Method for controlling neutral point potential of inverter of neutral point clamping type

摘要

A method for controlling a neutral point potential of an inverter of neutral point clamping type irrespective of the power factor by measuring or predicting the phase current in a simple way. An output state taken by an inverter of three-phase neutral point clamping type is represented by a vector. Depending on the phase state where the voltage vector outputted from the inverter is contained between which vectors, the occurrence time ratio of a specific vector corresponding to the voltage vector is changed to stabilize the neutral point voltage. The time of the three-phase output voltage, when six switched states wherein the positive bus, the negative bus, and the neutral line are connected to respective three-phase output terminals are set up, is controlled below a first preset value.