  Within electrical distribution networks, substation constraints management
requires that aggregated power demand from residential users is kept within
suitable bounds. Efficiency of substation constraints management can be
measured as the reduction of constraints violations w.r.t. unmanaged demand.
Home batteries hold the promise of enabling efficient and user-oblivious
substation constraints management. Centralized control of home batteries would
achieve optimal efficiency. However, it is hardly acceptable by users, since
service providers (e.g., utilities or aggregators) would directly control
batteries at user premises. Unfortunately, devising efficient hierarchical
control strategies, thus overcoming the above problem, is far from easy.
  We present a novel two-layer control strategy for home batteries that avoids
direct control of home devices by the service provider and at the same time
yields near-optimal substation constraints management efficiency. Our
simulation results on field data from 62 households in Denmark show that the
substation constraints management efficiency achieved with our approach is at
least 82% of the one obtained with a theoretical optimal centralized strategy.
