Introduction and Objectives Modeling Approach Results

FAULT-CURRENT LIMITER (FCL) APPLICATION 

IN A WIND POWER PLANT

Eduard Muljadi and Vahan Gevorgian • National Renewable Energy Laboratory • Golden, Colorado

Francisco DeLaRosa • Zenergy Power, Inc

3LG f lt t i f T 1 i d t bi In the years to come, there will be more and more wind power plants (WPPs) connected

to the electrical grid. With the scenario of 20% wind penetration by 2030, the WPP’s

operation should be well planned. The power system switchgear and power system

protection for WPPs should be carefully designed to be compatible with the operation of

conventional synchronous generators connected to the same grid.

POI or 

connection 

to the grid Collector System 

Station

Interconnection 

Transmission Line

FCL is installed at the low voltage side of 34.5-kV 

substation transformer

3LG fault current comparison for Type 1 wind turbine

Feeders and Laterals (overhead 

and/or underground)

Individual WTGs

As shown in above, a WPP consists of many (hundreds) of wind turbine generators

Typical layout of wind power plant

Type 1 Wind Turbine

SLG fault current comparison for Type 1 wind turbine

, y ( ) g

(WTGs). Currently, available WTG sizes are between 1 MW and 5 MW. The WTG is

connected at a low voltage level (e.g. 600 Volt), and a pad-mounted transformer is

connected to step up the voltage to 34.5 kV.

Several turbines are strung together and connected in a daisy chain fashion. The

collector system is connected to the substation transformer where the voltage is stepped

up to higher voltage (e.g., 230 kV) and the power is transmitted over long distance. Thus,

a 300-MW wind power plant may consist of 300 turbines connected to the grid.

In this analysis, the fault-current limiter (FCL) is proposed to be installed at the collector

side (34.5 kV) of the substation transformer. Thus, the FCL will be able to protect the

entire WPP.

Type 3 Wind Turbine

Transient torque reduction in Type 1 generator during SLG fault

3LG = 3 lines to ground, SLF = single line fault, LL = line-to-line fault, LLG = line-to-lineto ground fault.

Fault-Current Limiter Conclusions

The saturable core FCL consists of a set of coils wound around one or more

ferromagnetic cores. A high-temperature superconducting (HTS) magnet is coupled to the

core region in such a way that the DC magnetization force can saturate the magnetic

material. Each AC phase consists of two coils connected in series and wound around two

core regions. Under normal operating conditions, the operating point on the Φ-I curve is

always in the saturated region due to the DC bias.

Type 1 Type 2 Type 3

SCC Torque SCC Torque SCC Torque

3LG fault 0.44 0.63 0.5 0.62 0.99 0.99

SLF fault 0.33 0.55 0.34 0.55 0.75 0.71

LL fault 0.47 0.66 0.38 0.63 0.71 0.77

LLG fault 0.33 0.66 0.36 0.65 0.70 0.67

Reduction ratio of short-circuit current (SCC) and transient torques 

with and without FCLs for three wind turbine types

FCLs can effectively reduce the SCC for the Type I wind turbine generator. It is also

shown that for single line-to-ground and other types of unsymmetrical faults, the FCL

behaves like an equalizer such that not only a reduction in the positive, negative, and

zero sequence currents is achieved, but also the timing of the reduction is very beneficial.

The most significant reduction of those sequence currents occurs during the transient (at

the few cycles in the beginning of the faults), thus, as a result, the transient torque is

reduced very significantly.

The SCC contribution for different types of WTGs is tabulated as the ratio of SCC for a

WPP with FCLs to the SCC for a WPP without FCLs. A table showing the reduction in

transient torque for different faults and different WTGs is also tabulated in the same

fashion. As shown in the table above, there is significant improvement in the SCC and

the transient torque reductions for a WPP with FCLs.

The designs of the FCL for different types of WTGs must be designed specific to the WTG

Dual iron-core FCL Φ-I characteristic of the FCL for buck (dotted line) and boost (dashed line) coils

References

The designs of the FCL for different types of WTGs must be designed specific to the WTG

technologybecause the nature of the SCC contribution is unique for each type of WTG.

1. U.S. Department of Energy – Energy Efficiency and Renewable Energy, “20% Wind Energy by 2030 –

Increasing Wind Energy’s Contribution to U.S. Electricity Supply,” May, 2008. 

2. J. Charles Smith, Michael R. Milligan, Edgar A. DeMeo and Brian Parsons, "Utility wind Integration and 

operating impact state of the art," IEEE Trans. Power Systems, vol. 22, pp. 900-908, Aug. 2007.

3. Moriconi, F., Koshnick, N., De La Rosa, F. and Singh, A., “Modeling and Test Validation of a 15 kV 24 MVA 

Superconducting Fault Current Limiter”, in Proc. of IEEE/PES Transmission and Distribution Conference, 

New Orleans, USA, April 2010.

4. WECC Modeling and Validation Work Group, “WECC Wind Power Plant Power Flow Modeling Guide 

Prepared.” May 2008.

5. Short-circuit currents in three-phase AC systems–Part 0: Calculation of currents, IEC Standard 60909-0, 

July 2001.

6. IEEE Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis, IEEE 

Standard C37.10-2000, Sept. 2000.

7. J. Moren, S.W.H. de Haan, “Short-Circuit Current of Wind Turbines with Doubly Fed Induction Generator,” 

IEEE Transactions on Energy Conversion Vol 22 No 1 March 2007

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Back EMF across the FCL:

WINDPOWER 2011, Anaheim California, May 22 – 25, 2011 • NREL/PO-5500-51285

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

IEEE Transactions on Energy Conversion, Vol. 22, No. 1, March 2007.

8. IEEE PES Wind Plant Collector System Design Working Group, ”Power Transformer Application for Wind 

Plant Substation,” Proceedings of the 2009 IEEE Power and Energy Society General Meeting.

9. V. Gevorgian, E. Muljadi, " Wind Power Plant Short-Circuit Current Contribution for Different Fault and Wind 

Turbine Topologies", Presented at the 9th International Workshop on Large Scale of Wind Power into Power 

Systems, Quebec City, Quebec, Canada, July 18-19, 2010 

10. E. Muljadi, R. Schiferl, and T.A. Lipo, "Unsymmetrical Triggering of Phase Back Controller for Unbalanced 

Operation of Induction Machine", IEEE Transactions on Industry Applications, Vol. IA-21, No. 4, May/June 

1985, pp. 669- 677 

11. J. Oyama, F. Profumo, E. Muljadi and T.A. Lipo, " Design and Performance of a Digitally Based Voltage 

Controller for Correcting Phase Unbalance in Induction Machines." IEEE Transactions on Industry 

Applications Vol. 26, No. 3, May/June 1990, pp. 425-433. 

12. E. Muljadi, T.Batan, D.Yildirim, C.P. Butterfield, "Understanding the Unbalanced-Voltage Problem in Wind 

Turbine Generation," IEEE-Industry Applications Society Annual Conference, October 3-7, 1999 in Phoenix, 

Differential inductance for di Arizona. fferent operating currents Approximate voltage drop for different operating currents