| Abstract |
Single-phase transformerless photovoltaic (PV) inverters with voltage step-up capability are widely employed for integrating PV generation to the electric grid. Transformerless PV inverter topologies include special features to suppress common-mode (CM) leakage currents that can flow through parasitic capacitances that appear between the PV array and the ground. The Aalborg inverter belongs to the family of dual-mode time-sharing PV inverters, in which a voltage step-up (Boost) stage operates alternatively to a step-down (Buck) stage to create a rectified sine wave DC-link voltage, which is then unfolded to the grid. This paper analyses, quantifies and improves CM leakage current generation for Aalborg-type transformerless PV inverters. It highlights the factors that can lead to high peak and RMS values of leakage current for these topologies and proposes an output filter modification to reduce them by up to 70\%. The analytical results are supported by simulation in MATLAB-Simulink and are applicable to other topologies with rectified sine wave DC-link voltages. |
