Optimal Operation of EVs and HPs in the Nordic Power System

Abstract

The Nordic countries, including Denmark, Finland, Norway and Sweden, have great ambitions in seeking a fully carbon neutral or low-carbon electric power system by 2050. The large scale deployment of electric vehicles (EVs) and heat pumps (HPs) is considered not only as an efficient method to limit the greenhouse gas (GHG) emission and the fossil fuel consumption in the transportation and heating sectors but also as a potential approach to cope with the intermittency due to the further utilization of renewable energy sources (RES) in the Nordic region. With increasing amounts of RES in the power system, more reserves will be needed by the grid due to the inherent uncertainties of RES. EVs and HPs will play a more important role in the future power system of the Nordic region by providing extra flexibility to the grid. The main objective of the Ph.D. study is to investigate the impacts of the possible large scale deployment of EVs and HPs in the Nordic region on the electrical power system. To facilitate such objective, the study in the Ph.D. project focuses on the following aspects: • The modeling of the EV and HP demand in the Nordic context. • The optimal scheduling of EVs and HPs with a high penetration level in the market environment. • The feasibility investigation of EVs and HPs to provide frequency reserves to the Nordic power system. To accomplish the researches mentioned above, the driving patterns of the vehicles in the Nordic region and the impacts of the EV and HP demand on the day-ahead electricity market are also analyzed in the Ph.D. study. The electrical demand of EVs and HPs under non-market environments is modeled with the detailed driving and heating requirements in the Nordic countries. With the uncontrolled charging scheme, the peak EV charging demand coincides with the peak conventional demand. With the timed charging scheme, the EV charging demand is delayed to avoid the conventional peak demand to some extend. However, most of the charging congregates in a short period when the timed charging is set started. The HP demand with the least-energyconsumption control scheme is consistent with the environmental weather pro- files. The increasing HP demand in the evening coincides with the conventional peak hours of the power system which may stress the grid. A chance constrained programming model through mixed-integer programming (MIP) is proposed to formulate the EV demand in the day-ahead electricity market considering the stochastic characteristics of the EV driving patterns. The model guarantees that the driving requirements of the EVs are met by the day-ahead energy planning with the predefined confidence parameter. A robust optimization model is proposed to formulate the HP demand in the day-ahead electricity market considering the uncertainty of the weather forecast used in the HP energy planning. The heating requirements for the HPs are guaranteed by the day-ahead energy plans through the robust optimization model. An aggregative game model is proposed to model the demand of large scale deployment of EVs and HPs in the day-ahead electricity market. The impacts of the EV and HP demand on the electricity spot price are considered in the EV and HP day-ahead energy planning by the proposed model. With a high penetration level, the demand of EVs and HPs shows a "valley-fill" pattern to the grid when it is introduced into the day-ahead electricity market. A combined modeling of the EV and HP energy planning is proposed for both the energy plans in the day-ahead electricity market and the frequency reserve provision decisions in the ancillary service market. It is shown that both EVs and HPs can provide considerable frequency reserves to the power system along the day in the Nordic region. Vehicle-to-Grid (V2G) technologies which enable the EVs to discharge the batteries in the reserve operations can further utilize the capacity of the EVs and consequently increase the ability of EVs to provide frequency reserves to the power system. Further, the intense weather of the Nordic region in winter does not decrease the ability of EVs and HPs to provide frequency reserves to the power system.