Secondary VAr Controllers: A New Approach to Increase Solar Hosting Capacity in Distribution Grids

Abstract

High residential PV penetration in the distribution grid can cause large voltage variations due to sudden changes in PV generation. This ultimately degrades power quality, customer satisfaction, risks utility infrastructure, customer equipment and utility employees working in the field. As a result, controlling voltage becomes imperative given that most utilities have to maintain voltage within a service range of 114V to 126V. Conventional assets, such as LTCs and Cap Banks, do not respond fast enough to mitigate these voltage variations. Lack of fast distributed control limits further PV penetration. Newer approaches of using smart inverters moving forward are being proposed, however, most inverters in the field are still legacy inverters. This paper presents a novel approach of using Secondary VAr Controllers (SVC) to control voltage by injecting VArs dynamically. Through a pilot project on a system with 77% (4.8 MWPV) PV penetration at Hawaiian Electric, it is demonstrated that 61 SVCs distributed on two feeders can tighten the feeder-wide voltage profile by up to 4% (4.8V), which translates to nearly doubling (146% or 9.23 MWPV) of the PV hosting capacity.