  With the decrease in system inertia, frequency security becomes an issue for
power systems around the world. Energy storage systems (ESS), due to their
excellent ramping capabilities, are considered as a natural choice for the
improvement of frequency response following major contingencies. In this
manuscript, we propose a new strategy for energy storage -- frequency shaping
control -- that allows to completely eliminate the frequency Nadir, one of the
main issue in frequency security, and at the same time tune the rate of change
of frequency (RoCoF) to a desired value. With Nadir eliminated, the frequency
security assessment can be performed via simple algebraic calculations, as
opposed to dynamic simulations for conventional control strategies. Moreover,
our proposed control is also very efficient in terms of the requirements on
storage peak power, requiring up to 40% less power than conventional virtual
inertia approach for the same performance.
