Stability Control Strategy for DC Micro-grid Considering Constant Power Load

The electric load integrated in DC micro-grid is typically with the property of constant power which demonstrates negative resistor characteristics and can be a challenge for DC micro-grid stability control. Based on a large capacity DC micro-grid with variety of sources and loads and converters, the presented paper established an equivalent circuit model of the DC micro-grid system with droop control and discussed the stability issues of the system. Considering the nonlinearity of the system, this paper firstly determined the stability of the system equilibrium points. Secondly, the influence of constant power load and system parameters on the stability of the system was analyzed, and the load carrying capacity of the system under different system parameters was quantified and verified by simulation. Finally, according to the results of the stabilization mechanism analysis, the selection of control system parameters in the planning and design is discussed, and the stability control strategy of DC micro-grid was proposed from the system level combining with the hierarchical control of micro-grid, and the simulation and experimental verification were carried out.