Power board status:
Refers to the status of communication between the internal monitor board
of the power device and the external upper board.
Options:
1.normal(1) - indicates the normal state
2.fault(2) - indicates the faulty state
3.protecting(3)- indicates that the backup power supply works in the protection state
4.switched(4) - indicates that the main power supply is faulty, and is protected by backup power supply
5.invalid(-1) - indicates that the device can not get the value, e.g. the EMU does not support this operation, or the EMU state is abnormal