Frequency control in isolated island by using parallel operated battery systems applying H∞ control theory based on droop characteristics

Stand-alone ac power supply system such as isolated islands is subject to large frequency and voltage fluctuations caused by power deviations of wind turbine generator and load demand. The autonomous decentralised frequency control system of parallel operated decentralised generators based on droop characteristic is presented in this study. The conventional droop control methods proposed in past researches show slow and oscillating dynamic responses. Moreover, the conventional droop control is affected by measurement noise when the fast controllability of the system is emphasised. This study proposes the improved droop control system for load sharing of multi-operated decentralised generators by applying H_∞ control theory, improving transient response of droop control and robustness against measurement noise and parameter variations. Simulation results validate the effectiveness of the proposed control system.