Robust Control of an Electric Generator with Guaranteed Rotor Speed Confinement within Specified Limits

The article addresses the problem of control of an electric generator connected to the power grid while ensuring that the rotor speed remains within predefined limits set by the designer. Two methods are employed to solve this problem. The first method is based on disturbance compensation and allows for the identification and compensation of parametric uncertainty and disturbances in the power grid. Parametric uncertainty may arise due to unknown generator parameters and characteristics of network elements (such as transmission line resistance, transformer parameters, etc.). Disturbances are associated with sudden changes in network resistance due to load variations (e.g., connection or disconnection of generators, daily industrial operations, etc.) or short circuits in transmission lines. It is shown that the disturbance compensation method guarantees that the generator’s frequency remains within the specified range only in the steady-state mode, whereas in the transient mode, overshoot can be arbitrary. Excessive overshoot may lead to emergency situations where the rotor speed exceeds the regulatory limits set for the network. Additionally, if the overshoot is too high, the safety system may disconnect a working section of the power grid before the transient process in the control system is completed. To address this issue, an additional method of nonlinear coordinate transformation is used, which converts the constrained control problem into an unconstrained one. Subsequently, a control law in the new coordinates is proposed based on the disturbance compensation method. The inverse coordinate transformation ensures that the control goal is achieved. Simulation results confirm the theoretical findings.