| Abstract |
The single phase 16.7 Hz railway supply network in central Europe has no fixed frequency ratio to the public 50 Hz three phase mains. For this 16.7 Hz mains a frequency deviation to the 50 Hz line of -3.5% to 2.5% is the design basis for the system tie frequency converters. System tie frequency converters take part in power delivering into railway mains, especially for the controlling power, in order to hold the single phase frequency at its setpoint value. In this network some static system tie converters (Giubiasco, Muldenstein/Gebersdorf, Jübek, Bremen) are already in operation for the last years. A major power contribution is given by the rotating system tie converters, consisting of a three-phase induction machine and a single phase synchronous machine in power ranges of approx. 7.5 MW to 70 MW per unit. State of the art systems with rotating machines are composed of a relative small power converterr with GTO-PWM inverter in the rotor circuit of the three phase induction machine. The dynamic performance of the rotor circuit can be improved by new control strategies. For such a supply system a stable, robust and fail-safe restectively failure-surviving system is essential. Especially the DC voltage control system shall guarantee a constant voltage without excessive oscillations during load variations and without deviation from the setpoint value during the change of non-internittent to intermittent condition of the DC link current. |
