Nowadays, a wind turbine generator (WTG) is required to provide control capabilities regarding an output power. Under this scenario, this paper presents a frequency control method by coordination control of the WTG and a battery using load estimation by a disturbance observer for isolated island. The load variation is reduced by the WTG using pitch angle control in low frequency domain and the battery charge/discharge in high frequency domain. The output command for the battery is determined

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... ording to the battery energy storage ratio, the high frequency component of the frequency deviation and the load variation. By using the proposed method, the rated capacity of the battery can be reduced by reducing charge/discharge in long-term. Besides, generalized predictive control (GPC) is applied in the pitch angle control system of the WTG to obtain good response and robustness. Simulation results demonstrate the validity of the proposed method.