Three-level space vector PWM in low index modulation region avoiding narrow pulse problem

In using GTO, a few hundreds micro seconds longer than specified pulse width must be guaranteed for safety for each device to commutate with its inherent gate current sequences. This paper describes the mechanism of generating undesirable narrow pulses in conventional three-level space vector PWM inverters and suggests two new algorithms of space vector PWM using nonnearest three and four vectors in a control period to avoid such a narrow pulse problem. Experimental verifications for the suggested algorithms are also presented