A robust distributed secondary voltage control method for islanded microgrids

Abstract

This paper proposes a robust distributed secondary control approach for voltage restoration of an islanded microgrid with inverter-based distributed generators (DGs). In the proposed approach, each DG only requires the knowledge of its own and immediate neighboring information and dispenses with the need of complex communication network. Unlike most of the existing methods relied on detailed and accurate mathematic models, the proposed approach adopts an active disturbance rejection control (ADRC) technique that only requires minimal model information and can sufficiently eliminate the model uncertainties as well as unknown disturbances. By means of dynamically linearizing compensation, the proposed robust distributed secondary voltage controller can be built on a quasi-linear model with proportional feedback control design. Another novel idea in this paper is that it can estimate the state of voltage derivative through an extended state observer (ESO), which obviates the requirement of a differentiator which is hard to be physically realized. The control law design and parameter selection of the proposed ADRC-based distributed secondary voltage controller are discussed considering the closed-loop stability constraint for the composite system. The robust performance of the proposed control approach is verified based on a 4 DGs-based islanded microgrid test system. Results show that the proposed control approach is entitled with high robustness against both constant disturbance and time-varying disturbance.