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Electric vehicle power trains : high-performance control for constant power load stabilization

University of British Columbia

The development of sustainable transport systems has experienced great improvements in the last 15 years. As a result, electric vehicles, namely hybrid electric vehicles (HEVs) and all-electric or battery electric vehicles (BEVs), are slowly starting to coexist with regular internal combustion vehicles around the world. The complex powering structure of automotive electric systems can be described as a distributed multiconverter architecture. In pursuit of performance, constant-power behavior of tightly regulated downstream converters has raised as an important challenge in terms of system stability and controllability. The first part of this work presents the theory and experimental validation of the unstable behavior introduced by constant-power loads (CPLs) in power converters, more precisely in a Buck+Boost cascade converter as the battery charge/discharge unit. The second part of this work presents the derivation of the Circular Switching Surfaces (CSS) and the implementation of the CSS-based control technique for CPL stabilization. The analysis shows that the constant-power load trajectories and the proposed CSS present a wide, stable operating area and near-optimal transient response. Furthermore, impedance analysis of the converter in close-loop control shows advantageous reduced output source impedance. This extremely high dynamic capability prevents the use of bulky DC capacitors for bus stabilization, and allows the implementation of metal-film capacitors, which have reliability advantages over commonly employed electrolytic capacitors, as well as reduced ESR to improve system efficiency. Beyond the improved stabilization properties of the proposed CCS-based controller, a comparison with traditional compensated linear controller and nonlinear SMC highlights significant improvements in terms of dynamic response for sudden CPL changes. Simulation and experimental results are provided to validate the work. The last part of this thesis work presents the design, construction, and testing of a high-power 3-phase converter. This platform is intended for electric motor driving and is able to manage 20kW of power flow and above, making it suitable for high power traction system development. The platform features an Intelligent Power Module (IPM) to provide with flexibility allowing for changing the power module according to the requirements of the development. Testing of the platform was done in a 0.5HP AC induction motor drive controlled with Voltz-per-Hertz control technique. The integration of the BCDU and the high-power 3-phase motor drive platform conform a high-power bidirectional motor drive platform for the development and testing of control techniques for energy management in EV.

Text

2014-08-21

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/50093

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/