Three-phase and three-level inverter unit

PURPOSE: To utilize control operation characteristics as a three-phase and three- level inverter most effectively by driving switching elements according to a modulation method previously set for a region of voltage command thereby employing an optimal modulation method in a control system wherein voltage vectors are introduced. CONSTITUTION: A microprocessor 1 constituting a modulation circuit divides one period into six sections of 60° each of which is then divided into four triangular areas being defined by the apexes of voltage vector and an output voltage command is outputted in the form of a vector. A voltage vector selection circuit 8 is previously stored with voltage vectors of inverter and output sequence thereof which is determined such that the voltage vectors to be transferred are outputted sequentially by once switching any one phase. Modulation is made such that the time average of the sequentially outputted voltage vectors at that carrier period will match with a command vector thus driving a GTO through a switching signal generating circuit 9. COPYRIGHT: (C)1993,JPO&Japio