On the interaction between the Power System Stabilizer and the limiters

This paper discusses the importance of the contribution of the Power System Stabilizer (PSS) when the excitation control is changing its operation mode due to limitations of the generator capability. The present industry practice adopts several approaches to introduce the PSS signal into the control loop. This paper presents qualitative analysis of the different commonly used excitation control structures and highlights the critical points inherent in these structures. Furthermore the paper highlights critical network conditions under which the PSS may violate limiting criteria and drive the generator into critical operation conditions, which in the worst case may even trigger events of the generator protection equipment.