A New Paradigm for Large Brushless Hydrogenerators: Advantages Beyond the Static System

  • Date: –17:00
  • Location: Ångströmlaboratoriet, Lägerhyddsvägen 1 Häggsalen
  • Doctoral student: Nöland, Jonas Kristiansen
  • Organiser: Elektricitetslära
  • Contact person: Jonas Kristiansen Nöland
  • Phone: 004791358759
  • Disputation

The brushless excitation system is a well-established technology that eliminates the use of carbon brushes and slips rings that would be required in a static excitation system. However, the rotating diode bridge on the shaft of the conventional brushless system has no direct control opportunity and cannot apply negative field voltages for fast demagnetization of the synchronous generator. A slow step response of the generator field current is what has caused the brushless system to be a non-attractive alternative for larger synchronous generators.

This thesis explores an improved version of the brushless exciation system. A remotely controlled power electronic interface on the shaft solves the problem of the slow step response and the weak de-excitation capability. It has advantages beyond the static excitation system due to fewer components, the sysemt is more compact, it is less dependendent on the grid voltage and it is likely to need less regular maintenance. The proposed system can produce high ceiling voltages over the generator field winding, even during voltage dips in the grid. This has a huge benefit for enhancement of the fault ride-through capability of the generator.