Bus Voltage Control for DC Micro-grid Hybrid Energy Storage System Based on NDO

Aiming at the problem of bus voltage fluctuation caused by intermittent output of distributed generation and load mutation when DC Micro-grid is operating in isolated island, a hybrid energy storage system composed of power battery and energy battery is designed to give full play to the advantages of both. And the disturbance current feedforward control is designed in its control strategy to speed up the suppression of DC bus voltage fluctuation. In this paper, the vector sum of the equivalent load current and the output current of the energy type battery is taken as the equivalent disturbance current of the power battery, and a nonlinear disturbance observer (NDO) is designed to observe it, then feedforward control is used to eliminate the influence of equivalent disturbance current on bus voltage and suppress the fluctuation of DC bus voltage. Finally, the effectiveness of the method is verified by simulation.