A compensation method to reduce sampling delay of zero dead-time PWM using 3-level NPC PWM inverter

This paper proposed a compensation method for reducing sampling delay through ADC(Analog-to-Digital Converter) module of MCU(Micro Controller Unit) using ZDPWM method. In case of conventional PWM method of 3-level NPC inverter, the switching devices which is composed of silicon compounds are conducted complementary operation by both reference and carrier waveform. And this operating method needs to contain dead time state to prevent short-circuit fault. However, the phase voltage distortion is caused by the dead time state in conventional method. As a results, THD of phase current is increased when inverter system is operating. ZDPWM method which is non-complementary operation is suggested to compensate the distortion through dead time in 3-level NPC inverter. The ZDPWM method has some advantages such as simple operation through carrier waveform as same as conventional method and low harmonic factor at phase current based on non-complementary operation. However, the unexpected distortion of phase current can occur by phase angle delay through sampling of ADC module when the ZDPWM is used in experiment by MCU. Therefore, this paper proposed simple method to compensate sampling delay based on the modeling of delayed phase angle. The proposed method is demonstrated by experiment, and the method compares with same conditions as both conventional PWM method and the ZDPWM due to uncompensated sampling delay.