Abstract:

The future energy system， centered around electricity， must integrate a high proportion of volatile renewable energy sources on the supply side while addressing the large-scale and unpredictable charging demands of electric vehicles on the consumer side. Centralized charging of electric vehicles during peak load hours can significantly undermine the safety， reliability， and economic dispatch of the power grid. Thus， it is crucial to coordinate and guide the charging and discharging processes of electric vehicles to mitigate their adverse impact on the grid load curve and potentially transform them into high-quality energy storage units. This is vitally important for our country to handle the fluctuations posed by a substantial reliance on renewable energy.

A provincial power economic dispatch model is presented that covers 8，760 hours and incorporates characteristics of wind and solar fluctuations. It includes unit operational constraints， state transfer equations， power output limitations， ramping capabilities， and supply-demand balance constraints. The model bases the dispatch of generator units on external power supply and grid structural data， thereby determining the optimal hourly power output， startup， shutdown， and operational modes at the provincial level. Furthermore， the charging and discharging behavior of electric vehicles are integrated into the model to examine the synergistic effects between various operational modes of electric vehicles and the variability of renewable energy sources.

It focuses on Guangdong， Henan， Ningxia， and Sichuan as typical provinces for optimal dispatch and simulation analysis in this study. Differences among these provinces are primarily due to variations in power demand， supply structures， and resource endowments. The data from 2018 are used as a baseline， spanning all 8，760 hours of the year， sourced from public records. It outlines four scenarios： a baseline， disordered charging， coordinated charging， and Vehicle-to-Grid （V2G）.

Results indicate that disordered charging of electric vehicles exacerbates peak and valley disparities in grid load， increasing the operational costs of the power system. Conversely， adopting collaborative vehicle-grid models such as coordinated charging and V2G can effectively smooth the net load curve， yielding additional economic benefits. Therefore， it is essential to motivate users to charge during low grid load periods using demand response systems like peak and off-peak electricity pricing.

The main factors influencing the economic viability of electric vehicles connected to the grid include the availability of volatile renewable energy and the level of flexible resources within the power system. Different regions should develop tailored strategies based on their specific resource characteristics. In many areas of northwest and central China， the power system has limited flexible resources and a high proportion of wind and solar generation， making the economic value of grid-connected electric vehicles substantial. However， the current low number of electric vehicles in these regions suggests that if this economic value could be shared with users through an appropriate mechanism， it could significantly boost the adoption of electric vehicles.

As the penetration of wind and solar power continues to rise， coordinated charging and V2G strategies are poised to realize greater economic value once electric vehicles are integrated into the grid. Although an increase in vehicle ownership might slightly dilute the value per vehicle， this impact remains relatively limited. In pursuing carbon neutrality， China needs to shift from merely expanding the scale of low-carbon sectors， such as electric vehicles and renewable energy generation， to establishing a cross-sectoral integration and interoperability system， thereby constructing a new energy system that harmoniously integrates vehicles and the grid.

Key words: renewable energy, electric vehicle, volatility, economic assessment