An interharmonic dual switching frequency modulation strategy for impedance network inverters

Recently, a novel dual switching frequency modulation (DFM) has been proposed for impedance network inverters (INIs). The proposed approach allows the INIs to be designed optimally in size and efficiency, for motor drive applications. Moreover, DFM provides the possibility of operation with unity modulation index. However, DFM requires a high-frequency ratio between pulse-width modulation (PWM) and sinusoidal PWM (SPWM) switching frequencies. This paper proposes an improved modulation strategy to overcome this issue. The modulation called interharmonic dual frequency modulation (IDFM) utilizes the interharmonic areas of a conventional sinusoidal PWM to implement DFM. The proposed approach gives a low total harmonic distortion (THD) output voltage without increasing the frequency ratio of PWM and SPWM. IDFM provides the possibility of selecting a wide range of frequencies for both switching modulations. The approach is explained theoretically, compared with other switching strategies, and also the simulation and experimental results are used to validate its performance.