Power System Planning And Operation Strategies Considering Extensive Integration Of Electric Vehicles

Electric vehicles (EVs) is gradually gaining worldwide popularity due to the incentives of some relevant national subsidy policies, the improving battery performance in driving mileage, and as well as the increasing social environmental awareness. However, extensive utilization of plug-in EVs would challenge existing strategies regarding power system planning and operation. Significant negative impacts, such as increasing investment and energy losses, enlarging peak-valley gap and declining power quality, would be possibly imposed on the security and economic operation of the system concerned unless the charging behaviors of numerous EVs would be properly coordinated. Under aforementioned consideration, this dissertation is devoted to addressing potential issues which would probably arise from extensive integration of EVs and thus be encountered by power systems especially at the distribution level. The concerned issues are systematically investigated from two perspectives, namely palnning theories and operation strategies respectively. Specifically, the main focuses of this dissertation can be summarized as follows:1) A collaborative planning strategy is presented for integrated power distribution and EV charging systems. A simple but efficient method for deploying scattered charging posts is elaborately designed based on nodal EV charging demand. Additionally, a user equilibrium based traffic assignment model (UETSM) is employed to analyse the traffic flow capturing capability of fast charging stations (FCSs). Subsequently, a multi-objective collaborative planning model is formulated so as to deal with the optimal planning problem in integrated power distribution and EV charging systems. In the developed model, the overall annual cost of investment and energy losses is minimized simultaneously with the maximization of the annual traffic flow captured by FCSs. The proposed planning strategy would offer the investor an opportunity to make a proper coordination between expansion planging of distribution systems and deployment of EV charging infrastructures.2) A flexible planning strategy is presented for distribution systems considering extensive integration of EVs. First of all, future scenario set is constructed in line with three variables with uncertainty, namely conventional load level, EV penetration value and whether the coordinated charging strategy could be successfully implemented, respectively. Secondly, EV charging load calculating methods are separately proposed for free charging mode and coordinated charging mode. Furthermore, a practical real-time scheduling strategy is carefully designed so as to validate the feasibility of the charging scheme generated by the day-ahead dispatching model which is utilized to derive the EV charging load profile with coordinated charging. Finally, a flexible planning scheme for distribution systems is established with the adaptation cost fully considered. Simulation results indicate that the proposed planning strategy could assist the investor in avoiding some economic risks.3) A bi-level programming based coordinated dispatching scheme is proposed for aggregated EVs to provide peak load shifting service. A hierarchical and zonal dispatching framework is firstly constructed to coordinate the charging behaviors of numerous EVs. Meanwhile, corresponding vehicle grouping technique and information interaction mechanism are elaborately designed. Subsequently, a new bi-level optimization model for coordinating the charging and discharging behaviors of EVs is developed. The upper-level model is devoted to minimizing the system load variance so as to implement peak load shifting by dispatching each electric vehicle aggregator (EVA), and the lower one is aimed at tracing the dispatching scheme determined by the upper-level decision-maker through figuring out an appropriate charging and discharging schemes for EVs throughout a specified dispatching period.4) A coordinated dispatching strategy for conventional generators and numerous EVs is presented considering future electricity market environment. The electricity market environment considered is general in the sense that EV aggregators could be dispatched in a similar way as conventional generators. On this premise, a hierarchical decomposion approach is proposed to coordinate the behaviors of conventional generators and plug-in EVs. The major objective of the upper-level model is to minimize the total cost of system operation by jointly dispatching conventional generators and EV aggregators. On the other hand, the lower-level model aims at strictly following the dispatching instructions from the upper-level decision-maker by designing appropriate charging/discharging strategies for each EV individual in a specified dispatching period.5) A frequency regulation strategy is proposed for EVs with centralized charging. First of all, the business pattern of centralized charging and unified distribution battery swapping model is introduced. Afterwards, the dispatching ratio of the contracted frequency regulation capacity and the battery degradation cost due to V2G services are deeply investigated. A robust optimization model for EVs with centralized charging to provide frequency regulation service is formulated, so as to properly simulate and cope with the price uncertainties existed in day-ahead energy and frequency regulation markets. The developed model is capable of deriving a coordinated charging scheme and determining optimal frequency regulation capacity in each trading hour of the day-ahead energy and frequency regulation markets while with economic risks under acceptable level.The proposed planning theories and operation strategies are convinced to offer technical support for the issues arising from extensive integration of EVs, and further enrich the existing theoretical system and application framework in the area of power system planning and operation.