Patent ID: 11936237
Assignee: TOSHIBA MITSUBISHI—ELECTRIC INDUSTRIAL SYSTEMS CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. An uninterruptible power supply apparatus comprising:
a rectifier that converts first AC voltage supplied from a first AC power supply to DC voltage;
a capacitor that smooths DC output voltage from the rectifier;
an inverter that converts terminal-to-terminal voltage of the capacitor to second AC voltage;
a first switch having a first terminal receiving the second AC voltage and a second terminal connected to a load;
a second switch having a first terminal receiving third AC voltage supplied from a second AC power supply and a second terminal connected to the load;
a first current detector that detects AC current flowing between the first AC power supply and the rectifier;
a second current detector that detects load current;
a first controller that controls the first and second switches; and
a second controller that controls the rectifier based on results of detection by the first and second current detectors, wherein
the first controller
(i) in a first mode in which the second AC voltage is supplied to the load, turns on the first switch and turns off the second switch,
(ii) in a second mode in which the third AC voltage is supplied to the load, turns on the second switch and turns off the first switch, and
(iii) in a switching period in which one mode of the first and second modes is switched to the other mode, turns on the first and second switches and executes a third mode in which the second and third AC voltages are supplied to the load, and

the second controller
(iv) in the first and second modes, passes first AC current from the first AC power supply to the rectifier such that the terminal-to-terminal voltage of the capacitor becomes a first reference voltage, the first AC current including a first feedback component having a value corresponding to deviation between the first reference voltage and the terminal-to-terminal voltage of the capacitor, and a first feed forward component obtained by multiplying the load current by a first gain, and
(v) in the switching period, passes second AC current from the first AC power supply to the rectifier such that the terminal-to-terminal voltage of the capacitor becomes a second reference voltage, the second AC current including a second feedback component having a value corresponding to deviation between the second reference voltage and the terminal-to-terminal voltage of the capacitor, and a second feed forward component obtained by multiplying the load current by a second gain smaller than the first gain,
to prevent the terminal-to-terminal voltage of the capacitor from exceeding an upper limit voltage higher than the first and second reference voltages.