High efficient common-mode current suppression SVM method for three-phase three-level transformer-less photovoltaic inverters

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Three-phase three-level transformer-less inverters are widely used in photovoltaic (PV) generation systems because of their low cost and high efficiency. However, common-mode (CM) currents in these inverters are so large that they threaten security and aggravate EMI problems. Some space vector pulse width modulation (SVM) methods have been developed to reduce CM current through reducing CM voltage, but they would also sacrifice the modulation index or efficiency. This paper proposes a new SVM method that suppresses the CM current without reducing the efficiency or the modulation index. Moreover, simultaneous switching during dead time is analyzed thoroughly and a compensation method is proposed to eliminate the influence of dead time. Experiments verify that compared with other methods, proposed method shows the best CM current suppression performance as well as the best efficiency characteristic.