Method of detecting failure of antiparallel thyristor, and power control device

A power control device comprising:

• an antiparallel thyristor which includes a first thyristor and a second thyristor connected in parallel and in opposite directions, and is configured to control power supplied from an alternating current power supply to a load;
• and
• a controller configured to control the antiparallel thyristor,
• wherein the controller is configured to execute:
• detecting, as a third detection value, the voltage or the current supplied to the load when ceasing the output commands for the first thyristor and the second thyristor to determine whether a short failure occurs in one of the first thyristor and the second thyristor;
• and
• in response to the determination that the short failure has not occurred in at least one selected from the group of the first thyristor and the second thyristor, the controller is further configured to execute:
• detecting, as a first detection value, a voltage or a current supplied to the load when ceasing an output command for the second thyristor and issuing an output command for the first thyristor;
• detecting, as a second detection value, the voltage or the current supplied to the load when ceasing the output command for the first thyristor and issuing the output command for the second thyristor;
• and
• determining the failure of the antiparallel thyristor based on the third detection value and based on a difference between the first detection value and the second detection value.