Communication-less Control Strategy of Adaptive Harmonic Sharing and Power Quality Control Under Various Working Conditions in Islanded Microgrid

In islanded microgrid, nonlinear loads lead to harmonic sharing and power quality issues, which make designing a proper control strategy considering both two aspects significant. Impedance-reshaping-based methods are intuitive and effective solutions, where the inherent tradeoff between power quality and harmonic sharing accuracy must be designed properly. The most of existing methods share harmonic power according to the rated power of converters, lacking the full use of residual capacity. Besides, the fixed tradeoff results in the limited power quality improvement. Faced with these issues, an adaptive communication-less control strategy under different working conditions is proposed in this paper. A nonlinear droop scheme, between virtual impedance and residual capacity, is proposed to dynamically adjust the inherent tradeoff under different working conditions. The proposed strategy can render an optimal utilization of the converter capacity and optimize the power quality to the greatest extent while avoiding overload. In addition, the communication line is not needed, leading to high flexibility. The experimental results based on three converters have verified the feasibility and effectiveness of the proposed method.