Zhang Qinjin, Liu Yancheng, Zhao Youtao, Wang Ning
Marine Engineering College, Dalian Maritime University, Dalian 116026, People's Republic of China.
ISA Trans. 2016 Mar;61:188-198. doi: 10.1016/j.isatra.2015.11.027. Epub 2015 Dec 11.
Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results.
多模式运行和暂态稳定性是严重影响柔性微电网（MG）的两个问题。本文提出了一种基于三层分层结构的柔性微电网多模式运行控制策略。所提出的结构由自主控制器、协同控制器和调度控制器组成。自主控制器用于控制单个微源逆变器的性能。分别提出了一种自适应滑模直接电压环和一种基于虚拟负阻抗的改进下垂功率环，以提高系统的抗干扰性能和功率分配精度。协同控制器由二次电压/频率控制和相位同步控制组成，旨在消除自主控制器产生的电压/频率偏差并为并网做准备。调度控制器管理微电网与电网之间的功率流。具有改进分层控制方案的微电网能够实现从孤岛模式到并网模式的无缝切换，并具有良好的暂态性能。此外，所提出的工作还可以优化电能质量问题并提高并联电压源逆变器（VSI）之间的负载功率分配精度。最后，通过理论分析和仿真结果对所提出控制方案的暂态性能和有效性进行了评估。
