Environmental Engineering Reference
In-Depth Information
1. Calculate
P
L
by summing the connected loads.
2. Calculate
P
G
by summing the total generation.
3. Calculate
P
R
using Equation (3.6) .
4. Calculate
P
S
using Equation (3.9) .
5. Calculate the new
ω
(and
f
) using Equation (3.12) .
3.7.2 A Modelling Example
The model described above was used to assess the effect that a large wind power input would
have on the frequency stability of a power system. The example simulated is extreme and
has been chosen because it illustrates key issues.
Wind speed data from 23 UK sites were used in the simulation. A 50 hour period contain-
ing exceptional wind variability was chosen so as to provide a major challenge to integration.
It was assumed that the variation in wind speed and physical separation of the wind turbines
in each site would smooth second to second variations in power and thus the power system
could be adequately modelled on a minute to minute basis.
For each site, the power output was calculated on the assumption that a wind farm com-
prising 150 4 MW variable speed wind turbines was present at each site. A purely cubic
power-wind speed relationship was assumed with a cut-in wind speed of 2 m/s, a rated wind
speed of 15 m/s and a cut-out speed of 25 m/s. The output power from the 23 sites were added
together to give a total maximum generation capacity of 13.8 GW. This represents a level of
penetration of 25% as a fraction of peak demand.
The simulation results are shown in Figure 3.20. The maximum power reached in the 50
hours chosen was 4.6 GW and the minimum was 550 MW. During the period, the largest
sustained drop in wind power occurred during the 37th hour when 5.5 GW of wind was lost
in 4.5 hours.
Figure 3.20
Simulated wind power using measured wind speed data from 23 UK sites
