1. Field of the Invention
The invention relates to the field of power electronics. It is based on a power electronic circuit arrangement, in particular a static railway power converter.
2. Discussion of Background
Such a circuit arrangement has already been described on pages 4-10 of the journal "ABB Technik" No. 5/1995. This concerns a static frequency converter installation for railway power supply. It comprises a first power converter, in particular a thyristor power converter, which is connected to a first voltage supply system and is connected to a voltage intermediate circuit. A second power converter, in particular a GTO power converter, is connected to the voltage intermediate circuit and feeds a second voltage supply system (e.g. the railway grid). The second power converter has a two-point invertor structure with a positive terminal, a negative terminal and a neutral terminal. In the voltage intermediate circuit, a first filter for taking up the doubled supply-system frequency of the second voltage supply system is provided ("331/3 Hz filter" at a railway frequency of 162/3 Hz).
The use of the otherwise advantageous threepoint circuit results in undesirable in-phase currents of relatively high frequency in the intermediate circuit, and interfering in-antiphase and in-phase current components occur in the intermediate circuit. These undesirable components result in distortion of the voltage characteristic. It would be possible to counteract these instances of distortion e.g. by enlarging the capacitor bank of the voltage intermediate circuit. In the event of a short circuit, however, such a high energy would be stored in the capacitor bank, which would be discharged in an extremely short time via the components, that instances of destruction would have to be expected. It is therefore desirable not to have any excessively large capacitance in the intermediate circuit.