Abstract: In one aspect of the teachings herein, a self-commutated current source converter is operated in a manner that compensates for the reactive power consumption and/or harmonics generation of a line-commutated current source converter used in the transfer of electrical power between an AC power system and a DC power system. In this regard, the line-commutated current source converter is operated as a first converter in a hybrid converter apparatus and the self-commutated current source converter is operated as a second converter in the hybrid arrangement. According to one example, the first and second converters are stacked, such that each shares a portion of the DC voltage on the DC side of the hybrid converter apparatus, while in another example, the second converter is not used for power conversion and instead is used solely for compensation with respect to the first converter.

Abstract: In one aspect of the teachings herein, a self-commutated current source converter is operated in a manner that compensates for the reactive power consumption and/or harmonics generation of a line-commutated current source converter used in the transfer of electrical power between an AC power system and a DC power system. In this regard, the line-commutated current source converter is operated as a first converter in a hybrid converter apparatus and the self-commutated current source converter is operated as a second converter in the hybrid arrangement. According to one example, the first and second converters are stacked, such that each shares a portion of the DC voltage on the DC side of the hybrid converter apparatus, while in another example, the second converter is not used for power conversion and instead is used solely for compensation with respect to the first converter.

Abstract: A method, voltage source converter and computer program product for limiting the current in a DC power transmission system are disclosed. The voltage source converter has an AC side and a DC side and a fault current path between these sides. It furthermore includes a control unit and at least one switching unit of a first type provided in the fault current path and that includes a primary switching element together with an anti-parallel secondary controllable rectifying element. Based on a fault being detected in the DC power system when the primary switching elements of the converter are blocked, the control unit changes the control of the controllable rectifying element from acting as a non-controllable rectifying to acting as a controllable rectifying element.

Abstract: A Voltage Source Converter having at least one phase leg connected to opposite poles of a direct voltage side of the converter and including a series connection of switching cells has an arrangement configured to apply a pressure to opposite ends of stacks of semiconductor assemblies for pressing the assemblies towards each other so as to obtain electric contact between semiconductor assemblies in the stack while ensuring that the semiconductor assemblies of a first path of each switching cell of the converter go into a permanently closed circuit state in case of a failure of the respective switching cell. A second path of each switching cell has a member configured to keep the second path including an energy storing capacitor non-conducting upon occurrence of the failure.

Abstract: A method, voltage source converter and computer program product for limiting the current in a DC power transmission system are disclosed. The voltage source converter has an AC side and a DC side and a fault current path between these sides. It furthermore includes a control unit and at least one switching unit of a first type provided in the fault current path and that includes a primary switching element together with an anti-parallel secondary controllable rectifying element. Based on a fault being detected in the DC power system when the primary switching elements of the converter are blocked, the control unit changes the control of the controllable rectifying element from acting as a non-controllable rectifying to acting as a controllable rectifying element.

Abstract: A Voltage Source Converter having at least one phase leg connected to opposite poles of a direct voltage side of the converter and comprising a series connection of switching cells has an arrangement configured to apply a pressure to opposite ends of stacks of semiconductor assemblies for pressing the assemblies towards each other so as to obtain electric contact between semiconductor assemblies in said stack while ensuring that the semiconductor assemblies of a first path of each switching cell of the converter go into a permanently closed circuit state in case of a failure of the respective switching cell. A second path of each switching cell has means configured to keep said second path including an energy storing capacitor non-conducting upon occurrence of a said failure.