Multi‐mode control and operation of a self‐sufficient multi‐microgrid system

Abstract

In this study, a ring-type multi-microgrid (MG) system comprising of three MGs with solar energy-based generation, wind energy-based generation, and static synchronous compensator as primary sources along with batteries as emergency back-up is proposed. The voltage-source converters at the individual MG level serve as the interface between the neighbouring MGs and the grid. An augmented proportional sliding-mode-control-based approach is proposed in the primary control level to improve the power quality of the system during balanced and unbalanced loading conditions. A negative-sequence controller is also included to mitigate the negative-sequence voltage from the inverter output voltage. The multi-MG (MMG) system is capable of operation in grid-connected, islanded, or interconnected mode with balanced and unbalanced loads. The bidirectional DC -DC converters interfacing the batteries at the DC link is controlled by a hysteresis-function-based sliding-mode control. A comparison of the proposed inverter primary control with proportional -integral controller, quasi-proportional -resonant controller, and hysteresis-band current controller is carried out. The comparison reveals that the total harmonic distortion and voltage unbalance factor improves by employing the proposed control when compared with conventional control. The proposed MMG system with its control strategies is modelled in MATLAB/Simulink environment and is experimentally verified using OP4510 from OPAL-RT.