Environmental Engineering Reference
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because the values of control variables need to be determined in order to optimise
a desired function, being either a minimum or a maximum value. In other words,
the novelty of the OPF solution resides in obtaining the best possible value for an
objective function within an energy system while simultaneously respecting the system
operating constraints
[173].
For practical OPF solutions, the following tests are performed to verify a feasible
solution has been obtained [213]:
The gradient vector is equal to 0;
●
Power mismatches are within the specified tolerance;
●
Both equality and inequality constraints are satisfied;
●
Further alteration in the final value of the objective function is only possible if
constraints are breached.
●
The OPF calculation has many applications in power system studies. However,
the TCOPF introduced in this topic strictly focuses on operational issues, covering
topics that deal with optimal power delivery at a distribution level and the man-
agement of energy conversion and storage technologies. Hence, the scope and core
application of the TCOPF tool is to optimally coordinate the dispatch of PHEV and
CHP units, so they can have a seamless and more advantageous integration into
the grid.
In this work, the majority of the TCOPF problems focus on minimising a non-
linear objective function over multiple period intervals that are restrained by a set
of non-linear constraints. By analysing the state of energy service networks for
a full-time period, for example a daily load profile, it allows the TCOPF tool to
devise throughout a day the best moments to dispatch its available flexible controls
and technologies. Based on these characteristics,
the TCOPF mathematical prob-
lem formulation can be categorised as a typical multi-period non-linear constrained
optimisation problem that is composed of continuous and mixed-integer proper-
ties
[214].
To grasp a better understanding of the components which the TCOPF tool con-
siders for an integrated electric and natural gas network analysis, Figure 5.1 depicts
an example of radial networks subject to multiple energy flows.
For practical purposes, the TCOPF program can be seen as having an interest-
ing and useful application for utilities. The reasoning behind this argument is that
it can be anticipated that in a future scenario, one in which PHEVs and CHPs are
abundant in the grid, the distribution network operators (DNOs) will not want to
monitor and control every distributed resource individually. Instead, network opera-
tors will just prefer to have a partial control over the aggregate capacity these DER
technologies represent. Thus, it would be valuable for stakeholders if an independent
entity, functioning as an aggregator and decision-maker, would optimally coordinate
the interactions between DNOs and embedded technologies. The aggregation would
therefore allow utilities to dispose of a large predefined source of controllable gener-
ation and load. Hence, for the modelling studies conducted in this work, the so-called
'global coordinating entity' is portrayed by the TCOPF program.
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