# Power System Stabilizers for The Synchronous Generator

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The electromechanical oscillations damping through the synchronous generator is analyzed in this work. Traditionally, this has been achieved using a conventional Power System Stabilizer PSS controller, which has the aim of enhancing the dynamic stability of the generator through the excitation control system, therefore a PSS tuning methodology is developed and tested. Moreover, other damping control alternative for the synchronous generator based on signal estimation theory is proposed in this thesis. Initially, a detailed modelling of the Synchronous Machine Infinite Bus SM-IB system has been accomplished in order to study the electromechanical interaction between a single generator and the power system. The SM-IB system model is the base to analyze and to tune the PSS controller. It was concluded that it is not necessary to include the damper windings dynamics in the system phase lag analysis since, in the PSS frequency range of interest, the biggest phase lag difference including them was about 10◦. This difference could be considered not sufficient to include the sub-transient model in the PSS tuning analysis. Therefore, the linearized transient model of the system is a suitable model for the tuning process. Secondly, the main concepts for a PSS tuning methodology, which is based on linear control system theory, are established. Specifically, frequency response techniques are used to define the setting for the lead lag filters time constants and PSS gain. This is supported on the fact that the predominant trend in the industry is still to use frequency response based tuning methods [12], even more in the case of PSS providers who should tune the controller having detailed information about the generator but not exact details about the connecting grid. The methodology is implemented as a software tool in Matlab/Simulink R2011b using the mathematical model of the excitation system provided by the company VG Power AB and giving the option to chose between static and rotating type of exciters; it is also designed considering the rotor speed change as input signal to the PSS. The performance of the PSS with the achieved tuning is validated via simulations in the complete SM-IB system model. Furthermore, a sensitivity analysis of the local oscillation mode damping to changes in the system operating point is carried out verifying the robustness of the tuning process. In all analyzed cases, the minimum damping of the local mode was never less than 10%. Finally, the application of a Phasor Power Oscillation Damping POD controller to the excitation control system in the synchronous generator is studied. Nowadays, POD for inter-area oscillation modes in power systems is also achieved through FACTS. Control structures using low-pass filter based and recursive least square based estimation methods to extract the oscillatory component of a signal has been successfully applied to control FACTS [3], [17] and [5] achieving damping. The same idea is used in this work to define an alternative controller for the generator which is based on a low-pass filter based signal estimation algorithm. The analysis is done again using the SM-IB system. The obtained results indicate that the alternative controller is able to damp successfully the local oscillation mode that appear after applying a disturbance to the system. However, deeper studies are needed in order to be able to compare fairly the performance of the PSS and the Phasor POD controller when they are applied to the synchronous generator. Additionally, the proposed control approach should be test in a power system model of higher order. These are recommended topics for future work.

**Nyckelord: **Synchronous Generator, PSS Tuning, Signal Estimation, Phasor POD Controller.

Publikationen registrerades 2013-09-20. Den ändrades senast 2013-09-20

CPL ID: 183724

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