An improved modulation algorithm for the dual-output six-switch inverter with reduced switching frequency

The six-switch inverter has gained significant attention due to its ability to achieve dual AC voltage outputs with fewer semiconductor power devices. However, with existing pulse width modulation (PWM) algorithms, the switching frequency of the two middle-position power devices is twice that of the other four power devices at the upper and lower ends. Therefore, this paper proposes an improved PWM algorithm for the six-switch converter based on the unipolar modulation principle. The proposed algorithm can significantly reduce the switching frequency of the two middle-position power devices. Research results indicate that, under optimal conditions, the switching frequency of the two middle-position power devices is as low as the frequency of the AC output voltages, and in the worst-case scenario, it is only half the carrier frequency. Consequently, the efficiency of the inverter is effectively improved. Additionally, analysis results suggest that, given the same switching frequencies of power devices, the modulation algorithm proposed in this paper for controlling the converter also results in lower Total Harmonic Distortion (THD) for the output voltages compared to traditional modulation algorithms.