Design of sliding-mode controller via model reduction for automatic generation control of micro hydropower plants: Isolated-mode case

Compared with large hydro power plants, micro hydropower plants are emerging as a major renewable energy resource because they do not encounter the problems of population displacement and environmental problems. Micro hydropower plants are conducted in two different configurations. One is isolated mode and the other is grid-connected mode. Under any mode, controller plays a vital role for automatic generation control (AGC) of micro hydropower plants. Especially, frequency and load are regulated entirely by the controller under the isolated mode. But the controller design becomes challenging because the number of measurable state variables is usually less than the number of system state variables. This paper addresses a sliding-mode controller for the AGC problem of micro hydropower plants under the isolated mode. After modeling the AGC system, a reduced-order model is obtained from the initial model via the method of model reduction. Then, the sliding-mode controller is designed on basis of the reduced-order model, and is applied to the initial model for simulations. The simulation results illustrate the feasibility and robustness of the sliding-mode controller under the isolated mode for the AGC problem of micro hydropower plants.