BIDIRECTIONAL UNISOLATED DC-DC CONVERTER BASED ON CASCADED CELLS
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Accused Products
Abstract
A DC-DC converter (200) comprising a first (201) and a second (202) variable voltage source, a capacitor (203), an alternating current filter (204), and controlling means (205), is provided. A first DC voltage (UDC1) is provided over a series-connection of the first and the second voltage source, and a second DC voltage (UDC2), being lower in magnitude than (UDC1), is provided over the second voltage source. The conversion between (UDC1) and (UDC2) is effected by circulating an alternating current within a circuit comprising the two voltage sources and the capacitor, thereby exchanging power between the two voltage sources. The alternating current is driven by AC voltage components provided by the first and the second voltage source. The controlling means is arranged for controlling the first and the second voltage source so as to maintain a phase difference between the AC components to be close to π.
19 Citations
35 Claims
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1-17. -17. (canceled)
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18. A DC-DC converter for high voltage direct current (HVDC) power transmission and distribution and for converting a first DC voltage into a second DC voltage or vice versa and comprising:
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a first phase leg having a first, a second, and a third connection terminal, the first phase leg comprising; a first and a second variable voltage source being arranged for providing a first (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each voltage source having a first pole and a second pole, the first pole of the first voltage source being connected to the first terminal of the phase leg, the second pole of the first voltage source being connected to the first pole of the second voltage source, and the second pole of the second voltage source being connected to the second terminal of the phase leg, wherein the first DC voltage (UDC1)) is provided between the first terminal and the second terminal of the phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the phase leg, a first capacitor being connected between the first terminal and the second terminal of the phase leg, and an alternating current, AC, filter being connected between the first pole of the second voltage source and third terminal of the phase leg, and controlling means being arranged for controlling the first and the second voltage source of the first phase leg so as to circulate an AC current (IAC(t)) within a circuit comprising the first capacitor, the first voltage source, and the second voltage source, of the first phase leg. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
and wherein the controlling means is further arranged for controlling the first and the second voltage source of the second phase leg so as to circulate an AC current (IAC(t)) within a circuit comprising the first capacitor, the first voltage source, and the second voltage source, of the second phase leg.
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25. The converter according to claim 24, wherein the controlling means is further arranged for controlling the first and the second voltage source of each phase leg so as to maintain a phase difference between the AC current of first phase leg and the AC current of second phase leg to be close to π
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26. A DC-DC converter for high voltage direct current (HVDC) power transmission and distribution and for converting a first DC voltage into a second DC voltage or vice versa and comprising:
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at least two phase legs connected in parallel, each phase leg having a first, a second, and a third connection terminal, wherein each phase leg comprises; a first and a second variable voltage source being arranged for providing a first (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each voltage source having a first pole and a second pole, the first pole of the first voltage source being connected to the first terminal of the phase leg, the second pole of the first voltage source being connected to the first pole of the second voltage source, and the second pole of the second voltage source being connected to the second terminal of the phase leg, wherein the first DC voltage (UDC1) is provided between the first terminal and the second terminal of the phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the phase leg, and the third terminals of the phase legs are interconnected, and controlling means being arranged for controlling the first and the second voltage source of each phase leg to maintain a constant phase difference between the AC voltage components of the phase legs, where the phase difference between two adjacent phase legs is equal to 2π
/n, where n is the number of phase legs, so as to circulate an AC current (IAC1(t), IAC2(t), IAC3(t)) within a circuit comprising the first and the second voltage source of each phase leg, wherein a constant phase difference between the respective AC currents (IAC1(t), IAC2(t), IAC3(t)) of the phase legs is maintained.- View Dependent Claims (27, 28, 29, 35)
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30. A method of a DC-DC converter for high voltage direct current (HVDC) power transmission and distribution and for converting a first DC voltage into a second DC voltage or vice versa and comprising:
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a first phase leg having a first, a second, and a third connection terminal, the first phase leg comprising; a first and a second variable voltage source being arranged for providing a first (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each voltage source having a first pole and a second pole, the first pole of the first voltage source being connected to the first terminal of the phase leg, the second pole of the first voltage source being connected to the first pole of the second voltage source, and the second pole of the second voltage source being connected to the second terminal of the phase leg, wherein the first DC voltage (UDC1) is provided between the first terminal and the second terminal of the phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the phase leg, a first capacitor being connected between the first terminal and the second terminal of the phase leg, and an alternating current, AC, filter being connected between the first pole of the second voltage source and third terminal of the phase leg, wherein the method comprises; controlling the first and the second voltage source of the first phase leg so as to circulate an AC current (IAC(t)) within a circuit comprising the first capacitor, the first voltage source, and the second voltage source, of the first phase leg. - View Dependent Claims (31)
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32. A method of a DC-DC converter for high voltage direct current (HVDC) power transmission and distribution and for converting a first DC voltage into a second DC voltage or vice versa and comprising:
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at least two phase legs connected in parallel, each phase leg having a first, a second, and a third connection terminal, wherein each phase leg comprises; a first and a second variable voltage source being arranged for providing a first (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each voltage source having a first pole and a second pole, the first pole of the first voltage source being connected to the first terminal of the phase leg, the second pole of the first voltage source being connected to the first pole of the second voltage source, and the second pole of the second voltage source being connected to the second terminal of the phase leg, wherein the first DC voltage (UDC1) is provided between the first terminal and the second terminal of the phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the phase leg, where the third terminals of the phase legs are interconnected, wherein the method comprises; controlling the first and the second voltage source of each phase leg to maintain a constant phase difference between the AC voltage components of the phase legs, where the phase difference between two adjacent phase legs is equal to 2π
/n, where n is the number of phase legs, so as to circulate an AC current (IAC1(t), IAC2(t), IAC3(t)) within a circuit comprising the first and the second voltage source of each phase leg, wherein a constant phase difference between the respective AC currents (IAC1(t), IAC2(t), IAC3(t)) of the phase legs is maintained.- View Dependent Claims (33, 34)
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Specification