Unified centralised/decentralised frequency control structure for microgrids

Abstract

Abstract When the microgrid (MG) operates in islanded mode, the frequency adjustment is performed through the secondary control. This control can be achieved through centralised, distributed or decentralised strategies. The centralised strategies are the most applied in the MG due to the facility of the control and coordination of the distributed generations. However, due to centralisation of processing and information, these strategies depend on the continuous operation of the communication channels. The decentralised and distributed strategies are proposed in the literature to avoid the reliability issues of centralised strategies. This paper proposes a new control interface that can combine the centralised and decentralised secondary frequency control strategies in a unique control structure, merging the advantages of each technique. The proposed unified secondary frequency control structure (USFCS) can ensure the benefits of centralised control and can maintain the MG frequency regulation even during control or communication failures. The proposed USFCS is verified on an MG based on the CIGRE benchmark LV distribution network through simulation. The results have shown that the proposed control structure can guarantee the frequency regulation even during failures and can restore it to regular operation after failure.

Keywords

• Reliability
• Distribution networks
• Multivariable control systems
• Frequency control
• Control of electric power systems
• Distributed power generation