Dynamic Response of a Wind Farm Consisting of Doubly-Fed Induction Generators to Network Disturbance - Simulation and Modeling Methodologies, Technologies and Application - page 136

d

( ) ( )

0rri =+ +λ−ω−ωλ

(48)

r c dr dr e r qr

dt

d

( ) ( )

0rri =+ +λ−ω−ωλ q (49)

r c qr r e r dr

dt

2.10 Wind Farm Model

Combinations of several WCS constitute a WF and simulation of complete wind farm
with large numbers of WCS will be computationally intensive without much
difference in the assessment. Aggregate model reduces simulation time required by
detailed multi turbines system [19-21].The objective is to represent a large wind farm
with many WCS by a single turbine system[22]. The following criteria must be
fulfilled when reducing a large wind farm into an aggregate model assuming a regular
wind distribution [19, 22]
1. The MVA rating of the equivalent WF S is the sum of individual MVA rating of

wf

the WCS

n



S = S (50)

wf i

i1 =

where S is the MVA rating of WCS, i and n are the numbers of WCS in the WF
2.

n



P = P (51)

wf i

i1 =

P

Where is the electric power supplied by the equivalent WF,

P is the electric wf

power supply by t i WCS.
3. The dynamics of the wind generators are given by the slope of the PQ

−

characteristics of the induction generator.
n

dQ dQ



=

(52)

dP dP

i1 =

wf i

Where is the PQ characteristic of the equivalent WF and dQ / dP is the

dQ / dP

−

i wf

th

i

characteristic of the WCS.

PQ −

3 System under Study

The system considered for the study is shown in Fig. 12. It consists of 110MW,
50MVAR synchronous generator (SG) connected to bus 4 through a 20/400kV
transformer.