Design and optimal power management technique for resilient operation in an interconnected hybrid microgrid system

Abstract

The concept of networking multiple microgrids is one of the most promising initiatives in microgrid-based power generation frameworks to address the challenges of a single microgrid's resiliency and enhance supply security. Interconnected microgrids have the potential to serve as a fundamental framework for future distribution systems due to the extensive deployment of smart grid technology. Infrastructure planning and design, control theory, and communication technologies are required to regulate microgrid clusters in a flexible and efficient manner. That is, a proper control structure with robust and reliable control strategies is required to improve the performance of the interconnected microgrids in terms of power-sharing, power quality, and stability. The study introduces a novel control structure and a clustering method for interconnected hybrid microgrids to form an integrated framework. The proposed control structure for power flow control among hybrid microgrids places particular emphasis on the control strategies of three converters, such as the energy storage system, the interlinking converter of each hybrid microgrid, and the interconnecting converter for networking multiple microgrids. The control strategy of the hybrid microgrid’s interlinking converter is based on a voltage-frequency droop control to ensure proper operation in three operating modes, such as islanded, grid-connected, and interconnecting modes. The virtual inertia and state-of-charge-based controller of the energy storage system controls the battery bank's charging and discharging operations and provides an autonomous power flow inside each hybrid microgrid. Finally, the control strategy of a parallel interlinking converter structure is designed to interconnect and control the power flow among hybrid microgrids. vi The control structure allows both islanded and grid-connected operations without swapping between two controllers. This control framework reduces the number of activation operations in response to variations in conditions. Consequently, negative consequences like an uneven transition and system failure due to an inaccurate transition can be mitigated. In summary, the suggested control framework can function seamlessly upon the occurrence of unintended situational changes, such as main grid failure or islanding (with -0.11% variation in frequency), load variation (-0.038% variation during load increment and 0.02% variation during load decrement), source failure (-0.13% and 0.18% variations in frequency during wind generator failure), and grid synchronization (with 0.04% variation in frequency), without requiring a control mode transition. The clustering method and control structure of the interconnected microgrid system are designed in a MATLAB/Simulink environment. The OPAL-RT simulator (OP5600)-based real-time software-in-the-loop simulation technique is used to analyse the performance of the interconnected system in terms of load variations, source failure, power quality, mode transition, and energy storage system management. The results indicate that the control structure, with three control strategies, ensures reliable operation in all modes with reduced total harmonic distortion (less than 5%) and lower frequency fluctuation (less than 1%), and also maximizes power supply security.