چكيده به لاتين
Increase in contribution of distributed generation units in electric power systems has a significant influence in utilization of distribution systems that increaseingly encounters to voltage and frequency stability problems. As a result, it requires a coordinated approach to integrate units in the network that allows distributed generation units to cooperate in voltage and frequency regulation. Microgrids can provide this coordination by gathering distributed generation units, loads and storage devices in small scale networks which operate in islanded mode and grid connected mode. In this study, the islanded operation is considered.
Microgrid control usually includes three control levels named as hierarchical control. In this study, primary and secondary control levels of hierarchical control structure have been evaluated. Conventional droop control is one of the most common methods in primary control level which regulates voltage and shares active power well with out the need for any communication links. However, it can not control the voltage regulation and reactive power sharing well. This approach causes deviations in microgrid voltage and frequency due to load change. As a result, the secondary control level is employed to eliminate these deviations and share proportional reactive power. Centralized and distributed secondary control techniques require communication links and decrease reliability of system. Therefore, in this study decentralized secondary control methods are introduced to improve the reactive power sharing.
Keywords: Droop control, Decentralized secondary control, Reactive power sharing control, Frequency control
