Energy storage device and power system and control method thereof

A power system, comprising:

• a power generator electrically connected with a high voltage DC transmission grid;
• and
• an energy storage device electrically connected with the high voltage DC transmission grid, and comprising:
• at least one energy storage element;
• at least one bidirectional inverter module, wherein a DC terminal of each bidirectional inverter module is electrically connected with the corresponding energy storage element;
• at least one medium frequency transformer, wherein a first transmission terminal of each medium frequency transformer is electrically connected with an AC terminal of the corresponding bidirectional inverter module;
• and
• at least one bidirectional AC/DC conversion module, wherein an AC terminal of each bidirectional AC/DC conversion module is electrically connected with a second transmission terminal of the corresponding medium frequency transformer, and a DC terminal of each bidirectional AC/DC conversion module is electrically connected with the high voltage DC transmission grid.

A control method for a power system, the power system comprising a power generator and an energy storage device, the power generator and the energy storage device being electrically connected with a high voltage DC transmission grid, the energy storage device comprising at least one energy storage element, at least one bidirectional inverter module, at least one medium frequency transformer and at least one bidirectional AC/DC conversion module, a DC terminal of each bidirectional inverter module being electrically connected with the corresponding energy storage element, a first transmission terminal of each medium frequency transformer being electrically connected with an AC terminal of the corresponding bidirectional inverter module, an AC terminal of each bidirectional AC/DC conversion module being electrically connected with a second transmission terminal of the corresponding medium frequency transformer, a DC terminal of each bidirectional AC/DC conversion module being electrically connected with the high voltage DC transmission grid, the control method comprising steps of:

• (S1) determining an operation mode of the energy storage device;
• (S2) when the power generator generates electric energy, determining that the energy storage device is operated in a grid-connected mode, and allowing the energy storage device to regulate electric energy in the high voltage DC transmission grid;
• and
• (S3) when the power generator does not generate electric energy, determining that the energy storage device is operated in an off-grid mode, and allowing the energy storage device to provide auxiliary electric energy to the power generator.