Analysis of dead-time harmonics in single-phase transformerless full-bridge PV inverters

A short period, called dead time, is usually implemented (e.g., through adding extra hardware in gate drivers or modifying pulse-width modulation schemes) for voltage source inverters to prevent shoot-through incidents. Clearly, larger dead time provides more safety, but may also degrade the injected currents from inverters. It thus requires sophisticated compensation schemes to meet certain stringent standards. For single-phase transformerless full-bridge PV inverters, different modulation schemes can be employed to suppress leakage currents, which in return may affect the distribution of the dead time harmonics. Thus, this drives the analysis of dead time harmonics in single-phase transformerless full-bridge inverters considering two modulation strategies: bipolar and unipolar modulation schemes. Effects of modulation on the dead time harmonics are observed in simulations and experimental tests. Furthermore, a periodic controller is adopted to mitigate the harmonics, which is independent of the modulation schemes.