Design of optimal distributed linear feedback controllers to achieve a
desired aggregate behavior, while simultaneously satisfying state and input
constraints, is a challenging but important problem in many applications,
including future power systems with weather-dependent renewable generation.
System level synthesis is a recent technique which has been used to
reparametrize the optimal control problem as a convex program. However, prior
work is restricted to a centralized control design, which lacks robustness to
communication failures and disturbances, has high computational cost and does
not preserve data privacy of local controllers. The main contribution of this
work is to develop a distributed solution to the previous optimal control
problem, while incorporating agent-specific and globally coupled constraints in
a non-conservative manner. To achieve this, it is first shown that the dual of
this problem is a distributed consensus problem. Then, an algorithm is
developed based on the alternating direction method of multipliers to solve the
dual while recovering a primal solution, and a convergence certificate is
provided. Finally, the method's performance is demonstrated on a test case of
control design for distributed energy resources that collectively provide
stability services to the power grid