Date of Graduation

7-2020

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Fang Luo

Committee Member

Yue Zhao

Second Committee Member

Roy McCann

Keywords

digital active EMI filter, Field Programmable Gate Array (FPGA), Si-SiC hybrid switch, space vector modulation (SVM), three-level T-type inverter, wide bandgap devices

Abstract

Power converter exposes strong challenges to its efficiency, power density and reliability. For the grid-connected inverter application, three-level (3-L) T-type neutral-point-clamped (TNPC) inverters has higher efficiency and lower total harmonic distortion (THD) compared to two-level inverter. Hybrid switch concept combines the benefit of both silicon carbide (SiC) MOSFET and Si IGBT. By applying hybrid switch structure in 3-L T-type inverter, the total power density of 3-L TNPC inverter will be higher while the cost will be lower than that of all-SiC 3-L T-type inverter. The hybrid switch based 3-L TNPC inverter also imposes challenge to its modulation and control, a propoer modulation and control shceme need to be chosen to enable better inverter performance in terms of efficiency, neutral point balancing and electromagnetic interference (EMI). Morever, to shrink the EMI filter size for the power converter, an active EMI filter (AEF) structure is proposed. The proposed AEF provides superior performance than any of the conventional passive EMI filter and the existing AEFs. In this work, the system level design and testing of a 30 kW grid-connected 3-L T-type inverter with hybrid switch structure is discussed. Then, an improved space vector modulation (SVM) has been proposed, which enables neutral-point balancing (NPB) control in the proposed hybrid-switch-based TNPC inverters with loss and common-mode voltage reduction. Finally, the design, modelling, and testing of the proposed AEF is demonstrated.

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