Hybrid Discontinuous Space Vector PWM Strategy for Three-Level Inverters under Two-phase Loads Condition

The output performance of three-level inverters will be deteriorated under two-phase loads condition if conventional discontinuous PWM (DPWM) strategies are adopted. To solve the above issue, the amplitude and the phase angle of basic voltage vectors are modified in this article. Accordingly, sectors and triangles of the space vector diagram are reconsidered, duty cycles of basic vectors synthesized the reference vector are recalculated. And then four types of DPWM applicable for two-phase load are put forward. Although the harmonic distortion of the output waveform is reduced, discontinuous intervals are not optimum distributed. To further improve the output waveform quality, the amplitude of average current ripple vector is introduced as the evaluation index to redistribute discontinuous intervals of phase voltage in each fundamental period. Then, a hybrid DPWM strategy is presented and the harmonic distortion of the output waveform is minimized. Meanwhile, the neutral-point voltage ripple and the switching loss are also suppressed. The effectiveness of the hybrid DPWM strategy is verified by both simulation and experimental results.