Hormonics Compensation in an Islanded Ac Microgrid by an Enhanced Power Sharing Scheme

Abstract

In this paper, proposes Power sharing problems are associated with DG reactive power, imbalance power and harmonic power. To address unequal power sharing problems an enhanced hierarchical control structure with multiple current loop damping schemes for voltage unbalance and harmonics compensation (UHC) in ac islanded microgrid is proposed. An enhanced droop control method through online virtual impedance adjustment is used to solve power sharing problems. With the regulation of DG virtual impedance at fundamental positive sequence, fundamental negative sequence, and harmonic frequencies, an accurate power sharing can be realized at the steady state.. By using the proposed unbalance and harmonics compensation, the auxiliary control, and the virtual positive/negative-sequence impedance loops at fundamental frequency, and the virtual variable harmonic impedance loop at harmonic frequencies, an accurate power sharing is achieved. Moreover, the low bandwidth communication (LBC) technique is adopted to send the compensation command of the secondary control and auxiliary control from the microgrid control center to the local controllers of DG unit. By using the simulation results we can analyze the proposed method.