Offshore Electricity Infrastructure in Europe - European Wind Energy ...

Annex c – details on the Methodology and Models
A detailed European grid model including the countries
in Eastern Europe and power exchange capacities with
Russia is the fundamental input for the power flow
calculations. The inputs to the program are the grid
model, the generation capacity forecast and cost for
all generator types per country, hydro reservoir levels,
and time series for demand, wind power production
and hydro inflow.
For each hour the program updates the demand, wind
production and marginal cost of hydro units based on
reservoir levels, and runs an optimal power flow which
determines the power output of all generators and on
all lines. PSST keeps track of the reservoir level for hydro
units by calculating the inflow and hydro production
given by the hourly solution of the marked model. The
power output of the generators is dependent on the
minimum and maximum capacity, the marginal cost
relative to other generators as well as the limitations
of power flow on lines capacity and the impedances.
The European grid model used in this project is divided
into five synchronous regions: Continental Europe
(former UCTE), Great Britain, Ireland, the Nordic region
(former Nordel) and the Baltic region. The countries
included in the model are shown in Figure 12.3. The
zones within the countries are indicated by white dots,
interconnections are given as blue lines. As can be
seen, France is modelled as 4 zones, while Germany
is modelled as 6 zones.
By adding the network grid as constraints to the market
model the effect of network constraints on both prices
and bottlenecks is identified. Not only will it identify
production and consumption but also the utilisation
of individual branch and HVDC connections, showing
where power flows through the system, identifying
bottlenecks and main power transfer corridors. The results
from the market model optimisation are given on
a detailed level for individual branches and nodes, but
it is also aggregated to area/zone totals to ease the
analysis of the results for such a large model.
The total cost which is a direct output of the market
model, is a good parameter for evaluating the benefit
of introducing new capacities into the electrical power
system 62 , while the price difference between parts
of the system is an indication of where to introduce
such new capacities. In order to indentify the need for
interconnectors between countries price differences
between areas are required. However, the model
will produce nodal prices which reflect the marginal
cost of supplying power to a given node. The nodal
prices are a good basis for computing the area price,
i.e. the wholesale consumer price for power within a
geographic area. Such areas are typically countries or
zones within a country. Area prices in the PSST are
computed from nodal prices as a weighted average,
with weights given as the relative demand within the
area. That is, the nodal prices at heavy load nodes are
more important than the nodal prices at nodes with
light load. In this way the model is able to find area
prices, while still including the electricity network and
having the high degree of freedom given by the nodal
price model.
When comparing the infrastructure costs to the system
benefits for two different design options, the system benefits
are calculated as the present value of the difference
in total cost between both cases over a lifetime of 25
years, and calculated with a discount factor of 6%.
More information on the market and grid model can be
found in Deliverable D6.1 and D6.2 [29].
62 Doing the analysis via the total system costs means that the optimisation is done from European welfare point of view.
122 OffshoreGrid – Final Report