The invention discloses a controlling method of improving current quality of a grid-connected
inverter when operated in
low load. The controlling method of improving the current quality of the grid-connected
inverter when operated in
low load achieves judgment of the operating mode of the grid-connected
inverter according to the difference of the ratio of the actual output power and rated power of the inverter. When the ratio ranges from 0.6 to 1, the grid-connected inverter is in the normal working mode, and the classic
voltage current double closed-loop PI controlling is adopted; when the ratio ranges from 0.3 to 0.6, the grid-connected inverter is in the mild low-load working mode, the classic
voltage current double closed-loop PI controlling is adopted at the moment, and
software measurements are added, wherein the
software measurements comprise improving the switch frequency by one time, enabling an inner ring PI adjuster to be merged into a repetition controller and the like; when the ratio is less than 0.3, the grid-connected inverter is in the severe
low load working mode, at the moment hardware measurements are added on the basis of the mild low load controlling method, the hardware measurements comprise starting a controlling
relay and enabling a bridge-arm side addition
inductor to be merged. The controlling method of improving the current quality of the grid-connected inverter when operated in low load ensures grid current when the grid-connected inverter runs under low load, can reduce the quantity of the added
inductor, and saves cost.