Enhancing Flexibility of an Islanded Microgrid With Electric Springs

An electric spring (ES) is effective in enhancing the operational flexibility and facilitating renewable energy integration. An ES can determine the operation status of the connected noncritical loads (NCLs) by adjusting its output voltage. It is possible to use NCLs as operation resources for renewable integration. In this paper, a model predictive control (MPC)-based strategy is proposed to dispatch ESs with a water heating system (WHS) used as an NCL in an islanded microgrid to accommodate fluctuating renewables. Critical loads (CLs) in the microgrid can also benefit from ESs by obtaining a reliable supply voltage with smaller deviations than other loads. The CL is modeled using a ZIP static load model, which is commonly used to represent loads of a power system. The temperature constraint of the WHS and the ramping constraint of a diesel generator are considered and can be effectively managed by the proposed MPC strategy. Finally, the capabilities of NCLs with ESs to enhance operational flexibility are studied through sensitivity analyses with different ramping abilities of the microgrid.