Abstract: An electrical system and method include a DC link, a controlled rectifier connected between the DC link and a power source, an energy storage, a DC to DC converter connected between the DC link and the energy storage, a motor, and a DC to AC converter connected between the DC link and the motor. The converters are configured to transfer power in both directions. The rectifier controls the DC voltage of the DC link when the DC link voltage is in a first voltage range. The DC to DC converter controls the DC voltage of the DC link by charging the energy storage when the DC link voltage is in a second voltage range, which has higher voltage values than the first voltage range, or by discharging the energy storage when the DC link voltage is in a third voltage range, which has lower voltages than the first voltage range.

Abstract: The present disclosure describes an adjustment method and apparatus for implementing the method for a speed-controlled electric drive of an electric vehicle. In the method, a rotational speed of the electric drive is controlled by a frequency converter on the basis of a constrained speed reference. The method comprises determining the rotational speed, receiving an unconstrained speed reference, calculating the constrained speed reference on the basis of the unconstrained speed reference, wherein a rate of change of the constrained speed reference is limited to a predefined range, and if a value of the determined rotational speed is between the values of the constrained speed reference and the unconstrained speed reference, setting the value of the constrained speed reference the same as the value of the determined rotational speed.

Abstract: An electrical system and method include a DC link, a controlled rectifier connected between the DC link and a power source, an energy storage, a DC to DC converter connected between the DC link and the energy storage, a motor, and a DC to AC converter connected between the DC link and the motor. The converters are configured to transfer power in both directions. The rectifier controls the DC voltage of the DC link when the DC link voltage is in a first voltage range. The DC to DC converter controls the DC voltage of the DC link by charging the energy storage when the DC link voltage is in a second voltage range, which has higher voltage values than the first voltage range, or by discharging the energy storage when the DC link voltage is in a third voltage range, which has lower voltages than the first voltage range.