Secondary Reactive Power Balancing and Voltage Stability in Microgrid Using Prioritized Centralized Controller

In today’s world, where the grid structure becomes smarter day by day, microgrid, one of the fundamental methods for the integration of renewable energy, are taking firm steps to be building blocks of the modern electrical grid. Along with its advantages, the microgrid brings extra challenges which attracts the attention of many researchers in these days. This paper focuses on addressing two of the main challenges: voltage stability and reactive power sharing in islanded mode. Contents of this paper include: first, elaboration of general hierarchical control structures of inverter-based distributed generators (DGs), second, review of primary droop control methods and analysis of their drawbacks, third, review and comparison of current secondary reactive power control methods to find the gap of more practical secondary control method. In the paper, a centralized secondary controller based on intermittence level, effective-impedance to load and severity of voltage deviation is proposed to overcome the disadvantage of current secondary reactive power control methods. The proposed method takes practical aspects into consideration and prioritizes DGs in reactive power balancing and voltage stability. Performance of proposed method is illustrated by a simulation study.