Abstract: An inverter system includes an inverter bridge, an inductor and a controller. The inverter bridge includes first, second, third and fourth power switches. The inductor is connected between the inverter bridge and a power grid. The controller is configured to control both the second power switch and the third power switch to be turned on or both the first power switch and the fourth power switch to be turned on within a first time period of each power frequency cycle. The first time period is from a moment when a current of the power grid becomes zero to a moment when a voltage of the power grid becomes zero. The current of the power grid is in inverse phase with the voltage of the power grid in the first time period, so that reactive power is stored in the inductor.

Abstract: A three-level converter includes a first power switch, which has a first end connected to a first DC input end and a first end of a third power switch. A second end of a second power switch is connected to a second DC input end and a second end of a fourth power switch. A connection point between a second end of the first power switch and a first end of the second power switch is a first AC output end. A connection point between a second end of the third power switch and a first end of the fourth power switch is a second AC output end. Fifth and sixth power switches are connected in series between the first AC output end and a neutral end. A seventh power switch is connected between the second AC output end and a connection point between the fifth and sixth power switches.