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ENM052 - Ancillary services in power system
Stödtjänster i elkraftsystem
Syllabus adopted 2021-02-10 by Head of Programme (or corresponding)
Owner: MPEPO
7,5 Credits
Grading: TH - Pass with distinction (5), Pass with credit (4), Pass (3), Fail
Education cycle: Second-cycle
Major subject: Electrical Engineering

Teaching language: English
Application code: 21125
Open for exchange students: Yes
Block schedule: B
Maximum participants: 70
Status, available places (updated regularly): Yes

Module   Credit distribution   Examination dates
Sp1 Sp2 Sp3 Sp4 Summer course No Sp
0121 Examination 7,5c Grading: TH   7,5c   13 Jan 2022 am J,  13 Apr 2022 pm J,  18 Aug 2022 am J

In programs

TIELL ELECTRICAL ENGINEERING - Electrical Engineering, Year 3 (compulsory elective)


Peiyuan Chen

  Go to Course Homepage


General entry requirements for Master's level (second cycle)
Applicants enrolled in a programme at Chalmers where the course is included in the study programme are exempted from fulfilling the requirements above.

Specific entry requirements

English 6 (or by other approved means with the equivalent proficiency level)
Applicants enrolled in a programme at Chalmers where the course is included in the study programme are exempted from fulfilling the requirements above.

Course specific prerequisites

ENM055 or ENM056 or a similar course.
In addition to this course the student should fulfill the course specific prerequisites for MPEPO in the Admission Regulations.


The main aim of this course is that students should develop and demonstrate their knowledge and capability to explain and analyse different aspects of ancillary services in power systems for delivering electricity in a stable way with high power quality. In particular, this course focuses on the frequency and voltage ancillary services. Simulation projects and laboratory tests will be conducted to facilitate the understanding in theories.

Learning outcomes (after completion of the course the student should be able to)

Regarding knowledge and understanding,
1. Discuss the challenges and opportunities in power system operation and control when transitioning to renewable-based power system;
2. Explain what ancillary services are and why they are needed for a stable operation and control of power system;
3. Discuss and reflect on factors that affect grid frequency and the current practice to handle frequency variation; 
4. Explain the measure for frequency quality and stability, and the provider and system dimension of frequency ancillary services; 
5. Discuss and reflect on factors that affect grid voltage and the current practice to handle voltage variation at different voltage levels;
6. Explain the physical meaning of reactive power and the relation between power flow and grid voltage;
7. Explain characteristics of transmission lines and cables, and functions of different power transformers;

Regarding skills in calculations and modelling
8. Simulate a power system by using models of swing equation, generators and loads for analysing frequency variation phenomena; 
9. Implement and evaluate the impact of different frequency control strategies;
10. Simulate a power system by using models of generators, long transmission line, power transformers and loads for analysing voltage variation phenomena and power losses;
11. Implement and evaluate different voltage control and reactive power compensation strategies;
12. Perform calculations in actual and per unit systems;
13. Verify the results from computer simulation and lab tests by using analytical calculations;
14. Analyse, explain and reflect on results from computer simulation and lab tests by using related theories;

Regarding soft skills and ethics
15. Collaborate and work in a team with different backgrounds in projects as well as for other occasions throughout the course.
16. Argue relevant sustainable and ethical aspects that need to be considered in the design and operation of electric power systems.


The course focuses on frequency and voltage ancillary services to the power grid and analyze phenomena that occurs within 15 minutes in the power system subject to a disturbance. The course consists of lectures, tutorials, computer-based projects, and laboratory-based projects. ‘1L’ corresponds to a 2×45 min lecture.

1. Transition to renewable-based power system [1L]
a. Mission, challenges and opportunities
b. Role of different grid actors and need of ancillary services
c. Course overview
2. Frequency ancillary service to handle uncertainty in power imbalance [5L]
a. Why frequency varies and why it matters?
b. Frequency quality and stability measure
c. Framework to handle frequency variation
d. The buyer of frequency reserves and its need
e. The providers of frequency reserves and controller implementation
i. Hydro and other synchronous generators
ii. Load
iii. Converter-interfaced renewable generation and energy storage systems

3. Voltage ancillary service to handle long-distance transmission of electricity [9L]
a. Why voltage varies and why it matters? [1L]
b. What affect grid voltage? [4L]
i. Voltage variation analysis methods: phasor diagram, two-port equations
ii. Model of power transformer: parameter estimation & per unit system
iii. Model of a long transmission line: distributed parameters and pi-model
iv. Heavy & light load: Surge impedance loading, Ferranti effect
v. Load voltage-dependence characteristics: ZIP load
vi. Grid strength: short circuit capacity
c. Network code on voltage control and reactive power exchange [1L]
d. Principle of and devices for voltage control and controller implementation [3L]
i. hydro and thermal generators with excitation control, PQ diagram
ii. tap-changing transformers
iii. Shunt capacitor banks and reactors
iv. FACTS devices
v. Converter-interfaced renewable generation and energy storage systems 

4. Other ancillary services [2L]
a. Loss Compensation
i. Losses and efficiency in power lines and power transformers
ii. Means to reduce losses
b. Congestion management: market solutions vs. technical solutions
c. Black start capability
d. Others 


This course includes scheduled lectures, tutorials, computer project and laboratory work. 


The following books are the main textbooks used throughout the course.

[1] Prabha Kundur, Power System Stability and Control, McGraw-Hill, Inc., 1993
[2] Hadi Saadat, Power System Analysis, 3rd Edition, PSA Publishing, 2010

The textbooks are available at Cremona ( at the Student Union. The textbooks contain essential materials for the course. It should, however, not be viewed as the only source of information needed to prepare for the examination. Additional materials will be provided during lectures and/or be made available on the course homepage.

Examination including compulsory elements

The examination is based on the final exam. The participation in all the laboratory activities are compulsory and simulation project needs to be approved onsite by the supervisors to pass the course. The final grade will be 5, 4, 3 and U (fail). 

The course examiner may assess individual students in other ways than what is stated above if there are special reasons for doing so, for example if a student has a decision from Chalmers on educational support due to disability.

Page manager Published: Mon 28 Nov 2016.