A Simple Generalized PWM Algorithm for Three Phase Voltage Source Inverter Fed AC Drives

Abstract

This paper presents a simple Generalized Pulse Width Modulation (GPWM) algorithm for Three Phase Voltage Source Inverter fed AC Drives. The conventional space vector approach requires angle and sector estimation for the calculation of gating times of the inverter and hence increases the complexity of the PWM algorithm. However, the proposed algorithm uses the concept of imaginary switching times to calculate the gating times. These imaginary switching times can be evaluated by using the instantaneous phase voltages only. To generate various PWM algorithms, generalized expression for the offset time is derived. In the derived offset expression, by varying a constant (k0) value from zero to one, various Discontinuous PWM (DPWM) algorithms can be generated along with the Space Vector PWM (SVPWM) algorithm. Thus, the proposed GPWM algorithm gives all the possible modulators for 3-phase, two-level inverters. To validate the proposed PWM algorithms, numerical simulation and experimental studies have been carried out and the results have been presented.