METHOD FOR CONTROLLING INSTANTANEOUS CURRENT AT NEUTRAL POINT IN 3 LEVEL CONVERTER/INVERTER SYSTEM

摘要

PURPOSE: A method for controlling an instantaneous current at a neutral point in 3 level converter/inverter system is provided to control a voltage at a neutral point and instantaneously control a current flowing through a neutral point to zero. CONSTITUTION: A current outputted from a neutral point is calculated by multiplying an inverter output current by a vector. An offset voltage is obtained and the offset voltage is added to an initial command voltage of an inverter. A current flowing through a neutral point is transmitted to a converter controller. An output current of a converter is multiplied by the vector to calculate a current outputted by the neutral point. It is judged whether the current flowing through the neutral point is identical with a neutral point current which is calculated by multiplying an input current of the converter by a vector apply time. A power-factor is reduced to obtain a new command vector. A voltage offset value is obtained and is added to the command vector.