基于改进分级下垂控制的微电网运行研究

Research on Microgrid Operation Modes Based on Improved Hierarchical Droop Control

在使用传统下垂控制的微电网运行中,联网模式下无功功率无法跟踪至参考值,并且在不同运行模式切换时电压和频率出现强烈波动。针对这一问题,研究了一种改进的分级下垂控制。首先,分析了添加虚拟阻抗之后,逆变器等效输出阻抗由阻感性耦合变为接近纯感性的变化;其次,改进了联网模式下感性下垂控制中的无功算法,并与旋转坐标系的预同步策略相配合,将传统的三级控制简化至两级;最后,通过仿真验证了这种控制方式有良好的功率跟踪效果,并可以实现交流微电网运行状态的平滑切换。

In microgrid operation using conventional droop control,the reactive power cannot be tracked to the reference value in the connected mode,and there are strong fluctuations in voltage and frequency when switching between different operation modes.To address this problem,an improved hierarchical droop control is investigated in this paper.Firstly,it is analyzed that the inverter equivalent output impedance changes from resistive-inductive coupling to close to pure inductive after adding virtual impedance.Secondly,the reactive power algorithm in inductive droop control in the connected mode is improved and coupled with the pre-synchronization strategy of rotating coordinate system to simplify the traditional three-stage control to two stages.Finally,it is verified through simulation that this control method has good power tracking effect and can realize smooth switching of AC microgrid operation state.