Power transfer system between an AC network and a reversible hydraulic turbine

A power transfer system, comprising:

• a first branch and a second branch connected in parallel between a first connection interface configured to be connected to an AC network and a second interface configured to be connected to a reversible pump-turbine, the first branch comprising a controlled switch, the second branch comprising a variable frequency converter, the variable frequency converter comprising:
• a first AC/DC converter having a first AC interface connected to the first connection interface and a first DC interface, and
• a second AC/DC converter having a second AC interface connected to the second connection interface and a second DC interface, the first and second DC interfaces being connected by a DC link,
• a control circuit having a first mode wherein the control circuit simultaneously opens the switch of the first branch and transfers electrical power from the first AC interface to the second AC interface with an increasing frequency on the second AC interface until a frequency on the first interface is reached, and having a second mode wherein it closes the switch of the first branch;
• the system further comprises an energy storage system connected to the DC link;
• and
• a switching system controlled by the control circuit for selectively connecting the energy storage system to the DC link,
• wherein the energy storage system includes a DC electrical transducer and a DC/DC converter,
• wherein the DC electrical transducer comprises an energy storage device selected in a group consisting of a supercapacitor, a fuel cell, an electrochemical battery, an electrical motor driving a flywheel, an air compressor, and an electromagnetic storage,
• wherein the energy storage device is configured to convert electrical energy to another form of energy,
• wherein the first and second AC/DC converters are current source inverters, and wherein the DC/DC converter is a two-quadrant DC/DC converter, wherein the DC link comprises a first conductor connected between respective first ports of the first and second AC/DC converters and a second conductor connected between respective second ports of the first and second AC/DC converters, the DC/DC converter being series connected on the second conductor.