Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Patent
1998-06-12
2000-04-18
Berhane, Adolf Deneke
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
363 65, H02M 540, H02J 334
Patent
active
060522933
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for converting current and voltage between a first single-phase side and a second singe- or multi-phase side, which comprises at least two converter modules connected between these sides and each having two converters interacting with one of the sides each and an intermediate link interconnecting them.
In order to illustrate but not in any way restrict the invention two fields of use of such devices will hereinafter be described, but it is emphasized that a number of other fields of use for such devices are conceivable within the scope of the invention.
A first such field of use of such a device is in a so called power convertor station, placed along lines for electric railway traffic, primarily railway lines, so as to convert or transform voltage and current of a three-phase supply line to single phase having a suitable frequency and voltage of a single phase supply line for providing electrical energy to the vehicles driven on the railway. Such a device may have two converter modules, which at the second side are through the secondary winding of a transformer connected to the three phases of the three-phase supply, the transformer being adapted to carry out a transformation of the alternating voltage from, for example about 20 kV to for example, about 1-3 kV. The converter at the second side of the respective converter module causes a rectifying and this direct voltage is then led to a number, for instance four, converters connected in parallel between the direct voltage potentials of the intermediate link. The converters are controlled by pulse with modulation to emit an alternating voltage, formed by alternating positive and negative voltage pulses, which are added through primary windings of a transformer, the secondary winding of which is connected to the railway supply line and ground. The converters of the single-phase side are then controlled to produce an alternating current having a desired frequency, usually 162/3 Hz, while the three-phase supply line have a frequency of 50 Hz. Through the transformer on the single-phase side a voltage addition takes place while simultaneously obtaining a stair case curve shape, which will come closer to a sinus shape the greater is the number of converters arranged at the first side. A voltage adaption also takes place, so that the voltage at the single-phase side usually will be about 16 kV. The two transformers also ensure galvanical separation between the converter modules and between the single-phase and the multi-phase side.
Another field of use for a device defined in the introduction is in an electrically driven vehicle, such as a locomotive. Such devices already known for this field of use have had a single converter module, which have been connected to the single-phase supply line through a transformer, the transformer transforming the voltage down from for example 16 kV to 3 kV, and converters in the form of three-phase-bridges have been connected in parallel at the second side of the converter module and connected to a three-phase motor each for driving the vehicle.
Although these already known devices function well, it would of course be desirable to simplify them for cost saving.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a device of the type mentioned in the introduction, which is simpler and primarily may be manufactured at a lower cost than similar devices already known, without lowering the requirements of a good function of the device.
This object is according to the invention obtained by connecting the converter modules in series on the first side. Because to such a connection in series of the converter modules is made, no transformer is needed at the first side for adding voltages to achive a good curve shape when the device is used. The converters at the first side function as inverters and in the opposite case, i.e. when the latters function as rectifiers no transformer is needed either at the first side for transforming down the voltage t
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Ivner Sven
Lejonberg Tommy
Berhane Adolf Deneke
Daimler-Chrysler AG
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