Study of the dynamic performance boundaries of a converter's energy storage device

Maintaining frequency stability is one of the central objectives of power grid operation. While this task is currently primarily done by employing stored rotational energy, in a converter-dominated grid fed by renewables, sources, such as wind and photovoltaic, must be involved in the frequency control of the power grid in order to maintain a stable, efficient grid operation in the process of achieving carbon neutrality. However, due to the lack of rotational inertia reserves, the converter requires additional energy storage devices to respond to the grid's frequency regulation requirements. For modeling a converter-dominated grid, the behavior of such additional short-time storage must be modeled properly in order to obtain realistic simulation results, which allow drawing conclusions about the frequency stability behavior of the grid. This paper investigates the boundaries of the dynamic performance of the output current of the energy storage device so that the converter can achieve the function of frequency regulation in a more economical manner. In this paper, a dynamic supporting converter based on a phase-locked loop and a grid-forming converter, as well as the DC link of the converter containing an energy storage system, are modeled. On this basis, the optimal boundaries of the dynamic performance of the output current of the energy storage device are investigated. It is concluded that not only the proper sizing of grid-supporting energy storage devices is important for proper grid operation, but the dynamic behavior also has to be modeled and designed properly in order to guarantee a stable operation under all circumstances.