Investigation of an ANPC Inverter in Electrified Vehicles

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Investigation of an ANPC Inverter in Electrified Vehicles
Authors: Zhang, Zhenghua
Abstract: In this thesis, a three-level active neutral point clamped (ANPC) inverter for a permanent magnet synchronous machine (PMSM) drive is developed and its performance is investigated. The performance investigation is mainly based on comparison with a two level inverter including semiconductor devices’ selection, total harmonics distortion (THD) analysis, semiconductor devices losses evaluation as well as energy efficiency study with various drive cycles. Moreover, the losses distribution in the ANPC inverter is also analyzed. In the initial part of the thesis, theories of electric drive system used in this thesis are introduced. Based on the theories, an APNC inverter model is built. The modulation strategy is chosen and different switching states are discussed in detail. With the chosen modulation strategy, a space vector modulation (SVM) method is developed and studied carefully. A two level inverter with SVM method is implemented for performance comparison with the ANPC inverter. The simulation results show that the ANPC inverter has obvious total harmonics distortion (THD) reductions for both voltage and current. To evaluate the inverters’ performance in electrified vehicles, an electric vehicle system is set up. The required rated power of the inverter in the system is 125kW at a DC voltage of 800V. Accordingly, each semiconductor device in the ANPC inverter need to withstand a reverse voltage of 400V which is half of that in the two-level inverter, thus an IGBT module with a reverse blocking voltage of 650V is selected for the ANPC inverter while it is 1200V for the two-level inverter. Compared with the two level inverter, the ANPC inverter has lower total losses in the entire operation region. The maximum efficiency of the ANPC inverter can reach as much as 99.25 % while it is only 98.68 % for the two-level inverter. Furthermore, when operating with various drive cycles, the ANPC inverter has an energy efficiency improvement of 2.86 % in the EUDC drive cycles and 0.99 % in the ECE drive cycles. Finally, the losses distribution in the ANPC inverter is analyzed since the unbalancing losses distribution is a significant issue for the ANPC inverter. The losses distribution on each device varies when torque and speed are changing but the most stressed device is the same throughout all operating points. Moreover, with various power factors, the losses are always concentrated on the inner switches.
Keywords: Elkraftteknik;Electric power engineering
Issue Date: 2017
Publisher: Chalmers tekniska högskola / Institutionen för elektroteknik
Chalmers University of Technology / Department of Electrical Engineering
Collection:Examensarbeten för masterexamen // Master Theses

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