gridfollowing

Grid-following refers to a control strategy for grid-connected inverters that synchronize to the electrical grid and inject active and reactive power based on the grid voltage and frequency. It relies on the grid to define voltage, angle, and frequency references, rather than generating a stable voltage by itself.

Operation in grid-following systems uses a phase-locked loop (PLL) to estimate the grid voltage phase and frequency. It measures the grid voltage and, in a dq reference frame, controls the inverter current to track commanded active and reactive power. The inner current loop and outer P–Q or P–V/Q–V control loops determine dq currents from desired power, with decoupling terms to manage dynamic coupling. The inverter injects current into the grid to follow the setpoints and responds to grid disturbances through PWM switching and current limits.

Droop and voltage support: In practice, grid-following devices may implement P–Q droop or volt-VAR control to share generation and support grid voltage. They typically require a stable grid voltage at the point of connection and can struggle in weak networks or during large transients.

Comparison with grid-forming: Unlike grid-forming controllers, grid-forming inverters establish and regulate a grid voltage themselves, enabling operation during limited grid support or islanding. GFL devices generally rely on existing grid voltage and frequency references and may have reduced ability to ride through faults without additional support.

Applications and standards: Grid-following inverters are common in interconnected distributed energy resources, such as rooftop solar, battery storage, and small-scale DERs. Standards such as IEEE 1547 specify interconnection and performance requirements, including grid support functions that GFL systems may implement.