A Black Start Recovery Strategy for a PV-Based Energy Storage Microgrid, Considering the State of Charge of Energy Storage

To mitigate black start failures resulting from energy storage state of charge (SOC) exceeding operational limits, this study develops a restoration strategy incorporating SOC constraints. Firstly, an adaptive SOC control without bias for energy storage units is proposed to achieve SOC balance. Secondly, the maximum power point tracking (MPPT) mode for photovoltaic power generation is integrated with the load tracking mode, enabling effective tracking of load variations when the photovoltaic output is sufficient; conversely, when the photovoltaic output is inadequate, the energy storage output compensates for the shortfall, thus avoiding the SOC limit due to an insufficient remaining SOC of the energy storage, while also significantly reducing the quantity of charge and discharge cycles undergone by the energy storage units. Finally, the simulation results show that, according to the proposed control strategy for recovery, the maximum system frequency of the black start process does not exceed 50.11, and the minimum is not lower than 49.82, which are within reasonable limits. At the same time, the number of charge/discharge conversions of the three storage batteries is 12 when the PV system adopts the coordinated control of MPPT and load tracking, and the number of charge/discharge conversions of the storage batteries in the PV MPPT mode is 21. This ensures the success of the black start process and prolongs the life of the energy storage battery.