Introduction and Advantage of Space Opposite Vectors Modulation Utilized in Dual Two-level Inverters with Isolated DC Sources

In this paper, space opposite vectors modulation (SOVM) is proposed to decrease common-mode voltage (CMV), and also improve inverter switching losses compared to pulsewidth modulation 7 (PWM7) for dual two-level inverters (DTLI). Employing the control simplicity of DTLI to achieve multilevel winding voltages, the two conventional two-level inverters of DTLI are independently controlled; consequently, the capability of adjusting phase difference between the carriers (PDC) of two inverters is established. To mathematically evaluate and compare the performance of DTLI driven by SOVM and PWM7, CMV and losses for different PWMs are formulated. Moreover, contour, three- and two-dimensional analyses are conducted to investigate the effects of PDC and modulation index on CMV, voltage total harmonic distortion (THD), voltage weighted THD and switching losses. All theoretical bases, simulation results from MATLAB/Simulink and experimental results conducted by a DTLI prototype validate the superiority of SOVM over PWM7.