  With the increasing penetration of distributed energy resources (DERs) in
distribution grids, their impact on grid operations can no longer be ignored.
However, the individual control of these increasingly ubiquitous devices
remains a challenge due to their numbers. One solution is to control them in
groups via virtual power plants. Previous work has typically focused on
optimally dispatching a fixed set of DERs, eschewing methods for optimally
determining set membership. Intuitively, these fixed sets may not be optimal
from a control perspective. Here, we propose a method to cluster the DERs based
on a proxy for their covariances, with the goal of minimising the maximum
variance across all DER clusters. This method does not require the enumeration
and evaluation of all DER combinations, which are required for brute force
techniques. Simulation results show that while there is typically a loss in
optimality, it is generally small. More importantly, computational tractability
is greatly improved when compared to other methods, which require some form of
enumeration and evaluation of the DER combinations.

Optimization and Control