Two-port circuits based hybrid model of synchronous machine

The paper introduces the so-called hybrid state model of a synchronous machine based on the superposition principle of the two-port representation of d-axis (two-port circuits) and the single-port structure of q-axis equivalent circuits. The detailed formulation of the hybrid state model is developed in terms of the equivalent-circuit parameters of the machine. Analytical expressions of terminal voltages and the field current following the decrement tests are derived. A practical application of the model for the load rejection test analysis is investigated. Comparisons are made between simulation results and actual data obtained from a laboratory machine to assess the efficacy of the proposed synchronous generator framework analysis