Grid Forming Control with Inertial and Virtual Admittance Characteristics for Grid-tied Converters

With a considerable increase of renewable generation in the past decade, the concern for grid instability has also been increasing. The technology of grid forming control has been proposed for renewable power generation to support the grid, with some demonstrations in photovoltaic and wind power generation in recent years. This paper presents a grid forming control method named the Synchronous Power Controller (SPC), which combines the virtual inertia control with a virtual admittance. Considering the big difference in the control time scale between the power control loop and the current control loop, a simplified second-order transfer function model is adopted to analyze power control dynamics of the SPC-based power converter under different control parameters. Simulation and experimental tests are conducted on a 10-kW test bench, where the active and reactive power control dynamics under different parameters are observed. Test results demonstrate a good consistence with the response based on the mathematical model, as well as the effectiveness of the control method in offering auxiliary service that entails a certain amount of inertia and frequency droop, which contribute to the angle and frequency stability of a modern grid.