Analytical Modeling of Adjustable Speed Drive Load for Power System Studies

This paper presents the results of analytical modelling of two important load categories: directly connected induction motors and adjustable speed drive (ASD) controlled induction motors. Their steady state load models and active/reactive power consumption characteristics are compared and discussed in detail. The results are obtained for three different motor loading conditions and two of the most common controls of typical PWM ASD configurations: open-loop V-Hz control and closed-loop space vector control. Additional parameters considered in the analysis are: adjusted speed of the ASD-controlled motor and dc link inductance/capacitance. The effects of system/source inductance are also discussed.