Method for controlling a H.V.D.C. power transmission plant and a control means embodying the method
First Claim
1. A method for control of a high voltage direct current power transmission plant, the plant having first and second converter stations, one of the stations operating as a rectifier station and the other of the stations operating as an inverter station, said two stations being interconnected by a d.c. power transmission line, the plant further having a telecommunication link for the transmission of control information between the two stations, at least the first station having at least two a.c./d.c. converters which are parallel-connected on their d.c. sides, the plant furthermore having means for the protective blocking of one of these converters upon a fault arising in that converter;
- wherein, for maintaining the operation of the plant in case of protective blocking of a faulty converter in said first station when the telecommunication link is not available, the method comprising the step of;
temporarily reducing the voltage in that part of the plant operating as the rectifier station to a low value; and
wherein in the second station, where no protective blocking has occurred, the method further comprising the steps of;
sensing the d.c. voltage of the transmission line during a first predetermined time interval and, if the thus-sensed value is lower than a first predetermined low value, increasing the minimum value for the control angle of the converters of the second station from its normal value to a predetermined value chosen in dependence on whether the second station is operating as a rectifier or as an inverter,after termination of the voltage reduction of the rectifier station, measuring the current in the transmission line and setting the current order in the second station in accordance with the measured line current value, andthereafter, reducing the minimum value of the control angle to its normal value.
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Accused Products
Abstract
An HVDC power transmission plant with a rectifier station and an inverter station interconnected by a d.c. power transmission line is disclosed. The plant has a communication link for transmitting control information between the stations, at least one of which having at least two parallel-connected converters. If protective blocking of a faulty converter is made in a faulty station during a period when the communication link is not available, the line voltage and line current are temporarily reduced to zero in the rectifier station. In the faultless station, this state is detected and the minimum value of the control angle of the converters of the faultless station is temporarily increased. After output from the rectifier station has been restored, the line current is measured and the current order in the faultless station is set at the measured value, taking account of the current margin. Thereafter, the minimum value of the control angle is reduced to its normal value, thereby restoring normal operation of the plant.
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Citations
13 Claims
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1. A method for control of a high voltage direct current power transmission plant, the plant having first and second converter stations, one of the stations operating as a rectifier station and the other of the stations operating as an inverter station, said two stations being interconnected by a d.c. power transmission line, the plant further having a telecommunication link for the transmission of control information between the two stations, at least the first station having at least two a.c./d.c. converters which are parallel-connected on their d.c. sides, the plant furthermore having means for the protective blocking of one of these converters upon a fault arising in that converter;
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wherein, for maintaining the operation of the plant in case of protective blocking of a faulty converter in said first station when the telecommunication link is not available, the method comprising the step of; temporarily reducing the voltage in that part of the plant operating as the rectifier station to a low value; and wherein in the second station, where no protective blocking has occurred, the method further comprising the steps of; sensing the d.c. voltage of the transmission line during a first predetermined time interval and, if the thus-sensed value is lower than a first predetermined low value, increasing the minimum value for the control angle of the converters of the second station from its normal value to a predetermined value chosen in dependence on whether the second station is operating as a rectifier or as an inverter, after termination of the voltage reduction of the rectifier station, measuring the current in the transmission line and setting the current order in the second station in accordance with the measured line current value, and thereafter, reducing the minimum value of the control angle to its normal value. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An HVDC power station transmission plant having a first and a second converter station, the stations being interconnected via a d.c. power transmission line one of the stations operating as a rectifier station and the other of the stations operating as an inverter station, the plant further having a telecommunication link for the transmission of control information between the stations, at least the first station having at least two converters which are parallel-connected on their d.c. sides, the plant furthermore having means arranged to protectively block the converters, the plant comprising:
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means arranged to temporarily reduce the d.c. voltage of the station operating as a rectifier when a faulty converter in said first station has been protectively blocked; and
, in said second station, the plant further comprising;first voltage sensing and time measuring means arranged to sense whether the line voltage is lower than a first, low reference value during a first time interval and to influence control angle limiting means for increasing the minimum value for the control angle of converters of the second station from a normal value to a predetermined value, means arranged to select said predetermined value in dependence on whether the second station operates as a rectifier or as an inverter, a current measuring means arranged to measure the line current after power output from the rectifier station has been restored, and means arranged to set the current order of the second station in accordance with the measured value; and means arranged to cause a reduction of the minimum value of the control angle to the normal value after the measurement of the line current. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification