Page 272 - Decision Making Applications in Modern Power Systems

Distributed generation in deregulated Chapter | 9 235

where V rms and V rms are the minimum and maximum specified rms vol-
min max
tages at load bus, respectively. The minimum and maximum rms bus
voltage limits are considered as 0.95 and 1.05 p.u., respectively.
2. Line capacity constraint
The current flow in network’s branches is constrained by its thermal
limit, as expressed in Eq. (9.6):

I rms # I rms ð9:4Þ
L L;max
where I rms is the total current flowing in the branch and I rms is the max-
L L;max
imum current carrying capacity (ampacity) of the branch.
3. DG capacity constraint
The total active power produced by the DG unit is recommended to
be bounded by the total connected load capacity to avoid excessive
reverse power flows. In this study, 100% penetration level is considered
as an upper limit for the total DG size [23].
4. Power factor constraint
Power factor (PF) should be kept in its satisfactory range to ensure an
optimum energy transfer, thus PF is constrained as follows:

PF min # PF # PF max ð9:5Þ
where PF min and PF max are the minimum and maximum allowed PF lim-
its which are considered as 0.90 lagging and unity, respectively.
5. Reverse power flow constraint
To investigate the HC maximization, two approaches are considered:
first, inhibiting any reverse power flows in the network branches, and sec-
ond, allowing the reverse power flows while updating the network protection
settings and configurations to allow for these bidirectional power flows.
P J Line $ nul ’ðJAbÞ ð9:6Þ
where P Line is the net active power flow in branch J, with a network of a
total number of branches b.
This constraint will be activated in the first approach (inhibiting reverse
power flows), while it will be deactivated in the second approach (allowing
reverse power flows).

9.5.3 Load model

From a realistic perspective, the load active and reactive at each bus does
not have fixed values along the day. However, a daily load profile is consid-
ered to reflect the actual load variations during the day and night. A typical
daily load profile relative to rated values is considered in this work as shown
in Fig. 9.6 [24].