IEEE Power & Energy Magazine - March/April 2021 - 48

60
50

Wind
Solar

40
30
20
10
0

20
09
20
10
20
11
20
12
20
13
20
14
20
15
20
16
20
17
20
18
20
19

Share of Electricity Supply (%)

the regulation of European balancing markets and toward
the harmonization of monitoring and validation of services
offered by flexible resources.
The large increase in electricity demand and the utilization of demand-side flexibility on a system level may also
have some unintended consequences on the distribution
system. First, the expected large numbers of new loads due
to the electrification of demand will stress distribution networks, and costly reinforcements will be required over the
next decade. The efficient use of the flexibility and controllability of these new loads on a distribution level can eliminate or postpone the need for these reinforcements, with an
estimated socioeconomic benefit of US$3.2 billion in Denmark alone by 2030. This benefit increases to US$4.8 billion if reinforcements of the transmission system are also
considered. Second, the coordinated DER response (which
is installed at low or medium voltage levels) for offering system services may lead to the overloading of lines or transformers or to unacceptable voltage levels. For example, very
low spot prices at specific hours of the day may synchronize
consumption and result in congestion on certain low-voltage
feeders. The same could happen from the activation of balancing power that is offered by DERs or by the coordinated
DER response to a large frequency deviation when such
units are used as frequency-reserve providers.
DER participation in the energy markets creates a
need for cooperation between distribution system operators (DSOs) and the transmission system operator (TSO)
to avoid jeopardizing the safe operation of the power system. On one hand, the TSO needs the flexibility and fast
response of DERs. On the other hand, the utilization of this
flexibility may cause operational problems to DSOs due to
load synchronization.
If an appropriate TSO-DSO coordination framework to
manage these challenges during the participation of DERs in
the energy markets does not exist, then energy security may
be compromised. If congestion at the distribution network
occurs, the DSO may resort to load curtailment, disrupting

Year

figure 1. The evolution of wind and solar energy production in Denmark over the last decade.
48

ieee power & energy magazine

the energy supply of customers and causing a significant
reduction in the customers' quality of service. As a result
of those DSO actions, aggregators will not be able to offer
the contracted services to the TSO, putting the whole system at risk. In other words, the absence of an operational
framework may lead to both interruption of supply at the
distribution level and insufficient service delivery at the system level. As we will show next, a substantial part of Danish
research effort has been directed to address such DER system integration problems.

Danish Research Efforts on Demand-Side
Flexibility in the Past Decade
Denmark is a front runner in the green transition and has
long recognized the importance that research on demandside flexibility plays in the integration of large shares of volatile renewable production. The vital role of research activities in the Danish energy system is reflected in the country's
leading position in smart grid-related research in the European Union (EU). In this section, we provide an overview of
Danish research activities regarding demand-side flexibility.
Energiforskning.dk is a database where all Danish
research, development, and demonstration funding programs within energy and climate are registered. As of April
2020, 251 projects were listed under the " Smart Grid and
Systems " category. Of those, 166 were started after 2010,
had a total budget greater than US$235,000 each, and were
funded by the four major programs: the Energy Technology
Development and Demonstration Program, Innovation Fund
Denmark, ForskEl, and Green Labs DK. In our assessment,
only nationally funded projects were considered.
A large number of those projects have dealt with various
aspects of integrating flexibility and smart grid solutions in
the electricity sector. We have used four categories to classify these projects:
✔ flexibility-component level
✔ flexibility-aggregation level
✔ system integration
✔ market design and business models.
The first category refers to the investigation of issues
related to demand-side flexibility on a component level,
i.e., the control, monitoring, and modeling of flexible
loads. The second category refers to issues related to the
aggregation and control of large numbers of demand-side
flexible resources. The third category refers to projects that
have dealt with how flexibility and smart grid solutions can
be integrated into the power system, following a systemlevel approach. The last category looks into novel market
mechanisms, the redesign of the electricity markets, and
business models.
A significant number of projects did not fall into one of
these categories, i.e., high-voltage direct current systems, district heating, gas networks, or storage technology improvement, and are outside the scope of our analysis. The total budget of each project has been distributed equally throughout
march/april 2021

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IEEE Power & Energy Magazine - March/April 2021

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