Impact Of Large-scale Electric Vehicles On Power Grid And Application Of It To Frequency Regulation

With the popularity and the promotion of electric vehicles, electric vehicles will eventually encounter large-scale development period. While large-scale electric vehicles are connected to Power Grid to charge, it is a challenge for power grid, and at the same time, it brings new development opportunities for power grid. Different types of electric vehicles have different charging load characteristics. In the case of disorderly charging, the total charging load of large-scale electric vehicles will bring pressure to regional power grid operation. Meanwhile, electric vehicle as a controlled load, it has the feature of fast response, so it can participate in the grid frequency control, that can reduce the frequency modulation spare capacity of grid and bring some economic benefits.This paper firstly considers the factors which influence the electric vehicle charging load, and sets up the feasible charging load model of different types of electric vehicles, according to the date of the electric vehicle, which is demonstration operation, and the driving rule of various electric vehicles.Secondly, the impact of large-scale electric vehicles charging on power grid is studied. It will affect power grid load and operation. To study the impact on the grid load, this paper analyzes the load characteristics of electric vehicles when they achieve large-scale development in the public transport sector and official sector. By the time, the electric vehicles charging load has obvious early peak and night peak, the early peak can fill the load valley of regional power grid, while the night peak maybe bring new bigger grid peak load. When electric vehicles achieve large-scale development in the private sector, its load curve superposed with the residents' load curve, which will cause "peak-peak plus" and further expand the system peak difference. To study the impact on the grid operation, the paper analyzes the effect from two aspects: voltage deviation and network losses. The results show that the electric vehicles load in addition to the power grid will cause node voltage decrease. The sharpest voltage drop node is the access node. Network loss rate will increase with the increase of accessed electric vehicles.Finally, this paper studies the application of electric vehicles to power grid frequency modulation. First, the paper establishes the frequency controlling model of various parts of the power system and gives the frequency characteristics model of electric vehicles. Then the models of electric vehicles participating in power system's primary and secondary frequency adjustment are set up, and simulation is carried out. Simulation results show that the participation of electric vehicles in power system's primary and secondary frequency adjustment both can reduce the frequency deviation of power grid and shorten the time that power system need to return to a new steady state. The participation of electric vehicles in secondary frequency adjustment can reduce frequency modulation units' spare capacity, which is beneficial to the generators' economic operation. For the interconnected power systems, electric vehicles involved in the secondary frequency modulation can also decrease the tie line power fluctuation' amplitude and the time of fluctuation.