Electric power conversion systems – Current conversion – Including automatic or integral protection means
Reexamination Certificate
1999-12-09
2001-02-06
Sterrett, Jeffrey (Department: 2838)
Electric power conversion systems
Current conversion
Including automatic or integral protection means
C363S035000, C363S141000, C361S676000
Reexamination Certificate
active
06185116
ABSTRACT:
FIELD OF THE INVENTION AND PRIOR ART
The present invention relates to a device for supervising the cooling of a cooling system of a valve of a high voltage converter station located on high voltage potential level and having a plurality of valve units each having at least one semiconductor component of turn-on-type and for each semiconductor component a first control unit located on high voltage potential level and controlling said component, said first control units being connected to a valve control unit located on low potential level for communication between the valve control unit and the first control units, and said valve having an arrangement for cooling said semiconductor components with a cooling block associated with the respective semiconductor component and adapted to absorb heat from the semiconductor component and transfer it to a cooling medium.
Such high voltage converter stations may for example be stations in plants for transmitting electric power through High Voltage Direct Current (HVDC) for converting direct voltage into alternating voltage and conversely, but the invention is not restricted thereto, but is directed to supervising all types of high voltage converter stations, in which high voltage here typically may be voltages within the range 10-500 kV. Each valve unit has usually a plurality of semiconductor components of turn-on-type connected in series, such as thyristors, IGBTs or the like, which are controlled simultaneously, so that they act as one single switch, and among which the voltage to be held by the valve unit in a turned-off-state of said semiconductor components is distributed, since they normally only can hold 1-10 kV each.
Since high powers are handled by such a high voltage converter station and by that a drop out of parts thereof or the entire station during a certain period of time generates high costs, it is an important desire to be able to supervise different positions of said valve so as to be able to take necessary measures upon deviations from the normal state thereof for avoiding operation interruptions not planned as far as possible and minimise the closing times for maintenance by receiving information about exactly which components have a defect. Information about components starting to get deviating properties without being defect for that sake is also of interest, since correcting measures may be planned timely.
However, the different said positions are located on high voltage potential level, which makes the supervision thereof difficult, so that the way of proceeding has until now with respect to most of the positions been restricted to carrying out a measurement of a parameter associated with the position in question on ground potential level so as to then calculate a probable value of the parameter on high voltage potential level. The cooling of a said cooling system has been supervised by determining the temperature of the cooling water passing the semiconductor components for cooling thereof, in which this temperature has been determined indirectly by measuring the temperature of a cooling loop of the cooling system located on ground potential level so as to calculate the temperature of the cooling water in the valve in question therefrom. It is natural that the accuracy will not be an optimum and that there are sources of faults making it possible to obtain values not at all corresponding to the reality. Furthermore, the determination is very inaccurate, since for example a very increased temperature of a single semiconductor component may not be determined, since this high temperature will have a minor influence upon the temperature of the cooling liquid in said loop on ground potential level.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a device of the type defined in the introduction, which improves the possibilities to supervise the cooling of said cooling system considerably and by that be able to check the state of such a valve and by that avoid unnecessary breakdowns of components and unplanned operation interruptions.
This object is according to the invention obtained by providing a device of the type defined in the introduction which comprises temperature detecting members arranged at at least some of said cooling blocks and adapted to send values detected thereby to the first control unit associated with the respective semiconductor component for elaborating and transmitting data with respect to the temperature of said cooling block to an arrangement for supervising the valve located on low potential level. By measuring the temperature at said different cooling blocks on high voltage potential level and directly close to the semiconductor components it will be possible to arrive to conclusions with respect to the temperature of the semiconductor components with a high reliability, which enables an elimination of a part of the protection systems for supervising cooling medium of high voltage converter stations already known or improving the accuracy thereof.
According to a preferred embodiment of the invention said temperature detecting members are arranged in each cooling block for detecting the temperature at each said semiconductor component of the valve. A temperature increase locally in any of the semiconductor components may by this efficiently be detected with a short delay, so that measures required, such as for example refiring of a semiconductor component not turned on or the like, may be carried out so as to reduce the power dissipation in the semiconductor component in question, disconnecting thereof or other measures may be taken before an over-current protection present will be activated. The state in the region of each individual semiconductor component of the valve may by this be efficiently supervised, so that possible deviations from the desired values of the temperature may be discovered early and suitable measures may rapidly be taken for minimising the number of drop-outs of the components, operation interruptions and the like. Thus, a fault or defect of a quite particular semiconductor component is here discovered in place, i.e. on high voltage potential level, without the problem that such information about such a fault is smeared out by the good function of a number of other such semiconductor components or by the distance between the high voltage potential level and the low potential level.
According to another preferred embodiment of the invention, which is applicable to a high voltage converter station in which the first control units are connected with a valve control unit located on low potential level through light conductors for communication between the valve control unit and the first control units while separating them galvanically, the first control units have means for treating said values detected, and that first control units are adapted to utilise light conductors running back therefrom to the valve control unit for sending information resulting from said treatment to said arrangement for supervising said valve.
No additional arrangements for bringing the values in question down to “the ground” are by this required, since the light conductors already there are used for this purpose while obtaining the galvanic separation required between high voltage potential level and low potential level. It is only required that said first control units are supplemented by said means and that the different measuring members are applied in suitable places and connected to the first control unit, which may be achieved by conductors of electricity.
Further advantages as well as advantageous features of the invention appear from the following description and the other dependent claims.
REFERENCES:
patent: 4142230 (1979-02-01), Menju et al.
patent: 4475152 (1984-10-01), Ikegame et al.
patent: 4816983 (1989-03-01), Yoshizumi et al.
patent: 5953224 (1999-09-01), Gold et al.
Åström Urban
Asplund Gunnar
Bjorklund Hans
Nyberg Krister
Siljestrom Roland
ABB AB
Dykema Gossett PLLC
Sterrett Jeffrey
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