| 摘要 |
PURPOSE:To suppress the biased magnetization of a transformer regardless of the DC component generated from the power system side by taking the difference between the primary winding current and the secondary winding current of the transformer and detecting the DC component included in the difference to correct the output voltage command of a power converter. CONSTITUTION:When the winding ratio of the transformer is set to 1 for simplicity, the exciting current of the transformer is equal to the difference between the primary current and the secondary current. Since the exciting current approximately corresponds to the magnetic flux of the iron core of the transformer, the DC component included in the exciting current is detected to estimate the extent of DC biased magnetization. Therefore, the difference between the primary winding current and the secondary winding current is calculated by a subtractor 12, and the DC component is detected by a DC component detector 8, and the output voltage command value from a control circuit 7 is corrected so as to cancel the biased magnetization, thereby suppressing the biased magnetization of the transformer 2. Since the correction is performed by the exalting current, not only biased magnetization due to the DC component included in the output of a self-excited converter 3 but also that due to the DC component transiently included in a power system 1 is corrected. |
