Abstract: An AC power transformer includes primary and secondary windings for at least a first AC phase and a second AC phase, and a core for said at least first and second phases. The transformer further includes a control unit for transferring power from the first phase to the second phase via magnetic coupling in the core such that the sum of the phase vectors of all of the at least first and second phases is substantially zero.

Abstract: An AC power transformer includes primary and secondary windings for at least a first AC phase and a second AC phase, and a core for said at least first and second phases. The transformer further includes a control unit for transferring power from the first phase to the second phase via magnetic coupling in the core such that the sum of the phase vectors of all of the at least first and second phases is substantially zero.

Abstract: An apparatus includes a converter having an AC side and a DC side, a switch adapted to be connected to a transmission line on a first side and connected to a load on a second side connected to the AC side, an energy storage device, connected to the DC side. In a first operating mode, the switch is closed, such that an energy storage current flows to/from the energy storage device to charge/discharge the energy storage device, respectively. In a second operating mode, the switch is open, preventing current from flowing from the transmission line to the converter, and the energy storage device supplies a direct current which is converted to an alternating current by the converter. In the first operating mode, the apparatus is configured such that power transfer on the transmission line corresponds to a surge impedance loading of the transmission line, by affecting the energy storage current.

Abstract: An exemplary Multi-Terminal High Voltage Direct Current (MTDC) system includes at least three terminals, where each terminal including a Voltage Source Converter (VSC) controlled by a VSC controller. A method for controlling the MTDC system includes providing a converter schedule including at least one of a desired power flow value and a DC voltage; determining, by a MTDC master controller, a present state of the MTDC system including a dynamic topology of the MTDC system; determining, by the MTDC master controller, based on the present state of the MTDC system, based on the schedule and based on MTDC system constraints, VSC controller parameters including droop settings for local control by the VSC controllers; and transmitting the VSC controller parameters to the VSC controllers.

Abstract: The invention relates to a method in an electric power system including one or more power generation source(s) and a dynamic power compensator having a battery energy storage. The method includes the steps of: detecting a frequency disturbance within the electricity power system requiring an additional power generation source to be connected to the electricity power system in order to meet a power demand; and controlling the power output from the battery energy storage of the dynamic power compensator during start-up of the additional power generation source thereby limiting the frequency disturbance within the electric power system. The invention also relates to a controller, computer program, computer program products and electric power system.

Abstract: It is presented a method executed in a transmission system, the transmission system comprising an AC grid, a DC grid and at least two AC/DC converters connected between the AC grid and DC grid. The method comprises the steps of: obtaining set points for each one of the at least two AC/DC converters, each set point comprising a magnitude and direction of power through the respective AC/DC converter during normal operation generating, based on the set points, a virtual AC grid, the virtual AC grid corresponding to AC behavior of the DC grid, as viewed from each AC side of the at least two AC/DC converters; and controlling the at least two AC/DC converters to mimic a behavior in accordance with the virtual AC grid. A corresponding transmission system is also presented.

Abstract: It is presented a method executed in a transmission system, the transmission system comprising an AC grid, a DC grid and at least two AC/DC converters connected between the AC grid and DC grid. The method comprises the steps of: obtaining set points for each one of the at least two AC/DC converters, each set point comprising a magnitude and direction of power through the respective AC/DC converter during normal operation generating, based on the set points, a virtual AC grid, the virtual AC grid corresponding to AC behaviour of the DC grid, as viewed from each AC side of the at least two AC/DC converters; and controlling the at least two AC/DC converters to mimic a behaviour in accordance with the virtual AC grid. A corresponding transmission system is also presented.

Abstract: An exemplary Multi-Terminal High Voltage Direct Current (MTDC) system includes at least three terminals, where each terminal including a Voltage Source Converter (VSC) controlled by a VSC controller. A method for controlling the MTDC system includes providing a converter schedule including at least one of a desired power flow value and a DC voltage; determining, by a MTDC master controller, a present state of the MTDC system including a dynamic topology of the MTDC system; determining, by the MTDC master controller, based on the present state of the MTDC system, based on the schedule and based on MTDC system constraints, VSC controller parameters including droop settings for local control by the VSC controllers; and transmitting the VSC controller parameters to the VSC controllers.

Abstract: A method in a controller controlling a dynamic power compensator. The dynamic power compensator is arranged to provide active and reactive power to an electric power system, the dynamic power compensator including a battery energy storage. The method includes the steps of: monitoring a state of charge of the battery energy storage; detecting a voltage level in the electric power system requiring increased delivery of the reactive power to the electric power system; and controlling the battery energy storage in dependence on the monitored state of charge and detected voltage level. The invention also relates to a controller, computer programs and computer program products.

Abstract: A method in a converter station for communication within a DC power transmission system including two or more interconnected converter stations includes receiving, in the converter station, a synchronization signal for synchronizing the two or more converter stations; obtaining, in the converter station, an allocation of a communication time slot; changing, in the converter station, a set-point DC voltage level during the communication time slot; and measuring, in the converter station, a change of DC current in timeslots other than the communication time slot. A communication method utilizing the DC power transmission system itself is thus provided.

Abstract: The invention relates to a method in an electric power system including one or more power generation source(s) and a dynamic power compensator having a battery energy storage. The method includes the steps of: detecting a frequency disturbance within the electricity power system requiring an additional power generation source to be connected to the electricity power system in order to meet a power demand; and controlling the power output from the battery energy storage of the dynamic power compensator during start-up of the additional power generation source thereby limiting the frequency disturbance within the electric power system. The invention also relates to a controller, computer program, computer program products and electric power system.

Abstract: A method in a controller controlling a dynamic power compensator. The dynamic power compensator is arranged to provide active and reactive power to an electric power system, the dynamic power compensator including a battery energy storage. The method includes the steps of: monitoring a state of charge of the battery energy storage; detecting a voltage level in the electric power system requiring increased delivery of the reactive power to the electric power system; and controlling the battery energy storage in dependence on the monitored state of charge and detected voltage level. The invention also relates to a controller, computer programs and computer program products.

Abstract: A photovoltaic system for generating an output voltage that is uninfluenced by varying irradiation, includes a photovoltaic source having an input terminal and an output terminal. The photovoltaic system includes a voltage adding arrangement having a first input terminal and an output terminal. The voltage adding arrangement is connected in series with the photovoltaic source, and includes a first route having a voltage source and a second route as a voltage source bypass. The first and second routes extend between the first input terminal and the output terminal of the voltage adding arrangement. The first and second routes being alternately activateable.

Abstract: An arrangement to control an electrical property of a medium or high voltage AC system including a number n of phases with n being at least two includes a number n of phases, each phase including a series connection of at least two electrical elements with an intermediate connection point between each pair of the at least two electrical elements, where each of the n phases of the arrangement is connected on one side to an original common neutral point and on the other side to one of the n phases of the AC system. The arrangement further includes a number of first switchable interconnections, where the first switchable interconnections are each arranged between two intermediate connection points of two of the n phases of the arrangement, and at least one control unit arranged to control the first switchable interconnections.

Abstract: A method in a converter station for communication within a DC power transmission system including two or more interconnected converter stations includes receiving, in the converter station, a synchronization signal for synchronizing the two or more converter stations; obtaining, in the converter station, an allocation of a communication time slot; changing, in the converter station, a set-point DC voltage level during the communication time slot; and measuring, in the converter station, a change of DC current in timeslots other than the communication time slot. A communication method utilizing the DC power transmission system itself is thus provided.

Abstract: A method and a device for supervising the sensitivity of a protection function in an electrical power system including a metering device for measuring values of a feature, said protection function being configured to initialize an action based on a test value and a threshold value for the feature, wherein said test value is either a measured value or derived from the said measured values, the device includes a computing unit configured to receive the test values and, repeatedly during the operation of the protection function, to calculate a mean value and a deviation of the test values, to determine the probability of a false action based on the calculated mean value, the threshold value and the calculated deviation, and to indicate that the sensitivity is too high when the probability of a false action exceeds a first limit value for the probability of a false action.

Abstract: A wind mill apparatus for generating electric power to a grid point of an electric network. The apparatus includes a wind rotor, an electric generator operatively connected to the wind rotor, and an electric multiphase ac link operatively connecting the generator to the grid point. The ac link includes a first current path including a switchgear, a second current path including a dc link including a first converter operatively connected to the generator, a second converter operatively connected to the grid point, and a capacitor operatively connected between the conductors of the dc link. The ac link further includes a connectable multiphase dump load for blocking during a fault condition on the network the reactive power flow in the ac link, yet providing a reduced transfer of active power.

Abstract: A generator device for converting thermal energy to electric energy. A magnetic circuit includes at least a portion made of a magnetic material. A temperature-varying device varies the temperature in the portion made of the magnetic material alternately above and below a phase transition temperature of the magnetic material to thereby vary the reluctance of the magnetic circuit. A coil is arranged around the magnetic circuit, in which electric energy is induced in response to a varying magnetic flux in the magnetic circuit. A magnetic flux generator generates magnetic flux in the magnetic circuit. A controllable electric circuit device is connected to the coil and a control device controls the controllable electric circuit device.

Abstract: A device for transforming thermal energy to electric energy including a magnetic circuit including at least a portion made of a magnetic material, a temperature-varying device for varying the temperature in the portion made of the magnetic material alternately above and below a phase transition temperature of the magnetic material to thereby vary the reluctance of the magnetic circuit, and a coil arranged around the magnetic circuit, in which electric energy is induced in response to a varying magnetic flux in the magnetic circuit. A capacitor is connected in parallel with the coil to thereby form a resonant circuit, wherein the resonance frequency of the resonant circuit and the frequency of the temperature variation above and below the phase transition temperature of the magnetic material are dependent on one another to optimize the electric power output.

Abstract: An arrangement to control an electrical property of a medium or high voltage AC system including a number n of phases with n being at least two includes a number n of phases, each phase including a series connection of at least two electrical elements with an intermediate connection point between each pair of the at least two electrical elements, where each of the n phases of the arrangement is connected on one side to an original common neutral point and on the other side to one of the n phases of the AC system. The arrangement further includes a number of first switchable interconnections, where the first switchable interconnections are each arranged between two intermediate connection points of two of the n phases of the arrangement, and at least one control unit arranged to control the first switchable interconnections.