A Simple and Cost Effective Dead Time Elimination Scheme for Suppression of Vibrations in Elevator System

In this paper, a vibration suppression scheme is proposed for the riding comfort of elevator using dead time elimination scheme. Dead time is used for pulse width-modulation (PWM) controlled inverter/converter control to avoid shoot through of high-side and low-side power devices. To deal with dead time problems polarity of current detection is necessary The presented scheme does not require current sensors for polarity detection. Depending on the polarity of terminal voltage of each leg the current polarity is determined. Current polarity is detected regularly with a sampling frequency which is higher than the switching frequency to reduce the detection error. Hence separate power supplies are not required which reduces the bulkiness and cost of this scheme. Based on the polarity of sensed voltage the SPWM signals are generated to turn ON the switches of inverter. The presented scheme eliminates the dead time and therefore improves output voltage loss and current distortion and torque ripples. The corresponding elevator vibrations are conspicuously reduced. Simulation results for single phase and three phase inverter are done in MATLAB. The above scheme is verified by implementing it in a single phase inverter controlled motor. Hardware results are presented to demonstrate the effectiveness of the scheme.