Input-voltage-abnormality detection method and power source device

A power supply device comprising:

• a single-phase AC path from an input end to an output end in the power supply device;
• a first voltage sensor configured to detect an input voltage at the input end;
• a second voltage sensor configured to detect an output voltage at the output end;
• a conversion unit connected to the AC path and being capable of bidirectional power conversion;
• a storage battery connected to the AC path via the conversion unit;
• an AC switch provided between the input end and a point at which the conversion unit is connected to the AC path;
• and
• a control unit configured to control the conversion unit and the AC switch, thereby having a current conduction mode in which a power is supplied from the input end through the AC switch which is closed and the AC path, to reach the output end and thus supplied to a load connected to the output end, and a storage battery discharge mode in which the AC switch is opened and a power is supplied from the storage battery to the load via the conversion unit, wherein
• the control unit has a function of a phase locked loop, and sequentially generates a simulated voltage waveform with a phase synchronized with the input voltage, by using the phase locked loop, and
• within a period until a next update of the generated simulated voltage waveform, compares an instantaneous value of the input voltage with the simulated voltage waveform, and when the instantaneous value of the input voltage changes from a state of being along the simulated voltage waveform to a state of not being along the simulated voltage waveform, determines that the input voltage is abnormal, and shifts from the current conduction mode to the storage battery discharge mode.