Abstract: An apparatus for protecting a grid-connected inverter from a low grid voltage includes a first output current sensor configured to sense an output current of a grid-connected inverter, a first output current calculator configured to calculate a D-axis current and a Q-axis current of the output current to obtain the output current that is sensed, and a first output current controller configured to determine whether a difference between the output current and a reference current exceeds a predetermined range, and to decrease the output current by a predetermined value when the difference between the output current and the reference current exceeds the predetermined range.

Abstract: An apparatus for controlling overcurrent of a grid-connected inverter due to an abnormal grid voltage includes a grid voltage sensor configured to sense a grid voltage according to an output current of the grid-connected inverter, a voltage variation calculator configured to calculate a D-axis voltage and a Q-axis voltage of the grid voltage to obtain variation values of the D-axis voltage and the Q-axis voltage, and an output current controller configured to determine whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds a set value of the grid voltage variation, and decrease the output current by a predetermined value when one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.

Abstract: An apparatus for protecting a grid-connected inverter from a low grid voltage includes a first output current sensor configured to sense an output current of a grid-connected inverter, a first output current calculator configured to calculate a D-axis current and a Q-axis current of the output current to obtain the output current that is sensed, and a first output current controller configured to determine whether a difference between the output current and a reference current exceeds a predetermined range, and to decrease the output current by a predetermined value when the difference between the output current and the reference current exceeds the predetermined range.

Abstract: An apparatus and method for compensating for a ripple and offset of an inverter and an apparatus and method for compensating for a ripple and offset of an inverter which removes a ripple component by compensating for an offset component included in a signal input to the inverter from an inverter controller. A method that senses a direct current (DC) input to an inverter from an inverter controller and an alternating current (AC) output from the inverter and removes a ripple component included in the DC based on the sensed currents, a method that removes a ripple component included in a reference voltage that is output from an inverter controller and is input to an inverter, and a method that compensates for an offset component of an AC voltage/AC used for inverter control and reduces a ripple component corresponding to an output frequency of an inverter.

Abstract: An apparatus and method for compensating for a ripple and offset of an inverter and an apparatus and method for compensating for a ripple and offset of an inverter which removes a ripple component by compensating for an offset component included in a signal input to the inverter from an inverter controller. A method that senses a direct current (DC) input to an inverter from an inverter controller and an alternating current (AC) output from the inverter and removes a ripple component included in the DC based on the sensed currents, a method that removes a ripple component included in a reference voltage that is output from an inverter controller and is input to an inverter, and a method that compensates for an offset component of an AC voltage/AC used for inverter control and reduces a ripple component corresponding to an output frequency of an inverter.

Abstract: An apparatus for controlling overcurrent of a grid-connected inverter due to an abnormal grid voltage includes a grid voltage sensor configured to sense a grid voltage according to an output current of the grid-connected inverter, a voltage variation calculator configured to calculate a D-axis voltage and a Q-axis voltage of the grid voltage to obtain variation values of the D-axis voltage and the Q-axis voltage, and an output current controller configured to determine whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds a set value of the grid voltage variation, and decrease the output current by a predetermined value when one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.