A Reactive Power Control Scheme for DER-Caused Voltage Rise Mitigation in Secondary Systems

Abstract

Distributed energy resources (DERs) are a new class of disruptive technologies with rapidly increasing adoption levels due to favorable government policies and subsidies. However, these emerging technologies come with technical challenges for utilities and system operators; for instance, voltage rise issues in residential secondary distribution systems with high penetration of DERs. One of the low-cost mitigation options to alleviate the overvoltage problem is reactive power absorption. Nevertheless, secondary feeders exhibit a high R/X ratio more noticeably than primary distribution systems, requiring large amount of reactive power for voltage regulation that cannot be entirely provided by the DERs alone. It is also necessary to minimize the reactive power drawn from the primary distribution system to prevent any stress on the network and reduce extra system losses, while at the same time ensuring the voltage within admissible limits. To address these critical issues, this paper proposes a distributed reactive power management, where additional source is provided from inexpensive devices such as switchable shunt reactors. The proposed overvoltage mitigation is accompanied by detailed analytical investigation that estimates the minimum amount of required reactive power to manage the voltage with user specified voltage rise tolerances. Case studies have also been conducted on real residential distribution systems subjected to severe voltage rise issues provoked by large adoption of DERs.