Due to the vigorous development of new energy power generation and large-scale application in the power system, especially the rapid development of photovoltaic power generation on the user side of the power system, its uncertainty leads to a serious imbalance in the power distribution of power system in time and space, which seriously affects the balance and stability of the power system. How to effectively stabilize the output of photovoltaic and reduce the impact on the balance of the power system to a certain extent is the decisive factor for the large-scale development of photovoltaic power generation on the user side.
Shang Liqun from the School of Electrical Engineering and Control of Xi'an University of Science and Technology and Zhang Jiantao from Dayun Automobile Co., Ltd. wrote an article in the second issue of "Electrical Technology" in 2024, using the joint operation of energy storage and photovoltaic power generation to solve the method of new energy power generation affecting the balance and stability of the power system, and proposed a dynamic loss model of energy storage battery considering the impact of the number of charge and discharge times and charge and discharge depth on the life of the energy storage battery
Background:
With the continuous improvement of photovoltaic penetration, the impact on the stable operation of the power grid also increases, and the energy storage device is an effective means to absorb photovoltaic power generation and improve the stability of the system. At the same time, the user-side photovoltaic storage system can reduce the user's electricity expenditure and improve the reliability of power supply, so the research of the user-side photovoltaic storage system has become an important research direction for the energy transition of countries around the world.
The problem solved by the paper and its significance
The purpose of this research is to use the energy storage system to reduce the impact of photovoltaic power generation on the power system, reduce the load peak-to-valley difference, smooth the load curve, and reduce the curtailment rate of photovoltaic power generation on the user side. At the same time, the energy storage dynamic attenuation model proposed in this project can more accurately predict the service life of energy storage batteries, arrange the number of charging and discharging and the depth of discharge more reasonably, and maximize the economic benefits of the configured optical storage system.
Dissertation Methods and Innovations
Based on the existing experimental data, through the improved curve fitting method and linear segmentation processing method, a more accurate curve fitting function and a piecewise linear function more consistent with the original curve are obtained, and a dynamic loss model of energy storage battery is established that is more suitable for actual operation.
At the same time, in the example, the PV output and load demand per unit capacity in different scenarios are comprehensively considered, and different weight solving methods are used to obtain the PV output and load demand per unit capacity on a typical day, and the multi-objective particle swarm optimization is used to solve the configuration problem of the PV storage system in a residential area under different operation scenarios with the goal of maximizing the average annual income of the operator and the minimum load peak-to-valley difference.
1 Curve fitting and linear segmentation results
Fig.1 The relationship curve between energy storage SOH and the degree of life loss and the linear segmentation results
Equation 1
2. Processing of PV output and load demand data
2.1 Processing of photovoltaic output data
Fig.2 Typical daily PV output curves per unit capacity in different seasons
The analytic hierarchy process (AHP) is used to take the weights of the PV output per unit capacity in different seasons, and according to the weights, the weights of the PV output per unit capacity in different seasons are weighted and summed to obtain the typical daily PV output per unit capacity with comprehensive characteristics.
Fig.3 Typical daily PV output curve per unit capacity
2.2 processing of load demand data
Figure 4 Load curves of each scenario
The entropy method is used to take the weight factor of the load power on typical days in different seasons, and the load demand of the comprehensive typical days is obtained after weighting, which is used as the basic data of the load demand of residential communities.
Fig.5 Load curve of a typical day
3 Simulation verification
Three different scenarios are set to verify the effectiveness of the model and the best scenarios for the operation of optical storage:
Scenario 1: The method proposed in this paper is used to configure a photovoltaic storage system for residential areas, and the relationship between SOH and life loss of energy storage batteries is simply linearized in sections, without considering the impact of energy storage battery life loss on the operation of the energy storage system, and when the constraints are met, the energy storage system only uses photovoltaic output to supplement electric energy, and the stored electric energy is used for energy supply during peak load hours.
Scenario 2: When configuring ESS, the impact of energy storage battery operation on life loss and capacity attenuation is considered, and the other conditions are the same as those in Scenario 1.
Scenario 3: When configuring the ESS, the impact of the operation of the energy storage battery on the life loss and capacity attenuation is considered, and the energy storage system is connected to the grid, so that the energy storage can operate in the arbitrage mode of "low storage and high release", and the other conditions are consistent with Scenario 1.
conclusion
By comparing the simulation results in the three scenarios, the following conclusions can be drawn:
1) In this paper, the photovoltaic output under various climatic conditions and the load demand under different seasons are introduced to make the configuration results of the photovoltaic storage system in residential areas more accurate and practical. The allocation of energy storage for residential areas can not only obtain economic benefits, but also play the role of "peak shaving and valley filling" of energy storage systems. From the configuration results, it can be seen that the capacity of the configured energy storage system is not large, which can meet the requirements of small area of residential areas.
2) In order to make the energy storage system have a strong photovoltaic output and absorption capacity, the photovoltaic storage system should be operated in scenario 2 preferentially; In order to optimize the economy of the PV storage system and the ability of the energy storage system to smooth the load curve is outstanding, the PV storage system is preferably run in scenario 3. The model proposed in this paper is helpful to make more accurate and objective decisions on the optimal allocation and investment of photovoltaic energy storage system.
3) The energy storage dynamic attenuation model can be used to predict the service life of the energy storage battery more accurately, and the charging and discharging times and discharge depth can be arranged more reasonably to obtain greater economic benefits.
Meet the team
The researchers are affiliated to the School of Electrical and Control Engineering of Xi'an University of Science and Technology, and have long been committed to the research of power system control and protection, new energy power generation technology and other fields, mainly involving the distribution network single-phase grounding fault line selection and section positioning, distribution network single-phase grounding fault flexible arc suppression, power transformer fault diagnosis, photovoltaic power generation system fault diagnosis, renewable energy power generation and grid connection and other research directions.
- Shang Liqun (1968—), male, from Jiyuan City, Henan Province, Ph.D., professor, main research direction is power system protection and control, new energy power generation, etc.
- Zhang Jiantao (1996—), male, from Linfen City, Shanxi Province, master's degree candidate, his main research direction is the optimization of optical storage operation, energy consumption optimization of new energy vehicles, etc.
The results of this work were published in the second issue of Electrical Technology in 2024, and the title of the paper is "Optimal Allocation of Photovoltaic Storage in Residential Communities Considering the Life Attenuation of Energy Storage Batteries", and the authors are Shang Liqun and Zhang Jiantao. This project was supported by the Shaanxi Provincial Natural Science Basic Research Program.