The invention is a method of providing globally optimal control by means of a distributed control algorithm having a single common control variable as the basis for evaluating different figures of merit with respect to each other and requiring little or no central command, control, and communications function. Large scale systems, such 89 a electric power grid are controlled using a central or area control facilities from which all the major components of a system are monitored and controlled. The deployment of such large scale system requires a vast and highly reliable communications infrastructure to maintain a high system-wide performance and reliability. Small local failures or trivial topological changes in the system sometimes bring about a cascading system failure, possibly leading to widespread service outages. In addition, failure mitigation strategies in this kind of system are often designed more to protect equipment and permit rapid restoration of service rather than to assure maintenance of service. For example, centrally commanded rolling blackouts are used to prevent loads from too closely approaching the system capacity limits because volumary load curtailment strategies often fail to mitigate the problem. Distribute4 and automated load curtailment strategies to assist in reducing loads are not generally possible with the current control paradigm. Any control paradigm that does not depend so critically on the central command and control functions to maintain service has the potential to be more greatly scalable, possibly enabling distribution generation resources, and is more likely to provide enhanced global reliability, increased system efficiencies, greater flexibility and local autonomy, and reduced operational costs. Transactive control is designed to mitigate many of the shortcomings of central command and control systems and provide many of these additional benefits. most especially those which limit scalability of control scope and flexibility in system topology.