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A Zero-Voltage-Transition HERIC-Type Transformerless Photovoltaic Grid-Connected Inverter

A zero-voltage-transition highly efficient and reliable inverter concept (ZVT-HERIC) in transformerless photovoltaic grid-connected applications is derived from proposed basic resonant cells. By integrating resonant tanks and freewheeling switches, a compact resonant network is originated to make the switching transitions of high-frequency main switches softening. By utilizing the diode clamping scheme, the potential of the freewheeling loop of the ZVT-HERIC is suppressed on half of the input voltage and to restrict the leakage current. The derived inverter has the advantages of ZVT soft-switching, diode reverse-recovery alleviating, unipolar differential-mode voltage with low dv/dt, and constant common-mode voltage. The steady-state operation of the derived inverter is analyzed, and the circuit performance is discussed to explore the soft-switching region, voltage gain, as well as voltage and current stresses. Finally, the experimental results from a 3-kW prototype at 100-kHz switching frequency are provided to verify the effectiveness of the derived inverter.