Control device for motor drive system and vehicle incorporating the same

A vehicle, comprising:

• an AC motor having a magnet in a rotor;
• a DC power supply configured to be chargeable;
• a drive device for driving said AC motor with electric power from said DC power supply;
• and
• a control device for controlling said drive device,
• said drive device including
• an inverter for driving said AC motor, and
• a converter connected between said DC power supply and said inverter and configured to convert a voltage between said DC power supply and said inverter, and
• said control device
• generating a step-up command value for said converter based on a torque command value for said AC motor,
• determining whether to carry out field-weakening control for increasing a current in a direction weakening force of said magnet that is supplied from said inverter to said AC motor based on said step-up command value and a state of drive of said AC motor, and
• further increasing generated said step-up command value when said field-weakening control should be carried out and when an absolute value of said torque command value is smaller than a threshold value.