Central energy management method for photovoltaic DC micro-grid system based on power tracking control

To reduce the impact of high penetration of renewable energy on the utility grid and suppress the influence of micro-grid power fluctuation on power quality, a power tracking control strategy for DC micro-grid has been studied. Furthermore, a central energy management method (CEMM) based on this control strategy has been designed. The DC micro-grid, which contains renewable energy and hybrid energy storage unit, is used to build a complete control system model according to the distributed power supply and its control system model. The power tracking control strategy has been analysed and designed based on frequency domain method. With the designed control strategy, the system can realise coordinated operation of the hybrid energy storage unit by absorbing the load power fluctuation within different frequency range. Furthermore, based on the CEMM, the system is controlled to absorb/deliver predefined amount of power from/to the utility grid under grid-connected mode. In this way, smooth switching between different modes and the stable operation of the micro-grid are realised. Finally, the function of the system is verified with an emulated DC micro-grid system.