Impact of electric vehicle load response variation on frequency stability

Electric vehicle (EV) load in future power systems is likely to increase due to decarbonisation of the transport fleet. EV load can be utilised to provide primary frequency reserve (PFR), provided its variability with respect to system requirements is taken into consideration. EV based PFR can in certain cases negatively impact system frequency stability. Better estimation of EV reserve and consideration of its volume and responsiveness, relative to system PFR requirements, therefore becomes important. This paper presents a model for EV load estimation, and proposes control mechanisms which cater for available EV reserve variability and system requirements. The results show that the proposed control mechanisms are robust and ensure frequency stability, with negligible impact on the speed of response and hence the frequency nadirs.