State-space modelling and eigenvalue analysis of the slip energy recovery drive

A fifth order linearised state-space model of the slip energy recovery drive (SERD) is elaborated, based on a simplified dq dynamic model which represents (with good accuracy) the dynamic behaviour of the drive. The eigenvalues of the SERD, calculated with the linearised model, are correlated with those of the conventional induction machine, and the effect of the external DC link filter and the inverter DC voltage is demonstrated. The variation of the drive eigenvalues for different operating conditions is presented both for motor and generator operation and a comparison is made with an equivalent voltage source inverter drive. Important transfer functions of the SERD, such as those concerning the response of the drive speed and torque for mechanical load and supply voltage disturbances and the design of the control system, are derived and their characteristics are discussed