New hybrid pulse-width modulation technique to reduce current distortion and extend current reconstruction range for three-phase inverter using only DC-link sensor

The paper proposes a new modulation technique which can reduce the current distortion and extend the current reconstruction range for three-phase inverter using only DC-link sensor. The proposed PWM technique is a hybrid method which consists of space vector modulation method and the PWM method without using null switching states. The former provides low current distortion, however it is with narrower current reconstruction range. In contrast, the later extends the current reconstruction range at the cost of higher current distortion. For the proposed method, in the measurable region of space vector modulation method, space vector modulation is used to reduce the current distortion. Moreover, as the modulation range is out of that measurable region, the PWM method without using null switching states is applied to extend the current re-construction range. Furthermore, the current reconstruction limitation using only DC-link sensor is analyzed. The analysis shows that reduction of PWM switching frequency and acquisition time can extend the current re-construction range. Comparison of experimental results derived from an FPGA-based controlled inverter is included. It will be demonstrated that using the proposed hybrid PWM technique the three-phase current signals of inverter can be reconstructed even under very low modulation index range while providing low current harmonic distortion of inverter output. (6 pages)