Frequency–Stability–Domain-Based Coordinated Frequency Regulation Control Strategy for Wind Turbine and Electrolytic Aluminum Systems to Avoid Secondary Frequency Dip

In power systems with a high penetration level of wind power, wind turbines are required to temporarily extract stored rotor kinetic energy to provide primary frequency support, thereby compensating for the limited frequency regulation (FR) capability of the overall system. However, wind turbine participation may lead to underresponse (insufficient frequency support) or overresponse, potentially causing a secondary frequency dip (SFD). Electrolytic aluminum load (EAL), as an industrial load with FR potential, can rapidly adjust its active power input by controlling the electrolytic cell voltage, equivalently increasing the system’s FR capacity and thereby enhancing the load disturbance resistance of power systems with high wind power penetration. This paper first analyzes the causes and mechanisms of the SFD induced by wind turbine overresponse based on a Unified transfer function structure (UTFS) model and introduces the concept of a frequency stability region. Within this region, the virtual droop and virtual inertia coefficients for wind turbines are tuned to prevent SFD during FR. Simultaneously, by involving EAL in system FR, the analysis reveals that its participation essentially equivalently expands the system’s frequency stability region. Building on this analysis and considering spatiotemporal influencing factors, a coordinated wind-aluminum FR control strategy across multiple timescales is proposed to avoid SFD. Finally, a 39-bus simulation system built in DIgSILENT is used for validation. The simulation results indicate that the proposed control strategy effectively suppresses SFD under high wind power penetration conditions, and that the incorporation of EAL significantly expands the frequency stability region of the power system.