Three level Neutral -Point-Clampered-Converters- State-of-the-art- and Recent Advances in Control Solutions and Reliabilty (2025)
Doctoral School of Engineering and Science at Aalborg University
Welcome to Three-Level Neutral-Point-Clamped Converters: State-of-the-art and Recent Advances in Control Solutions and Reliability (2025)
Description: The three-level neutral-point-clamped (3L-NPC) converters have been widely applied in several applications including motor drives and grid integration such as wind and solar energy systems. Key performance metrics of the 3L-NPC converters like power quality, efficiency, power density and reliability are strongly affected by the used control methods. Therefore, different control methods have been proposed for the 3L-NPC topology to address certain aspects.
This course aims to address basic concepts and control design challenges of NPC converter applications. It will start with basic operating principles of the topology and their control challenges such as neutral point voltage balancing and thermal stress distribution. Then, two different control approaches will be presented: 1) carrier-based PWM techniques and 2) model predictive control techniques. For each control technique, basic concept and step-by-step implementation guideline will be provided, followed by more application-oriented examples and implementation challenges.
An approach to analyze the reliability of power electronics converters will also be introduced, which includes thermal stress modeling, lifetime prediction, and reliability evaluation (Monte Carlo simulation). It will be demonstrated that control algorithm selection has a major impact on the reliability of semiconductor devices and DC-link capacitors in NPC converters. In the last part of the course the focus will be set on practical application cases of NPC converters in the industry.
The course is intended both for academia researchers and industry, who do not have previous knowledge about the NPC topology (basic operating principles will be explained), and for those who are familiar with the topology and would like to learn more about ongoing research directions and novel control solutions.
Key words: Control algorithm, lifetime, multilevel converters, neutral point clamped, modulation, model predictive control, reliability
Prerequisites:
- Fundamentals of power electronics
- Experience with MATLAB/Simulink is recommended for the exercises
Learning objectives:
- Understand fundamentals of 3L-NPC and required control objectives (neutral point voltage balance, thermal stress distribution)
- Implement the basic carrier-based control methods for 3L-NPC
- Implement the model predictive control methods for 3L-NPC
- Understand how control selection affects the reliability of components in the 3L-NPC
- Practical design considerations for NPC converters
Teaching methods: Lectures, Excercise, Presentations
Form of evaluation: Students are required to solve exercises using the knowledge acquired in the course and submit a short project report with solutions within three weeks after the course, which will be assessed by the lecturers.
Criteria for assessment: Completed exercises (2) submitted as a short report
Remarks: In total about 46 hours (Preparation: 12 hours, Lecture: 16 hours, Exercise and final report: 18 hours)
Key literature: TBA
Organizer: Frede Blaabjerg, fbl@energy.aau.dk
Lecturers:
Assistant Prof. Ariya Sangwongwanich
Assistant Prof. Mateja Novak
External lecturers: Radu Dan Lazar, Reserach Engineer, Danfoss Drives
ECTS: 2.0
Time: 25 and 26 September 2025
Place: Aalborg University, AAU Energy (Room: TBA)
Zip code: 9220
City: Aalborg
Maximal number of participants: 20
Deadline: 4 September 2025