Abstract: It is presented a DC/DC converter for converting power between a first DC connection comprising a first positive terminal and a first negative terminal, and a second DC connection comprising a second positive terminal and a second negative terminal. The DC/DC converter comprises: a first multilevel converter and a second multilevel converter connected serially between the first positive terminal and the first negative terminal, wherein the second positive terminal is connected to a point between the first multilevel converter and the second multilevel converter; and a first filter connected between an AC terminal of the first multilevel converter and an AC terminal of the second multilevel converter, wherein the first filter comprises a capacitor and an inductor.

Abstract: It is presented a DC/DC converter for converting power between a first DC connection comprising a first positive terminal and a first negative terminal, and a second DC connection comprising a second positive terminal and a second negative terminal. The DC/DC converter comprises: a first multilevel converter and a second multilevel converter connected serially between the first positive terminal and the first negative terminal, wherein the second positive terminal is connected to a point between the first multilevel converter and the second multilevel converter; and a first filter connected between an AC terminal of the first multilevel converter and an AC terminal of the second multilevel converter, wherein the first filter comprises a capacitor and an inductor.

Abstract: Multi-terminal HVDC systems and control methods therefore are disclosed. Methods for controlling multi-terminal HVDC systems having a plurality of converter stations may include receiving a plurality of measurements from a plurality of measurement units disposed on the HVDC system, identifying from the measurements a disruption within the HVDC system, monitoring the measurements to identify a steady-state disrupted condition for the HVDC system, calculating a new set point for at least one of the plurality of converter stations, which new set point may be based on the steady-state disrupted condition and the measurements, and transmitting the new set point to the at least one of the plurality of converter stations. In some examples, the HVDC systems may include an HVDC grid interconnecting the plurality of converter stations and a controller communicatively linked to the plurality of measurement units and the plurality of converter stations.

Abstract: Connection schemes for offshore power generation with an internal collection grid include a power generation system which includes a plurality of generator-rectifier subsystems. The scheme further includes a medium voltage DC (MVDC) collection network with positive pole cables and negative pole cables connected to the DC outputs of the generator-rectifier subsystems. At least one offshore substation includes a positive bus bar and a negative bus bar correspondingly connected to the positive pole cables and negative pole cables of the MVDC collection network and a plurality of main DC-DC converters. Each main DC-DC converter includes multiple modules connected to the MVDC bus bars and each module has a positive and a negative output such that the modules' outputs are serially connected to one another. The schemes may also include a high voltage DC (HVDC) transmission system connected to the modules' outputs and at least one DC/AC converter at an onshore substation.

Abstract: A system for producing electrical power based on wind energy is capable of predicting its power output. The system includes a set of wind turbine units, a first plurality of sensors each adapted to sense at least one wind characteristic at some of the wind turbine units, and a second plurality of sensors remotely located. At least one wind characteristic is estimated at the wind turbines not having one of the first plurality of sensors based on sensing by the first plurality of sensors and an estimate of changes in wind characteristic at wind turbine units caused by presence of other wind turbine units. The magnitude of electrical power production by the set of wind turbine units at at least one predefined point in time in the future is predicted based on the estimated wind characteristics and sensed wind characteristics.

Abstract: A protection system for high voltage direct current, HVDC, transmission lines is provided. The protection system includes a direct current, DC, bus, a device configured to connect an HVDC transmission line to the bus, at least one DC circuit breaker arranged for disconnecting the transmission line from the bus upon reception of a trip signal, current and voltage sensors, an inductor arranged such that the current through the transmission line passes the inductor, and a fault detection unit. The fault detection unit is arranged for assessing, on the basis of current and/or voltage measurements, whether a fault exists on the transmission line, and sending, if a fault is detected on the transmission line, a trip signal to the circuit breaker. The additional inductance limits the rise in fault current and facilitates a selective fault detection. Further, a method of fault protection for an HVDC transmission line is provided.

Abstract: Connection schemes for offshore power generation with an internal collection grid include a power generation system which includes a plurality of generator-rectifier subsystems. The scheme further includes a medium voltage DC (MVDC) collection network with positive pole cables and negative pole cables connected to the DC outputs of the generator-rectifier subsystems. At least one offshore substation includes a positive bus bar and a negative bus bar correspondingly connected to the positive pole cables and negative pole cables of the MVDC collection network and a plurality of main DC-DC converters. Each main DC-DC converter includes multiple modules connected to the MVDC bus bars and each module has a positive and a negative output such that the modules' outputs are serially connected to one another. The schemes may also include a high voltage DC (HVDC) transmission system connected to the modules' outputs and at least one DC/AC converter at an onshore substation.

Abstract: A protection system for high voltage direct current, HVDC, transmission lines is provided. The protection system includes a direct current, DC, bus, a device configured to connect an HVDC transmission line to the bus, at least one DC circuit breaker arranged for disconnecting the transmission line from the bus upon reception of a trip signal, current and voltage sensors, an inductor arranged such that the current through the transmission line passes the inductor, and a fault detection unit. The fault detection unit is arranged for assessing, on the basis of current and/or voltage measurements, whether a fault exists on the transmission line, and sending, if a fault is detected on the transmission line, a trip signal to the circuit breaker. The additional inductance limits the rise in fault current and facilitates a selective fault detection. Further, a method of fault protection for an HVDC transmission line is provided.

Abstract: Multi-terminal HVDC systems and control methods therefore are disclosed. Methods for controlling multi-terminal HVDC systems having a plurality of converter stations may include receiving a plurality of measurements from a plurality of measurement units disposed on the HVDC system, identifying from the measurements a disruption within the HVDC system, monitoring the measurements to identify a steady-state disrupted condition for the HVDC system, calculating a new set point for at least one of the plurality of converter stations, which new set point may be based on the steady-state disrupted condition and the measurements, and transmitting the new set point to the at least one of the plurality of converter stations. In some examples, the HVDC systems may include an HVDC grid interconnecting the plurality of converter stations and a controller communicatively linked to the plurality of measurement units and the plurality of converter stations.