an engine;

a hydraulic pump driven by the engine;

a hydraulic cylinder driven by hydraulic fluid delivered from the hydraulic pump;

a work device moved with elongation and contraction of the hydraulic cylinder;

a motor generator rotated by the engine to generate electric power;

a first inverter that controls the motor generator;

a traveling electric motor driven by the electric power generated by the motor generator;

a second inverter connected to the first inverter through a DC bus to control output torque of the traveling electric motor; and

a controller that controls a voltage of the DC bus, wherein,

the controller is configured to decrease the output torque of the traveling electric motor according to an amount of decrease in the voltage of the DC bus when the voltage of the DC bus drops below a first threshold value as a load on the traveling electric motor increases; and wherein,

the controller is configured to decrease the output torque of the traveling electric motor to a value within a range of magnitude with which the work vehicle stays stationary on a level ground when the voltage of the DC bus drops below a second threshold value lower than the first threshold value.