A primary frequency control strategy for variable-speed pumped-storage plant in generating mode based on adaptive model predictive control

Variable-speed pumped-storage (VSPS) has great potential in helping solve the frequency control problem caused by low inertia, owing to its remarkable flexibility beyond conventional fixed-speed one, to make better use of which, a primary frequency control strategy based on adaptive model predictive control (AMPC) is proposed in this paper for VSPS plant in generating mode. Under AMPC, the mechanical and electrical power of VSPS units are further coordinated such that stronger response to frequency variation can be provided. To make AMPC applicable, a simplified prediction model is adopted and equivalent control constraints are established to represent VSPS unit's operating limits that are omitted due to the simplification. Based on a test system modified from IEEE 24-bus system, a case study is conducted through hardware-in-the-loop simulation to verify the effectiveness and feasibility of AMPC, and the results show that when AMPC is applied to VSPS plant, the maximum frequency deviation of the system under disturbance is reduced by up to 49.07%, compared with that when fixed-speed units are adopted, and up to 21.30%, compared with that when virtual inertia, droop and feedforward controls are applied.