System Identification Based Grid Agnostic Adaptive Droop Control Strategy

The conventional droop control schemes have been developed assuming predominantly inductive power lines, however, at the distribution level the feeder impedance comprises both inductive and resistive components, leading to the problem of power coupling. Large magnitude droop coefficients contribute to the improved reactive power sharing but cause lightly damped modes in the system, leading to decreased small stability margins. In this paper, an adaptive droop strategy is proposed where the droop coefficients are updated with the goal of improving reactive power sharing while ensuring small signal stability margins. The proposed control strategy perturbs the reactive power droop coefficient and estimates the system damping coefficient from the subsequent inverter response. The reactive power droop coefficient is updated until the inverter response exhibits critically damped behavior. Proposed damping-coefficient based adaptive droop control brings two main advantages: (i) the system agnostic approach regardless of the grid impedance composition, (ii)improved reactive power sharing while ensuring power certain small signal stability margins.