Modified voltage source converter structure

摘要

The invention concerns a voltage source converter (26) comprising a group of phase legs, at least three connection terminals (AC1, AC2, AC3, DC+, DC−) for connecting the phase legs to power transmission elements, a first group of cells (C1p1, C2p1, C1n1, C2n1, C1p2, C2p2, C1n2, C2n2, C1p3, C2p3, C1n3, C2n3) in each phase leg and a second group of cells (C3p1, C3n1, C3p2, C3n2 C3p3, C3n3). The cells (C1p1, C2p1, C1n1, C2n1, C1p2, C2p2, C1n2, C2n2, C1p3, C2p3, C1n3, C2n3) in the first group are only capable of providing unipolar voltage contributions to the converter and connected for only being capable of such unipolar voltage contributions, while the cells (C3p1, C3n1, C3p2, C3n2 C3p3, C3n3) in the second group are connected to the corresponding cells of the first group and arranged to have bipolar voltage contribution capability.

主权项

1. A voltage source converter for connection between power transmission elements related to a power transmission system, and comprising:
three interconnected phase legs connected in parallel between two direct current terminals of the voltage source converter, where each phase leg has a first and a second end point via which said interconnection is achieved; at least-three connection terminals for connecting the phase legs to said power transmission elements; a first group of cells and a second group of cells, wherein each cell includes a group of switching elements and one energy storage element, and the group of switching elements is connected in parallel with the one energy storage element, the cells in the first group of cells are only capable of providing unipolar voltage contributions to an operation of the voltage source converter and also connected in the phase legs for only being capable of such unipolar voltage contributions, the cells in the second group of cells are connected to the corresponding cells of the first group of cells and configured for being capable of providing bipolar voltage contributions to the operation of the voltage source converter, the cells in the first group of cells are dedicated to an AC-DC or DC-AC conversion function of the voltage source converter, the cells in the second group of cells are dedicated to providing additional AC voltages; a control unit configured to provide control signals to the cells in the first group of cells to control the operation of the voltage source converter according to the AC-DC or DC-AC conversion function and to provide control signals to the cells in the second group of cells for making the cells in the second group of cells provide the additional AC voltages; and wherein each phase leg further comprises:
a positive arm and a negative arm;cells of the first group of cells and cells of the second group of cells in each of the positive and negative arms, wherein the number of cells according to type and their orientation is the same in each of the positive and negative arms; andone inductor included within the positive arm and another inductor included within the negative arm.