Has the control of DC magnetic deviation suppression of 3 phase transformers the inverter control unit

摘要

PURPOSE:To reduce the volume of an inverter by a method wherein the DC components of three-phase output voltages of the inverter are so controlled as to be balanced to suppress the DC-bias magnetization of a three-phase transformer. CONSTITUTION:A DC-bias magnetization suppression signal calculating circuit 107 outputs the unbalanced components of the DC components iRd, iSd and iTd of the output AC currents iR, iS and iT of an inverter 1, which are supplied by a current DC component detecting circuit 106, as two-phase inverter output voltage correction signals vRd and vTd. An output reference correcting circuit 108 adds the two-phase output correction signals vRd and vTd to the output references of the two phases of three phases of the inverter 1 to output three- phase corrected output references vRs, vSc and vTc. Then the output voltage or output currents of the inverter 1 are determined by a control circuit 105 from the three-phase corrected output references to suppress the DC-bias magnetization of a transformer 3.