A hybrid automobile runs by transmitting a power from an engine and a power from a motor-generator MG2, and can store a part of the power from the engine and an electric power generated by a motor-generator MG1. In this hybrid automobile, a power requirement Pr* of a drive shaft is set based on an accelerator opening, and a battery charge electric power Pbi is set based on SOC, and the sum of the power requirement Pr* and the battery charge electric power Pbi are set as an engine target power Pe*. When the engine target power Pe* is less than a predetermined minimum value Plow, the engine target power Pe* is changed to the minimum value Plow. Further, in accordance with this change, the battery charge electric power Pbi is also changed, and the engine and the motor-generators MG1, MG2 are operated. Since the minimum value Plow is set to be a value such that the efficiency with respect to the output of the engine becomes optimal, it is possible to prevent the engine from being operated in a low output region where the efficiency is low.
In response to a decrease in observed battery voltage Vb to or below a preset threshold value Vs1, the control procedure of the invention closes the gates of an inverter for an air conditioner to stop a supply of electric power to the air conditioner (at a time point t1). In response to a further decrease in observed battery voltage Vb to or below a preset threshold value Vm1, the control procedure closes the gates of inverters for motors MG1 and MG2 to stop supplies of electric power to the motors MG1 and MG2 (at a time point t2). The threshold values Vs1 and Vm1 are set to keep the battery voltage Vb at or above a minimum required voltage for proper operations of an electric power steering (EPS). This arrangement guarantees the minimum required voltage for proper operations of the EPS and accordingly ensures the stable steering performance even in the event of a voltage decrease of the battery.
