ON THE ORDER REDUCTION AND STABILITY ANALYSIS OF LARGE ELECTRIC MACHINES

This paper deals with the model reduction of electric machines, in ord er to study their steady-state stability. The modelling of these machi nes is described on the base of the state-space representation. A stat e-equation form has beet? established, which is valid for different ki nds of electric machines. The reduction condition is formulated as a n on-linear Riccati equation. In a first step, this equation is resolved under the assumption of an infinite inertia. Under such condition, th e popular damping and synchronizing torque approach has been expressed in terms of the reduced model parameters. In a second step, this stud y is generalized taking into account the inertia, by resolving iterati vely the Riccati equation. Thus, the damping and synchronizing torques in terms of inertia have been established for the first time. In orde r to illustrate the above results, two examples concerning the synchro nous and the doubly-fed machines are treated.