Optimised compensation for voltage stability and reliability enhancement in radial distribution systems with electric vehicle integration

The rapid growth of electric vehicles (EVs) puts significant pressure on radial distribution systems (RDS), causing voltage instability and reduced reliability. This paper presents an optimised shunt compensation framework combined with stochastic EV load modelling to improve system performance. The method uses the current injection load flow (CILF) technique. It identifies candidate locations using a voltage stability index and refines these through an optimisation-based placement of shunt capacitors. Unlike traditional studies that focus on static loads, this method considers probabilistic EV charging patterns, peak demand clustering, and different penetration levels. Capacitor ratings of 50 kVAr and 100 kVAr are chosen according to IEEE standards and practical utility use. The method is tested on three benchmark IEEE RDS systems (15, 33, and 69 bus) to show scalability. The results demonstrate consistent improvements in voltage stability margin and reliability indices. Even small numerical gains lead to meaningful operational benefits, such as a lower risk of voltage collapse and delayed infrastructure upgrades. The study also explores the role of smart charging, demand response, and vehicle-to-grid (V2G) integration as supportive strategies. The findings confirm that the proposed framework is a practical and scalable solution for maintaining stability and reliability in EV-integrated distribution networks.