Damping Torque Through Mechanical Torque Control From Secondary Power System Stabilizer Lau, Andy Yu Ho
This paper presents an alternative method to add damping torque to synchronous generators (e.g. hydro generators) through a secondary power system stabilizer (PSS). Traditionally, a single PSS is used to add damping torque through controlling the field excitation system to change the electrical torque. When the PSS provides a sufficient amount of compensation to produce an electrical torque in phase with speed deviation, rotor oscillations will damp. There are two factors of speed deviation—electrical torque and mechanical torque. The traditional (primary) PSS acts on the electrical torque. In this paper, an alternative (secondary) PSS is designed to act on the mechanical torque. A power system study is conducted to evaluate the independent and combined use of the two PSS’s after introducing a disturbance. The results from comparing the independent use of the primary and secondary PSS show an improved damping of rotor oscillations compared to a system without any PSS. When operating two PSS’s in parallel (i.e. both primary and secondary PSS enabled), the damping of rotor oscillations are further reduced. However, with the parallel use of PSS’s, the speed deviation took longer before reaching a steady state compared to solely using the primary PSS.
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