Distributed Active Network Management Based on Locally Estimated Voltage Sensitivity

Abstract

Two challenges need to be addressed in designing active network management (ANM) for distribution networks that use non-firm connection agreements for quicker and cheaper connections of distributed energy resource (DER). First is the replacement of scripted actions based on priority lists by real-time selection of actions offered as ancillary services and judged on efficacy and cost. Second is the need to decentralize or distribute ANM decision making to avoid unrealistic communication and computation burdens as the number of controllable devices increases. This paper proposes a distributed form of ANM for radial networks, based on local estimation of the voltage sensitivities to offered adjustments of real or reactive power and then uses message passing between local controllers to arrive at near-optimum choices of actions. To manage a voltage constraint, the minimum volume (or cost) of ancillary services is found by selecting services from DERs with highest voltage sensitivity to the service offered. A method of sensitivity estimation for individual nodes is extended to all terms of the inverted Jacobian matrix. The accuracy of this approximation is discussed and explored in a case-study network. The format of message passing from one local controller to another is described. Simulations demonstrate that the proposed distributed ANM closely approaches the solution found by a centralized optimal power flow. It is confirmed that the use of locally estimated voltage sensitivity to identify the most effective DER can minimize the volume of power flow adjustment service that the ANM needs to manage voltage and thermal constraints.