Superconducting Fault Current Limiter (SFCL)

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This IEEE Topic on Superconducting Fault Current Limiter discuss about use working of SFCL. With the increase of electricity demand and change of concerning environment, the capabilities of renewable energy generation systems are being expanded.Renewable energy sources considered as clean and prospective energy sources of the future world. 12% of world’s electricity is generated from wind power. The wind-turbine generation system (WTGs) is a representative renewable energy system.

  • Does not cause pollution problem. 
  • Lowest maintenance cost.

WTGs increases the level of short-circuit current during a fault in a distribution system.

A high temperature superconducting fault current limiter (SFCL) can be solution to reduce the level of short-circuit current during fault.

Why Superconducting Fault Current Limiter (SFCL)?

  • Reduces the peak value of fault current.
  • Improves the transient stability of the power system.
  • Provides the system effective damping for low-frequency oscillations.
  • Causes no power loss in steady-state condition.

Connection of SFCL to an electric power grid:

  • Optimal place to install the SFCL.
  • Optimal resistive value of the SFCL occurred in series with a transmission line during a short circuit fault.
  • Potential protection-coordination problem with other existing protective devices such as circuit breakers.

Modelling Of SFCL

Modelling of a resistive (non-inductive winding) SFCL consists of:

  • Stabilizer resistance of the n'Th unit, Rns.
  • Superconductor  resistance of the n'Th unit, Rnc(t) connected with Rns in parallel.
  • Coil inductance of the n'Th unit, Ln.
Normal steady state condition, the values of Rnc(t) and Rns(t) are normally zero. Total resistance of parallel connection becomes zero in steady state condition. Total resistance (Rsfcl) of the SFCL during fault depends on total number of units in series. Value of Ln determined by the wound coils. Coil wound to have very small. inductivity.
Doubly-Fed Induction Generator (DFIG)
Induction generator widely used as wind generators because Brushless and rugged construction, Low cost, Maintenance free and Operational Simplicity. DFIG mostly used as variable speed wind generator. DFIG wind turbines are based on wound-rotor induction machines where rotor circuit is fed through back-to-back voltage source converter. Two types of wind generator topologies are
  • Fixed speed wind generator
  • Variable speed wind generator
DFIG System Power Factory

DFIG generator model is a built in model which integrates the induction machine and rotor-side converter (RSC). DFIG and RSC modelled in rotor reference frame (RRF) rotating at generator speed. RSC controller operates in a stator flux oriented reference frame (SFRF) rotating at synchronous speed. RSC control modifies the active (P) and reactive(Q) power by regulating the q and d axis rotor currents.

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