A power conversion system includes a power conversion device supplying electric power to a motor and a power supply device supplying electric power to the power conversion device. The power conversion device includes a reverse converter that converts the electric power, a control circuit that controls the reverse converter, and a current detector that detects current flowing through the reverse converter. The power supply device includes a storage device that stores electric power in accordance with a voltage, a step-up/down power supply circuit that changes the voltage of the storage device based on a voltage command, and a voltage command computing circuit that computes the energy stored in the storage device and output it as the voltage command to the step-up/down power supply circuit. When the characteristics of the motor are restricted, the voltage command computing circuit temporarily changes the voltage command to improve the motor characteristics.