Distributed and cooperative control Research Papers (original) (raw)

The work presented investigates the dynamics of a reverse droop current controller and a conventional droop voltage controller in a distributed cooperative secondary control environment operating with the consensus aided communication network for a 5-bus DC microgrid (MG). The microgrid system considered has multiple distributed energy resources (DER) i.e. photovoltaic array and battery connected to 4 buses while the last bus serves as an interconnection for a remote load terminal. This aids in bolstering the performance analysis of the aforementioned controllers under various operating scenarios like switching networks, delay, plug-n-play,etc. The current dynamics being faster than the voltage dynamics, a single current controller could be employed instead of voltage controller or a cascaded voltage-current controller for reducing system complexity and achieving faster convergence. A low voltage DC microgrid test-system (48 V) assuming (semi) dispatchable energy sources at its inputs catering to local and remote resistive & constant power loads is considered in the study to investigate and validate the controllers' transient responses. Index Terms-Muti-agent systems (MAS),hierarchical control, reverse droop, sliding mode control (SMC), constant power load (CPL). I. INTRODUCTION Distributed control employing cooperative networks being the cynosure of research in parallel multi-converter systems continues to intrigue the intellect and presents ample problem statements to be embarked upon. The centre-flocking and collision avoiding features of animals and birds,natural phenomena like thermodynamic laws, insect swarming, flocking of birds, phase transitions etc. in physical, chemical and biological processes, etc. were studied using consensus algorithms and later correlated to multi-agent systems, communication networks[1],[2] which endow mobility to control decisions via exchange of information among agents in accordance with the designed or inherent communication protocols. These laws were then further extended to microgrids (MGs) realizing its strong potential for the correction of the flaws that arise owing to the line impedances superimposing the effect of droop control using virtual impedances for accurate load current sharing in DC and AC parallel multi-converter systems[3]-[6] and to eliminate single-point-of-failure and ameliorate high communication channel bandwidth requirements on account of centralized communication infrastructure.This symbiosis of electrical properties and communication networks commonly known as networked multi-agent systems (MAS) have garnered legit attention owing to their flexibility ,scalability and computational efficiency [7]. It also presents the concept of independent, mobile, distributed agents (controllers) that could take decisions of their own by processing information of their nearest agents (controllers). Tracking and synchronization of these agents are the broad classifications in the distributed control theory [8], wherein it concerns leaderless and leader configurations respectively. It is noteworthy to mention that the sudden inclination towards DC distribution systems reverberated on account of its supremacy over AC supply for not including issues related to power quality, avoiding multiple stages of conversion, enhanced efficiency, higher renewable penetration (DC in nature),etc. The multifaceted benefits