Frequency control strategy for coordinated energy storage system and flexible load in isolated power system

The isolated power system has a simple structure with small inertia and no support from the large-scale power system, so the frequency stability problem is more prominent. A frequency control method based on coordinated control of flexible loads (FL) and energy storage systems (ESS) is proposed in this paper. The ESS adopts the droop control considering the state of charge (SOC) to quickly respond to the system frequency deviation and provide fast frequency support. Based on the load power–voltage sensitivity, the FL participates in frequency control by adjusting the load voltage and thus the load demand. Based on the two frequency regulation resources, the active–reactive cooperative control strategy is proposed to adopt the fast response characteristics of ESS to cooperate with the synchronous unit to prioritize frequency regulation and enable the FL reactive control strategy when the system disturbance is larger than the primary frequency regulation capacity of the synchronous unit. The effectiveness of the proposed control strategy for isolated power systems is verified by building a modified IEEE33 node islanding system simulation in the real-time digital simulator (RTDS).