Abstract:
A circuit breaking arrangement is disclosed, which is adapted to be coupled to a transmission line arranged to carry direct current for controllably effecting discontinuation of flow of direct current in the transmission line. The circuit breaking arrangement includes a current interrupter unit, which is adapted to, when actuated, interrupt current in the transmission line, and at least one resonance circuit. The resonance circuit is connected in parallel with the current interrupter unit and includes at least one capacitor, at least one inductor and at least one switch element. The resonance circuit is adapted to, upon actuation of the current interrupter unit, generate a resonance current superposing current of any arc generated in the current interrupter unit after actuation thereof, upon closing of the switch element by means of successive discharging and charging of the at least one capacitor. An auxiliary power supply unit is coupled to the resonance circuit and adapted to selectively and controllably convey power to the at least one capacitor, thereby charging it. On a condition that voltage of the transmission line and/or voltage of the at least one capacitor does not comply with a selected voltage criterion, the auxiliary power supply unit is caused to convey power to the at least one capacitor. The circuit breaking arrangement may be arranged so as to allow for conveyance of power transmitted in the transmission line to the at least one capacitor, thereby charging it.
Abstract:
A multilevel converter converting between AC and DC includes a phase arm with a number of cells between a DC pole and an AC terminal, the cells include at least one hybrid full bridge cell including a first cell connection terminal for coupling to the DC pole, a second cell connection terminal for coupling to the AC terminal, an energy storage element having a positive and a negative end, a first group of series connected semiconducting units in parallel with the energy storage element, where a junction between these forms one cell connection terminal, and a second group of series connected semiconducting units in parallel with the energy storage element and including a third semiconducting unit and a fourth semiconducting unit consisting of a number of unidirectional conducting elements including at least one unidirectional conducting element, where a junction between these forms a further cell connection terminal.
Abstract:
A method, field user presenting arrangement and a computer program product for enabling an operator of a process control system to determine the location of field users in the process control system are provided. The arrangement includes a presentation control unit that obtains position data of the position of a field user, obtain the positions of objects in the process control system, compares the position of the field user with the positions of the objects, determines that the field user is in the vicinity of an object if the distance between the position of the field user and the position of the object is below a proximity threshold, and presents the field user on graphics depicting the process, where a field user deemed to be in the vicinity of an object is presented at this object in the graphics.
Abstract:
A control system for an electric three-phase variable speed motor includes an inverter for providing power to the motor and a control arrangement for controlling the inverter. The control arrangement includes a d and q axis currents determining module configured to repeatedly determine d and q axis currents based on detected currents of the motor. An MTPA control block repeatedly generates reference d and q axis currents based on the determined d and q axis currents and a ratio value such that the ratio of the reference d and q axis currents is equal to the ratio value, which is set to unity. A switching signal generation module repeatedly generates switching signals to control the inverter based on the reference d and q axis currents. A fine adjustment module calculates a magnitude of a current or power of the motor and determines an optimum compensation ratio value.
Abstract:
A method to facilitate fault detection in the protected unit after connection to the at least a portion of the power system. A current is sensed in the protected unit during a plurality of different time periods. Compliance of at least one of the sensed currents with a respective first current criteria is determined based on a first current threshold value. On a condition that there is determined that at least one of the sensed currents comply with the respective first current criteria, a fault in the protected unit is detected.
Abstract:
The present invention relates to an electrical transformer comprising an electrical insulator and a winding of an electrical conductor around a core, said insulator being formed of an essentially non-porous composite material comprising a resin matrix and up to 85% by weight of insulating fibres surrounded by the resin matrix, the composite material having a maximum moisture content of less than 0.5% by weight at 23° C. and 50% relative humidity.
Abstract:
The method relates to an electric device comprising at least two electrodes which are separated by dielectric part. At least one of said electrodes is arranged to be at a floating potential. The dielectric part comprises at least one turn of at least one non-impregnatable electrically insulating film between two neighbouring electrodes. The electrodes are bonded to adjacent turns of non-impregnatable insulating film, and adjacent turns of non-impregnatable insulating film, if any, are bonded to each other, so that the turns of non-impregnatable insulating film and the electrodes form a solid body. The invention further relates to a method of manufacturing an electric device, where bonding of at least one turn is performed upon forming of said turn, so that the bonding of said turn to the turn/electrode underneath will commence before said turn has been completely covered by the next turn.
Abstract:
For controlling a robot in a safe way, a highest voltage required for a desired robot movement is calculated. A voltage level in a DC-bus is set on the basis of the highest voltage, and current is supplied to a motor at a robot axis from the DC-bus. By limiting the voltage level in the DC-bus to correspond to an actual need for a desired robot movement at each instant unnecessary fast robot movements are prevented even in the event that an inverter controlling motor currents would by mistake attempt to drive the motor faster than desired by the operator.
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:
A method for synchronizing and connecting a first sub power system with a second sub power system with an intelligent electronic device (IED) by use of at least one switching device between the first sub power system and the second sub power system in an electrical power system is provided. The TED monitors power supply parameters such as voltage magnitude, phase and other derived parameters such as voltage and phase differences in the first sub power system and the second sub power system to identify at least one instance for fast bus transfer where the two sub systems have acceptable differences in magnitude and phase. The TED performs phase shifting and voltage magnitude correction in anticipation for synchronizing power supplies on connection at the identified instance.