  This paper presents a novel Dynam-i-c Droop (iDroop) control mechanism to
perform primary frequency control with gird-connected inverters that improves
the network dynamic performance. The work is motivated by the dynamic
degradation experienced by the power grid due to the increase in asynchronous
inverted-based generation. We show that the widely suggested virtual inertia
solution suffers from unbounded noise amplification (infinite $\mathcal H_2$
norm) when measurement noise is considered. This suggests that virtual inertia
could potentially further degrade the grid performance once broadly deployed.
  This motivates the proposed solution in this paper that overcomes the
limitations of virtual inertia controllers while sharing the same advantages of
traditional droop control. In particular, our iDroop controllers are
decentralized, rebalance supply and demand, and provide power sharing.
Furthermore, our solution can improve the dynamic performance without affecting
the steady state solution. Our algorithm can be incrementally deployed and can
be guaranteed to be stable using a decentralized sufficient stability condition
on the parameter values. We illustrate several features of our solution using
numerical simulations.
