Cooperative and Distributed Control Strategies of Microgrids

With recent advances in information and communication technologies (ICT) and internet of things (IoT) devices, microgrids are becoming ever more reliant on distributed control systems. A distributed control scheme offers several benefits compared to a centralized counterpart, including improved scalability, reliability, flexibility, efficiency, and resilience to a single point of failure. Due to heavy reliance on communication networks and distributed control infrastructures, microgrids represent a class of cyber-physical systems (CPSs), where there is a tight interconnection between physical components (power electronics converters, loads, etc.) and computing elements (cyber layer). Although CPSs are becoming ubiquitous due to rapid advances in computation and communication technologies, they have witnessed critical issues originating from the control and communication systems (cyber layer). Such issues are the results of the vulnerability of the cyber layer to cyberattacks, heavy computation burdens, and uncertainties in the communication topology due to the plug-and-play operation of distributed generation units. Due to a tight coupling between the physical and cyber layers in microgrids, any issues/failures in the cyber layer might adversely impact the normal operation of microgrids, threaten their stability, and cause damage to the physical components. This chapter briefly introduces distributed secondary control systems and their functions in islanded AC microgrids. Conventional cooperative distributed secondary controllers are presented. Several important technical challenges that are of central relevance in the context of distributed secondary control in microgrids are provided for readers’ interests, with some of them discussed in detail. The recent developments in the distributed secondary control of microgrids are presented. In particular, this chapter focuses on actuator faults and control input saturation in the distributed secondary control mechanisms of islanded inverter-interfaced microgrids. To this end, a fault-tolerant distributed secondary control scheme is proposed that improves the reliability of islanded microgrids against faults and control input saturation. Simulation and comparative case studies and results are presented. Several concluding remarks and remaining challenging problems in the context of distributed secondary control in cyber-physical microgrids are provided.