(No. 1 of the serialized articles)

With the sales of new energy vehicles increasing exponentially, the demand of new energy vehicle owners for supercharging has surged, and the era of super charging has arrived. It is urgent to add super charging equipment to traditional charging stations. The large-scale construction of charging infrastructure and the transformation of charging stations have seriously impacted and burdened the existing power grid. At the same time, it is difficult to increase the capacity of charging stations, the investment cost is high and there are too many uncertainties.

Factors such as the low power factor and frequent power quality issues like harmonics caused by traditional charging stations during operation have made the installation of energy storage in charging stations the primary choice.

What is an Energy Storage Charging Station?

An energy storage charging station is an intelligent charging infrastructure that integrates photovoltaic power generation, energy storage system and EV charging piles. Its main function is to achieve the efficient utilization of clean energy and the stability of power supply through energy storage and optimal configuration.

Compared with the traditional single charging station, this type of station has significant advantages such as complementary multi-energy sources, energy saving and environmental protection, peak shaving and valley filling. In the actual operation process, economic and social benefits can be maximized by optimizing configuration and dispatching management.

Advantages

• Reduce operating costs. At present, the time-of-use electricity price calculation method is adopted nationwide. By configuring energy storage, charging during off-peak hours and discharging during peak hours can reduce peak electricity consumption and lower electricity costs. At the same time, afterconfiguring energy storage, the station’s trafficflow can be increased by reducing the service fee during peak hours. Some stations are equipped with photovoltaic power generation, and the photovoltaic power is stored spontaneously for its own use, so that the stored electricity can be used at peak hours to reduce electricity costs. Configuring energy storage can also allows participation in the demand-side response of the power grid, assisting the power grid to carry out peak shaving and frequency modulation, earning In the future, it can participate in the spot market transaction of electricity as well, with diverse revenue sources and promising prospects.

2. Virtual capacity expansion. It is in line withall-weather detection of power and distribution capacity; the charging and discharging power of energy storage dynamically adapts to the power demand of the station. The super storage and charging are integrated, ensuring worry-free fast charging.
3. Improve power quality. When the charging station is equipped with energy storage, in situations such as when the transformer is overloaded, power is rationed, or charging is impossible due to a power outage, it can improve power quality and maintain the normal operation of the charging station.

Sub-scenario of Energy Storage Applications in Charging Station

1. Power generation side

From the power generation side, the end-users of energy storage demand are power plants. Due to the different impacts of various power sources on the power grid and the dynamic mismatch between power generation and power consumption caused by unpredictable load, there are many types for energy storage demand on the power generation side, including six scenarios such as energy time shift, capacity unit, load tracking, system frequency modulation, reserve capacity and renewable energy grid connection.

• Energy time shift

Energy time shift achieves peak shaving and valley filling of the electricity load through energy storage, that is, the power plant charges the battery during the off-peak period of the power load and releases the stored electricity during the peak period of the power load. In addition, it is also an energy time shift to store the curtailed wind and solar power of renewable energy and then move it to other time periods for grid connection. Energy time shift is a typical energy-based application, which has no strict requirements for charging and discharging time and wide requirements for charging and discharging power. However, the application frequency of energy time-shift is relatively high, more than 300 times a year, due to the power load of users and the power generation characteristics of renewable energy.

• Capacity unit

Due to the differences in electricity load at different time periods, coal-fired power units need to undertake peak load regulation capabilities. Therefore, it is necessary to reserve a certain generation capacity for corresponding peak loads, which makes the thermal power units unable to reach full capacity and affects the economy of unit operation. Using energy storage can charge during the low electricity load period and discharge during the peak electricity load period to reduce the peak load. Taking advange of the substitution effect of the energy storage system to release the capacity units of coal-fired power, thereby improving the utilization rate of thermal power units and increasing their economic efficiency. Capacity unit is a typical energy-based application, which has no strict requirements for charging and discharging time and wide requirements for charging and discharging power. However, due to the power load of users and the power generation characteristics of renewable energy, the application frequency of capacity time shift is relatively high, about 200 times a year.

• load tracking

Load tracking is an auxiliary service that dynamically adjusts to achieve real-time balance for the slow-changing and constantly changing load. The continuously changing load with slow change can be further divided into basic load and ramp load according to the actual situation of generator operation, and load tracking is mainly applied to ramp load, that is, by adjusting the output, the ramp rate of traditional energy units is minimized as much as possible, allowing it to smoothly transition to the dispatching instruction level. Compared with capacity units, load tracking requires higher discharge response time, and the corresponding time is required to be in minutes.

• System frequency modulation

Change in frequency will have an impact on the safe and efficient operation and life of power generation and electrical equipment. Therefore, frequency adjustment is very important. In the traditional energy structure, the short-term energy imbalance of power grid is adjusted by traditional units (mainly thermal power and hydropower in China) by responding to AGC signals. With the grid connection of new energy sources, the volatility and randomness of wind and solar power have intensified the short-term energy imbalance of power grid in a short period of time. Traditional energy sources (especially thermal power) are lagging behind in responding to power grid dispatching instructions because of their slow frequency modulation, and sometimes there will be wrong actions such as reverse adjustment, so they cannot meet the new demand. Comparatively speaking, the frequency modulation speed of energy storage (especially electrochemical energy storage) is fast, and the battery can be flexibly switched between charging and discharging States, making it a very good frequency modulation resource.

Compared with load tracking, the load component of system frequency modulation changes in minutes and seconds, which requires higher response speed (generally second response), and the adjustment method of load component is generally AGC. However, system frequency modulation is a typical power application, which requires fast charge and discharge in a short time, and requires a large charge and discharge rate when electrochemical energy storage is used, which will shorten the life of some types of batteries and thus affect their economy.

• Reserve capacity

Reserve capacity refers to the active power reserve reserved for ensuring power quality and safe and stable operation of the system in case of emergency besides meeting the expected load demand. Generally, the standby capacity needs to be 15-20% of the normal power supply capacity of the system, and the minimum value should be equal to the capacity of the unit with the largest installed capacity in the system. Sicne the reserve capacity is for emergencies, the annual operation frequency is generally low. If the battery is used as the reserve capacity service alone, the economy cannot be guaranteed, so it is necessary to compare it with the cost of the existing reserve capacity to determine the actual substitution effect.

• Renewable energy grid connection

Due to the random and intermittent characteristics of wind power and photovoltaic power generation output, the power quality is worse than that of traditional energy. Since the fluctuation of renewable energy power generation (frequency fluctuation, output fluctuation, etc.) ranges from a few seconds to several hours, there are both power-based and energy-based applications, which can be generally divided into three types: energy time shift of renewable energy energy, solidification of renewable energy power generation capacity, and smoothing of renewable energy output. For example, in order to solve the problem of light rejection in photovoltaic power generation, it is necessary to store the remaining electricity generated during the day for discharge at night, which belongs to the energy time shift of renewable energy. For wind power, due to the unpredictability of the wind, the output of wind power fluctuates greatly and needs to be smoothed, so it is mainly used a power-based application.