| 摘要 |
PURPOSE:To suppress a thyristor overcurrent due to harmonic distortion by detecting the quantity of higher harmonics included in a system voltage and making the ignition phase angle of the thyristor constant if this quantity exceeds a prescribed value. CONSTITUTION:The system voltage is detected by a voltage transformer 7, and higher harmonics included in this system voltage are taken out by a high-pass filter circuit 84, and the quantity of higher harmonics is discriminated by a level detecting circuit 85. When this quantity exceeds a certain value, this discrimination signal is inputted as an interrupt signal to a phase control circuit 83 to interrupt a normal reactive power control and performs an operation to make the ignition phase of the thyristor constant. The ignition phase angle to be made constant is determined by protection co-ordination of the thyristor. Thus, the overcurrent of the thyristor due to harmonic distortion of the system voltage is suppressed, and abnormal resonance between a compensating reactor 91 and the other equipment is also suppressed. |
