| CPC H02J 3/38 (2013.01) [H02J 3/001 (2020.01); H02J 7/0013 (2013.01); H02J 7/0047 (2013.01); H02J 7/35 (2013.01); G01R 31/52 (2020.01); H02J 2207/20 (2020.01); H02J 2300/24 (2020.01)] | 21 Claims |

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1. An energy storage system including a photovoltaic system and a battery system and connected with a power grid, the energy storage system comprising:
a power conversion system configured to be connected with the power grid and selectively connected to at least one of the photovoltaic system and the battery system;
a first switch selectively connecting the photovoltaic system and a direct current (DC) link of the power conversion system;
a second switch selectively connecting the battery system and the DC link of the power conversion system;
a controller configured to control a ground structure of at least one of the photovoltaic system, the battery system, and the power conversion system by controlling the first switch and the second switch based on a state of the photovoltaic system and a state of the battery system; and
a first ground fault detector configured to detect a ground fault of the photovoltaic system,
wherein the first ground fault detector is selectively connected to negative terminals of the photovoltaic system through a third switch being in a closed state.
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