Open AccessA Small-AC-Signal Injection-Based Decentralized Secondary Frequency Control for Droop-Controlled Islanded Microgrids
Author(s) -
Baojin Liu,
Teng Wu,
Zeng Liu,
Jinjun Liu
Publication year - 2020
Publication title -
ieee transactions on power electronics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.159
H-Index - 266
eISSN - 1941-0107
pISSN - 0885-8993
DOI - 10.1109/tpel.2020.2983878
Subject(s) - power, energy and industry applications , aerospace , communication, networking and broadcast technologies , components, circuits, devices and systems , computing and processing , engineered materials, dielectrics and plasmas , fields, waves and electromagnetics , general topics for engineers , nuclear engineering , signal processing and analysis , transportation
In an islanded microgrid composed of droop-controlled parallel inverters, the system frequency endures deviations as the load changes. To compensate for frequency deviation without involving communication infrastructures among distributed generators (DGs), the proportional-integral regulator based secondary frequency control (PI-SFC) method has been proposed in the literature. However, PI-SFC may incur real power-sharing errors because the integrator accumulates disturbances and noise in each DG, leading to different compensation values of nominal real power. To achieve frequency restoration while maintaining equal real power sharing among DGs, this article proposes a small-ac-signal injection-based secondary frequency control (SACS-SFC) method, which is implemented by injecting an additional ac signal into the output voltage of each DG. Furthermore, a droop relation between the frequency of the injected SACS and the compensation value of nominal real power is innovatively established to trim the output real power of each DG to be equal. Frequency deviations caused by primary droop control are thus eliminated, and even real power sharing can be maintained among DGs. Moreover, the control parameters of the proposed SACS-SFC are comprehensively designed via steady state and dynamic model of the system. Simulation and experimental results demonstrate the effectiveness of the proposed method.