Environmental Engineering Reference
In-Depth Information
If not mentioned otherwise, the input data of the optimisation problems solved
by the TCOPF program are based on the following simplifications:
All nodes and branches are classified so as to build the connectivity matrices;
●
The first node of each network is the 'slack' or reference point and has no load
demand, meanwhile the rest of the nodes begin the TCOPF solution process by
assuming they have either a voltage or pressure value of 1 PU;
●
Electric, thermal and transport power loads are at all nodes piecewise constant
for each time interval evaluated;
●
The optimisation is performed for multiple time-periods that represent a daily
profile divided into 48 time intervals (
i.e.
30-minute time steps);
●
Electric cables and gas pipe data values (
i.e.
admittance and friction factor) are
constant throughout the networks independent of their length;
●
The linear conversion and storage efficiency parameters of DER technologies
are the same at all nodes;
●
All the weight factors influencing grid-to-vehicle (G2V) and V2G capabilities,
as well as thermal storage elements, are enabled for all time intervals (
i.e.
equal
to1or
true
);
●
The market spot prices given are fixed and do not vary in value due to the energy
required or provided by DER technologies.
●
The time horizon performed in this research confines the analysis to the energy
demands the utilities are expected to supply on a daily basis. Hence, daily load profiles
for electric and thermal power demands are required as input data to run the model.
Electricity and gas demands used here are taken from historical data of different
customer types in the UK [216]. Due to this fact, and because confusion may arise
when dealing with different energy infrastructures and technologies, all power flows
and capacities are converted from their standard units into kilowatts and then into per
unit (PU) quantities (using the conversion factors found in Appendix F). A similar
approach is taken for both cable and pipe data and length characteristics, regarding
electric and natural gas networks respectively. This measure is taken because a PU
system gives a clear idea of the relative magnitudes for the various variables present
in a complex energy system, such as the one assessed in Chapter 6.
The TCOPF tool assumes energy transactions are allowed only up to the substation
level so that, for example, when demand response services are requested it is to meet
the needs of a particular substation in the network. Consequently, the DER units
connected to the distribution networks are optimally coordinated to ensure feasibility
and efficiency. Overall, the coordinating role the TCOPF plays has similar purposes
to previous load control programs used extensively for smaller devices such as water
heaters, refrigeration systems and air conditioners [217].
The control variables present in the TCOPF problem have the following
assumptions:
The operating range for both OLTC and compressor devices are predefined and
when idle have a value of 1 PU;
●
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