A Unified Strategy for Frequency Regulating and MPPT for Photovoltaic Sources Based on a Novel Three-Parameter Characteristic Curve

Abstract

The large-scale integration of Photovoltaic (PV) sources may reduce system inertia and power quality, resulting in increased frequency fluctuations and diminished system stability due to lack of the primary frequency regulation (FR) capability. To address these challenges, this paper proposes a unified strategy for frequency regulating and Maximum Power Point Tracking (MPPT) for PV sources to provide ancillary services to the power grid. The strategy employs a specifically designed active power control (APC) method to enable rapid and flexible power adjustments of PV sources, with which further FR function may be achieved. The presented APC algorithm adopts an iterative technique with a novel three-parameter PV characteristic curve, making it possible to reconstruct the real-time PV generation model, clarify the relationship between the system frequency, output power, and operating voltage. Its high control accuracy, fast convergence rate, and strong explainability offer significant practical value. Additionally, this adaptive control strategy features autonomous switch between the FR and MPPT modes adapting to real-time irradiation changes, without the need for additional irradiation or temperature sensors. The integration enhances both solar utilization efficiency and the FR capability, while eliminating the controller transitions during operating mode switches. Hardware-in-the-loop tests validate the feasibility and effectiveness of the proposed strategy.