Reliability evaluation of power systems considering electric vehicle charging

Abstract

Three issues in regard to reliability evaluation of power systems incorporating electric vehicles (EVs) are addressed in this thesis: Well-being analysis of generating systems considering EVs grid participation as interruptible load and spinning reserves; The uncertainties of EV charging and their effects on the well-being analysis of generating systems; Reliability evaluation of distribution systems incorporating EVs grid contribution. With increasing demand for EV charging, power grids can take advantage of the distinctive features of EV charging load. In response to outages, the charging load can be interrupted with no penalty until additional generation becomes available, as long as charging requirements can be fulfilled, to improve system health. Moreover, EVs can further provide emergency capacities back to the grid (i.e. vehicle-to-grid (V2G)). The generating system operating health analysis is extended by taking EV charging into consideration. This is the first work that proposes the idea of EV charging being treated as interruptible load and serving as emergency units to improve system well-being. Numerical results show that V2G is more effective for well-being improvement than the interruptible EV charging. In the V2G enabled scenario, EVs are able to provide more capacities to help the system. The contribution of EVs is uncertain because they serve both the power system and the transportation sector. Scheduled EV charging can be affected either by failures of components such as charging facilities, or by human errors such as punctuality, rounding of time and errors in forecast of energy consumption. Moreover, with the introduction of the aggregator, the realization of EVs grid services also plays an important role. Major uncertainties that can affect EV charging are identified. They are punctuality, rounding of time, forecast error of energy consumption, charging component failure and EV absence, and aggregator failure and grid realization. Methodologies are developed to consider these elements in well-being analysis. As expected, results show the uncertainties identified directly affect EVs contribution to the system well-being. The evaluation of reliability of the classical distribution system is also extended to incorporate the grid contribution of EVs in different modes of operation. For each load point, two topologiescentralized and dispersed EV chargingare considered. During the islanding mode of operation, household demand can be supported by vehicle-to-home (V2H) and/or local V2G, depending on the charging topologies applied. In grid connected mode of operation, energy not supplied can be further reduced by interregional V2G, which allows energy exchange among load points through healthy mains and laterals by sectionalizing the failure parts of the grid. Evaluation methods are proposed to determine the capacity contribution of EVs for each scenario. For the scenario of interregional V2G, optimal power flow is conducted to maximize the energy exchange. From the results of a case study, V2H and V2G, on both local and system levels, show great promise for reliability enhancement.