Electric Vehicle Powertrains with Modular Battery Banks Tied to Multilevel NPC Inverters

Abstract

Nowadays, the internal combustion engine in vehicles is being replaced by electric motors, giving way to the electric vehicle, which results in reduced environmental impact, higher efficiency and lower emission of greenhouse gases. The powertrain of an electric vehicle is its most prominent subsystem, with the batteries and traction inverter being key components. Thus, due to their relevance, advances in the design of both components are of paramount importance. In this paper, the potential benefits achieved through a powertrain design approach based on combining a modular battery bank with multilevel NPC traction inverter topologies were analyzed, in comparison to a conventional two-level powertrain design. Several aspects were analyzed: modularity, complexity, battery-pack state-of-charge balancing, inverter loss, motor ac voltage harmonic distortion, motor common-mode voltage and reliability. Particularly, from the comparison study developed under the selected design scenario, the proposed design approach, based on modular battery packs and multilevel technology, shows a potential reduction of up to 55% in inverter losses, up to 65% in motor ac-voltage total harmonic distortion, and up to 75% in rms common-mode voltage.

A Survey on the State-of-the-Art and Future Trends of Multilevel Inverters in BEVs

“…The potential benefits when NPC MLI is tied to a modular battery bank were analyzed in [47]. A comparison with a conventional 2-level inverter was performed under the selected design scenario for a small power (50 kW) BEV with a 300-V DC link, a medium power (100 kW) BEV with a 600-V DC link, and a high power (150 kW) BEV with a 900-V DC link in several terms: complexity, modularity, battery SoC balancing, inverter loss, ac voltage harmonic distortion of the electric motor, common mode motor voltage, and reliability.…”

Calculation of Losses in a Motor Fed by a Conventional Inverter and a Battery Distributed Inverter

“…There is thus a growing interest in the research and design of batteries, converters, and electric machines. The greatest margins for improvement concern the cost reduction, the energy efficiency of the processes [4], and the study of breakthrough architectures [5][6][7][8]. This is the context in which a new architecture called "IBIS" (Intelligent Battery Integrated System) was developed.…”