| 摘要 |
PURPOSE:To perform stably a power conversion control even when on the AC voltage of a power system its negative-phase-sequence voltage is superimposed, by sensing the accurate phase angle of its positive-phase-sequence voltage, and by performing the conversion control based on the sensed value. CONSTITUTION:The instantaneous voltage data of two-phase voltage ealpha, e obtained by the two-phase conversion of a power system voltage are inputted to adders 602, 603 respectively, and concurrently, the instantaneous voltage data ealpha(-90 deg.), ebeta(-90 deg.) whose phases are delayed by 90 deg. from the ones of the instantaneous voltage data ealpha, ebeta are stored in a memory 601. Then, by the computations performed in the adders 602, 603, the negative-phase-sequence component of the power system voltage is removed, and only its positive-phase-sequence component is extracted. Subsequently, the ratio of the output of the adder 602 to the one of the adder 603 is computed by a divider 604, and by the computed value through a computer 605, the phase angle theta1 of the positive-phase-sequence voltage is found. Therefore, even when the power system voltage is made unbalanced and its negative-phase-sequence voltage is superimposed, after its removal, only the positive-phase-sequence voltage is extracted, and the accurate phase angle theta1 can be computed, and as a result, the power conversion control of the power system can be performed always in a stable state. |
