Power management and coordinated control strategy of flexible interconnected AC/DC hybrid microgrid with back-to-back converters

In order to improve power regulation capability and system reliability, an interconnected hybrid microgrid (MG) topology with back-to-back (BTB) converters is a promising solution, but it also brings new technical challenges to the control system. The paper proposes a two-level power management and coordinated control strategy for hybrid MG with BTB converters to ensure the stable operation of the system. Firstly, the structure of hybrid MG is analyzed, and model of BTB converters, photovoltaic (PV) cell and battery are established. Secondly, multiple constraints and operation characteristics of DG, ESS, and BTB converters are considered, the detailed operation modes are analyzed, and system-level power management strategy is developed under grid normal, single-terminal grid fault, and island operation conditions. A local-level coordinated control strategy of BTB converters, battery energy storage system (BESS), and PV units is presented to ensure stable operation of the system in multi operation modes. The control coordination between the BTB converters and the ESS can ensure the stability of the AC voltage and frequency in the fault area and achieve uninterrupted power supply for important loads. Meanwhile, voltage recovery and current sharing control are proposed based on the voltage and current information provided by the upper power management system to eliminate DC voltage deviation and realize accurate current allocation. The current sharing and voltage recovery control is embedded in the local devices and will not have any impact on the upper power management system. Finally, the effectiveness of proposed method is verified by simulation and experimental results.