Apparatus and method for protecting grid-connected inverter from occurrence of low grid voltage

A method of protecting a grid-connected inverter from a low grid voltage, the method comprising:

• sensing an output current of the grid-connected inverter by using a first output current sensor;
• calculating a first output current based on a D-axis current and a Q-axis current of the output current by using a first output current calculator;
• determining whether a difference between the first output current and a reference value exceeds a pre-determined range by using a first output current controller;
• and
• when the difference between the first output current and the reference value exceeds the predetermined range, decreasing the output current to less than the reference value by the first output current controller;
• wherein the reference value is an output current when a grid voltage is normal;
• wherein the predetermined range is a range limit from the reference value, in which the output current does not cause breakdown of the grid-connected inverter.