Novel discontinuous PWM control method to improve IGBT reliability at low speed

Discontinuous PWM method (DPWM) has been widely used in industrial area to reduce the overall losses; however, it is only effective at higher output frequency condition for an adjustable speed drive (ASD). At low speed condition, the time constant of the IGBT thermal system is much lower than that of the fundamental frequency of the inverter. The harmonics contents as well as the IGBT junction temperature may be higher under DPWM than that of the space vector PWM (SVPWM). Consequently, the benefit of DPWM to reducing the IGBT junction temperature does not apply at low speed as more. This paper proposes a new DPWM (NPWM) method address the junction temperature issue. It is shown that the proposed method can demonstrate the benefit of reduce IGBT temperature at low speed. Analytical, simulation and experimental results will be presented to show its effectiveness.