Stability analysis and optimal control strategy of DC microgrids

DC microgrid is an important part of the new power system. However, DC microgrids are prone to a wide range of fluctuations in bus voltage when subjected to external disturbances, which affects the stability of their own operation. This paper proposes the control strategy of photovoltaic unit and energy storage unit in two modes, and on this basis, adopts large-signal stability analysis method to design the filtering link of the constant power load loop, and adds damping filter circuit in the filtering link of the constant power load loop in order to inhibit the generation of resonance spikes, which ensures the stability of the dc microgrid in the presence of large disturbances. The equivalent power weight method is used to estimate the lifetime of the energy storage battery. Taking the maximum daily net gain, the minimum battery equivalent charge/discharge and the minimum carbon dioxide emission as the objective functions, the optimal Pareto solution set is initially obtained by the multi-objective gray wolf algorithm, and then the optimal solution is obtained by using the TOPSIS algorithm. The design of related experiments proves that the stability of DC microgrid can be improved by increasing the capacitance value and decreasing the inductance value. Under the optimal control strategy of this paper, the maximum fluctuation amplitude in most of the fluctuation phases is only 1.5%, which shows that the optimization strategy of this paper achieves the effective suppression of bus voltage dips and optimizes the control capability of DC bus stability.