Performance improvement of V/f induction -motor control in the low-frequency range

Open-loop V/f controlled induction-motor drive can experience undesirable sustained oscillations at low frequencies. To reduce these oscillations, this paper first synthesizes the basic V/f speed control for achieving appropriate V/f ratios and boost voltages under light and high loads in the low-frequency range. It also highlights and includes in tuning the impacts of motor parametric variations occurring during operation. The paper then optimizes a closed-loop control scheme for slip compensation with a PI (proportional-integral) controller by applying GA (genetic algorithm) for tuning its parameters. Simulation results show that the optimized closed-loop control stabilizes the operation of the motor drive at low frequencies. The optimized control achieves also near-zero steady-state speed errors for both light and high loads at frequencies above the motor minimum starting frequency.