Tentin tekstisisältö

1. Wind turbines
Explain and analyze the reasons for the growth of wind power in Finland and globally.

Describe the wind farm. What components are included and what are the roles and purposes of those
components. Remember to give a good overview, but also explain the most important details. Provide
also a short comparison of onshore and offshore wind farms from electricity grid perspective.

Describe the methods how wind turbines are extracting and maximizing the power from wind. Consider
also the differences between different wind turbine schemes.

Describe the three main wind turbine schemes (fixed-speed, double-fed induction generator and full
rated converter) on overall level. Compare the schemes also from component and performance
viewpoints.

2. Generators

Describe the general structure of model of one wind turbine scheme. Explain also the purpose of each
component in the general model. You may select the wind turbine scheme (fixed-speed, double-fed
induction generator and full rated converter) based on you own favor.

Describe the electrical characteristics of fixed-speed induction generation wind turbine scheme. Give the
answer based on information related to grid connected induction generator. Consider both the steady-
state and dynamic characteristics of fixed-speed wind turbine. Name also which of these characteristics
are the most important from grid integration perspective.

Describe the electrical characteristics of double-fed induction generation wind turbine scheme. Give the
answer based on information related to grid connected induction generator (stator) and rotor
connected converter. Consider both the steady-state and dynamic characteristics of double-fed wind
turbine. Name also which of these characteristics are the most important from grid integration
perspective.

Describe the electrical characteristics of full rated converter wind turbine scheme. Give the answer
based on information related to grid connected converter. Consider both the steady-state and dynamic
characteristics of full rated converter wind turbine. Name also which of these characteristics are the
most important from grid integration perspective.

Explain the role of power electronic converters/technologies in wind turbine schemes. Explain also what
power electronic technologies are typically utilized in wind farms.

3. Steady-state grid impacts

Describe and explain the most important and influential grid code requirements for the wind turbines.

Explain why those requirements are important from grid perspective. In similar way explain why those
are influential from wind turbine perspective.

Large wind farm needs to participate in grid voltage control. At the same time the wind farm should
maintain as good reactive power balance as possible. Describe and explain different possibilities how
the wind farm may realize the voltage control and reactive power management. In addition to described
solutions of voltage control and reactive power management, describe and explain also the challenges
related to those in case of a wind farm.

Explain what kind of power flow variations will happen due to large-scale wind power connected to high
voltage and extra high voltage distribution and transmission grids. Explain local, regional and system
level power flow impacts due to wind power. Provide reasons for the local, regional and system level
impacts and provide explanation for the differences between them.

Large-scale expansion of wind power will require the extension of grid capacity as well. Consider what
challenges and solutions grid companies have to answer this task cost effectively from the whole
electricity system viewpoint in the long ru. Consider all levels of grid expansion: wind farm connection,
regional grid, national transmission grid and import/export capacity to neighboring countries and
market areas.

Describe what is the overplanting of a wine farm and how it may be realized, Explain also why it may be
beneficial for the owner of the wind farm,
4, Dynamic grid impacts

Large-scale wind power may endanger power system security if not properly taken into consideration.
Explain first what the power system security is and how the large-scale wind power may endanger it.
Explain also in detail few mechanisms/solutions already implemented or to be implemented in near
future in wind turbines in order to support power system security. Explain also how those
mechanisms/solutions help power system and what impacts they have for wind turbine design and
operation.

Describe what is the fault-ride-through capability and how it is related to power system security. Explain
also how a wind turbine may fulfil this requirement.

Wind farm may participate in frequency control. Describe different methods how wind farm may
participate in frequency control from technical perspective and how those methods may be
implemented in wind farms.

Wind farm may provide ancillary services for distribution and transmission grids. Describe and explain

what ancillary services wind farms may provide and how they may realize those. Consider both the
technical and market aspects of ancillary service provision.

How the frequency stability of low-inertia power system may be enhanced? Explain alternative solutions
and what kind of role they may have in future 100 % renewable based power system.

5. Market impacts

Forecasting of wind power has important role in the market operation of producer. Explain
shortly the main idea of large-scale wind power forecasting. What consequences forecasting
error has for the producer? What factors influence on wind power forecasting error? How the
error might be reduced?

Explain why and how the smoothing of wind power variation is realized. Explain also what kind
of benefits smoothing has for power system operation.

What kind of impacts large-scale wind power has for the prices of day-ahead and regulation power
markets. Provide explanations.

Explain why the volatility of electricity maiket price (e.g. day-ahead market system price) will increase
due to large-scale wind power production.

Describe what kind of impacts large-scale wind power has for control and disturbance reserves. Explain
why these happen.