The present invention provides a control device for an
uninterruptible power supply apparatus. When the current failure state of an
AC power supply (1) is releases, an information that the
AC power supply (1) is in a
normal state is notarized, a synchronization control is performed for making the
uninterruptible power supply apparatus (20) to generate an output
voltage synchronous with the
voltage of the
AC power supply (1), in a state that the difference of the frequency of the AC power supply (1) be about to start and the output frequency of the
uninterruptible power supply apparatus (20) is big, a synchronization control through a path of a
phase difference /
frequency detection circuit (21), a setting device (23), an
adder(24), a limiting circuit (25), a setting device (26), a multiplier (27), an
adder (28), a contact point (22b), an LPF (29), an
adder (30), a V / F converter (16), and an
inverter driving circuit (17). In the synchronization control of the path, the output
voltage of an
inverter circuit (12) and the voltage of the AC power supply (1) can be synchronized quickly without any impacts.