Output Voltage Modulation for Cascaded H-Bridge Inverters including Thermal and Battery SoC Balancing in Vehicle Traction Applications
Typ
Examensarbete för masterexamen
Program
Electric power engineering (MPEPO), MSc
Publicerad
2020
Författare
Baum, Lukas
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In traction applications, two-level inverters are commonly used. Multilevel inverters can provide
benefits in efficiency and output voltage quality, as known for power system applications. This
work analyzes different aspects of cascaded H-bridge multilevel inverters especially for traction
applications. The inverter is simulated, considering efficiency and harmonic distortions, for
the whole operating region of a permanent magnet synchronous machine. The findings are
verified using a representative laboratory setup. Compared to a two-level inverter, the analyzed
cascaded H-bridge multilevel inverter allows for significant increases in efficiency as inverter
losses are approximately halved. Different switching strategies are analyzed, such as pulse width
modulated switching and fundamental frequency switching with selective harmonic elimination.
A strategy is developed, combining the advantages of both switching techniques. Additionally,
a thermal balancing strategy is proposed, resulting in a reduction of the temperature differences
between switches with up to 67%. Furthermore, cascaded H-bridge multilevel inverters allow
for novel possibilities of balancing the individual battery packs. Here, different state of charge
balancing strategies are proposed and experimentally validated.
Beskrivning
Ämne/nyckelord
Conduction Losses , Electric Vehicle , Efficiency , Multilevel Converters , Multilevel Inverters , SoC Balancing , Switching Losses , Thermal Balancing