Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Patent
1996-10-09
1998-09-29
Wong, Peter S.
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
363 51, 363 79, H02J 300, H02H 700, H02M 324
Patent
active
058153853
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for control of an installation for transmission of high-voltage direct current in dependence on at least one stress parameter for a valve in a converter included in the installation, and to a means for carrying out the method.
The means comprises monitoring devices for continuously calculating a value of the stress parameter, based on predetermined relationships and in dependence on supplied values of the operating parameters of the installation, and for generating, in dependence on a comparison with a comparison value for the parameter, an influencing signal for influencing the control equipment of the converter.
BACKGROUND OF THE INVENTION
An installation for transmission of high-voltage direct current between two ac networks comprises at least two converters and a dc connection, which connects the direct-voltage terminal of one of the converters to the corresponding direct-voltage terminal on the other converter. The converters are each connected with their alternating-voltage terminals to one of the ac networks via transformers equipped with on-load tap-changers. Further, shunt-connected filters connected to the alternating-voltage network are usually included. For filtering harmonics generated by the converters, the filters are designed to be tuned, or with high-pass characteristic, but they are also often dimensioned to generate reactive power for compensation of the reactive power consumed by the converters during operation. Also, purely capacitive shunt filters, the only duty of which is to generate reactive power, occur. The filters mentioned may be distributed on a plurality of units, which makes possible connection and disconnection in dependence on the operating case of interest and the need of filtering and of generation of reactive power. During normal operation, one of the converters, hereinafter referred to as the rectifier, operates in rectifier operation, and the other converter, hereinafter referred to as the inverter, operates in inverter operation. The converters are each controlled by its own control equipment in such a way that the inverter determines the level of the direct voltage whereas the rectifier determines the level of the direct current, and hence of the transferred power. The inverter is normally controlled to a maximum possible voltage level, taking into consideration safety margins with respect to commutating errors, voltage variations on the alternating-voltage side, and other deviations from nominal operation which may occur. The rectifier is controlled in current control in dependence on a current order formed by a power order and the actual direct voltage.
To ensure rapid correction of disturbances occurring by influencing the control angles of the converters, the control angle .alpha. of the rectifier and the extinction angle .gamma. of the inverter during stationary operation should be allowed to vary both upwardly and downwardly around chosen nominal values, which are typically in the order of magnitude of .alpha.=15.degree. and .gamma.=17.degree.. By means of a control unit for controlling the tap-changers, which operates in dependence on reference values for control angle and extinction angle, respectively, the ideal no-load direct voltage of the converters in the current operating case is adapted such that the angles are near their respective reference values.
The control equipment of both the rectifier and the inverter may comprise a reference value-forming control unit which calculates reference values for direct voltage, control and extinction angles, respectively. These reference values are passed to the control unit for the tap-changers and to a control unit for control of the control and commutating angles. The reference value-forming control units for the rectifier and the inverter communicate with each other via a telecommunications link, which also transmits information about other operating parameters in the installation, for example ordered current in the dc connection.
The control unit of
REFERENCES:
patent: 4126892 (1978-11-01), Ekstrom et al.
patent: 4222097 (1980-09-01), Rogowsky
patent: 4263517 (1981-04-01), Konishi
patent: 4264951 (1981-04-01), Konishi et al.
patent: 4279009 (1981-07-01), Andronov et al.
patent: 4330815 (1982-05-01), Konishi
patent: 4425624 (1984-01-01), Planche
patent: 4516198 (1985-05-01), Liss
patent: 4555750 (1985-11-01), Matsumura et al.
patent: 4672519 (1987-06-01), Liss
patent: 5099409 (1992-03-01), Bando et al.
patent: 5249141 (1993-09-01), Vanderbroek et al.
Patent Abstracts of Japan, vol. 14, No. 328, Abstract of JP-A-2-111219, Apr. 1990.
Hyttinen Mats
Spjut Henrik
Asea Brown Boveri AB
Vu Bao Q.
Wong Peter S.
LandOfFree
Control of an installation for transmission of high-voltage dire does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control of an installation for transmission of high-voltage dire, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control of an installation for transmission of high-voltage dire will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-692056