Frequency Control Strategy of Energy Storage System Based on SOC under Distributed Photovoltaic Intensive Access

With the increasing permeability of new energy generation, a large number of conventional thermal power units have been replaced, and the equivalent inertia of the system has been reduced. The randomness and fluctuation of distributed photovoltaic output may lead to serious frequency fluctuations. It is necessary to fully exploit other frequency modulation equipment in the power grid. Because of its ability to smooth the fluctuation in new energy, energy storage systems have been widely studied and applied in power system. The energy storage system is connected to the power grid through the inverter, but there is no inertia link. This paper simulates the traditional synchronous generator operation mode, and adds virtual inertia link in the inverter control process to slow down the frequency change rate when the system fails. At the same time, the charging state of the battery energy storage system is incorporated into the inverter droop control to correct the inverter droop control coefficient in time. In this paper, the effectiveness of the algorithm is verified in the simplified model of a real power grid. The results show that the system’s frequency transient stability is improved.