This paper proposes a procedure to apply a damping control to induction motor driven system in the singlepulse mode. In this mode, the amplitude of voltage vector is kept constant and it is determined by the filter capacitor voltage. Therefore, there is a possibility that the oscillation of the filter capacitor voltage deteriorates the torque control performance by fluctuation of the rotor flux. In this regard, this paper examines the oscillation of filter capacitor voltage and the dynamics of rotor magnetic flux by the frequency characteristics. This study reveals that the inversed value of the resonance frequency of LC input filter should be lower than the secondary time constant of the induction motor in order to avoid influence of the oscillation of the filter capacitor voltage to the rotor flux fluctuation. The proposed method is verified by the experimental tests with 0.75-kW-class miniature-model.

This paper deals with the vector control, including both the direct vector control (DVC) and the indirect vector control (IdVC), of induction motors. It is well known that the estimation of rotor flux plays a fundamental role in the DVC and the estimation of rotor resistance is vital in the slip compensation of the IdVC. In these estimations, the precision is significantly affected by the motor resistances. Therefore, online estimation of motor resistances is indispensable in practice.For a fast estimation of motor resistances, it is necessary to slow down the convergence rate of the current estimate. On the other hand, for a fast estimation of the rotor flux, it is necessary to speed up its convergence rate. It is very difficult to realize such a trade-off in convergence rates in a full order observer.In this paper, we propose to decouple the current observer from the flux observer so as to realize independent convergence rates. Then, the resistance estimation algorithm is applied to both DVC and IdVC. In particular, in the application to IdVC the flux observer needs not be used, which leads to a simpler structure. Meanwhile, independent convergence rates of current observer and flux observer yield an improved performance. A superior performance in the torque and flux responses in both cases is verified by numerous simulations.

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