NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

Symmetrical and Unsymmetrical 

Fault Currents of a Wind Power 

Plant

Preprint

V. Gevorgian, M. Singh, and E. Muljadi 

To be presented at the IEEE Power and Energy Society General 

Meeting

San Diego, California

July 22-26, 2012

Conference Paper

NREL/CP-5500-53463

December 2011
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1 

Symmetrical and Unsymmetrical Fault Currents of a Wind Power Plant

V. Gevorgian

Member IEEE

vahan.gevorgian@nrel.gov

M. Singh

Member IEEE

mohit.singh@nrel.gov

E. Muljadi

Fellow, IEEE

eduard.muljadi@nrel.gov

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401, USA 

Abstract – The size of wind power plants (WPPs) keeps getting

bigger and bigger. The number of wind plants in the U.S. has

increased very rapidly in the past 10 years. It is projected that 

in the U.S., the total wind power generation will reach 330 GW 

by 2030. As the importance of WPPs increases, planning engineers must perform impact studies used to evaluate short-circuit 

current (SCC) contribution of the plant into the transmission 

network under different fault conditions. This information is 

needed to size the circuit breakers, to establish the proper system protection, and to choose the transient suppressor in the 

circuits within the WPP. This task can be challenging to protection engineers due to the topology differences between different 

types of wind turbine generators (WTGs) and the conventional 

generating units.

This paper investigates the short-circuit behavior of a WPP

for different types of wind turbines. Both symmetrical faults 

and unsymmetrical faults are investigated. Three different software packages are utilized to develop this paper. Time domain 

simulations and steady-state calculations are used to perform the 

analysis.

Index Terms — Fault contribution, induction generator, protection, short circuit, wind power plant, and wind turbine. 

I. INTRODUCTION

nergy and environmental issues have become one of the 

biggest challenges facing the world. In response to energy 

needs and environmental concerns, renewable energy technologies are considered the future technologies of choice [1], 

[2]. Renewable energy is harvested from nature, and it is 

clean and free. However, it is widely accepted that renewable 

energy is not a panacea that comes without challenges. With 

the federal government’s aggressive goal of achieving 20% 

wind energy penetration by 2030, it is necessary to understand the challenges that must be overcome when using renewable energy.

In the years to come, there will be more and more wind 

power plants (WPPs) connected to the grid. With the goal 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. This paper attempts to illustrate the behavior of short-circuit current (SCC)

contributions for different types of WTGs.

The power system model used for WPP short-circuit behavior simulation was adopted from a modeling guide developed by the Western Electricity Coordinating Council 

(WECC) Wind Generator Modeling and Validation Work 

Group (WGMG) [3]. The WGMG recommends the use of a 

single-machine equivalent representation of multiple wind 

turbines operating in a single WPP. Based on industry experience, this representation is also considered adequate for positive-sequence transient-stability simulations. The WECC 

single-machine equivalent representation of a WPP is shown 

in Figure 1. The interconnection transmission lines, transformers, and reactive power compensation are present in this 

representation.

Figure 1: A single-machine equivalent representation of a WPP

Organization of the Paper

The organization of this paper is as follows; in section II, 

the SCC characteristics of different WTG types will be presented for a symmetrical fault. In section III, the characteristics of SCC for unsymmetrical faults will be discussed. Finally, in section V, the conclusion will summarize the paper’s

findings. Detailed dynamic modeling of four different types 

of WTGs is simulated in PSCADTM. 

II. SHORT-CIRCUIT BEHAVIOR UNDER SYMMETRICAL FAULTS 

A utility-sized wind turbine is larger than non-grid wind 

turbine applications. In the early days, the turbines were

sized from 10 kW to 100 kW. Nowadays, wind turbines are 

sized above 1000 kW (1 MW).

A. SCC from a Type 1 WTG 

The first generation of utility-sized WTGs were fixedspeed turbines with a squirrel-cage induction generator 

(SCIG) and is called a Type I generator in wind-related applications. The SCIG generates electricity when it is driven 

above synchronous speed. Normal operating slips for an inE
2 

duction generator are between 0% and -1%. The simplified 

single-phase equivalent circuit of a squirrel-cage induction 

machine is shown in Figure 2 [4]. 

The circuit in Figure 2 is referred to the stator side where 

RS and Rr are stator and rotor resistances, Lsσ and Lrσ are stator and rotor leakage inductances, Lm is magnetizing reactance, and s is rotor slip. The example single-line connection 

diagram of a Type I generator is shown in Figure 3. In the 

case of a fault, the inertia of the wind rotor drives the generator after the voltage drops at the generator terminals, the pitch 

controller must be deployed to avoid a run-away problem. 

The rotor flux may not change instantaneously right after the 

voltage drop due to a fault. Therefore, voltage is produced at 

the generator terminals causing fault current flow into the 

fault until the rotor flux decays to zero. This process takes a 

few electrical cycles. The fault current produced by an induction generator must be considered when selecting the rating 

for circuit breakers and fuses. The fault current is limited by 

generator impedance (and can be calculated from parameters 

in Figure 2) and impedance of the system from the short circuit to the generator terminals. 

Figure 2: Equivalent circuit of a Type 1 generator 

Figure 3: Connection diagram for a Type 1 WTG 

The initial value of fault current fed in by the induction 

generator is close to the locked rotor-inrush current. Assuming a three-phase symmetrical fault, an analytical solution can 

be found to estimate the current contribution of the generator. 

The SCC of an induction generator can be calculated as [5]: 

݅ሺݐሻ ൌ √2ܸௌ

ܼௌ

ᇱ ቈ݁ି ௧

்ೄ

ᇲ

sinሺߙሻ െ ሺ1െߪሻ݁

ି ௧

்ೝ

ᇲ

sinሺ߱ݐ ൅ ߙሻ቉ ሺ1ሻ

Where α is the voltage phase angle for a given phase, σ is 

the leakage factor, ܼௌ

ᇱ ൌ ܺௌ′ ൌ ߱ܮௌ′ is stator transient reactance, and ܶௌ

′

 and ܶ௥

′

 are stator and rotor time constants representing the damping of the DC component in stator and rotor 

windings. The transient stator and rotor inductances ܮ௦

ᇱ and 

௥ܮ

ᇱ can be determined from the equation (2). 

ௌܮ

ᇱ ൌ ܮௌఙ ൅ ௅ೝ഑௅೘

௅ೝ഑ା௅೘

௥ܮ 

ᇱ ൌ ܮ௥ఙ ൅ ௅ೄ഑௅೘

௅ೄ഑ା௅೘

 ሺ2ሻ

ܶௌ

ᇱ ൌ ௅ೄ

ᇲ

ோೄ

; ܶ௥

ᇱ ൌ ௅ೝ

ᇲ

ோೝ

 ሺ3ሻ

ߪൌ1െ ௅೘

మ

௅ೄ௅ೝ 

 ሺ4ሻ 

ܮௌ ൌ ܮௌఙ ൅ ܮ ; ௠ܮ ௥ൌ ܮ௥ఙ ൅ ܮ ௠ሺ5ሻ

As shown in Figure 4, the fault current is driven by the decaying flux trapped in the rotor winding as represented by the 

right portion of equation (1). The larger the leakage inductances (σ), the smaller is the fault current amplitude. The fault 

current dies out after the flux driving the fault current depleted to zero. Note that the DC and AC transient components of 

the SCC flowing out of the stator windings induce fault currents in the rotor winding and vice versa until the magnetic 

flux is depleted. 

Figure 4: SCC from a Type I WTG 

The current calculated from equation (4) is shown in Figure 

4 using parameters for a typical 2-MW induction generator 

when and pre-fault voltage of 0.7 p.u. The current reaches the 

maximum value at π (first half a period). Therefore, it may be 

a good approximation to calculate the maximum (peak) current by substituting ݐ ൌ ܶ/2 into (1). The resulting equation 

for peak current will be: 

݅௠௔௫ ൌ √ଶ௏ೄ

௓ೄ

ᇲ ቈ݁ି ೅

మ೅ೄ

ᇲ

൅ ሺ1െߪሻ݁

ି ೅

మ೅ೝ

ᇲ

቉ ሺ6ሻ

 

 

It was demonstrated experimentally in [6] that equation (6) 

gives satisfactory accuracy for peak current assessment. 

C. SCC from a Type 2 WTG 

The variable slip generator is essentially a wound-rotor induction generator with a variable resistor connected in series 

to the rotor winding (for Type 2 WTGs, refer to Figure 5 and 

Figure 6). 

Min Isc-peak

Max Isc-peak
3 

Figure 5: Equivalent circuit for a Type 2 generator 

The modified rotor time constant can be calculated by adding 

the effect of the external resistor Rext, where Rext is the value 

of external resistance that happens to be in the circuit at the 

time of the fault. So, adding the external resistors increases 

the overall rotor resistance. 

Figure 6: Connection diagram for a Type 2 WTG 

D. SCC from a Type 3 WTG 

A Type 3 WTG is implemented by a doubly-fed induction 

generator (DFIG). It is a variable speed WTG where the rotor 

speed is allowed to vary within a slip range of +30%. Thus, 

the power converter can be sized to about 30% of rated power. The DFIG equivalent circuit is similar to one for a regular induction generator except for additional rotor voltage, 

representing voltage produced by a power converter. Under 

normal operation, this voltage is actually from a currentcontrolled power converter with the ability to control the real 

and reactive power output instantaneously and independently. 

Figure 7: Connection diagram for a Type 3 WTG 

The typical connection diagram for a DFIG (Type 3) WTG 

is shown in Figure 7. In an ideal situation, the power converter connected to the rotor winding should be able to withstand the currents induced by the DC and AC components 

flowing in the stator winding. However, the components of 

the power converter (IGBT, diode, and capacitor, etc) are 

designed to handle only normal currents and normal DC bus 

voltage. A crowbar system is usually used for protecting the 

power electronics converter from overvoltage and thermal 

breakdown during short-circuit faults. A crowbar is usually 

implemented to allow the insertion of additional resistance 

into the rotor winding to divert the SCC in the rotor winding 

from damaging the power converter. Additional dynamic 

braking on the DC bus is also used to limit the DC bus voltage. 

E. Type 4 WTGs 

A typical connection diagram for a Type 4 WTG is shown 

in Figure 8. The SCC contribution for a three-phase fault is 

limited to its rated current or a little above its rated current. It 

is common to design a power converter for a Type 4 wind 

turbine with an overload capability of 10% above rated. Note 

that in any fault condition, the generator stays connected to 

the power converter and is buffered from the faulted lines on 

the grid. 

 

Figure 8: PMSG direct-drive WTG diagram 

F. SCC Comparison for Symmetrical Faults 

The SCC for different types of wind turbines are not the 

same. For each turbine type, the peak value of the magnitude 

of the SCC is affected by the transient reactance, the pre-fault 

voltage, the effective rotor resistances, and other circumstances at the instant the fault occurs. 

As shown in Figure 9, the Type 1 WTG has the largest SCC 

and the shortest settling time. The Type 2 WTG has an additional rotor resistance that is activated above rated wind speed 

to limit the output power of the generator. Below rated wind 

speed, the SCC behavior of the Type 2 WTG is similar to the 

Type 1 WTG. Above rated wind speed, the SCC behavior of 

Type 2 WTG is affected by the external rotor resistance. The 

settling time of the SCC of Type 2 WTG is lower than the 

settling time of the SCC of Type 1 WTG. 

The SCC behavior of the Type 3 WTG is affected by the 

crowbar and the dynamic braking actions. For a very near 

fault, the crowbar may be fully deployed and thus, short circuiting the rotor winding, and the SCC behavior resembles 

the Type 1 WTG; however, if the crowbar and the dynamic 

braking can maintain the operation of the rotor side power 

converter, the SCC behavior is very close to a Type 4 WTG. 

For almost all of the SCC for Type 3 WTGs, only a small 

amount of SCC current is passed through the power converter 

because of the current limit of the power semiconductors. 

The Type 4 WTG has a full power converter between the 

generator and the grid, thus, the SCC is very well regulated 

with SCC maintained at 1.1 p.u. rated current. 

G. Summary of the Symmetrical Fault SCC 

To summarize, the SCC for a symmetrical faults can be approximated by the values listed in Table I [7]. Both the maximum and the minimum values are shown. 
4 

TABLE I 

MAXIMUM AND MINIMUM POSSIBLE VALUE OF THE SCC 

WTG Type 1 Type 2 Type 3 Type 4 

Max 

ISC_PEAK '

2

2

S

s

X

V

'

2

2

S

s

X

V

'

2

2

S

s

X

V 1.1 

IRATED

Min 

ISC_PEAK '

2

S

s

X

V 2' 2 ' )9(

2

S r

s

RX

V

+

1.1 

IRATED

0 

For a Type 1 WTG, the maximum SCC is based on the assumption that the DC offset is at the worst condition, and the 

minimum SCC is calculated by assuming that the DC offset is 

zero. For a Type 2 WTG, the maximum value is computed when 

ܴ௘௫௧= 0 Ω. The minimum value is computed when the slip 

reaches 10% above synchronous speed. And for a Type 3 WTG, 

the maximum value is computed when the crowbar shorts the 

rotor winding and the minimum value is computed when the 

power converter can follow the commanded current (i.e., in case 

the fault occurs far away from the point of interconnection (POI), 

the remaining terminal voltage is sufficiently high enough to let 

the power converter operate normally and supply the commanded currents). Note that for a symmetrical fault, the actual fault 

current for each phase is different from the other phases due to 

the fact that the time of the fault occurs at a different phase angle 

for different phases, thus affecting the DC offset. For a Type 4 

WTG, the stator current can always be controlled because of the 

nature of power converter, which is based on a current-controlled 

voltage source converter. 

A time domain simulation is performed in PSCAD, and the 

steady-state calculations are performed using Mathcad and 

Cyme software for a symmetrical fault. The results are tabulated in Table II. The calculated results from different software platforms are very close to the approximation listed in 

Table I. Note, that only Type 1 and Type 4 are listed. The 

Type 2 and Type 3 WTGs will respond differently because of 

the existence of the external rotor resistance in a Type 2 WTG 

and the activation of the crowbar circuit in a Type 3 WTG, 

which will respond non-linearly to the fault. The SCC for a 

Type 2 and Type 3 WTG, as indicated in Table I, will have 

the size difference between the SCC of the Type 1 and Type 4 

WTGs. 

TABLE II 

ISC_PEAK COMPARISON FOR DIFFERENT SOFTWARE PLATFORMS

WTG 

Type 

Table I 

PSCAD Cyme MathMin Max cad 

1 3.4 p.u. 6.3 

p.u. 5 p.u. 5.5 p.u. 3.8 p.u. 

4 0 p.u. 1.1 

p.u. 1.1 p.u. 1.1 p.u. 1.1 p.u. 

III. UNSYMMETRICAL FAULTS

The nature of the fault produces a different response for 

different wind turbine types. In this section, the observation 

of the short-circuit behavior for unsymmetrical faults on different types of WTGs will be presented. 

Note that operating an induction generator under an unbalanced condition creates torque pulsation and unbalanced currents. If this condition persists for a long period of time, it 

may excite other parts of the wind turbine, and the unbalanced currents may create unequal heating in the three-phase 

windings, thus, shorten the life of the winding insulation. 

Unlike in a symmetrical three-phase fault, the positivesequence voltage source continues to drive the fault current during the fault. As shown in Figure 11 and Figure 12, the remaining un-faulted (normal) phases continue to maintain the air-gap 

flux. The initial conditions of the fault currents are different for 

each phase. The three line currents usually show a different DC 

offset, which eventually settles out over time. 

A. Single Line-to-Ground (SLG) Faults 

The single line-to-ground fault is the most likely to occur in 

a) Type 1 WTG. 

b) Type 2 WTG. 

c) Type 3 WTG. 

d) Type 4 WTG. 

Figure 9: SCC of a symmetrical fault for four types of WTGs 
5 

a power system. The magnetic flux in the air gap, although 

smaller than normal and unbalanced, is maintained by the 

remaining un-faulted lines. Thus, the short circuit in SLG 

faults will continue to flow until the circuit breaker removes 

the fault from the circuit. 

Figure 10 shows the sequence circuits of the WPP shown in 

Figure 1. The sequence circuits are arranged to compute the 

SLG fault currents. Although present in the actual simulation, the cable capacitance and the capacitor compensation 

shown in Figure 1 are not drawn in Figure 12 to avoid clutter 

and to simplify the drawing. We represent the transformer 

winding connections in the zero sequence equivalent circuit 

as an on-off switch indicating the availability of the zero sequence current path. Since the low side of the pad-mounted 

transformer is connected in delta, there is no sequence current 

flowing out of the WTG. 

We also placed a switch at the negative sequence equivalent circuit for the WTG to indicate that there is no negative 

sequence current contribution from a Type 4 WTG because it 

is controlled to provide symmetrical currents regardless of the 

terminal voltage. 

Figure 10: The equivalent circuit for an SLG fault 

In Figure 13, the SCC for a Type 1 WTG is shown both for 

the three-phase currents and the corresponding sequence 

components. The changes in positive sequence and the sudden appearance of the negative sequence are also shown. The 

absence of the zero sequence current is a consequence of 

winding connections. 

Figure 13: SCC for a single line-to-ground in a Type 1 WPP 

Figure 14: SCC for a single line-to-ground in a Type 4 WPP 

a) At the point of interconnection 

b) At the wind generator terminals 

In Figure 14, the SCC for a Type 4 WTG shows the fault 

currents in its sequence current components. At the POI 

(Figure 14a), there exist both the zero sequence and the negative sequence currents because of the substation transformer 

winding connection (YgYg) and collector system capacitances 

respectively. As shown in Figure 14b, at the generator terminals however, there is a pad-mounted transformer (YgΔ) 

that will block the zero sequence component, and the Type 4 

WTG produces a positive sequence component (refer to neg. 

sequence switch in the equivalent circuit shown Figure 12). 

In Table III, the SCC at the POI is computed for a SLG 

fault using different software platform. It is shown that the 

Main : Graphs

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 

0.00 

0.20 

0.40 

0.60 

0.80 

1.00 

1.20 

1.40 

1.60 

1.80 

y

I2+ I2- I2o

0.00 

0.20 

0.40 

0.60 

0.80 

1.00 

1.20 I6+ I6- I6o

Figure 11: SCC for SLG for a Type 3 WTG 

Figure 12: SCC for LLG fault of a Type 2 WTG 

-20

-10

0

10

20

1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4

CURRENT (kA)

TIME (sec)

I3a 

I3b 

I3c 

Type 4 

Other 

Types 
6 

SCC results match for all software for Type 1 WTG. A small 

mismatch between the MathCAD and PSCAD results can be 

seen in Table 3. This discrepancy exists because in 

MathCAD, we remove the capacitances from the circuit. 

TABLE III 

COMPUTED SCC AT THE POINT OF INTERCONNECTION OF THE WPP 

IN SEQUENCE COMPONENTS IN PER UNIT 

FOR AN SLG FAULT WITH DIFFERENT SOFTWARE PLATFORMS

 WTG I_Seq PSCAD Cyme Math-cad 

Type 1 

0 1.42 1.58 1.67 

1 0.58 0.57 0.55 

2 0.63 0.57 0.65 

Type 4 

0 1.4 1.44 1.35 

1 1.0 0.95 1.0 

2 0.25 0.0 0.0 

TABLE IV 

COMPUTED SCC AT THE GENERATOR TERMINALS 

IN SEQUENCE COMPONENTS IN PER UNIT 

FOR AN SLG FAULT WITH DIFFERENT SOFTWARE PLATFORMS

 WTG I_Seq PSCAD Cyme MathCAD 

Type 1 

0 0.0 0.0 0.0 

1 0.58 0.56 0.55 

2 0.62 0.59 0.65 

Type 4 

0 0.0 0.0 0.0 

1 1.0 1.0 1.0 

2 0.0 0.0 0.0 

 In Table IV, the SCC at the generator terminal is computed 

for an SLG fault for Type 4 WTG. It is shown that the SCC 

results match for all software for a Type 4 WTG. Because of 

the mismatch between the MathCAD and the PSCAD results, 

we remove the capacitances in the circuit. 

Figure 15: An example of typical output panel for SCC calculation with 

Cyme. 

Comparing Table IV to Table III for a Type 4 turbine, it is 

shown that the zero sequence and negative sequence components do not exist. As shown in Figure 14, the absence of 

zero and negative sequence currents can be observed at the 

generator terminals. 

A snapshot of the computer output from Cyme is presented 

in Figure 15, where the line currents and the sequence currents are presented on the same output panel. 

B. Line-to-Line (LL) and Line-to-Line-to-Ground (LLG) 

Faults 

The line-to-line fault and the line-to-line-to-ground fault also maintained the air-gap flux during the fault. The SCC will 

continue to flow until the circuit breaker removes the fault 

from the circuit. 

In Table V the SCC at the POI is presented for a LL fault. 

It is shown that we have a very good match between PSCAD, 

Cyme, and MathCAD calculations. The absence of the zero 

sequence current can be expected because the fault does not 

involve the ground. 

TABLE V 

COMPUTED SCC AT THE POINT OF INTERCONNECTION OF THE WPP 

IN SEQUENCE COMPONENTS IN PER UNIT 

 FOR AN LL FAULT WITH DIFFERENT SOFTWARE PLATFORMS

 WTG I_Seq PSCAD Cyme Mathcad 

Type 1 

0 0.0 0.0 0.0 

1 0.95 0.86 0.95 

2 0.8 0.86 1.05 

Type 4 

0 0.0 0.0 0.0 

1 1.0 1.0 1.0 

2 0.4 0.0 0.0 

 

In Table VI, the SCC at the POI is presented for LLG fault. 

It is shown that we have a very good match between PSCAD, 

Cyme, and MathCAD calculations. In comparison to Table 

V, we can see the presence of the zero sequence current in 

LLG fault as expected in Table VI. 

TABLE VI 

COMPUTED SCC AT THE POINT OF INTERCONNECTION OF THE WPP 

IN SEQUENCE COMPONENTS IN PER UNIT 

 FOR AN LLG FAULT WITH DIFFERENT SOFTWARE PLATFORMS

 WTG I_Seq PSCAD Cyme Mathcad 

Type 1 

0 1.55 1.63 1.48 

1 1.17 1.11 1.1 

2 0.55 0.62 0.8 

Type 4 

0 1.4 1.49 1.7 

1 1 0.9 1 

2 0.25 0.0 0 

As an illustration, the currents at the POI for LL faults and 

LLG faults for Type 1 WTGs are presented in Figure 16, and 
7 

the corresponding sequence components are presented in Figure 17. As shown in Figure 16, it is difficult to discern the 

type of faults that occur in the line. In comparison, from Figure 17, it is obvious there is a distinction between the fault 

currents for the LL fault and the LLG fault. 

a) LL fault currents at POI 

b) LLG fault abc currents at POI 

Figure 16: Phase currents at the POI for a) LL fault and b) LLG fault 

a) LL fault currents at POI 

b) LLG fault abc currents at POI 

Figure 17: Sequence currents at the POI for a) LL fault and b) LLG 

fault 

IV. CONCLUSIONS

In this paper, the SCC contributions of different WTGs for 

faults at the terminal of the generator were simulated using 

time domain simulations and steady-state calculations. Two 

power system commercial software platforms were used 

(PSCADTM, and CymeTM), and a multipurpose mathematical 

computer program (MathCADTM) is also used to compute the 

SCC. 

A simplified method to compute the SCC for a symmetrical fault is presented and it is tabulated in Table I. The SCC 

results were tabulated in Table II, comparing the size of the 

SCC at the POI for three different methods. Note that only 

Type 1 and Type 4 WTGs are used because they represent the 

maximum and minimum SCC contribution. The calculations 

for Type 2 and Type 3 WTGs are affected by time-of-fault 

occurrence and the action of the external rotor resistance control and the crowbar action, thus, the SCC contribution is usually lower than the Type 1 WTG, but it is higher than the 

Type 4 WTG. 

The unsymmetrical faults were simulated and tabulated. 

As shown in the Table III through Table V, the unsymmetrical fault calculations from three different software packages 

shows a good agreement for unsymmetrical fault calculations. 

Each WPP is unique. Therefore, recommended practice 

from local reliability organizations, manufacturers, transmission planners, wind plant developers, and local utilities should 

be followed very closely when performing studies of WPP. 

V. ACKNOWLEDGMENT

 This work is supported by the U.S. Department of Energy. 

The authors wish to acknowledge the technical support from 

Cyme and PSCAD during the development of this paper. 

VI. REFERENCES

[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] IEEE PES Wind Plant Collector System Design Working Group, “Wind 

Power Plant Grounding, Overvoltage Protection, and Insulation Coordination,” Proceedings of the 2009 IEEE Power and Energy Society 

General Meeting. 

[4] Nader Samaan, Robert Zavadil, J. Charles Smith and Jose Conto, 

“Modeling of Wind Power Plants for Short Circuit Analysis in the 

Transmission Network,” in Proc. of IEEE/PES Transmission and Distribution Conference, Chicago, USA, April 2008.

[5] 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. 

[6] Sulawa, Zabara, et al. Short circuit current of induction generators. 

IEEE ISCAS 2007 proceedings. 

[7] E. Muljadi, V. Gevorgian, “Short Circuit Modeling of a Wind Power 

Plant,” in Proc. 2011 IEEE Power Engineering Society General Meeting. 

Main : Graphs

sec 1.00 1.20 1.40 1.60 1.80 2.00 

-1.00 

-0.75 

-0.50 

-0.25 

0.00 

0.25 

0.50 

0.75 

1.00 

1.25 I SCC POI

Main : Graphs

sec 1.00 1.20 1.40 1.60 1.80 2.00 

-1.00 

-0.75 

-0.50 

-0.25 

0.00 

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8 

VII. BIOGRAPHIES

Vahan Gevorgian (M’97) graduated from the Yerevan Polytechnic Institute (Armenia) in 1986. During 

his studies he concentrated on electrical machines. His 

thesis research dealt with doubly-fed induction generators for stand-alone power Systems. He obtained his 

Ph.D. degree in Electrical Engineering Dept. from the 

State Engineering University of Armenia in 1993. His 

dissertation was devoted to a modeling of electrical 

transients in large wind turbine generators.

Dr. Gevorgian is currently working at the National 

Wind Technology Center (NWTC) of National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA, as a research engineer. His current 

interests include modeling and testing of various applications of small wind 

turbine based power systems.

Mohit Singh (M’2011) received his M.S. and Ph.D. 

in Electrical Engineering from the University of Texas, 

Austin in 2007 and 2011 respectively. His research is 

focused on dynamic modeling of wind turbine generators. 

Dr. Singh is currently working at the National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA, as a post-doctoral researcher in transmission and grid integration of renewable energy. His

current interests include modeling and testing of various applications of wind 

turbine generators and other renewable energy resources. He is a member of 

the IEEE. He is involved in the activities of the IEEE Power and Energy

Society (PES). 

Eduard Muljadi (M’82-SM’94-F’10) received 

his Ph. D. (in Electrical Engineering) from the University of Wisconsin, Madison. From 1988 to 1992, 

he taught at California State University, Fresno, CA. 

In June 1992, he joined the National Renewable 

Energy Laboratory in Golden, Colorado. His current 

research interests are in the fields of electric machines, power electronics, and power systems in 

general with emphasis on renewable energy applications. He is member of 

Eta Kappa Nu, Sigma Xi and a Fellow of the IEEE. He is involved in the 

activities of the IEEE Industry Application Society (IAS), Power Electronics 

Society, and Power and Energy Society (PES). 

He is currently a member of various committees of the IAS, and a member 

of Working Group on Renewable Technologies and Dynamic Performance 

Wind Generation Task Force of the PES. He holds two patents in power 

conversion for renewable energy.