Dead time compensation with variable resonant controller for induction motor drive system

For an inverter drive induction motor control system, a typical problem encountered is the nonlinear voltage gain caused by the non ideal characteristics of the power inverter. The switch dead time will introduce waveform distortion and fundamental voltage drop to the system. If not compensated, such distortions will introduce harmonic components which will cause additional loss in the induction machine. Therefore, the impact of harmonics caused by switching dead time are essential to induction motor drive design, especially when the motor is running at low speed. In this paper, a dead time compensation method is proposed. By adding a 6
^th
order resonant controller to the existing current loop PI controller, the negative sequence 5
^th
order and positive sequence 7
^th
order current harmonics caused by the dead time are eliminated. The overall control scheme is implemented in synchronous rotating d-q reference frame. The controller resonant frequency is 6 times to the synchronous frequency, which is calculated with mechanical speed and slip. Experiment results of steady state and dynamic response studies are presented to validate the effectiveness of the proposed method.