Bidirectional unisolated DC-DC converter based on cascaded cells
First Claim
1. 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:
- a first phase leg having a first, a second, and a third connection terminal, the first phase leg comprising;
a first variable voltage source and a second variable voltage source being arranged for providing a first voltage (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each variable voltage source having a first pole and a second pole, the first pole of the first variable voltage source being connected to the first terminal of the first phase leg, the second pole of the first variable voltage source being connected to the first pole of the second variable voltage source, and the second pole of the second variable voltage source being connected to the second terminal of the first phase leg, wherein the first DC voltage (UDC1) is provided between the first terminal and the second terminal of the first phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the first phase leg,a first capacitor being connected between the first terminal and the second terminal of the first phase leg, and being arranged between an input end of the first phase leg of the DC-DC converter and an output end of the first phase leg of the DC-DC converter, wherein the input end of the first phase leg is provided with the first DC voltage (UDC1) and the output end of the first phase leg of the DC-DC converter is provided with the second DC voltage (UDC2), andan alternating current, AC, filter being connected between the first pole of the second variable voltage source and third terminal of the first phase leg,anda control unit configured to control the first variable voltage source and the second variable voltage source of the first phase leg so as to circulate an AC current (IAC(t)) within a loop of the first capacitor, the first variable voltage source, and the second variable voltage source, of the first phase leg.
5 Assignments
0 Petitions
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.
11 Citations
18 Claims
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1. 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 variable voltage source and a second variable voltage source being arranged for providing a first voltage (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each variable voltage source having a first pole and a second pole, the first pole of the first variable voltage source being connected to the first terminal of the first phase leg, the second pole of the first variable voltage source being connected to the first pole of the second variable voltage source, and the second pole of the second variable voltage source being connected to the second terminal of the first phase leg, wherein the first DC voltage (UDC1) is provided between the first terminal and the second terminal of the first phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the first phase leg, a first capacitor being connected between the first terminal and the second terminal of the first phase leg, and being arranged between an input end of the first phase leg of the DC-DC converter and an output end of the first phase leg of the DC-DC converter, wherein the input end of the first phase leg is provided with the first DC voltage (UDC1) and the output end of the first phase leg of the DC-DC converter is provided with the second DC voltage (UDC2), and an alternating current, AC, filter being connected between the first pole of the second variable voltage source and third terminal of the first phase leg, and a control unit configured to control the first variable voltage source and the second variable voltage source of the first phase leg so as to circulate an AC current (IAC(t)) within a loop of the first capacitor, the first variable voltage source, and the second variable voltage source, of the first phase leg. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. 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 variable voltage source and a second variable voltage source being arranged for providing a first voltage (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each variable voltage source having a first pole and a second pole, the first pole of the first variable voltage source being connected to the first terminal of the phase leg, the second pole of the first variable voltage source being connected to the first pole of the second variable voltage source, and the second pole of the second variable 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 a control unit configured to control the first variable voltage source and the second variable 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 variable voltage source and the second variable 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 (10, 11, 12, 13)
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14. 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 variable voltage source and a second variable voltage source being arranged for providing a first voltage (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each variable voltage source having a first pole and a second pole, the first pole of the first variable voltage source being connected to the first terminal of the first phase leg, the second pole of the first variable voltage source being connected to the first pole of the second variable voltage source, and the second pole of the second variable voltage source being connected to the second terminal of the first phase leg, wherein the first DC voltage (UDC1) is provided between the first terminal and the second terminal of the first phase leg, and the second DC voltage (UDC2) is provided between the third terminal and the second terminal of the first phase leg, a first capacitor being connected between the first terminal and the second terminal of the first phase leg, and being arranged between an input end of the first phase leg of the DC-DC converter and an output end of the first phase leg of the DC-DC converter, wherein the input end of the first phase leg is provided with the first DC voltage (UDC1) and the output end of the first phase leg of the DC-DC converter is provided with the second DC voltage (UDC2), and an alternating current, AC, filter being connected between the first pole of the second variable voltage source and third terminal of the first phase leg, wherein the method comprises; controlling the first variable voltage source and the second variable voltage source of the first phase leg so as to circulate an AC current (IAC(t)) within a loop of the first capacitor, the first variable voltage source, and the second variable voltage source, of the first phase leg. - View Dependent Claims (15)
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16. 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 variable voltage source and a second variable voltage source being arranged for providing a first voltage (U1(t)) and a second voltage (U2(t)), respectively, each voltage having an AC voltage component and a DC voltage component, each variable voltage source having a first pole and a second pole, the first pole of the first variable voltage source being connected to the first terminal of the phase leg, the second pole of the first variable voltage source being connected to the first pole of the second variable voltage source, and the second pole of the second variable 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, and wherein the method comprises; controlling the first variable voltage source and the second variable 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 variable voltage source and the second variable 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 (17, 18)
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Specification