Constitution of V/f control for reducing the steady-state speed error to zero in induction motor drive system

In order to extend the applicability of a V/f (voltage/frequency)-controlled induction motor drive system, the authors treat the problem of reducing the steady-state speed error, caused by load changes from no-load, to zero without using a rotor speed sensor. The theoretical basis for this is given, and a scheme for constituting the control system is presented. In the scheme, the frequency of the stator voltage is controlled to compensate for the error, a strategy called frequency compensation control (FCC). Transforming an induction motor into the corresponding idealized induction motor (IIM), which is defined as a motor having no stator resistance and leakage inductance, plays an essential role in realizing the FCC. The V/f control can exhibit excellent abilities when and only when it is applied to IIM and is of the open loop type in terms of the rotor speed