Resumen de Analysis and implementation of a bidirectional dc-dc converter with coupled inductor for an electric vehicle powertrain
The electric vehicles powertrain configuration have a common system that is formed by the battery, the power converter and the electric motor. Each one of these components has been the subject of an extensive research in recent years and a high level of development, with the aim of improving the performance of the automotive traction systems. However, these three components represent a great research challenge given the complexity of the integration of these elements in electric vehicles application. There are two basic configurations to implement the power converter in electric vehicles powertrain: first, the power converter is directly connected to the battery and, second configuration uses a bidirectional dc-dc converter between the battery pack and the traction inverter. In the literature the most commonly used converter for this application has been based on the bidirectional dc-dc boost converter. Nevertheless, design of electric vehicles powertrain based in boost converter is challenging because electric vehicle applications require efficiency optimization in a wide range of speeds instead of optimizing efficiency at the maximum power of the inverter traction. In this work a dc-dc bidirectional buck-boost converter is proposed to regulate the dc voltage in an electric vehicle powertrain. The converter is based on the versatile buck-boost converter, which has been used as a building block in several fuel-cell applications, it has shown a great performance in low voltage and hard-switching applications. Two bidirectional noninverting buck-boost converter prototypes are presented, with an input voltage range of 200 V to 400 V, output voltage between 100 V and 400 V and 1.6 kW rated power. They validate that the pair of coupled inductors of the power stage that operates with the higher efficiency has the proposed coils arrangement that uses only one toroidal core, with a very low parasitic winding-to-winding capacitance and loose magnetic coupling. Adapting the power stage damping network to the new parameters of the loosely coupled inductors is straightforward. To regulate the ouput voltage of the converter, a two-loop is programmed controller using the digital signal controller TMS320F28377S. Two diffierent inner current programmed controllers where proposed which corresponds to a discrete-time sliding-mode current control and a multisampled average current control. A hardware emulation system is used to taste the strategy control under realistic operation which imitates the actual vehicle dynamics for city driving conditions.
