  Behavioral homogeneity is often critical for the functioning of network
systems of interacting entities. In power grids, whose stable operation
requires generator frequencies to be synchronized--and thus homogeneous--across
the network, previous work suggests that the stability of synchronous states
can be improved by making the generators homogeneous. Here, we show that a
substantial additional improvement is possible by instead making the generators
suitably heterogeneous. We develop a general method for attributing this
counterintuitive effect to converse symmetry breaking, a recently established
phenomenon in which the system must be asymmetric to maintain a stable
symmetric state. These findings constitute the first demonstration of converse
symmetry breaking in real-world systems, and our method promises to enable
identification of this phenomenon in other networks whose functions rely on
behavioral homogeneity.
