Optimal Control Strategy for DC Microgrid Scheduling

On the premise of stable DC bus voltage, in order to solve the problem that the output of DC microgrid fluctuates greatly and it is difficult to schedule, a new optimal control strategy for DC microgrid scheduling is proposed. Taking the minimum root-mean-square error between external active output and planned active output of DC microgrid and the minimum root-mean-square error of DC bus voltage deviation as the optimization objective function, and considering the constraints of state of charge of energy storage battery and DC bus voltage deviation, an optimization model of DC microgrid scheduling is established. Firstly, the structure of DC microgrid is analyzed, and the mathematical model of power electronic equipment whose main structural modules are incorporated into DC bus is established. Secondly, the maximum output power of photovoltaic cells is calculated by disturbance observation method, and the photovoltaic output control strategy is determined. Based on the planned output curve issued by the main grid, the charging and discharging current of the energy storage battery is controlled by using the active power output from the microgrid. Then the traditional control strategy of energy storage system is improved, and the traditional voltage outer loop is changed into active power loop, and the traditional PQ control mode of DC/AC inverter is optimized, and the traditional active power and reactive power loop is changed into DC bus voltage and reactive power loop. Finally, based on MATLAB/simulink simulation platform, the simulation system of DC microgrid is established with 24 hours as the scheduling cycle. The simulation results show that the proposed control strategy is effective.