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On Grid Converter Reliability: Preserving the Life of Power Electronics Through Active Thermal Boundary Control

Lewis, Patrick (2019) On Grid Converter Reliability: Preserving the Life of Power Electronics Through Active Thermal Boundary Control. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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This dissertation proposes a method of preserving the lifetime of power electronic conversion systems through apt control design. Leading up to the inception of the contribution herein, this work involved exploring the impacts of advanced grid converter capabilities and control methods upon semiconductor device reliability. As distributed generation and loads are increasingly interfaced with the electric grid through power electronics, adverse challenges arise including voltage and frequency instability due to a reduction in system inertia. Said challenges incentivize various advanced grid converter features such as dynamic reactive compensation for grid voltage support, but such features can threaten to quicken the pace of device degradation, decreasing converter lifetime.

The reliability of power electronic conversion systems is correlated to the thermal stress experienced by the semiconductor device materials. The longevity of the device diminishes with high amplitudes of junction temperature fluctuations experienced by the device. This work introduces a control method designed to preserve converter life by minimizing thermal cycling amplitudes, particularly preventing the cooling of device materials when grid interactions would have situationally allowed cooling.

The solution is based upon natural switching surface (NSS) control, previously applied in the literature to the dual active bridge for efficiency gains. Utilizing NSS control for the purpose of actively controlling thermal cycling behavior lays the foundational contribution of the work. In contrast to conventional pulse-width modulation strategies, this approach bears unique merit for the management of thermal behavior because of the unique ability to control the switching trajectories according to desired switching and conduction losses. With appropriate design measures this methodology is also applicable to various converter topologies.

This dissertation initially provides groundwork for the reliability of power electronics. Extensive case studies of electro-thermal performance assessments are presented for both reactive compensation and virtual synchronous machine control, evaluating the impacts of such advanced grid converter features upon device reliability. Theoretical foundation as well as an application case study are provided for natural switching surface control. The contributed work includes the development of active thermal boundary control for the dual active bridge operating under interval loading.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Lewis, Patrickptl7@pitt.eduptl7
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee CoChairGrainger, Brandonbmg10@pitt.edubmg10
Committee CoChairReed, Gregorygfr3@pitt.edugfr3
Committee MemberMao, Zhi-Hongzhm4@pitt.eduzhm4
Committee MemberKwasinski, Alexisakwasins@pitt.eduakwasins
Committee MemberKerestes, Robertrjk39@pitt.edurjk39
Committee MemberRosu,
Date: 24 January 2019
Date Type: Publication
Defense Date: 20 November 2018
Approval Date: 24 January 2019
Submission Date: 15 November 2018
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 217
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Electrical and Computer Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Reliability, Power Electronics, Power Electronics Reliability, Life Preservation, Active Thermal Control, Boundary Control, Natural Switching Surface Control, Geometric Control, Trajectory Control, State Plane Analysis, Semiconductor Device Modeling, Electro-Thermal Device Modeling, Grid Converter
Date Deposited: 24 Jan 2019 15:50
Last Modified: 24 Jan 2019 15:50


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