To provide an optimal usage of the electric brake capability from an energy efficiency point of view during, for example, transmission shifting and quick vehicle direction reversals, wherein the prior art PI-based voltage control scheme assisted by hysteretic brake resistor control cannot offer the optimal usage.
An electric drive system 12 comprises a generator 14, a traction motor 16, a brake resistor 18, a bus 20, and a control unit 22. The generator 14, the traction motor 16, and the brake resistor 18 are coupled electrically to the bus 20. The control unit 22 is configured to determine a pulse-width-modulation duty cycle for the brake resistor 18 ("brake duty") and control operation of the brake resistor 18 according to the brake duty, wherein the brake duty can be a value intermediate of constant OFF and constant ON. A method of operating the electric drive system 12 is also disclosed.
Yasushi Kobayashi
Akio Chiba
Hiroyuki Tomita
Motoharu Nakanishi