Research on optimization of multi-energy coupling source-network-load-storage based on micro energy network

Based on the architecture of the micro energy network system, a “source network load storage” multi-energy coupling hub system for regional energy internet with electricity gas interconnection is proposed. The lowest operating is set as the optimization goal for the operation of the regional energy internet. A dynamic economic scheduling model for regional energy interconnection based on the sky and an optimization scheduling model for regional energy internet are established. A mixed integer linear programming program based on Matlab is written and solved using CPLex. The results show the operation of the “source grid load storage” regional energy internet with multiple energy coupling hubs as the core is lower than that of traditional micro-grids When adding an energy storage system, the daily operating of the micro-grid system is 16.7% less than that of Control Scenario 1 and 14.3% less than that of Control Scenario 2 The proposal of a regional energy internet “source network load storage” multi-energy coupling hub system based on the micro energy network system architecture provides a feasible basis for the planning and construction research of the regional energy internet.


Introduction
The micro-energy network has achieved efficient use of energy, connecting energy and user end, and ultimately developing deeply through the energy internet, integrating the conversion, scheduling, production, and use of energy, achieving maximum coordination and cooperation in the utilization of various energy sources [1].From the energy production system to the energy use system, uninterrupted integration and cross-regional connections between energy sources have been achieved throughout the entire region [2].Various forms of energy have been reasonably planned, ultimately achieving efficient and clean energy use, and saving the cost of the entire energy system.In a true sense, the important role of the energy internet has been realized [3].Both governments in China, the United States, and Japan attach great importance to the use of energy, which will affect the country's economic strength and social status.It is also for the benefit of future generations' development.Therefore, a rational solution to the problem of energy use and energy shortage is an important shortcut to prosperity and strength.Its characteristics are source network linkage and load storage synergy, with the aim of improving energy utilization efficiency, improving energy structure, and achieving sustainable development.
The development of micro-grids will drive the development of various industries in our country, drive the rapid development of our economy, and ultimately achieve the integration and development of micro-grid systems and renewable energy systems under the high attention of our country, bringing huge benefits to our country [4][5][6].Finally, through continuous research and breakthroughs by various universities, China's micro-grid has accelerated its unprecedented development, rapidly entering the era of smart grids, and even today's energy internet [7][8][9][10].At the same time, due to the continuous development of integrated energy systems and energy internet, the optimization and scheduling of power systems have gradually become a very popular research topic.
The research objective of this article is to comprehensively consider the coordination and coordination of various parts such as source, network, load, and storage in the optimization process of regional energy internet, achieve the overall optimization and scheduling of the "source network load storage (SNLS)" system of the entire regional energy internet system, and improve the integrity of the system.

Models and methods
The optimization scheduling model is solved using CPLex, and the basic form of the multi-energy coupling hub system is shown in Figure 1.The optimization scheduling model is shown in Figure 2 for its solution process.A regional energy system is composed of multiple forms of energy, which can include gas, electricity, and other energy sources.The optimization of multi-energy coupling in regional energy internet is achieved by establishing a general model for optimizing the "SNLS" operation of regional energy internet based on economic indicators, as shown in Equation (1).min ( ) . .( ) 0 ( ) 0 where f (x) is the optimization objective function; X is the optimization variable; Å is decision space; g(x) and h(x) are inequality constraints and equality constraints.
After overall collaborative optimization of the various models of "SNLS", an objective function is established based on economic indicators, as shown in Equations (2)(3)(4)(5). n where i is the type of construction unit; αi is the construction cost per unit capacity; Mi is the number of i type of construction units; Ci is the capacity of the i-th individual unit.γi,t and ηi,t represent 0-1 variables, indicating the start and stop status of the energy supply unit at different time periods; COP is unit maintenance cost; POP is unit output power.α,i,t and βi,t represents 0-1 variables, and their sum is 1.

Testing and optimization
A small park was selected to validate and solve the model.The interaction power between the microgrid and power grid is 40 kW, and the micro-grid and main gas grid is 45 kW.The relevant information of various synchronous power generation units is shown in Figure 3. Natural gas is selected at 3.4 yuan/m 3 , with a unit heat value price of 0.349 yuan/(kW h).The source refers to the energy supply side, including renewable energy such as solar, wind, and hydropower, as well as traditional energy.

Running scenario settings
This article sets up the following scenarios based on the different types of energy interaction between different energy supply network systems.
Scenario 1: Under real-time electricity prices, priority is given to utilizing the energy provided by the micro-grid itself to meet various load supplies, and free interaction between the main grid and the micro-grid is chosen; Scenario 2: Under real-time electricity prices, priority is given to utilizing the energy provided by the micro-grid itself to meet various load supplies, and free interaction between the main grid and the main gas grid the micro-grid is chosen; Scenario 3: Under real-time electricity prices, priority is given to utilizing the energy provided by the micro-grid itself to meet various load supplies, selecting to freely interact with the main grid, the main gas grid, and the micro-grid, and adding energy storage units.
The various scenario systems in this article will interconnect and complement various forms of energy to explore the economic operation efficiency and cleaning ability of the energy internet, whether it can achieve efficient utilization of various energy sources and the energy-saving and environmental protection of the system.This article takes the power grid as the main network, joins the gas network, and constructs a multi-energy complementary electricity gas interconnection system.Adding the participation ratio of photovoltaic and wind power in this system can not only improve the system's economy but also achieve efficient energy utilization and reduction of carbon emissions.

Result analysis
Based on various energy systems and equipment models within the micro-grid, the lowest operating is set as the optimization goal for the operation of regional energy internet, and a dynamic economic scheduling model for regional energy interconnection is established based on the current situation.This article selects a typical daily wind and solar PV as shown in Figure 4.The selection of a typical daily load for cold, hot, and electrical loads is shown in Figure 5.The real-time tiered electricity price can be obtained from the city's municipal.1) In Control Scenario 1, under real-time electricity pricing, free interaction between the main power grid and the microgrid can be chosen.The operation optimization results are shown in Figure 6.During this period, the electricity consumption of residents has sharply decreased, and various loads have also been continuously reduced, resulting in a decrease in the load on the system network.However, at the same time, the wind turbine is still running, which will generate excess electricity.If the excess electricity is not consumed in a timely manner, it will cause the entire network system to be paralyzed and even cause serious consequences.Therefore, the large power grid is called to regulate the reliability of the system.From 7:00 to 22:00, the various load demands of users have sharply increased, so natural gas is used for power supply, and fuel cells are also used for supply.During this period, various loads are relatively large compared to at night, and the absorption capacity of wind and solar power generation is relatively strong.Therefore, the entire system coordinates and cooperates to supply energy to the entire system network, improving the economy of the system.From 22:00 to 24:00, user demand decreased, natural gas stopped running, and synchronous generators continued to operate, selling excess electricity to the large power grid.The security and reliability of the entire network system are adjusted by selling electricity to the large power grid.At the same time, integrating the large power grid, gas turbines, and fuel cells into an organic whole enhances the system's coordination and control capabilities, and also improves the system's economy.
(2) In Control Scenario 2, under real-time electricity prices, the use of energy provided by the microgrid itself is prioritized to meet various load supplies.The operation optimization results are shown in Figure 7.It can be seen that during the operation of wind power generation and synchronous power generation units from 0:00 to 7:00, the excess electricity generated not only meets the load needs of some users, but also is sold to the gas grid and the power grid.At this point, due to the extremely reduced consumption of various loads during this time period, in order to reduce the wind energy abandonment rate, it is necessary to reduce the use of thermal power units, which can increase the efficiency of wind energy usage and reduce the use of fossil energy, improving the environmental protection and economy of the system.From 7:00 to 22:00, the various load demands of users have sharply increased, so natural gas is used for power supply, and fuel cells are also used for supply, which has a strong absorption capacity for wind and solar power generation.Therefore, the entire system coordinates and cooperates to supply energy to the entire system network, improving the economy of the system.During this period, various loads will increase, so each unit will be used based on the lowest operating.At this point, solar and wind energy have the highest utilization efficiency, and the coordinated use of various units enhances the coordination and complementarity ability of the entire system.From 22:00 to 24:00, user demand decreased, the gas grid stopped running and fuel cells also stopped running.However, synchronous generators and wind turbines continued to operate, selling excess electricity to the large power grid and gas grid.The natural gas has stopped running, and the synchronous generator is still running, selling excess electricity to the large power grid.The security and reliability of the entire network system are adjusted by selling electricity to the large power grid.At the same time, integrating the large power grid, gas grid, gas turbine, and fuel cell into an organic whole enhances the system's coordination and control capabilities, and also improves the system's economy.
(3) In Control Scenario 3, under real-time electricity prices, the use of energy provided by the microgrid itself is prioritized to meet various load supplies.However, synchronous generators and wind turbines continued to operate, selling excess electricity to the large power grid and gas grid.The natural gas has stopped running, and the synchronous generator is still running, selling excess electricity to the large power grid.The security and reliability of the entire network system are adjusted by selling electricity to the large power grid.At the same time, integrating the large power grid, gas grid, gas turbine, and fuel cell into an organic whole enhances the system's coordination and control capabilities, and also improves the system's economy.The operation optimization results are shown in Figure 8.As can be seen from Figure 8, during the operation of wind power generation and synchronous power generation units from 0:00 to 3:00, the excess electricity generated will not only meet the load needs of some users, but also be sold to the gas grid and the power grid.From 3:00 to 5:30, the user's demand is too small, so they directly choose to purchase electricity from the large power grid for economic efficiency, and charge the battery from 3:00 to 8:00.From 7:00 to 22:00, the various load demands of users have sharply increased, so natural gas is used for power supply, and fuel cells are also used for supply.During this period, various loads are relatively large compared to at night, and the absorption capacity of wind and solar power generation is relatively strong.Therefore, the entire system coordinates and cooperates to supply energy to the entire system network, improving the economy of the system.
In Control Scenario 1, the daily operating cost is 3600 yuan.In Control Scenario 2, the daily operating cost is 3500 yuan, which is 100 yuan less than the operating cost in Control Scenario 1.The difference in daily operating costs between Control Scenarios 1 and 2 is 100 yuan, but the daily operating costs of the energy internet system with electricity gas interconnection have decreased, so the daily operating IOP Publishing doi:10.1088/1742-6596/2728/1/0120697 costs of the electricity gas interconnection system are better than those of the micro-grid system.In Control Scenario 3, adding an energy storage system resulted in a daily operating cost of only 3000, which is 16.7% less than that of Control Scenario 1 and 14.3% less than that of Control Scenario 2. Therefore, Control Scenario 3 is superior to Control Scenario 1 and Control Scenario 2.

Conclusion
This article proposes an "SNLS" multi-energy coupling system for the regional energy internet based on the micro energy grid system architecture.The results show that: 1.The operating of the "source grid load storage" regional energy internet with multiple energy coupling hubs as the core is lower than that of traditional microgrids.
2. When adding an energy storage system, the daily operation of the micro-grid system is only 3000 yuan, which is 16.7% less than that of Control Scenario 1 and 14.3% less than that of Control Scenario 2, 2. The proposal of a regional energy internet "SNLS" multi-energy coupling hub system based on the micro energy network system architecture provides a feasible basis for the planning and construction research of regional energy internet.

Figure 1 .
Figure 1.Basic form of the multi-energy coupling hub system.

Figure 2 .
Figure 2. Solution flowchart of the system.

Figure 3 .
Figure 3. Characteristic diagram of the generator.

Figure 4 .
Figure 4. Wind and photovoltaic properties of typical days.

Figure 5 .
Figure 5. Cooling, heating, and electrical load attributes of typical days.
Photovoltaic power Wind power