Characterization of the Common Mode Features of a 3-Phase Full-Bridge Inverter Using Frequency Domain Approaches

• Other Authors: Mohebali, Behshad (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Electrical engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_2016SP_Mohebali_fsu_0071N_13066

In this thesis a practical approach for characterizing the common mode behavior of the power electronic devices (PED) on board a next generation All-Electric ship (AES) power system is proposed. As the topic of AES design is becoming more and more relevant for the US navy, addressing the AES design challenges get more importance and attention. The AES power system is designed ungrounded to make the system capable of operating after a single phase to ground fault (which is the most common type of fault in power systems). However, the inevitable parasitic coupling in the system can cause overvoltages and spike currents in the case of ground faults. The mentioned parasitic coupling can also form a common mode loop consisting of the system conductors, the parasitic coupling effect at different locations of the system, and the ground path (which is the Ship hull in this case). High frequency contents produced by the fast switching of the power converters can circulate in the so called common mode loop. To design the best grounding scheme for AES power system accurate and reliable models of the common mode characteristics of the shipboard power systems components is needed. Among the components seen in a shipboard power system the PEDs are the most difficult parts of the system to characterize due to their non-linear time-variant nature. At the Center for Advanced Power Systems (CAPS) at Florida State University the researchers developed a general guideline for characterizing the common mode behavior of the passive components of the power system using scattering parameters measurement. In practical cases the access to the internal parts of a PED may not be available or may have significant safety issues. On the other hand, the detailed information on the operation of the PED, which is needed to characterize the common mode sources in the system, may not be given by the manufacturer. In this thesis, the impedance of the low pass filter is measured using the mentioned Scattering parameter guideline with additional considerations. A frequency domain approach is utilized to reconstruct the common mode voltage of the PED (specifically a full-bridge 3-phase inverter) at the switches by measuring the common mode current in a previously characterized test setup; which included a DC source, a common mode low pass filter, a 3-phase transmission line, and a rotational load with grounded casing. The results show that the common mode voltage of the inverter can be estimated without accessing inside the device while in operation. === A Thesis submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the requirements for the degree of Master of Science. === Spring Semester 2016. === February 26, 2016. === Common mode, Grounding, Power Electronics === Includes bibliographical references. === Chris S. Edrington, Professor Directing Thesis; Mischa Steurer, Committee Member; Helen Li, Committee Member; Lukas Graber, Committee Member.