A Novel Decentralized Control Scheme for Enhanced Nonlinear Load Sharing and Power Quality in Islanded Microgrids

摘要

The sharing of nonlinear loads among different distributed generation units (DGs) is always a tradeoff between accuracy and voltage quality. This paper proposes a virtual harmonic conductance for each harmonic as a family of droop characteristics in terms of conductance versus current. Assigning a variable conductance for each harmonic current improves the DG controllability, thus offering accurate nonlinear load sharing, which is crucial at the near-rated loading and enhanced voltage quality. This paper also unveils a tuning methodology for the droop characteristics that sets a maximum permissible value for each individual harmonic to comply with international standards. Lastly, a hybrid voltage and current control system is suggested to accurately track the DG harmonic conductance designated by the proposed droop characteristics. While the proposed algorithm is capable of accurately distributing common nonlinear loads among DGs, it also enjoys the advantage of supplying local nonlinear loads by their dedicated DGs. A comprehensive performance evaluation assures the effectiveness of the proposed control strategy.