Region of Attraction Estimation for Island DC Microgrid with Large Shifting Load: The Mixed Potential Theory Approach

In this paper, the region of attraction (ROA) for microgrid is investigated. Microgrid is usually composed of renewable generation unit (RGU) and energy storage unit. Thus, the energy quality of island microgrid is arduous to regulate since the power generation of RGU is stochastic. Meanwhile, The widespread constant power load (CPL) may easily cause instability, especially in the case of large load shifting and bus voltage fluctuation. These issues force the system state to deviate from the equilibrium point (EP). To this end, we first introduce the concept of ROA from the perspective of transient disturbance and constant disturbance in microgrid. Then the ROA of the specific operating point of microgrid is estimated by mixed potential theory (MPT). The estimated ROA delimitates the maximum deviation that system can tolerate, which provides a guideline for microgrid design and operation control. Simulations and experiments illustrate the effectiveness of the theoretical results.