From the perspective of the entire power system, the application scenarios of energy storage can be divided into three scenarios: energy storage on the generation side, energy storage on the transmission and distribution side, and energy storage on the user side. In practical applications, it is necessary to analyze energy storage technologies according to the requirements in various scenarios to find the most suitable energy storage technology. This paper focuses on the analysis of three major application scenarios of energy storage.
From the perspective of the entire power system, the application scenarios of energy storage can be divided into three scenarios: energy storage on the generation side, energy storage on the transmission and distribution side, and energy storage on the user side. These three scenarios can be divided into energy demand and power demand from the perspective of the power grid. Energy-type demands generally require a longer discharge time (such as energy time shift), but do not require high response time. In contrast, power-type requirements generally require fast response capabilities, but generally the discharge time is not long (such as system frequency modulation). In practical applications, it is necessary to analyze energy storage technologies according to the requirements in various scenarios to find the most suitable energy storage technology. This paper focuses on the analysis of three major application scenarios of energy storage.
1. Power generation side
From the perspective of the power generation side, the demand terminal for energy storage is the power plant. Due to the different impacts of different power sources on the grid, and the dynamic mismatch between power generation and power consumption caused by the unpredictable load side, there are many types of demand scenarios for energy storage on the power generation side, including energy time shifting, capacity units, load following, Six types of scenarios, including system frequency regulation, backup capacity, and grid-connected renewable energy.
energy time shift
Energy time-shifting is to realize the peak-shaving and valley-filling of power load through energy storage, that is, the power plant charges the battery during the low power load period, and releases the stored power during the peak power load period. In addition, storing the abandoned wind and photovoltaic power of renewable energy and then moving it to other periods for grid connection is also energy time shifting. Energy time-shifting is a typical energy-based application. It does not have strict requirements on the time of charging and discharging, and the power requirements for charging and discharging are relatively wide. However, the application of time-shifting capacity is caused by the user’s power load and the characteristics of renewable energy generation. The frequency is relatively high, more than 300 times per year.
capacity unit
Due to the difference in electricity load in different time periods, coal-fired power units need to undertake peak-shaving capabilities, so a certain amount of power generation capacity needs to be set aside as the capacity for corresponding peak loads, which prevents thermal power units from reaching full power and affects the economy of unit operation. sex. Energy storage can be used to charge when the electricity load is low, and to discharge when the electricity consumption peaks to reduce the load peak. Utilize the substitution effect of the energy storage system to release the coal-fired capacity unit, thereby improving the utilization rate of the thermal power unit and increasing its economy. The capacity unit is a typical energy-based application. It has no strict requirements on the charging and discharging time, and has relatively wide requirements on the charging and discharging power. However, due to the user’s power load and the power generation characteristics of renewable energy, the application frequency of the capacity is time-shifted. Relatively high, about 200 times a year.
load following
Load tracking is an auxiliary service that dynamically adjusts to achieve real-time balance for slow-changing, continuously changing loads. Slowly changing and continuously changing loads can be subdivided into base loads and ramping loads according to the actual conditions of generator operation. Load tracking is mainly used for ramping loads, that is, by adjusting the output, the ramping rate of traditional energy units can be reduced as much as possible. , allowing it to transition as smoothly as possible to the scheduling instruction level. Compared with the capacity unit, the load following has higher requirements on the discharge response time, and the response time is required to be at the minute level.
System FM
Frequency changes will affect the safe and efficient operation and life of power generation and electrical equipment, so frequency regulation is very important. In the traditional energy structure, the short-term energy imbalance of the power grid is regulated by traditional units (mainly thermal power and hydropower in my country) by responding to AGC signals. With the integration of new energy into the grid, the volatility and randomness of the wind and the wind have aggravated the energy imbalance in the power grid in a short period of time. Due to the slow frequency modulation speed of traditional energy sources (especially thermal power), they lag behind in responding to grid dispatching instructions. Sometimes Misoperations such as reverse adjustment will occur, so the newly added demand cannot be met. In comparison, energy storage (especially electrochemical energy storage) has a fast frequency modulation speed, and the battery can flexibly switch between charge and discharge states, making it a very good frequency modulation resource.
Compared with load tracking, the change period of the load component of the system frequency modulation is at the level of minutes and seconds, which requires higher response speed (generally at the level of seconds), and the adjustment method of the load component is generally AGC. However, system frequency modulation is a typical power-type application, which requires fast charging and discharging in a short period of time. When using electrochemical energy storage, a large charge-discharge rate is required, so it will reduce the life of some types of batteries, thereby affecting other types of batteries. economy.
spare 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 emergencies, in addition to meeting the expected load demand. Generally, the reserve capacity needs to be 15-20% of the normal power supply capacity of the system, and the minimum The value should be equal to the capacity of the unit with the largest single installed capacity in the system. Since the reserve capacity is aimed at emergencies, the annual operating frequency is generally low. If the battery is used for the reserve capacity service alone, the economy cannot be guaranteed. Therefore, it is necessary to compare it with the cost of the existing reserve capacity to determine the actual cost. substitution effect.
Grid connection of renewable energy
Due to the randomness and intermittent characteristics of wind power and photovoltaic power generation, their power quality is worse than that of traditional energy sources. Since the fluctuations of renewable energy power generation (frequency fluctuations, output fluctuations, etc.) range from seconds to hours, the existing Power-type applications also have energy-type applications, which can generally be divided into three types: renewable energy energy time-shifting, renewable energy generation capacity solidification, and renewable energy output smoothing. For example, in order to solve the problem of abandoning light 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 wind power, the output of wind power fluctuates greatly, and it needs to be smoothed, so it is mainly used in power-type applications.
2. Grid side
The application of energy storage on the grid side is mainly three types: relieving transmission and distribution resistance congestion, delaying the expansion of power transmission and distribution equipment, and supporting reactive power. is the substitution effect.
Alleviate transmission and distribution resistance congestion
Line congestion means that the line load exceeds the line capacity. The energy storage system is installed upstream of the line. When the line is blocked, the electric energy that cannot be delivered can be stored in the energy storage device. Line discharge. Generally, for energy storage systems, the discharge time is required to be on the hour level, and the number of operations is about 50 to 100 times. It belongs to energy-based applications and has certain requirements for response time, which needs to be responded at the minute level.
Delay the expansion of power transmission and distribution equipment
The cost of traditional grid planning or grid upgrade and expansion is very high. In the power transmission and distribution system where the load is close to the equipment capacity, if the load supply can be satisfied most of the time in a year, and the capacity is lower than the load only in certain peak periods, the energy storage system can be used to pass the smaller installed capacity. Capacity can effectively improve the power transmission and distribution capacity of the grid, thereby delaying the cost of new power transmission and distribution facilities and prolonging the service life of existing equipment. Compared with relieving transmission and distribution resistance congestion, delaying the expansion of power transmission and distribution equipment has a lower frequency of operation. Considering battery aging, the actual variable cost is higher, so higher requirements are put forward for the economy of batteries.
Reactive support
Reactive power support refers to the regulation of transmission voltage by injecting or absorbing reactive power on transmission and distribution lines. Insufficient or excess reactive power will cause grid voltage fluctuations, affect power quality, and even damage electrical equipment. With the assistance of dynamic inverters, communication and control equipment, the battery can regulate the voltage of the transmission and distribution line by adjusting the reactive power of its output. Reactive power support is a typical power application with a relatively short discharge time but a high frequency of operation.
3. User side
The user side is the terminal of electricity use, and the user is the consumer and user of electricity. The cost and income of the power generation and transmission and distribution side are expressed in the form of electricity price, which is converted into the user’s cost. Therefore, the level of electricity price will affect the user’s demand. .
User time-of-use electricity price management
The power sector divides 24 hours a day into multiple time periods such as peak, flat, and low, and sets different electricity price levels for each time period, which is the time-of-use electricity price. User time-of-use electricity price management is similar to energy time shifting, the only difference is that user time-of-use electricity price management is based on the time-of-use electricity price system to adjust the power load, while energy time-shifting is to adjust the power generation according to the power load curve.
Capacity Charge Management
my country implements a two-part electricity price system for large industrial enterprises in the power supply sector: the electricity price refers to the electricity price charged according to the actual transaction electricity, and the capacity electricity price mainly depends on the highest value of the user’s power consumption. Capacity cost management refers to reducing the capacity cost by reducing the maximum power consumption without affecting normal production. Users can use the energy storage system to store energy during the low power consumption period and discharge the load during the peak period, thereby reducing the overall load and achieving the purpose of reducing capacity costs.
Improve power quality
Due to the variable nature of the operating load of the power system and the non-linearity of the equipment load, the power obtained by the user has problems such as voltage and current changes or frequency deviations. At this time, the quality of the power is poor. System frequency modulation and reactive power support are ways to improve power quality at the power generation side and transmission and distribution side. On the user side, the energy storage system can also smooth voltage and frequency fluctuations, such as using energy storage to solve problems such as voltage rise, dip, and flicker in the distributed photovoltaic system. Improving power quality is a typical power application. The specific discharge market and operating frequency vary according to the actual application scenario, but generally the response time is required to be at the millisecond level.
Improve power supply reliability
Energy storage is used to improve the reliability of micro-grid power supply, which means that when a power failure occurs, the energy storage can supply the stored energy to end users, avoiding power interruption during the fault repair process, and ensuring power supply reliability. The energy storage equipment in this application must meet the requirements of high quality and high reliability, and the specific discharge time is mainly related to the installation location.
Post time: Aug-24-2023