| 摘要 |
PROBLEM TO BE SOLVED: To suppress an overcurrent caused by a negative-phase voltage generated by an AC system failure, etc., by a method wherein a voltage at the linkage point of a self-excited converter and an AC system is detected and an negative-phase component contained therein is detected and the voltage signal of the negative-phase component is added to the voltage signal of a positive-phase component to generate a control output. SOLUTION: A voltage at the junction of a self-excited converter and an AC system is detected by an AC voltage transformer 111, and 3-phase AC voltages are converted into 2-phase AC voltages of d-axis and q-axis by a 2nd conversion circuit 112. The positive-phase components of the converted 2-phase signals are detected by positive- phase component detection circuits 113a and 113b and multiplied by a gain. Also, the negative-phase components of the converted 2-phase signals are detected by negative-phase component detection circuits 114a and 114b and multiplied by a gain. A PWM pulse is generated by using signals obtained by adding the negative-phase component voltage signals to other signals by 3rd 4th adding circuits 115 and 116. With this constitution, the negative-phase component in a system voltage is added to a control voltage by feed-forward and an output voltage whose negative-phase component is compensated can be obtained. Therefore, an overcurrent is not generated. |
