Abstract: An arrangement, method and computer program product are provided for limiting circulating currents in a converter converting between AC and DC. The converter has a number of AC and DC terminals and includes a number of converter arms, where a first and a second converter arm are connected in parallel between a first DC terminal and a first AC terminal. Each converter arm includes a string of series-connected converter cells. The arrangement includes a control unit that obtains a current of the first converter arm and a current of the second converter arm, forms an average of the two converter arm currents, forms a first and a second voltage control signal based on the average and uses the first and second voltage control signal in the control of the voltage provided by the first and second converter arm.

Abstract: An arrangement, method and computer program product are provided for limiting circulating currents in a converter converting between AC and DC. The converter has a number of AC and DC terminals and includes a number of converter arms, where a first and a second converter arm are connected in parallel between a first DC terminal and a first AC terminal. Each converter arm includes a string of series-connected converter cells. The arrangement includes a control unit that obtains a current of the first converter arm and a current of the second converter arm, forms an average of the two converter arm currents, forms a first and a second voltage control signal based on the average and uses the first and second voltage control signal in the control of the voltage provided by the first and second converter arm.

Abstract: It is presented a converter arm for power conversion. The converter arm comprises: a plurality of converter cells, wherein each converter cell comprises a plurality of semiconductor switches, an energy storage element and at least three control signal connections arranged to control the conducting state of the plurality of semiconductor switches. Each converter cell is connected to receive a control signal from at least three entities via said control signal connections, wherein at least two of the three entities are neighboring converter cells, and each converter cell is arranged to forward a control signal to all connected neighboring converter cells via said control signal connections. A corresponding converter device is also presented.

Abstract: It is provided a mechanical bypass switch device arranged to bypass a converter cell in a power converter. The mechanical bypass switch device includes: a mechanical switch; a mechanical switch actuator arranged to make the mechanical switch conduct when supplied with an electric signal; a first control input; and a second control input. The mechanical bypass switch device is arranged such that a control signal, provided on either one of the first control input and the second control input or on both of the first control input and the second control input, causes the mechanical switch to conduct. A corresponding converter arm and bypass converter are also presented.

Abstract: A high voltage DC circuit breaker includes a semiconductor switching assembly in series with a mechanical switch. When the semiconductor switching assembly is switched off due to a current fault, a residual current flowing through arresters of the semiconductor switching assembly is switched off by the mechanical switch. A capacitor arranged parallel to the mechanical switch leads to passive resonance effects, which in turn induce current zero crossings in its arc. The current zero crossings allow for reliable extinguishing of the arc. The mechanical switch can be an AC circuit breaker.

Abstract: It is provided a mechanical bypass switch device arranged to bypass a converter cell in a power converter. The mechanical bypass switch device includes: a mechanical switch; a mechanical switch actuator arranged to make the mechanical switch conduct when supplied with an electric signal; a first control input; and a second control input. The mechanical bypass switch device is arranged such that a control signal, provided on either one of the first control input and the second control input or on both of the first control input and the second control input, causes the mechanical switch to conduct. A corresponding converter arm and bypass converter are also presented.

Abstract: It is presented a converter arm for power conversion. The converter arm comprises: a plurality of converter cells, wherein each converter cell comprises a plurality of semiconductor switches, an energy storage element and at least three control signal connections arranged to control the conducting state of the plurality of semiconductor switches. Each converter cell is connected to receive a control signal from at least three entities via said control signal connections, wherein at least two of the three entities are neighbouring converter cells, and each converter cell is arranged to forward a control signal to all connected neighbouring converter cells via said control signal connections. A corresponding converter device is also presented.

Abstract: A switching module, intended to be used in a medium or high voltage DC breaker or a DC current limiter, includes at least one power semiconductor switching element, a gate unit arranged to turn the at least one power semiconductor switching element on and off, respectively, according to a switching control signal, and an energy storage capacitor arranged to provide power to a power supply input of the gate unit. The switching module further includes a power transformation device arranged to receive an optical power signal, to transform the optical power signal into an electrical power signal and to provide the electrical power signal to the energy storage capacitor.

Abstract: A gate control device for a semiconductor device includes at least one power supply module, at least one optical communication interface for receiving optical signals from two valve control units and converting them to electric signals for supply to a corresponding power supply module, where in normal operations mode one valve control unit is an active valve control unit and the other is a standby valve control unit, where the optical signal of an active unit energizes the gate control device and provides semiconductor device controlling data, a semiconductor device control module and a reliability control module that performs selection of active valve control unit.

Abstract: A high voltage direct current (HVDC) hybrid circuit breaker is provided. The circuit breaker includes a solid-state main breaker, a mechanical fast disconnector and a solid-state auxiliary breaker connected in series, the series-connection of the disconnector and the auxiliary breaker being connected in parallel to the main breaker, a snubber circuit including a capacitor, and a switching device being arranged for disconnecting the snubber capacitor in response to the auxiliary breaker being opened. By disconnecting the snubber capacitor, an uncontrolled discharging of the capacitor through the disconnector and the main breaker, and the resulting non-zero current flowing through the disconnector during the breaking action, may be avoided. Further, a method of an HVDC hybrid circuit breaker is provided.

Abstract: A high voltage direct current (HVDC) hybrid circuit breaker is provided. The circuit breaker includes a solid-state main breaker, a mechanical fast disconnector and a solid-state auxiliary breaker connected in series, the series-connection of the disconnector and the auxiliary breaker being connected in parallel to the main breaker, a snubber circuit including a capacitor, and a switching device being arranged for disconnecting the snubber capacitor in response to the auxiliary breaker being opened. By disconnecting the snubber capacitor, an uncontrolled discharging of the capacitor through the disconnector and the main breaker, and the resulting non-zero current flowing through the disconnector during the breaking action, may be avoided. Further, a method of an HVDC hybrid circuit breaker is provided.

Abstract: It is presented a gate control circuit comprising: a main gate unit arranged to supply, via a plurality of main gate unit outputs, a gate signal to respective gates of a plurality of power switches, for controlling a main current; and an auxiliary gate unit comprising an optical power converter for converting incoming optical power to an auxiliary electrical gate signal. The auxiliary gate unit is arranged to, when a failure occurs in one of the plurality of power switches, provide the auxiliary electrical gate signal to respective gates of any of the plurality of power switches still being in operation. A corresponding power module and method are also presented.

Abstract: A voltage surge protection device for protection of a high voltage device includes a varistor having a first part and a second part separated by varistor material. The voltage surge protection device further includes an expandable member arranged to act on a movable electrical contact for short-circuiting the voltage surge protection device upon a threshold voltage being applied between the first part and the second part of the varistor. A high voltage circuit breakers includes one or more semiconductor devices connected in series and the voltage surge protection device connected in parallel thereto.

Abstract: A voltage surge protection device for protection of a high voltage device includes a varistor having a first part and a second part separated by varistor material. The voltage surge protection device further includes an expandable member arranged to act on a movable electrical contact for short-circuiting the voltage surge protection device upon a threshold voltage being applied between the first part and the second part of the varistor. A high voltage circuit breakers includes one or more semiconductor devices connected in series and the voltage surge protection device connected in parallel thereto.

Abstract: The present invention relates to an HVDC switchyard arranged to interconnect a first part of a DC grid with a second part of the DC grid. By means of the invention, a first part of the DC grid is connected to the busbars of the HVDC switchyard via a fast DC breaker, while further part(s) of the DC grid are connected to the busbars of the HVDC switchyard by means of switchyard DC breakers of lower breaking speed. By use of the inventive HVDC switchyard arrangement, the cost for the HVDC switchyard can be considerably reduced, while adequate protection can be provided. In one embodiment, the fast DC breaker is an HVDC station DC breaker forming part of an HVDC station. In another embodiment, the fast DC breaker is a switchyard DC breaker.

Abstract: A gate control device for a semiconductor device includes at least one power supply module, at least one optical communication interface for receiving optical signals from two valve control units and converting them to electric signals for supply to a corresponding power supply module, where in normal operations mode one valve control unit is an active valve control unit and the other is a standby valve control unit, where the optical signal of an active unit energizes the gate control device and provides semiconductor device controlling data, a semiconductor device control module and a reliability control module that performs selection of active valve control unit.

Abstract: It is presented a power supply for providing power to control a power switch for a high voltage application. The power supply comprises: a high voltage divider arranged to be connected to a first current terminal of the power switch; a step down DC/DC converter connected to an output of the high voltage divider, wherein the step down DC/DC converter is arrange to provide an output voltage for control of the at least one power switch to an output of the power supply; and a bypass control unit arranged to control the high voltage divider to short circuit an main input and a main output of the high voltage divider when the voltage across the power switch is lower than a threshold voltage.

Abstract: It is presented a power supply for providing power to control a power switch for a high voltage application. The power supply comprises: a high voltage divider arranged to be connected to a first current terminal of the power switch; a step down DC/DC converter connected to an output of the high voltage divider, wherein the step down DC/DC converter is arrange to provide an output voltage for control of the at least one power switch to an output of the power supply; and a bypass control unit arranged to control the high voltage divider to short circuit an main input and a main output of the high voltage divider when the voltage across the power switch is lower than a threshold voltage.

Abstract: It is presented a gate control circuit comprising: a main gate unit arranged to supply, via a plurality of main gate unit outputs, a gate signal to respective gates of a plurality of power switches, for controlling a main current; and an auxiliary gate unit comprising an optical power converter for converting incoming optical power to an auxiliary electrical gate signal. The auxiliary gate unit is arranged to, when a failure occurs in one of the plurality of power switches, provide the auxiliary electrical gate signal to respective gates of any of the plurality of power switches still being in operation. A corresponding power module and method are also presented.

Abstract: DC current in a high voltage AC/DC or DC/AC converter station can be measured via the Faraday effect in one or more loops of an optical sensing fiber located at the base of a bushing extending through a wall of the hall. This arrangement can exploit the base of the bushing being at ground potential, which can simplify mounting work and maintenance.