Transformerless power converter for grid-connected PV system with no-ripple input current and low ground-leakage current

The application of boost converters is highly favored in PV module integrated converter (MIC) systems. The conventional boost converter operating in continuous inductor-current mode (CICM), however, has a pulsating, high-ripple input current, which causes power loss and decreases the energy flowing from non-linear sources like the PV panel. Therefore, this paper proposes a new modified boost converter that has a no-ripple input current. The proposed converter uses a series of input inductance to produce zero-ripple input current during continuous inductor-current mode, without any LC or C filter elements. It is capable of high power-conversion efficiency for the whole system without the use of any transformer or galvanic isolation components. In addition, this proposed boost converter is integrated with an H-Bridge inverter for a transformerless PV grid-connected system. The issue of electrical safety of the high ground-leakage current (due to the parasitic capacitance of the PV panel and frame and lack of galvanic isolation) is resolved by bipolar SPWM technique in the H-Bridge inverter, without any additional hardware. The proposed DC-AC transformerless inverter grid-connected PV system, which has a new modified boost converter and bipolar H-Bridge inverter, is verified by a 1-kW hardware prototype simulated and validated by experiment. The results show zero-ripple input current, high power-conversion efficiency, near-unity power factor, low current-THD, and low ground-leakage current.