Nonlinear Synergetic Governor Controllers for Steam Turbine Generators to Enhance Power System Stability

Abstract

This paper proposes a decentralized nonlinear synergetic governor controller (NSGC) for turbine generators to enhance power system stability by using synergetic control theory and the feedback linearization technique. The precise feedback linearization model of a turbine-generator with a steam valve control is obtained, at first, by using a feedback linearization technique. Then based on this model, a manifold is defined as a linear combination of the deviation of the rotor angle, speed deviation, and speed derivative. The control law of the proposed NSGC is deduced and the stability condition of the whole closed-loop system is subsequently analyzed. According to the requirement of the primary frequency regulation, an additional proportional integral (PI) controller is designed to dynamically track the steady-state value of the rotor angle. Case studies are undertaken based on a single-machine infinite-bus system and the New England system, respectively. Simulation results show that the proposed NSGC can suppress the power oscillations and improve transient stability more effectively in comparison with the conventional proportional-integral-derivative (PID) governor controller. Moreover, the proposed NSGC is robust to the variations of the system operating conditions.

Keywords

• turbine-generator
• governor controller
• steam-valve control
• feedback linearization
• synergetic control
• manifold