VOLTAGE SOURCE CONVERTER AND CONTROL THEREOF
First Claim
1. A voltage source converter comprising:
- a plurality of phase limbs connected between high and low DC terminals;
wherein each phase limb comprises;
a high side director switch connecting the high DC terminal to an AC node for that phase limb;
a low side director switch connecting the AC node to the low DC terminal; and
a chain-link circuit, a first end of the chain-link circuit being connected between the high side and low side director switches to be electrically coupled to the AC node;
first and second additional chain-link circuits, wherein first ends of the first and second additional chain-link circuits are connected to the high side DC terminal and low side DC terminals respectively; and
a converter controller configured to control the director switches of each phase limb in a power cycle and to control the chain-link circuits of each phase limb in a voltage mode to provide a controlled voltage transition at the AC node during the power cycle, wherein said converter controller is operable to control at least some of said chain-link circuits in a current mode to provide a defined current at times during the power cycle;
wherein each chain-link circuit comprises a plurality of series-connected chain-link modules, each of the chain-link modules comprising at least one energy storage element that can be selectively connected in series with the other modules or bypassed; and
wherein a second end of each of the chain-link circuits is connected to a common node such that, in use, a current can flow from one phase limb to another via the respective chain-link circuits.
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Accused Products
Abstract
Embodiments relate to a voltage source converter of the controlled transition bridge type, having three phase limbs, each phase limb having a high side director switch (Sw1, SW3, SW5) and a low side director switch (Sw4, SW6, SW2) connecting a respective DC terminal (DC+, DC−) to an AC node for that phase limb. Chain-link circuits for each phase limb comprise a plurality of series connect cells, each cell having an energy storage element that can be selectively connected in series or bypassed. The chain-link circuits are operated in a voltage mode to provide a defined voltage transition at the AC node during a transition between one director switch being turned off and the other directors switch being turned on. In some embodiments, chain-link circuits are connected to a common node such that, in use, a current can flow from one phase limb to another via the respective chain-link circuits.
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Citations
22 Claims
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1. A voltage source converter comprising:
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a plurality of phase limbs connected between high and low DC terminals;
wherein each phase limb comprises;a high side director switch connecting the high DC terminal to an AC node for that phase limb; a low side director switch connecting the AC node to the low DC terminal; and a chain-link circuit, a first end of the chain-link circuit being connected between the high side and low side director switches to be electrically coupled to the AC node; first and second additional chain-link circuits, wherein first ends of the first and second additional chain-link circuits are connected to the high side DC terminal and low side DC terminals respectively; and a converter controller configured to control the director switches of each phase limb in a power cycle and to control the chain-link circuits of each phase limb in a voltage mode to provide a controlled voltage transition at the AC node during the power cycle, wherein said converter controller is operable to control at least some of said chain-link circuits in a current mode to provide a defined current at times during the power cycle; wherein each chain-link circuit comprises a plurality of series-connected chain-link modules, each of the chain-link modules comprising at least one energy storage element that can be selectively connected in series with the other modules or bypassed; and wherein a second end of each of the chain-link circuits is connected to a common node such that, in use, a current can flow from one phase limb to another via the respective chain-link circuits. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of operating a voltage source converter having:
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a plurality of phase limbs connected between high and low DC terminals; wherein each phase limb comprises; a high side director switch connecting the high side DC terminal to an AC node for that phase limb; and a low side director switch connecting the AC node to the low DC terminal; and a chain-link circuit comprising a plurality of series-connected chain-link modules, a first end of the chain-link circuit being connected between the high and low director switches to be electrically coupled to the AC node; first and second additional chain-link circuits, where first ends of the first and second additional chain-link circuits are connected to the high side DC terminal and low side DC terminals respectively; wherein each of the chain-link circuits comprise at least one energy storage element that can be selectively connected in series with the other modules or bypassed, and a second end of each of the chain-link circuits is connected to a common node such that, in use, a current can flow from one phase limb to another via the respective chain-link circuits; wherein the method comprises; controlling the director switches in a power cycle and controlling the chain-link circuits of each phase limb in a voltage mode to provide a controlled voltage transition at the AC node during the power cycle; and operating at least one chain-link circuit in a current mode to provide a defined chain-link current at times during the power cycle.
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Specification