Vector control of voltage-source-converter (VSC)-fed ac motor drives has been an intense area for research ever since the 1970s. VSC-fed drives are today commonplace, in industrial applications as well as in rail and highway vehicles. Since almost 20 years, VSCs have been used for high-voltage dc (HVDC) transmission and flexible ac transmission system (FACTS) devices. Today, renewables – mainly wind and solar – are rapidly growing applications for VSCs. During the last five years, the modular multilevel converter (MMC) has become the topology of choice for HVDC transmission, due to its low losses. The aim of this course is to cover most aspects of importance in control of VSCs connected to the grid as well as powering ac motors.
Information for research students about course offerings
The course is given when there is sufficient demand. Please contact the examiner if you are interested in taking the course.
Content and learning outcomes
Methods for design and analysis of control algorithms applied to grid-connected converters and electric drives:
· Quick review of the dc motor and its control; current, speed, field weakening
· Review of theory for linear systems: transfer functions and state-space models
· Three-phase circuits, space-vector theory, and per-unit systems
· Two-level VSCs and their pulsewidth modulation
· Fundamentals of nonlinear systems theory
· Current control of VSCs: fundamental, negative sequence, harmonics; antiwindup
· Synchronization of VSCs: the phase-locked loop
· Active- and reactive-power control of VSCs
· DC-bus-voltage control of VSCs
· Power-synchronization control of MMCs
· Fault ride through of MMCs
· Modeling and internal control of the MMC
· Dynamic model of the induction motor
· VSC-fed drives: similarities and differences to grid-connected VSCs
· Induction motors: principles of direct and indirect field orientation, equivalence
· Induction motors: the current and voltage model for flux estimation
· Induction motors: sensorless control principles
· Field-weakening operation
· Direct torque control
· Permanent-magnet motors: dynamic modeling
· Permanent-magnet motors: current control, speed control and field-weakening operation
· Permanent-magnet motors: low-, medium- and high-speed sensorless control
· Permanent-magnet motors: signal injection, polarity detection, startup, and synchronization
Intended learning outcomes
After completion of the course the student shall be able to:
· Design robust current controllers for induction motors, permanent-magnet motors, and grid-connected VSCs
· Explain the operation and internal control of MMCs
· Explain similarities and differences between grid-connected VSCs and VSC-fed drives
· Explain the principles and equivalences of direct and indirect field orientation of induction motors
· Explain and simulate sensorless closed-loop induction and permanent-magnet motor control systems
· Explain the basic operation of variable-reluctance type resolvers
Literature and preparations
PhD students at KTH, PhD students from other universities
The course is intended for PhD students at KTH and from other universities.
Examination and completion
If the course is discontinued, students may request to be examined during the following two academic years.
- EXA1 - Examination, 5.0 credits, grading scale: P, F
Based on recommendation from KTH’s coordinator for disabilities, the examiner will decide how to adapt an examination for students with documented disability.
The examiner may apply another examination format when re-examining individual students.
Since the key parts of the course comprises of the description of a number of control methods, there is no written examination and the examination consists of a project work where the student demonstrates that he/she has obtained the necessary knowledge to be able to implement the methods in practice. The project work consists of a number of simulation tasks in where central parts of the material presented at the lectures will be implemented and evaluated. The results shall then be compiled into a written project report clearly showing how the models have been implemented together with comments on the obtained results. The project work and the associated project report should be carried out individually.
Other requirements for final grade
An approved project work. A project report is deemed approved (by the course examiner) if all tasks have been solved and given a clear account for.
Opportunity to complete the requirements via supplementary examination
Opportunity to raise an approved grade via renewed examination
- All members of a group are responsible for the group's work.
- In any assessment, every student shall honestly disclose any help received and sources used.
- In an oral assessment, every student shall be able to present and answer questions about the entire assignment and solution.
Further information about the course can be found on the Course web at the link below. Information on the Course web will later be moved to this site.Course web FEJ3230