An overcurrent protection circuit includes a load drive portion that drives a load based on a power supply voltage; a wire that connects the load and the load drive portion; a current detection portion that detects a load current showing a value of a current flowing through the load; a voltage detection portion; and a controller that controls the load drive portion to control a drive of the load, the controller determining an addition-and-subtraction value, controlling the load drive portion to cut off the load current, and stopping driving the load to protect a protection target from an overcurrent. The controller subtracts the integration value based on an elapsed time after cutoff of the load current. The controller controls the load drive portion to again start to drive the load, and also calculates a post-correction integration value lower than a pre-correction integration value by correcting the pre-correction integration value.

A protection mode control circuit includes an auto-restart counter configured to count the cycle of a first signal in a protection condition and to generate an auto-restart signal when a result of the count reaches a protection reference value and a latch mode unit configured to generate a latch mode signal for changing protection mode to latch mode when the auto-restart signal is consecutively generated by a predetermined threshold number.

A protection mode control circuit includes an auto-restart counter configured to count the cycle of a first signal in a protection condition and to generate an auto-restart signal when a result of the count reaches a protection reference value and a latch mode unit configured to generate a latch mode signal for changing protection mode to latch mode when the auto-restart signal is consecutively generated by a predetermined threshold number.

A resonant converter includes a first switch on the primary side and a second switch coupled to the first switch, a synchronization rectification switch on a secondary side configured to conduct during a conduction period in response to a switching operation of the first switch, and a switch control circuit configured to determine an operating region of the resonant converter to be below resonance based on a result of a comparison between the conduction period and an on period of the first switch.

A resonant converter includes a first switch on the primary side and a second switch coupled to the first switch, a synchronization rectification switch on a secondary side configured to conduct during a conduction period in response to a switching operation of the first switch, and a switch control circuit configured to determine an operating region of the resonant converter to be below resonance based on a result of a comparison between the conduction period and an on period of the first switch.

An overcurrent protection circuit includes a load drive portion that drives a load based on a power supply voltage; a wire that connects the load and the load drive portion; a current detection portion that detects a load current showing a value of a current flowing through the load; a voltage detection portion; and a controller that controls the load drive portion to control a drive of the load, the controller determining an addition-and-subtraction value, controlling the load drive portion to cut off the load current, and stopping driving the load to protect a protection target from an overcurrent. The controller subtracts the integration value based on an elapsed time after cutoff of the load current. The controller controls the load drive portion to again start to drive the load, and also calculates a post-correction integration value lower than a pre-correction integration value by correcting the pre-correction integration value.

A method is provided for controlling operation of an air conditioning unit. The method comprises supplying line voltage to activate a motor configured to operate the air conditioning unit, and monitoring a supply of control voltage in order to control operation of the air conditioning unit, the supply of control voltage being derived from line voltage. In response to detecting a control voltage below a predetermined threshold and/or by a predetermined percentage, a time delay is initiated. The method further comprises deactivating the motor if a predetermined increase in control voltage is not detected before the time delay expires.

A method is provided for controlling operation of an air conditioning unit. The method comprises supplying line voltage to activate a motor configured to operate the air conditioning unit, and monitoring a supply of control voltage in order to control operation of the air conditioning unit, the supply of control voltage being derived from line voltage. In response to detecting a control voltage below a predetermined threshold and/or by a predetermined percentage, a time delay is initiated. The method further comprises deactivating the motor if a predetermined increase in control voltage is not detected before the time delay expires.

The present disclosure relates to calculating a fault location in an electric power transmission system based on traveling waves. In one embodiment, a system consistent with the present disclosure may be configured to detect a fault in an electric power transmission system. The system may include a traveling wave detection subsystem configured to detect and measure traveling waves on a transmission line and a fault location estimation subsystem. The fault location estimation subsystem may receive from the traveling wave detection subsystem a first plurality of traveling waves on the transmission line generated during a reference event. The fault location estimation subsystem may receive from the traveling wave detection subsystem a second plurality of traveling waves generated during an unplanned event. An unmatched traveling wave in the second plurality of waves may be detected and a location of the unplanned event based on the unmatched traveling wave.

The application relates to a method for protecting a microgrid from a voltage drop or sag occurring in a main grid connected to said microgrid, the method comprising the following steps: a. supplying (105) power to the microgrid through the main grid; b. ascertaining that the voltage drop or sag is occurring in the main grid by executing the following steps: i. measuring (110) an instantaneous output voltage; ii. comparing (130) the measured instantaneous output voltage with a reference instantaneous output voltage; iii. Incrementing (140) a counter when the measured instantaneous output voltage differs from the reference instantaneous output voltage by more than a voltage threshold; and iv. ascertaining (150) that the voltage drop or sag is occurring in the main grid when the counter holds a value that exceeds a counter threshold; and c. disconnecting the microgrid from the main grid when the voltage drop or sag occurring in the main grid has been ascertained.