Leakage-ground currents compensation in a transformerless HB-NPC topology using a DC-link-tied LC filter for photovoltaic applications

Iturriaga-Medina, Samuel, Martinez-Rodriguez, Panfilo Raymundo, Escobar-Valderrama, Gerardo, Vazquez-Guzman, Gerardo, Langarica-Cordoba, Diego, Rosas-Caro, Julio Cesar, Sosa-Zuniga, Jose Miguel and Mayo-Maldonado, Jonathan C. (2021) Leakage-ground currents compensation in a transformerless HB-NPC topology using a DC-link-tied LC filter for photovoltaic applications. IEEE Journal of Emerging and Selected Topics in Power Electronics, 10 (4), 4725-4737. (doi:10.1109/JESTPE.2021.3132239).

Abstract

In this article, a solution to mitigate the leakage-ground currents (LGCs) in a grid-tied H-bridge neutral-point-clamped inverter is presented. This solution consists in splitting the LC filter capacitor and connecting each capacitor to a dc-link terminal. The proposal is referred to as the dc-link-tied LC output filter. Out of this hardware modification, it is not necessary to increase the number of switches nor design a new modulation scheme. Furthermore, a formal analysis is provided based on the common-mode (CM) model describing the role of this particular connection of the output LC filter on the minimization of the LGC. In addition, a closed-loop control strategy has been implemented to allow testing the prototype connected to the electrical grid. The mitigation of the LGCs has been evaluated under this condition as well. To validate the proposed circuit modification, numerical simulations and experimental tests have been performed in a 1-kW laboratory prototype of the H-bridge neutral-point-clamped inverter with the dc-link-tied LC filter solution.

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Contributors

Author: Jonathan C. Mayo-Maldonado

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