| 摘要 |
PURPOSE:To improve system interruption detecting accuracy so that the individual operating state of an inverter can surely be detected by reducing the output power of the inverter when the steeply increasing state of a harmonic component does not continue for a fixed period of time and detecting the voltage drop at a tie point. CONSTITUTION:Third harmonic extracting signals from an integration circuit are sampled at regular time intervals and the average value of the sampled extracting signals is fetched as a detected value Vin (S1). Then it is judged whether or not the difference between the detected value Vin and a reference voltage value Vref is larger than a prescribed threshold el (S3). Thereafter, whether or not counting operations are carried on is judged from the counter of a time-limiting timer and, when the counting operations are carried on, the counting operations are started and the continuation of the counting operations for a fixed period of time is judged (S5, S7, and S9). From the above-mentioned operations, the individual operation of an inverter is surely detected by judging the steeply increasing state of a harmonic component resulting from a system interruption by judging the continuation of the steeply increasing state of the harmonic component for a fixed period of time T1 and suppressing the influence of noise. |
