Abstract: A method and device for modulating a five-level inverter, and a photovoltaic system are provided. The method includes: acquiring a voltage command value Vcmd of a phase bridge; controlling a first and a fourth switching devices to be switched on alternately when Vcmd?V1Pos+Vthrs1; controlling the first and a third switching devices to be switched on alternately when V1Pos?Vthrs2?Vcmd<V1Pos+Vthrs1; controlling the fourth and the third switching devices to be switched on alternately when 0?Vcmd<V1Pos?Vthrs2; controlling the third and a fifth switching devices to be switched on alternately when ?V1Neg+Vthrs3?Vcmd<0; controlling the third and a second switching devices to be switched on alternately when ?V1Neg?Vthrs4?Vcmd<?V1Neg+Vthrs3; controlling the fifth and the second switching devices to be switched on alternately when Vcmd<?V1Neg?Vthrs4.

Abstract: A method and device for switching an operation mode of a five-level inverter are provided. The method includes: determining a first three-level operation mode as a three-level operation mode to be switched to from a five-level operation mode in a case that a PV input voltage is higher than a bridge line-line voltage command value; switching, after the operation mode is switched to the first three-level operation mode, the operation mode from the first three-level operation mode to a second three-level operation mode, in a case that a junction temperature of a switching device operating in the first three-level operation mode exceeds a first preset value; and switching the operation mode from the second three-level operation mode to the first three-level operation mode in a case that the junction temperature of a switching device operating in the second three-level operation mode exceeds a second preset value.

Abstract: A method and device for switching an operation mode of a five-level inverter are provided. The method includes: determining a first three-level operation mode as a three-level operation mode to be switched to from a five-level operation mode in a case that a PV input voltage is higher than a bridge line-line voltage command value; switching, after the operation mode is switched to the first three-level operation mode, the operation mode from the first three-level operation mode to a second three-level operation mode, in a case that a junction temperature of a switching device operating in the first three-level operation mode exceeds a first preset value; and switching the operation mode from the second three-level operation mode to the first three-level operation mode in a case that the junction temperature of a switching device operating in the second three-level operation mode exceeds a second preset value.

Abstract: A method and device for modulating a five-level inverter, and a photovoltaic system are provided. The method includes: acquiring a voltage command value Vcmd of a phase bridge; controlling a first and a fourth switching devices to be switched on alternately when Vcmd?V1Pos+Vthrs1; controlling the first and a third switching devices to be switched on alternately when V1Pos?Vthrs2?Vcmd<V1Pos+Vthrs1; controlling the fourth and the third switching devices to be switched on alternately when 0?Vcmd<V1Pos?Vthrs2; controlling the third and a fifth switching devices to be switched on alternately when ?V1Neg+Vthrs3?Vcmd<0; controlling the third and a second switching devices to be switched on alternately when ?V1Neg?Vthrs4?Vcmd<?V1Neg+Vthrs3; controlling the fifth and the second switching devices to be switched on alternately when Vcmd<?V1Neg?Vthrs4.