Two-level prediction-based reactive power coordination and voltage restoration strategy for microgrid

Voltage control is a fundamental requirement to ensure secure operation of microgrid, especially for islanded microgrid. This paper proposes a two-level reactive power coordination and voltage restoration strategy for microgird using model predictive control (MPC) approach. In supervisory level, reactive power set-point of each participating distributed generation source (DER) is calculated and distributed through communication link, while a droop based controller is utilized to control each participating DER to follow the reactive power set-point in primary level. One of the advantages of the proposed controller is that it takes system dynamic model into consideration to predict the possible voltage trajectory, the other is that the controller has the capability to calculate reactive power mismatch so as to coordinate each DER to provide reactive power compensation for voltage regulation. Simulation results show that the proposed controller is stable and effective to restore voltage to nominal after disturbances. Moreover, it can keep a smoother voltage profile in the presence of output variations of renewable sources.