Phd Defence by Meng Chen


20.12.2021 kl. 13.00 - 16.00


Meng Chen, AAU Energy, will defend the thesis "Modeling and Control of Solid-State Synchronous Generator"


Modeling and Control of Solid-State Synchronous Generator


Meng Chen


Professor Frede Blaabjerg


Associate Professor Dao Zhou


Professor Huai Wang


Professor Birgitte Bak-Jensen, Aalborg University, Denmark (Chairman)
Associate Professor Jon Are Wold Suul, Norwegian University of Science and Technology
Professor George Weiss, Tel Aviv University


Solid-state synchronous generator (SSSG), namely virtual synchronous generator (VSG), is a promising way to integrate inverter-interfaced generators (IIGs) into the power system. Nevertheless, differences in modeling, control, and application between the SSSG and synchronous generator (SG) pose new challenging issues for the stable operation of the power system with SSSGs.
Firstly, various models used for an SSSG to emulate an SG inevitably lead to different characteristics of the power system. Meanwhile, the structure of the power system itself is becoming more distributed and may not be strong as usual. The existing analysis of an SG such as based on a single-machine-infinite-bus (SMIB) system can not provide a comprehensive evaluation on the SSSG. Thus, further detailed characteristics analysis of the SSSG is necessary.
Secondly, a power-electronic-based SSSG provides the possibility of adding more favorable features, which an SG does not internally have in order to provide a superior and robust performance by advanced control algorithm. Meanwhile, in order to optimize the performance of the SSSG, the coupling among several control loops should also be taken care of. Therefore, the advanced control is of importance to fully take advantages of the power-electronic-based SSSG.
To cope with the aforementioned issues, this Ph.D. project investigates the characteristics analysis and advanced control of the SSSG. Specifically, various modelings of SSSG are compared with each other and also with the SG. Further, the impact of the SSSG on the electromechanical oscillation is studied in details by using a small-signal and participation factor analysis. How the SSSG changes the electromechanical modes of the power system by influencing the significant states is revealed.
Afterwards, an equivalent coefficient model for a non-stiff grid is proposed in this project. With the derived equivalent coefficients, the relationship between the dynamic characteristics of the SSSG and the main parameters are revealed. Furthermore, by using the proposed equivalent coefficient model, the conditions to achieve dynamic active power sharing are discussed and an inertia control strategy to take care both of the local load disturbance and the set-point variation are proposed, respectively.
The stability analysis and control of the SSSG are also addressed in this thesis. On one hand, to cope with the active power oscillation of the basic SSSG, a damping control strategy is proposed based on the acceleration control. The root locus-based small-signal stability is guaranteed by proper parameters design. On the other hand, the transient of the SSSG internal voltage is investigated quantitatively, which reveals how the internal voltage deteriorates the transient angle stability of the traditional SSSG. Then, an enhanced SSSG is proposed with better a transient angle stability. 
Further, the coupling of different control loops is considered in this thesis, too. Unlike seeing the DC source as ideal and power loops being independent, a multivariable feedback control structure is proposed. All of the control targets of both DC and AC sides are taken care of simultaneously, which enables the SSSG to have superior and robust performance. An H-infinity optimization is used to tune all the parameters of the controller simultaneously.
The findings of this Ph.D. project enables a better integration of the SSSGs in the power system.


THE DEFENCE will be IN ENGLISH - all are welcome.




AAU Energy


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