Transformerless Grid-connected PV Converter With Leakage Current Suppression Ability: A novel solution based on active zero-sequence current injections

Transformerless photovoltaic (PV) grid-connected systems lack isolation stages, which lead to leakage currents flowing into the AC grid and cause problems such as grid-connected current distortion. A transformerless grid-connected converter topology based on active zero-sequence loop and a new leakage current control method based on active zero-sequence current injection with leakage current suppression, common-mode voltage stabilization, etc., are proposed. In terms of structure, the common-mode loop for leakage current flow is constructed by shorting the neutral point of the filter capacitor to the negative terminal of the DC bus to avoid leakage current flowing into the AC grid; in terms of control, the active damping control is based on active zero sequences current injection, which provides a new idea to solve the leakage current problem of A transformerless PV grid-connected systems. Experiments are conducted using the StarSim Modeling Tech power electronics simulation experimental platform to verify the effectiveness of the proposed topology and the proposed control method on leakage current suppression and common-mode voltage stabilization.