适用于三电平逆变器低调制比区域的双极性载波脉宽调制策略研究

When the three-level inverter operates in the low modulation index region, the distortion of output voltage caused by narrow pulse is particularly significant, and even makes the inverter operation uncontrollable. However, the traditional space vector PWM (SVPWM) strategy has narrow pulse in the low modulation index region. To solve the above problems, this paper first analyzes the causes of narrow pulse in traditional SVPWM, and then designs the bipolar SVPWM which can eliminate narrow pulse in the low modulation index region. On this basis, in order to implement bipolar SVPWM more conveniently, the equivalent double modulation wave of bipolar SVPWM is deduced. By formulating the comparison rules between double modulation wave and triangular carrier, the bipolar carrier-based PWM (BCBPWM) strategy is further proposed. In addition, the neutral-point voltage balance control and dead time compensation method are designed for BCBPWM. Finally, the pulse width characteristics, neutral-point voltage fluctuation, harmonic performance, and DC voltage utilization of BCBPWM are analyzed. Simulation and experimental results prove that compared with traditional SVPWM, BCBPWM can eliminate narrow pulse completely and improve current harmonic performance in the low modulation index region. It can control the neutral-point voltage balance, and has the advantages of simple calculation and convenient implementation.