Speaker
Description
Due to the successful program of ASDEX Upgrade (AUG) the high current converters come to their limits. At the same time the risk of failure increases because of ageing. At the moment all converters are in use and thus the area of operations is fixed. Low power, high density discharges of AUG are limited by the OH transformer flux. Therefore a new thyristor converter group, called “Group 7”, is planned.
In combination with an existing converter (called “Group 6”), the OH supply will be increased from +/-40 kA / 5 s to +/-45 kA / 10 s for each polarity.
The new converter includes the so called “phase-to-neutral voltage control” with 2 thyristors more for the star point of the converter transformer, which allows a substantial reduction of the reactive power demand under partial-load operation.
While the design of the power section (transformers, thyristor-stacks, dc-chokes, …) will be in most parts a copy of Group 6, the control system will be a completely new design.
Group 7 gets a fully digital control system, which will increase the reliability and simplify the design using more standard components. While fast control issues like the control loops and the firing pulse generation are processed on a FPGA, less time-critical tasks will be done one a PLC (programmable logic controller).
To integrate this digital control system, also the interface to the AUG control system will be transformed from an analog plug, to a mostly digital interface via Ethernet.
The design phase is currently ongoing and in parallel preliminary works to integrate the new converter in our power supply network, like the extension of the 10kV-switchgear, the thyristor-crowbar-system and the crossbar-distributor, started.
