C.-P. Käsemann

145 MVA modular thyristor converter system with neutral control for ASDEX upgrade

The power supply of the ASDEX Upgrade (AUG) tokamak consists of 11 thyristor converter modules which feed the poloidal field coils. All converters installed are powered by 10.5 kV flywheel generators starting at a frequency of 110 Hz, running down to 85 Hz during a pulse. For quasi-stationary advanced tokamak experiments with enlarged flat-top phase, the power supply system must be extended. The variable frequency of the pulsed network, fast load changes, together with the different parameters of the load coils require a very sophisticated converter design with reduced reactive power consumption. The paper describes the design and testing of the modular Thyristor Converter Group 6 with neutral control and four quadrant possibilities. It presents the various configurations available for operation on AUG magnetic coils, analyses the results of measurements obtained during commissioning, compares them to the calculated (design) values and reports on the performance achieved in fast four quadrant operation, improving the possibilities of the AUG feedback control of plasma shape and position.

Operational experience with reactive power control methods optimized for tokamak power supplies

Abstract The power and energy of the ASDEX Upgrade (AUG) tokamak are provided by two separate 10.5 kV, 110–85 Hz networks based on the flywheel generators EZ3–EZ4 in addition to the generator EZ2 dedicated to the toroidal field coil. The 10.5 kV networks supply the thyristor converters allowing fast control of the DC currents in the AUG poloidal field coils. Two methods for improving the load power factor in the present experimental campaign of AUG have been investigated, namely the control of the phase-to-neutral voltage in thyristor converters fitted with neutral thyristors, such as the new 145 MVA modular thyristor converter system (Group 6), and reactive power control achieved by means of static VAr compensators (SVC). The paper shows that reliable compensation up to 90 MVAr was regularly achieved and that electrical transients in SVC modules can be kept at an acceptable level. The paper will discuss the results from the reactive power reduction by SVC and neutral thyristor control and draw a comparative conclusion.

Pulsed power supply system of the ASDEX upgrade Tokamak research facility

The Max Planck Institute for Plasma Physics (IPP) researches the basic principles for a power plant which - similar to the sun - will produce energy by fusion of light atomic nuclei. The operation of the ASDEX Upgrade (AUG) Tokamak relies on three large flywheel generators. These generators feed the pulsed power supply system for the magnetic confinement (high current) and additional heating (high voltage) of the plasma. 17 high current thyristor converters supply the copper magnet coils that induce the plasma current and provide positioning, shaping and ohmic heating of the plasma. For the heating and current drive of the plasma by neutral beam injection and electron and ion cyclotron resonance frequencies, 28 high voltage modules are available. This article gives an overview of the AUG 580 MVA pulsed power supply system. It presents the challenges to integrate new technologies into an up to 40 year old, grown system and reports on the performance achieved during AUG plasma experiments.