State estimation of voltage and phase-shift transformer tap settings

Abstract

A transformer tap estimation technique is presented that overcomes earlier limitations because of a direct algorithmic approach. The procedure provides for turn ratio and phase angle measurements, and treats each transformer tap setting as an independent state variable. The problem of discrete tap positions is addressed, and an appropriate integer variable technique is presented. The method is general and is compatible with state estimation techniques which are based on network measurements and the Jacobian matrix. Because of the simultaneous solution of taps with complex bus voltages, the method is not predicated on the presence of transformer tap position, terminal voltage, or reactive flow measurements, although the method exploits such measurements if available. The method allows for bad data detection of anomalous tap measurements. Test results for an actual 300-bus network demonstrated the tap estimation capability. >