High power induction motor VVVF drives system with IGCTs in thermal power plant

In this paper, a variable voltage variable frequency (VVVF) drive system with IGCTs (integrated gate commutated thyristors) for a high power induction motor (IM) has been developed. The designed VVVF system includes a 24-pulse rectifier and a three-level neutral point clamped (NPC) voltage source inverter (VSI). The three-level inverter with two IGCTs in series connection in each cell with an output LC- filter was used to obtain a 6 kV high voltage output. The digital signal processor (DSP) with field programmable gate array (FPGA) controller is adopted to fulfill an optimized constant V/Hz control strategy. According to the pumps and fans load, an optimized constant V/Hz control strategy is adopted. The pulse width modulation-selective harmonic elimination (PWM-SHE) pattern is carried out to keep sine wave output with minimal harmonics and minimal torque ripple.