Leakage Current Suppressing Strategy for Multiple Transformerless Grid-Connected Inverters

There is a parasitic capacitance between the photovoltaic (PV) panel and the earth, which forms a common-mode loop with the single-phase transformerless PV grid-connected inverters. With the increasing PV permeability of distribution network, collected leakage current (i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</inf>_<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tot</inf>) will be generated in the distribution station area. Excessive i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</inf>_<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tot</inf> will not only lead to the increase of harmonics and losses, but also trigger leakage protection to cause power failure accidents. Firstly, the double Fourier expression of the i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</inf>_<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tot</inf> is derived, and on this basis, a uniform carrier phase shift strategy is proposed to suppress the i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</inf>_<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tot</inf>, and a dynamic tracking method of the minimum i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</inf>_<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tot</inf> based on disturbance-observation is proposed, and a simulation model is established to verify the effectiveness of the scheme, and the actual suppression effect can reduce the i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</inf>_<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tot</inf> by 90%.