An Analytical Prediction Model of Balanced and Unbalanced Faults in Doubly Fed Induction Machines

Abstract

This paper presents the exact transient solution to the unbalanced and balanced faults in the doubly-fed induction machine (DFIM). Stator currents, rotor currents, and stator fluxes have been validated using simulation and experiment. The work is meant to strengthen and fasten the predictability of large DFIMs in the design stage to comply with mechanical constraints or grid fault issues. Moreover, the analytical approach reduces the computational costs of large-scale stability studies and is especially suited to the initial phase, where a of plethora design computations must be carried out for the DFIM before it is checked for its transient interaction with the power system. The possibility to dynamically estimate the DFIM performance is simplified by original equations derived from first principles. First, case studies of two large 265 MVA DFIMs are used to verify the analytical approach, and to justify the proposed "large machine approximation" using simulation with an exact match. Finally, laboratory measurements were conducted on a 10.96 kVA and a 1.94 kVA DFIM to validate the transient current peaks predicted in the proposed analytic expressions for two-phase and three-phase faults, respectively.

Evaluating the Precision of the DC Decay Test Method for Characterizing Wound-Field Synchronous Machines in Power Plants

“…These results presented show the minimum and maximum errors obtained. The simulations, separately validated using SIMSEN [27], were performed with a system of state equations written in MATLAB. It can be concluded from the robustness study that the maximum error is less than 1 %, which verifies the quality and accuracy of the identification method.…”