitigation-PWM (SHM-PWM), current references are used to compensate the current harmonics due to both grid voltage harmonics and rectifier input voltage harmonics so as to meet the current harmonic requirements and total demand distortion within the whole harmonic spectrum. Furthermore, the techniques to design the critical parameters including switching frequency, the highest harmonic order that can be mitigated using the proposed current-reference-based technique, and the coupling inductance that can attenuate the current harmonic orders above the highest order are investigated. With the same switching frequency, the proposed SHCM-PWM technique uses smaller coupling inductance to meet higher orders of current harmonic requirements than the conventional SHE-PWM technique. Finally, simulations and experiments were conducted to validate the proposed technique.

This paper investigated the CM noise model for multi-winding switching transformers. Based on the proposed model, a Flyback transformer is investigated. A measurement technique is used to characterize and evaluate switching transformer’s CM noise performance. Only a signal generator and an oscilloscope are needed in this measurement technique. Because there is no any in-circuit tests are needed, the technique can help quickly design and evaluate transformers in mass testing. CM noise reduction techniques including balance capacitor technique, core shielding technique, balance winding technique and winding design technique are investigated based on the developed twocapacitance model and measurement technique without introducing extra power loss. The near field capacitive coupling due to transformer magnetic cores is analyzed and a core shielding technique is applied to reduce the coupling. Experimental results validated the proposed model and the developed CM noise reduction techniques. The Flyback converter can finally meet EMI standards without using CM EMI filters and Y capacitors.

To analyze the radiated EMI generated by isolated power converters, this paper proposes a technique to develop a general radiation model for the converters. The radiated electric field can be predicted from the developed model. The interaction between the impedance of the converter and the undesired antenna in the converter's power delivery paths is explored in detail based on the developed model. Moreover, a dual active bridge converter is taken as an example to demonstrate the developed modeling technique based on the converter's topology. The radiated electric field of the dual active bridge converter is predicted from the developed model. Experiments are conducted to validate the developed model and the predicted interaction between the converter impedance and the undesired antenna impedance in the power delivery paths.

This paper firstly developed an inductance model that includes the parasitic mutual inductance between parallel current path segments for SiC multichip power modules. Based on the developed model, the SiC multichip module's transient response was analyzed, important parasitic inductances were identified. The layout was improved based on transient analysis. The improved package layout can reduce the parasitic inductance without increasing the fabrication difficulty. Experiments were conducted to validate the reduction of parasitic inductances. The parasitic ringing and the crosstalk effect were significantly reduced with the proposed technique. The thermal performance was also improved with the proposed layout.

This paper first develops a radiated EMI model for a GaN IC-based active clamp flyback converter. Important capacitive couplings, which play a big role in the radiated EMI, are identified, extracted, and validated in the converter. The radiated EMI model is improved to characterize the impact of capacitive couplings. Based on the improved model, techniques to reduce capacitive couplings and the radiated EMI are proposed and experimentally validated.