Controllable reactor with HTS control winding Dr. Torbjörn Wass, ABB Corporate Research, Västerås, Sweden

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1 Controllable reactor with HTS control winding Dr. Torbjörn Wass, ABB Corporate Research, Västerås, Sweden ABB AB, Corporate Research - 1

2 Topic The design and construction of a small scale prototype of a controllable reactor with a HTS control winding The work is a collaboration between ABB and Royal Institute of Technology (KTH) and supported by the ELEKTRA program and ABB Torbjörn Wass, ABB Corporate Research, Sven Hörnfeldt, Royal Institute of Technology (KTH), Stefan Valdemarsson, ABB Corporate Research ABB AB, Corporate Research - 2

3 Background Shunt reactors are needed for power compensation of long transmission power lines and cables The need of shunt reactance changes with the load If the reactance could be continuously adjusted to the load the transmission of active power would increase ABB AB, Corporate Research - 3

4 Dynamic reactance Thyristor controlled reactor, SVC (Static VAr compensator) Synchronous condenser, (Rotating VAr compensator) ABB AB, Corporate Research - 4 Saturable reactor, (Transductor)

5 Basic idea A reactor store magnetic energy Conventional reactors store most magnetic energy in air gaps Reactive power VAr/m 3 Q = πfbh = πfb μ μ 2 r The controllable reactor store magnetic energy in the iron core the magnetizability of the iron core is controlled with a DC current through a control winding ABB AB, Corporate Research - 5

6 Basic idea I AC ABB AB, Corporate Research - 6 A hollow cylinder with two windings I DC B z μ H = 2 2 ( H z ) + ( H ) ϕ B and H in cylindrical coordinates when the iron is saturated. z

7 Losses at DC transport currents and longitudinal AC magnetic fields P (mw/m) mt 15 mt 1 mt 5 mt mt I B ABB AB, Corporate Research J DC (A/mm 2 ) Losses for AMSC High strength wire as functions of DC transport current at different longitudinal AC magnetic field. The lines are given by the model. P ( B, I, T ) = P + P + hyst eddy P ff

8 Design: HTS Control winding coil #3 52 mm Hollow cylinder 3 mm coil #1 coil #2.8 mm 7 mm ABB AB, Corporate Research - 8 coil #4

9 Design: Iron core ABB AB, Corporate Research - 9 The iron core of the reactor, with the hollow cylinder in the middle surrounded by the yokes and the return limbs.

10 Construction Finished reactor ABB AB, Corporate Research - 1

11 Magnetic circuit H z (ka/m) U AC (V) 8 6 H ϕ =13 ka/m 1 B z (T) ABB AB, Corporate Research H ϕ =74 ka/m H ϕ =44 ka/m H ϕ =15 ka/m I AC (A) U AC as functions of I AC at different DC currents through the control winding..5 B z Lines from the model μ H = 2 2 ( H z ) + ( H ) ϕ z

12 Harmonics.15.2 B z =1.6 T Harmonic distorsion.1.5 Harmonic distorsion B z =1.3 T B z (T) H ϕ (ka/m) ABB AB, Corporate Research - 12 The harmonic distortion as a function of B z at H φ =13 ka/m. The solid line is given by the model. The harmonic distortion as a function of H φ at B z =1.3 T and 1.6 T. The lines are given by the model.

13 Reactive power U AC =1 V U AC =8 V U AC =6 V U AC =4 V U AC =2 V I DC (A) P R (kva) ABB AB, Corporate Research - 13 Comparison with a copper control winding 2 A/mm 2, 25 times lower current density and higher losses J DC (A/mm 2 ) Reactive power as functions of DC current through the control winding at different AC voltages

14 Losses HTS control winding P (W) Tape, 123 m Coil, 123 m, 2 turns The coil in the reactor exposed to AC magnetic field U AC =1 V Model 1 ABB AB, Corporate Research J DC (A/mm 2 ) Losses as functions of DC current

15 Losses HTS control winding 1 P/I DC (mw/am) U =2 V AC U =4 V AC U =6 V AC U =8 V AC U AC =1 V The losses for a copper conductor that carries 2 A/mm 2 at 85 C is 4 mw/am..2 ABB AB, Corporate Research J (A/mm 2 ) DC Losses per unit current and unit length.

16 Loss factor HTS control winding 5 P/P R (x1-3 ) I =3 A DC I =4 A DC I =5 A DC I =6 A DC I =7 A DC 1 ABB AB, Corporate Research U AC (V) The total losses in the HTS winding divided by the reactive power of the reactor as function of voltage over the main winding.

17 Summary, comparison with copper control winding Control winding material J (A/mm 2 ) P R (kva) Dynamic range (-) P (W) Loss factor P/P R (-) Cost Control winding ($) HTS, AMSC High strength wire (with penalty factor 1).25-.6% 4 Copper % 2 ABB AB, Corporate Research - 17

18 Main conclusion Compared to a copper control winding the HTS control winding increases the dynamic range and the reactive power due to the high current density and reduces the losses of the control winding A large scale three phase reactor will need considerable development work The main drawback is the cost ABB AB, Corporate Research - 18

Transmission Problem Areas. Bulk power transfer over long distances Transmission Limitations/Bottlenecks have one or more of the following:

Transmission Problem Areas. Bulk power transfer over long distances Transmission Limitations/Bottlenecks have one or more of the following: Transmission Problem Areas Bulk power transfer over long distances Transmission Limitations/Bottlenecks have one or more of the following:» Steady-state stability limits» Transient stability limits» Power