06-04-2012, 04:30 PM
Wind Farms with Energy Storages integrated at the Control Power Market
Wind Farms with Energy Storages integrated at the Control Power Market.pdf (Size: 1.03 MB / Downloads: 73)
INTRODUCTION
Today renewable energy is an important and constant growing part of the worldwide energy
supply. In Germany, the most important renewable source is wind energy. It is to be expected,
that the installed wind power in Germany will reach 60 % of the total load by 2020 [1]. In
comparison to conventional power plants, most renewables have the main disadvantage of
delivering fluctuating energy. Thus, they cannot be used optimally to guarantee a steady
supply. In spite of this disadvantage, the renewable energy is extra supported, because it is a
sustainable and environment friendly energy form and an important alternative for future
energy supply. In Germany, this official support is regulated by law by the government
through the Renewable Energy Sources Act (EEG) [2]. The owners of renewable production
facilities get a priority feed-in into the grid, where the grid operator must take-over the energy
and pay a fix refund for the generated energy.
FREQUENCY CONTROL
For a secure operation of the electrical grid, it is necessary to use control power (CP) for the
regulation of energy and frequency fluctuations. There exist two types of control power: first
is positive control power, which demands extra energy feed into the grid (e.g. increased
supply from power plants) and the second is negative control power, which reduces the
energy feed into the grid or increases the load (e.g. with pumped hydro storages). Today for
this issue typically large power plants are used to fulfill the requirements for delivery. They
make offers at an auction platform where the Transmission System Operators (TSO) buys the
required amount of CP. The different forms of control power, showed in Fig. 2, are described
hereafter [3].
Primary Control
The primary control power (PCP) must be fully activated automatically within 30 seconds.
The maximum time of delivery is 15 minutes. All participating power plants deliver PCP and
the costs are solidly shared. The power plants have to deliver at least ±5 MW, provide the
control power for the whole day and the bidding is for the next month [4].
Secondary Control
The secondary control power (SCP) also must be fully activated automatically not later than
900 seconds. That means, after 900 seconds the full primary control power must be replaced
with SCP. The maximum time of delivery is 60 minutes. Secondary control must be actively
self controlled from the affected TSO. Suppliers have to deliver at least ±10 MW, provide the
control power for the whole day and the bidding is also for the next month [5].
2.3 Tertiary Control
The manually activated tertiary control (TCP), also named “minute reserve”, takes place after
900 seconds up to 1 hour and replaces the SCP full or partly. Like before, the TSO is
responsible. Suppliers have to deliver at least ±15 MW. The providing of the tertiary control
power is separated in 4-hour-blocks during a day and the bidding is for the next day. [6].
CONCLUSIONS
The present work has demonstrated that with the two types of wind energy plants it is possible
to participate in the control power market. To investigate this possibility, models were used to
find out if the WEP are able to deliver the control power in the required time. After the
technical benefits of the integration of wind farms and storages to the grid, the work showed
that it is already worthwhile today for the wind farm owner to participate at the energy
market.