| 摘要 |
A method of estimating winding current of a wye-delta or delta-wye transformer is provided to accurately estimate winding current by using an induced voltage, which is calculated at a wye winding portion. A variable(sat_ind) is set to 0 before saturation(S15). Voltages and currents of primary and secondary windings are measured. Induced voltages(eA,eB,eC) at the primary winding are calculated by using the primary voltage and current, and a core loss current(icA) is measured by using a core loss resistance(S20). A non-circulating current and a circulating current(iDelta) are calculated(S22), and a winding current(iab) is calculated by using the non-circulating and circulating currents(S25). When it is determined that a transformer is not saturated(S30), a compensation difference current is calculated(S32). When the compensation difference current is smaller than a threshold value, the transformer is determined to operate normally(S34), and whether an error occurred is determined(S45) by using the compensation difference current. When the compensation difference current is greater than the threshold value, a magnetic flux at that timing is defined as an initial value(S34). |
