Modelling the impact of uncoordinated plug-in electric vehicles’ charging patterns on the low voltage distribution network

Abstract

South Africa’s existing infrastructure predates the widespread adoption of Plug-in Electric Vehicles (PEVs). Given the current energy crisis, the introduction of PEVs’ charging activities into residential Low Voltage Distribution Networks (LVDNs) is anticipated to have an adverse impact on various LVDN system parameters, such as the potential for overloading transformers and lines, as well as the possibility of exceeding the voltage’s safe operational limits. This study models the impact of PEV charging activities on South Africa's LVDNs. Key factors to the study are the Voltage Unbalance Factor (VUF) and the Voltage Profile. Three scenarios are presented as case studies and simulated on DigSilent Power Factory, the simulations are conducted through a Quasi Dynamic Simulation(QDS) Load Flow Calculation. Case Study 1 and Case Study 2 assess PEV charging activities on the most and least loaded phases of the provided unbalanced network, including upstream and downstream charging at 50% and 100% charging rates, respectively. Results show that integration on heavily loaded phases could potentially destabilise the network, while charging on a least loaded phase reduces the unbalance factor. Case Study 3 adopts a stochastic approach to integrating PEVs into the network, providing a more realistic and dynamic overview of its potential impact. The LVDN and load profiles utilised in this study are derived from real-life data obtained from the City of Cape Town (CoCT).