Distributed cooperative control for autonomous hybrid AC/DC microgrid clusters interconnected via back-to-back converter control

Abstract

In this paper, the authors have attempted to address the problem of power sharing in networked hybrid AC/DC micro-grid clusters by utilising back-to-back converter. The hierarchical distributed cooperative control strategy is employed for both the AC and DC microgrid clusters (intra-microgrid control) and an inter-microgrid control strategy employing back-to-back converter for enabling power sharing among the clusters according to the required needs. The distributed secondary control for both the AC and DC MGs aid to reprimand the voltage drops due to presence of cable resistance and droop characteristics. It thus helps to achieve a regulated voltage at both the AC and DC PCC. Particularly in AC MG, it enhances the voltage and power quality. Further, it is worth noting that most of the consensus algorithms are asymptotically convergent and hence in order to achieve finite-time convergence, a modified consensus approach is used for the DC microgrid cluster. This is done to achieve faster consensus irrespective of the unforeseen disturbance / transients that may occur in the AC microgrid clusters. The distributed dynamic averaging consensus algorithm based on PI controllers (DAC-PI) is also investigated for robustness against physical and communication failures. With the proposed inter and intra-microgrid cluster control mechanism, power balance between three phase AC MGs and DC MG is illustrated in this work. This could be utilised as practical applications in stand-alone microgrids, marine power systems, more electric aircraft power systems and can be equipped with mode selection algorithms to enable connection to the utility thereby endowing flexibility and reliability to the network of microgrid clusters. Extensive simulations of test-cases are provided with MATLAB/Simpowersystems platform to elucidate the performance of the proposed control strategy and the hybrid infrastructure.