Cognitive Control and Operation Management of Islanded Microgrids

With the extensive use of distributed power supply, microgrids have gradually become one of the hot research topics. In islanded microgrid, both reactive power and active power required by load are provided by distributed generators, needs to accurately distribute power according to its own capacity. If the power cannot be accurately distributed and voltage, frequency deviation occurs, the stability and power quality of the system will be seriously affected. In order to solve the problem of distribution of power, frequency and voltage, this paper proposes a distributed hierarchical control strategy based on improved multi-agent system.
First, the inconsistency of line impedance of distributed generator in the islanded microgrid is an important factor affecting the stability of islanded microgrid. The use of traditional droop control cannot realize the reactive power sharing accurately, which leads to the problem of reactive power decoupling. To solve this problem, a new adaptive virtual impedance is proposed to be added to traditional droop control to realize precise reactive power distribution. Secondly, in islanded microgrid with multiple inverters in parallel, distributed power supply such as solar energy and wind energy will cause power fluctuation due to external environmental factors, resulting in unbalanced load distribution. That will lead to voltage and frequency deviating from rated value in steady state. In order to eliminate voltage, frequency deviation and precise power sharing, a distributed secondary compensation control based on improved multi-agent is used to the control system to enhance the stability of the system and achieve the global optimal operation of the microgrid. Thirdly, the problem of heavy communication burden exists in distributed secondary control of islanded microgrid based on periodic communication. On the basis of improving multi-agent secondary compensation system, a new communication strategy is proposed to solve various problems in actual situation, reduce communication burden. Make reasonable use of limited communication resources while ensuring the accuracy of distributed frequency and voltage control. Finally, an experimental platform is built to verify the effectiveness of the proposed strategies.