Rural power distribution network three-level layered energy storage configuration method based on daily degree balance mechanism

Abstract

The invention relates to a rural power distribution network three-level hierarchical energy storage configuration method based on a daily degree balance mechanism, and the method comprises the following steps: 1, constructing a rural power distribution network hierarchical energy storage configuration system: solving a problem of maximum local and nearby consumption of new energy through the coordinated and cooperative operation of the energy storage of each voltage level; 2, establishing a rural power distribution network energy storage configuration principle by taking distributed new energy efficient consumption as an object, and carrying out energy storage configuration step by step from bottom to top; 3, aiming at energy storage configuration of the energy autonomous rural micro-grid, constructing an energy storage configuration method based on a day degree balance mechanism based on rural area and feeder line operation data, and guiding energy storage configuration of the energy autonomous rural micro-grid; 4, performing typical distribution and storage instance analysis on the transformer area / feeder line; the method has the advantages that the energy storage device is reasonably configured, energy storage is coordinated and matched for operation, local and nearby consumption is maximized, and the safety is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution networks, and in particular relates to a three-level hierarchical energy storage configuration method for a rural distribution network based on a daily balance mechanism. Background Art

[0002] In recent years, the pace of new energy development in rural areas has accelerated, especially the development of distributed photovoltaics, which has shown an explosive growth trend. The rural electricity load has increased by an average of 13% per year, while the annual growth rate of distributed photovoltaic installed capacity is 54.8%. The mismatch between the source and load growth rates has led to the photovoltaic output far exceeding the load absorption capacity, causing the reverse power to converge layer by layer and be sent up step by step, and even leading to the reversal of the power flow of the UHV AC interconnection line; the source and load time are not synchronized, the photovoltaic output is random and volatile, and the peak load regulation of the power grid is difficult. The characteristics of distributed photovoltaic power generation determine that its output is concentrated in the period of sufficient sunshine, and the power generation drops sharply in the morning and evening or on rainy days, while the rural electricity load is concentrated in the morning and evening peak hours. At the same time, the distribution The lack of regulation capability of distributed photovoltaic itself leads to huge pressure on the peak regulation of the power grid; the large-scale access of distributed photovoltaic brings about the prominent problem of new energy consumption at noon, and the almost complete abandonment of centralized new energy in the power grid cannot meet the regulation demand. In order to meet these challenges, reduce the photovoltaic abandonment rate, improve energy utilization efficiency, promote the local consumption and utilization of new energy and the clean and low-carbon transformation of energy, it is necessary to solve them through various measures such as adjusting resource allocation; therefore, it is very necessary to provide a three-level hierarchical energy storage configuration method for rural distribution networks based on the daily balance mechanism, which can reasonably configure energy storage devices, coordinate and cooperate in energy storage operation, realize maximum local consumption, and improve safety. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a three-level hierarchical energy storage configuration method for rural distribution networks based on a daily balance mechanism, which can reasonably configure energy storage devices, coordinate energy storage operations, maximize local consumption, and improve safety.

[0004] The object of the present invention is achieved by: a three-level hierarchical energy storage configuration method for a rural distribution network based on a daily balance mechanism, the method comprising the following steps:

[0005] Step 1: Construct a hierarchical and graded energy storage configuration system for rural distribution networks;

[0006] Step 2: Establish the energy storage configuration principles for rural distribution networks and carry out energy storage configuration from bottom to top;

[0007] Step 3: For energy autonomous rural microgrid energy storage configuration, based on the operation data of substations and feeders in rural areas, a storage configuration method based on the daily balance mechanism is constructed to guide the energy autonomous rural microgrid energy storage configuration;

[0008] Step 4: Analysis of typical storage configuration examples in substations / feeders.

[0009] The step 1 of constructing a hierarchical and graded energy storage configuration system for a rural distribution network includes the following steps:

[0010] Step 1.1: County power grid autonomy: At the county 220 kV power grid level, through the storage of new energy stations or the configuration of large-scale independent energy storage, the county power grid can be self-sufficient or the 220 kV section interactive power can be adjusted;

[0011] Step 1.2: Local consumption of distributed power sources: Taking “distributed renewable energy power generation will not be transferred to the 220 kV grid” as the main principle for the energy storage configuration of the distribution network, that is, by configuring energy storage, distributed renewable energy can be consumed at the 110 kV and below grid level;

[0012] Step 1.3: Safe operation of equipment: At the 380V substation level, consider using distributed new energy storage and configuring energy storage in the substation.

[0013] The local consumption of distributed power sources in step 1.2 includes two aspects: ① At the 110 / 35 kV grid level, consider using new energy station storage and energy storage configuration to achieve full consumption of distributed new energy and ensure that the distributed new energy power does not increase to the 220 kV grid; ② At the 10 kV grid level, consider using distributed new energy storage and energy storage configuration on the bus or feeder side to achieve maximum local consumption of distributed new energy.

[0014] The establishment of the rural distribution network energy storage configuration principle in step 2 includes the following steps:

[0015] Step 2.1: 380 / 220V level storage: Follow the principle that the distribution transformer equipment will not be overloaded by the distributed photovoltaic power generation, and configure the energy storage with the distribution transformer area unit;

[0016] Step 2.2: 10 kV level storage configuration: Follow the principle of maximizing local consumption of distributed new energy and maximizing energy storage utilization efficiency, and configure energy storage using 10 kV feeder / bus as a unit;

[0017] Step 2.3: Configure energy storage at 35 / 110 kV: Follow the principle of “distributed new energy will not be upgraded to 220 kV” for energy storage.

[0018] The energy storage configuration method based on the daily balance mechanism constructed in step 3 specifically includes the following steps:

[0019] Step 3.1: Objective function setting: including the area storage objective function, household distributed photovoltaic storage objective function and 10 kV feeder / busbar storage objective function;

[0020] Step 3.2: Operation constraints: including energy storage power station operation constraints and power balance constraints;

[0021] Step 3.3: Setting economical storage conditions: The planning goal of the energy storage device site selection and sizing planning model is to minimize the comprehensive cost of the distribution network, including the investment cost of the energy storage device, the operation and maintenance cost of the energy storage device, the main grid power purchase cost, and the loss cost of the distribution network.

[0022] The objective function of the energy storage allocation in step 3.1 is as follows: considering that the power station does not have a reverse overload, for the day when the power station exceeds the reverse 80% load rate and the maximum amount of electricity turned over, the ideal amount of energy storage absorbed is the area enclosed by the net load curve of the day and the reverse 80% load rate value, so as to achieve the phenomenon of no reverse overload in the power station: Among them, P load-d (t) is the load power of the substation; P pv-d (t) is the photovoltaic output of the station area; Respectively represent the charging and discharging power of the energy storage in period t; It is the rated capacity of the distribution transformer in the substation.

[0023] The household distributed photovoltaic storage objective function in step 3.1 is specifically: for the red area of ​​carrying capacity (the area where the maximum reverse load rate exceeds 80%), it is required that the newly added distributed photovoltaic power generation does not increase: Among them, P load-u (t) is the user load power, P pv-u (t) is the photovoltaic output of the newly added users; for the yellow area of ​​carrying capacity (the area with the maximum reverse load rate not exceeding 80%), it is required that the newly added distributed photovoltaic power generation does not cause the reverse overload of the area:

[0024] The 10 kV feeder / busbar storage allocation objective function in step 3.1 is specifically as follows: considering that 100% of the distributed photovoltaic power generation under the 10 kV feeder / busbar is consumed locally, then for the day with the maximum amount of feeder / busbar power turnover, the ideal amount of energy storage absorbed is the amount of power turnover on that day: Among them, P load-l (t) is the feeder / bus load power; P pv-l (t) is the feeder / bus photovoltaic output.

[0025] The energy storage power station operation condition constraints in step 3.2 include: energy storage power station power constraints, energy storage power station capacity constraints and energy storage power station operation constraints.

[0026] The power balance constraints in step 3.2 include: substation power balance constraints, single-household power balance constraints, 10 kV feeder / bus power balance constraints, substation or feeder interaction power constraints, and main grid interconnection branch power constraints.

[0027] The planning goal of the economic storage allocation condition setting in step 3.3 is specifically: minC = C Ess +C f +C buy +C loss (twenty two), In the formula, C Ess is the investment cost of the energy storage device; n is the number of energy storage devices; ξ is the discount rate; y is the service life of ESS; is the investment cost per unit capacity of the energy storage device; The rated capacity of the i-th energy storage device; P is the investment cost per unit power of the energy storage device; i ESS The rated power of the i-th energy storage device; C f is the operation and maintenance cost of the energy storage device; T is 8760h per year; The operation and maintenance cost per unit charge and discharge capacity of the energy storage device; is the charge and discharge power of ESS at time t. A positive value represents ESS discharging, and a negative value represents ESS charging. C buy The cost of purchasing electricity for the main grid; n cp The number of main network liaison branches; is the real-time electricity price of the main grid at that moment; P gridt is the power on the main network connection branch at time t; C loss is the network loss cost of the distribution network; C l Represents unit network loss cost; N z is the total number of branches; I i is the current value flowing through branch i during period t; r i is the resistance value of branch i.

[0028] Beneficial effects of the invention: The present invention is a three-level hierarchical energy storage configuration method for rural distribution networks based on a daily balance mechanism, which aims to achieve maximum local and nearby consumption of new energy by configuring energy storage devices with reasonable capacities at multiple levels of the distribution network, and coordinated operation of energy storage at various voltage levels, thereby improving the safety of the distribution network; in use, the rural microgrid energy storage configuration method under high-proportion new energy access proposed by the present invention can solve the problems of local and nearby consumption and safe operation of new energy in rural microgrids under high-proportion new energy access, improve the utilization rate of new energy, reduce dependence on traditional fossil energy, and establish a reasonable distribution network energy storage configuration; the present invention has the advantages of reasonable configuration of energy storage devices, coordinated operation of energy storage, maximum local and nearby consumption, and improved safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a schematic diagram of the energy storage configuration at each level of the present invention (taking Lankao as an example).

[0030] Figure 2 It is a schematic diagram of the energy storage configuration method based on the daily balance mechanism of the present invention.

[0031] Figure 3 This is a schematic diagram of verifying the energy storage configuration strategy for the substation area of ​​the present invention.

[0032] Figure 4 This is a schematic diagram of a typical household energy storage configuration strategy verification according to the present invention.

[0033] Figure 5 It is a schematic diagram of verifying a 10kV feeder energy storage configuration strategy of the present invention. DETAILED DESCRIPTION

[0034] Energy storage is a "power warehouse" that can realize the division of electricity production and consumption in time and space, taking into account both power supply and new energy consumption. It has a short construction period and a flexible method. It is a key equipment to support the new power system. It is also an important means to solve the rural distribution network with a high proportion of distributed photovoltaic access in the province. Energy storage should be guided by meeting the power system regulation needs and the new energy development and consumption capacity, combined with the actual distribution of new energy and power load, adhere to source-load matching, and focus on configuration near the fluctuation source of the power system. It can effectively smooth out new energy and load fluctuations, promote the improvement of power security and regulation capabilities, and achieve local and nearby supply and demand balance.

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] Example 1

[0037] like Figure 1-5 As shown, a three-level hierarchical energy storage configuration method for a rural distribution network based on a daily balance mechanism comprises the following steps:

[0038] Step 1: Construct a hierarchical and graded energy storage configuration system for rural distribution networks: Through the coordinated operation of energy storage at various voltage levels, the problem of maximizing the local consumption of new energy can be solved;

[0039] In this embodiment, considering that the types and capacities of renewable energy accessed at different voltage levels are different, and the source-load characteristics are also different, the problem of spatiotemporal matching of source and load of high-proportion renewable energy access to the distribution network is solved through energy storage configuration. It is necessary to build a hierarchical and graded energy storage configuration system, and solve the problem of maximizing the local and nearby consumption of renewable energy through coordinated operation of energy storage at various voltage levels. Specifically, it includes the following aspects:

[0040] ① County power grid autonomy: At the county 220 kV power grid level, the county power grid can be self-sufficient or the 220 kV section interactive power can be adjusted through storage at new energy stations or configuration of large-scale independent energy storage (leasing by new energy enterprises and accepting unified dispatching by the power grid).

[0041] ② Local consumption of distributed power sources: According to the Guidelines for the Assessment of the Carrying Capacity of Distributed Power Sources Connected to the Grid, the main principle for the configuration of energy storage in the distribution network is that “the amount of distributed renewable energy will not be transferred to the 220 kV grid”, that is, by configuring energy storage, distributed renewable energy can be consumed at the 110 kV and below grid level;

[0042] 1) At the 110 / 35 kV grid level (all distributed renewable energy sources are absorbed), consider using renewable energy station distribution and energy storage configuration to solve the problem of absorbing the electricity of centralized / distributed renewable energy stations connected to this voltage level on the one hand, and on the other hand, to solve the problem of absorbing the distributed renewable energy electricity that cannot be absorbed at the 10 kV level, and ensure that the distributed renewable energy electricity does not flow up to the 220 kV grid;

[0043] 2) At the 10 kV grid level (maximum local consumption of distributed renewable energy), consider maximizing local consumption of distributed renewable energy through distributed renewable energy storage and configuring energy storage on the bus or feeder side.

[0044] ③ Safe operation of equipment: At the 380V substation level, consider solving the problem of reverse heavy overload in the substation caused by distributed new energy through distributed new energy distribution and storage, and configuring energy storage in the substation to ensure the safe operation of distribution and transformation equipment.

[0045] Step 2: Focusing on the efficient consumption of distributed renewable energy, establish the energy storage configuration principles for rural distribution networks and carry out energy storage configuration from bottom to top;

[0046] In this embodiment, with the efficient consumption of distributed new energy as the object, the rural distribution network is focused on building a three-level distribution and storage system of "380V-10kV-35 / 110kV", and energy storage configuration is carried out step by step from bottom to top, including the following aspects:

[0047] ①380 / 220V level distribution and storage: At the 380 / 220V level, the principle of avoiding reverse overload of the distribution transformer equipment due to distributed photovoltaics is followed, and energy storage is configured with the distribution transformer area unit;

[0048] For the substations with a maximum reverse load rate exceeding 80% (red area): 1) configure substation energy storage, and the energy storage scale is determined according to the standard of "controlling the maximum reverse load rate of the substation within 80%", and the energy storage construction and operation and maintenance costs are borne by the existing distributed photovoltaic users; 2) New distributed photovoltaic users provide their own energy storage, and the energy storage scale is determined according to the standard of "distributed photovoltaic power generation is not reversely transmitted to the substation";

[0049] For areas where the maximum reverse load rate does not exceed 80% (yellow area): new distributed photovoltaic users are required to provide their own energy storage, and the scale of energy storage is determined according to the standard of "the reverse load rate of the area does not exceed 80% due to their own distributed photovoltaic power generation".

[0050] ②10 kV level storage: At the 10 kV level, follow the principle of maximizing local consumption of distributed new energy and maximizing energy storage utilization efficiency, and use 10 kV feeders / busbars as units to configure energy storage;

[0051] Consider the day with the largest annual increase in feeder / busbar electricity:

[0052] a) If the daily turnover is less than the daily power supply of the power grid, the energy storage scale is determined according to the standard of "100% daily consumption of distributed renewable energy". In this case, energy storage can be configured to achieve local consumption of all distributed renewable energy under the feeder / busbar;

[0053] b) If the daily turnover of electricity is greater than the daily power supply of the grid, the scale of energy storage is determined according to the standard of "maximizing daily consumption of distributed renewable energy". In this case, it is impossible to realize on-site consumption of distributed renewable energy at the 10 kV level by configuring energy storage, and the consumption problem needs to be solved at the 35 / 110 kV level.

[0054] ③35 / 110 kV energy storage configuration: At the 35 / 110 kV power grid level, the storage is configured in accordance with the principle of “distributed new energy does not go up to 220 kV”.

[0055] Step 3: For energy autonomous rural microgrid energy storage configuration, based on the operation data of substations and feeders in rural areas, a storage configuration method based on the daily balance mechanism is constructed to guide the energy autonomous rural microgrid energy storage configuration;

[0056] Step 4: Analysis of typical storage configuration examples in substations / feeders.

[0057] The present invention is a three-level hierarchical energy storage configuration method for rural distribution networks based on a daily balance mechanism, which aims to achieve maximum local and nearby consumption of new energy by configuring energy storage devices with reasonable capacities at multiple levels in the distribution network, and coordinate the operation of energy storage at various voltage levels, thereby improving the safety of the distribution network. In use, the present invention proposes a hierarchical and graded energy storage configuration system at the 220 kV county power grid, 35-110 kV power grid, and 380V substation level to solve the problems of reverse overload of substation equipment and safe operation of distribution transformers, achieve maximum local and nearby consumption of distributed photovoltaics, and prevent the reverse transmission of electricity to 220kV At the county power grid level, the grid dispatching pressure is reduced; the present invention utilizes the daily balancing mechanism of energy storage electricity to maximize the efficiency of energy storage utilization and optimize the configuration economy; the rural microgrid energy storage configuration method under the high proportion of new energy access proposed in the present invention can solve the problems of local and nearby consumption and utilization of new energy in rural microgrids under the high proportion of new energy access and safe operation, improve the utilization rate of new energy, reduce dependence on traditional fossil energy, and establish a reasonable distribution network energy storage configuration; the present invention has the advantages of reasonable configuration of energy storage devices, coordinated operation of energy storage, maximum local and nearby consumption, and improved safety.

[0058] Example 2

[0059] like Figure 1-5 As shown, a three-level hierarchical energy storage configuration method for a rural distribution network based on a daily balance mechanism comprises the following steps:

[0060] Step 1: Construct a hierarchical and graded energy storage configuration system for rural distribution networks;

[0061] Step 2: Establish the energy storage configuration principles for rural distribution networks and carry out energy storage configuration from bottom to top;

[0062] Step 3: For energy autonomous rural microgrid energy storage configuration, based on the operation data of substations and feeders in rural areas, a storage configuration method based on the daily balance mechanism is constructed to guide the energy autonomous rural microgrid energy storage configuration;

[0063] In this embodiment, the microgrid storage can not only improve the stability of the microgrid, reduce the reverse overload rate of the substation and feeder, but also promote the local consumption of new energy; this aspect conducts research on the energy storage configuration method of energy-autonomous rural microgrids, and constructs a storage configuration method based on the daily balance mechanism based on the operation data of substations and feeders in rural areas to guide the energy storage configuration of energy-autonomous rural microgrids;

[0064] Step 3 specifically includes the following steps:

[0065] Step 3.1: Objective function setting, including:

[0066] ① Substation storage objective function: Considering that there is no reverse overload in the substation, for the day when the substation exceeds the reverse 80% load rate and the maximum amount of electricity turned over, the ideal amount of energy storage absorbed is the area enclosed by the net load curve of the day and the reverse 80% load rate value, so as to achieve no reverse overload in the substation: Among them, P load-d (t) is the load power of the substation; P pv-d (t) is the photovoltaic output of the station area; Respectively represent the charging and discharging power of the energy storage in period t; It is the rated capacity of the distribution transformer in the substation.

[0067] ②Household distributed photovoltaic storage objective function: For the red area of ​​carrying capacity (the area where the maximum reverse load rate exceeds 80%), it is required that the newly added distributed photovoltaic power generation should not be increased: Among them, P load-u (t) is the user load power, P pv-u (t) is the photovoltaic output of the newly added users; for the yellow area of ​​carrying capacity (the area with the maximum reverse load rate not exceeding 80%), it is required that the newly added distributed photovoltaic power generation does not cause the reverse overload of the area:

[0068] ③10 kV feeder / busbar storage objective function: Considering that 100% of the distributed photovoltaic power generation under the 10 kV feeder / busbar is consumed locally, for the day with the largest amount of power flowing over the feeder / busbar, the ideal amount of energy storage absorbed is the amount of power flowing over on that day: Among them, P load-l (t) is the feeder / bus load power; P pv-l (t) is the feeder / bus photovoltaic output.

[0069] Step 3.2: Run the constraints, including:

[0070] ① Constraints on the operating conditions of energy storage power stations, including:

[0071] 1) Energy storage power station power constraint: At any time, the charging and discharging power of the energy storage system should not be greater than the rated power of the energy storage system, and the energy storage system cannot be charged and discharged at the same time: in, is the charging state of the energy storage at time t, and the charging time is 1, and is 0 when idle or discharging; is the discharge state of the energy storage in period t. is 1, and is 0 when idle or charging; is the rated power of the energy storage system.

[0072] 2) Energy storage power station capacity constraints: In order to increase the service life of energy storage, the remaining power of the energy storage system should not be greater than 90% of the rated capacity at any time, and cannot be less than 10% of the rated capacity: Among them, E S (t) represents the remaining power of the energy storage at time period t; Represents the rated capacity of the energy storage system.

[0073] 3) Energy storage power station operation constraints: The energy storage system has a certain power loss during the charging and discharging process: Among them, Δt represents the unit time interval; in order to meet the normal daily charging and discharging of energy storage, the energy storage system's daily starting and ending power should be consistent, that is, the daily charging and discharging power should be consistent: The power of the microgrid system is kept balanced in real time: Among them, P grid (t) is the interaction power with the upper power grid; P load (t) is the total load power of the microgrid; They are the charging and discharging efficiency of energy storage respectively.

[0074] ②Power balance constraints, including:

[0075] 1) Power balance constraints of power distribution and storage in the substation area: Where P l (t) represents the power flowing on a 10 kV feeder at time t; P load-d,i (t) represents the total load of the feeder downlink area i at time t; P pv-d,i (t) represents the total PV output in the feeder downlink area i at time t; represents the total energy storage charging power in the feeder downlink area i at time t; represents the total energy storage discharge power in the feeder downlink area i at time t; P l,i (t) is the interaction power between the feeder and the station area i. It is positive when the power flows from the feeder to the station area, and negative when the power flows from the feeder to the station area. d,ij (t) is the interaction power between area i and its interconnected area j. It is positive when power flows from area j to area i, and negative otherwise.

[0076] 2) Constraints on storage power for single-family homes: Where P d (t) represents the net power of a certain area at time t; P load-u,i (t) represents the total load of household i in the area at time t; P pv-u,i (t) represents the total PV output in the feeder downlink area i at time t; represents the total energy storage charging power in household i in this area at time t; P represents the total energy storage discharge power of household i in the area at time t; d,i (t) is the interaction power between household i and the substation under the feeder. It is positive when power flows from the substation to the household, and negative otherwise.

[0077] 3) 10 kV feeder / busbar storage constraints:

[0078] Where P b (t) represents the power flowing to the load from a distribution transformer at time t; P load-l,i (t) represents the total load of feeder i under the substation at time t; P pv-l,i (t) represents the total photovoltaic output in feeder i of the distribution transformer at time t; represents the total energy storage charging power under the distribution transformer feeder i at time t; represents the total energy storage discharge power of the distribution transformer feeder i at time t; P b,i (t) is the interaction power between the feeder i and the distribution transformer under the distribution transformer. It is positive when the power flows from the distribution transformer to the feeder, and negative otherwise. l,ij (t) is the interaction power between feeder i and its flexible interconnected feeder j. It is positive when power flows from feeder j to feeder i, and negative otherwise.

[0079] 4) Interaction power constraints between stations or feeders: P l min ≤|P linr,i,t |≤P l max (20), where P l max , P l min They represent the upper and lower limits of the power allowed to be transmitted on the tie line l between stations or feeders, respectively, and can be set according to autonomous requirements; P line,i,t It represents the power flowing on the tie line l between stations or feeders at time t.

[0080] 6) Power constraint condition of main network interconnection branch: P grid,t ≥0(21), where P grid,t Represents the power on the branch connecting to the main grid at time t.

[0081] Step 3.3: Setting economical storage conditions: The planning goal of the energy storage device site selection and sizing planning model is to minimize the comprehensive cost of the distribution network, including the investment cost of the energy storage device, the operation and maintenance cost of the energy storage device, the main grid power purchase cost, and the loss cost of the distribution network.

[0082] The planning goal of setting economic storage conditions is: minC = C Ess +Cf +C buy +C loss (twenty two),

[0083] In the formula, C Ess is the investment cost of the energy storage device; n is the number of energy storage devices; ξ is the discount rate; y is the service life of ESS; is the investment cost per unit capacity of the energy storage device; The rated capacity of the i-th energy storage device; P is the investment cost per unit power of the energy storage device; i ESS The rated power of the i-th energy storage device; C f is the operation and maintenance cost of the energy storage device; T is 8760h per year; The operation and maintenance cost per unit charge and discharge capacity of the energy storage device; is the charge and discharge power of ESS at time t. A positive value represents ESS discharging, and a negative value represents ESS charging. C buy The cost of purchasing electricity for the main grid; n cp The number of main network liaison branches; is the real-time electricity price of the main grid at that moment; P grid,t is the power on the main network connection branch at time t; C loss is the network loss cost of the distribution network; C l Represents unit network loss cost; N z is the total number of branches; I i is the current value flowing through branch i during period t; r i is the resistance value of branch i.

[0084] In this embodiment, the distributed new energy storage and energy storage conversion cost is not loss-making as the energy storage configuration boundary condition; the conversion cost is the dynamic total cost of the project divided by the power generation of the new power source over the entire life cycle; the project cost includes project construction cost, financial cost, and operation and maintenance costs. The project operation cycle is 25 years.

[0085] Construction cost: With reference to the winning bid price of distributed photovoltaic EPC in Henan Province, the unit cost of photovoltaic projects in 2023 is set at 2 yuan / watt; with reference to the average winning bid price of new electrochemical energy storage EPC projects in the first quarter of 2022, 2023 and 2024 of 2.195 yuan / Wh, 1.67 yuan / Wh and 1.351 yuan / Wh, respectively.

[0086] Financial cost: Repayment is in equal installments of principal over a 10-year period. The self-raised capital ratio is 20%. The loan interest rate is calculated based on the latest loan market interest rate (LPR for more than five years) announced by the People's Bank of China, which is 3.95%.

[0087] Power supply operation and maintenance costs: labor cost 15 yuan / kilowatt-year, insurance premium rate 0.25%, material cost 8 yuan / kilowatt-hour, repair fee rate 0.2% in the 1st to 5th years, 0.25% in the 6th to 10th years, and 0.5% in the 11th to 25th years.

[0088] Energy storage operation and maintenance costs: The average annual labor cost is 7.5 yuan / kWh, the insurance premium rate is 0.25%, the material cost is calculated at 7.5 yuan / kWh, and the repair cost is 27 yuan / kWh.

[0089] Energy storage replacement cost: Considering that the energy storage life is 12 years, the energy storage battery will be replaced once in the middle of the project, and the battery replacement cost is 0.6 yuan / watt-hour.

[0090] Step 4: Analysis of typical storage configuration examples in substations / feeders.

[0091] In this embodiment, ① Typical area storage example

[0092] Take a substation in a county in northern China as an example: the substation has a distribution transformer capacity of 200 kVA, a maximum load of 241.39 kW, and a photovoltaic installed capacity of 263.53 kW. The power increased for 315 days throughout the year, of which reverse overload occurred 21 times, with the maximum reverse overload power being 220.19 kW.

[0093] On May 24, 2023, the substation experienced a maximum reverse power transmission of 220.19 kilowatts; on April 29, 2023, the reverse power exceeded 80% of the rated capacity for the largest number of days.

[0094] According to the objective function requirements of the area storage allocation: The maximum charging and discharging power of the energy storage system is 67 kilowatts.

[0095] According to the capacity constraints of energy storage power stations: The energy storage configuration capacity is 142 kWh.

[0096] In summary, the substation should be equipped with 71 kW / 142 kWh of energy storage.

[0097] The energy storage configuration results of the substation were verified to meet the requirement that the energy storage system's daily power consumption should remain consistent; through economic calculations, the energy storage cost per kilowatt-hour was found to be 0.224 yuan / watt-hour, which is more economical.

[0098] ② Typical household storage example

[0099] Take a villager's family in a northern rural area as an example: the family wants to achieve self-sufficiency in electricity supply with all clean energy. The household photovoltaic installed capacity is 25 kilowatts. On a high-load day in winter, the family's daily electricity consumption is 115 kWh; the maximum power consumption is 14.25 kilowatts, and the maximum photovoltaic output is 20.05 kilowatts.

[0100] According to the household storage objective function requirements: The maximum charging and discharging power of the energy storage system is 20 kilowatts.

[0101] According to the capacity constraints of energy storage power stations: The energy storage configuration capacity is 120 kWh.

[0102] In summary, farmers' households should be equipped with 20 kW / 120 kWh of energy storage.

[0103] In order to verify the results of household energy storage configuration, the daily power consumption of the energy storage system should be kept consistent; for some farmers who want to achieve self-sufficiency in clean energy, the energy storage configuration capacity ratio is high and the economy is poor.

[0104] ③Typical feeder storage example

[0105] Take a 10kV feeder under a northern county power grid as an example: after energy storage was configured in the feeder's downstation area, the feeder still experienced an upward power flow phenomenon; on April 25, 2023 (the day with the largest upward power flow), the maximum reverse power transmission of the feeder was 0.42 MWh; on May 7, 2023 (the day with the largest upward power flow), the maximum reverse power of the feeder was 0.29 MW.

[0106] According to the feeder storage objective function requirements: The maximum charging and discharging power of the energy storage system is obtained to be 0.3 MW.

[0107] According to the capacity constraints of energy storage power stations: The energy storage configuration capacity is 0.42 MWh.

[0108] In summary, the feeder is configured with 0.3 MW / 0.6 MWh of energy storage.

[0109] In order to verify the energy storage configuration results of the feeder, the energy storage system should maintain the same power at the beginning and end of each day; after configuring the energy storage, there is no power increase in the feeder. The energy storage cost per kilowatt-hour is 0.158 yuan / watt-hour through economic calculation, which is relatively economical.

[0110] The present invention is a three-level hierarchical energy storage configuration method for rural distribution networks based on a daily balance mechanism, which aims to achieve maximum local and nearby consumption of new energy by configuring energy storage devices with reasonable capacities at multiple levels in the distribution network, and coordinate the operation of energy storage at various voltage levels, thereby improving the safety of the distribution network. In use, the present invention proposes a hierarchical and graded energy storage configuration system at the 220 kV county power grid, 35-110 kV power grid, and 380V substation level to solve the problems of reverse overload of substation equipment and safe operation of distribution transformers, achieve maximum local and nearby consumption of distributed photovoltaics, and prevent the reverse transmission of electricity to 220kV At the county power grid level, the grid dispatching pressure is reduced; the present invention utilizes the daily balancing mechanism of energy storage electricity to maximize the efficiency of energy storage utilization and optimize the configuration economy; the rural microgrid energy storage configuration method under the high proportion of new energy access proposed in the present invention can solve the problems of local and nearby consumption and utilization of new energy in rural microgrids under the high proportion of new energy access and safe operation, improve the utilization rate of new energy, reduce dependence on traditional fossil energy, and establish a reasonable distribution network energy storage configuration; the present invention has the advantages of reasonable configuration of energy storage devices, coordinated operation of energy storage, maximum local and nearby consumption, and improved safety.

Claims

1. A three-level hierarchical energy storage configuration method for rural distribution networks based on a daily balance mechanism, characterized by: The method comprises the following steps: Step 1: Construct a hierarchical and graded energy storage configuration system for rural distribution networks; Step 2: Establish the energy storage configuration principles for rural distribution networks and carry out energy storage configuration from bottom to top; Step 3: For energy autonomous rural microgrid energy storage configuration, based on the operation data of substations and feeders in rural areas, a storage configuration method based on the daily balance mechanism is constructed to guide the energy autonomous rural microgrid energy storage configuration; Step 4: Analysis of typical storage configuration examples in substations / feeders.

2. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 1, characterized in that: The step 1 of constructing a hierarchical and graded energy storage configuration system for rural distribution networks includes the following steps: Step 1.1: County power grid autonomy: At the county 220 kV power grid level, through the storage of new energy stations or the configuration of large-scale independent energy storage, the county power grid can be self-sufficient or the 220 kV section interactive power can be adjusted; Step 1.2: Local consumption of distributed power sources: Taking "distributed renewable energy power generation will not be transferred to the 220 kV grid" as the main principle for the energy storage configuration of the distribution network, that is, by configuring energy storage, distributed renewable energy can be consumed at the 110 kV and below grid level; Step 1.3: Safe operation of equipment: At the 380V substation level, consider using distributed new energy storage and configuring energy storage in the substation.

3. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 1 is characterized by: The establishment of the rural distribution network energy storage configuration principle in step 2 includes the following steps: Step 2.1: 380 / 220V level storage: Follow the principle that the distribution transformer equipment will not be overloaded by the distributed photovoltaic power generation, and configure the energy storage with the distribution transformer area unit; Step 2.2: 10 kV level storage configuration: Follow the principle of maximizing local consumption of distributed renewable energy and maximizing energy storage utilization efficiency, and configure energy storage using 10 kV feeder / busbar as a unit; Step 2.3: Configure energy storage at 35 / 110 kV: Follow the principle of "distributed new energy will not be upgraded to 220 kV" to configure energy storage.

4. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 1, characterized in that: The energy storage configuration method based on the daily balance mechanism constructed in step 3 specifically includes the following steps: Step 3.1: Objective function setting: including the area storage objective function, household distributed photovoltaic storage objective function and 10 kV feeder / busbar storage objective function; Step 3.2: Operation constraints: including energy storage power station operation constraints and power balance constraints; Step 3.3: Setting economical storage conditions: The planning goal of the energy storage device site selection and sizing planning model is to minimize the comprehensive cost of the distribution network, including the investment cost of the energy storage device, the operation and maintenance cost of the energy storage device, the main grid power purchase cost, and the loss cost of the distribution network.

5. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 4 is characterized by: The objective function of the energy storage allocation in step 3.1 is as follows: considering that the power station does not have a reverse overload, for the day when the power station exceeds the reverse 80% load rate and the maximum amount of electricity turned over, the ideal energy storage absorption amount is the area enclosed by the net load curve of the day and the reverse 80% load rate value, so as to achieve the phenomenon of no reverse overload in the power station: Among them, P load-d (t) is the load power of the substation; P pv-d (t) is the photovoltaic output of the station area; Respectively represent the charging and discharging power of the energy storage in period t; It is the rated capacity of the distribution transformer in the substation.

6. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 5 is characterized by: The household distributed photovoltaic storage objective function in step 3.1 is specifically: for the area where the maximum reverse load rate exceeds 80%, it is required that the newly added distributed photovoltaic power generation does not increase: Among them, P load-u (t) is the user load power, P pv-u (t) For newly added PV output of users; for areas where the maximum reverse load rate does not exceed 80%, it is required that the newly added distributed PV does not cause reverse overload in the area:

7. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 6 is characterized by: The 10 kV feeder / busbar storage allocation objective function in step 3.1 is specifically as follows: considering that 100% of the distributed photovoltaic power generation under the 10 kV feeder / busbar is consumed locally, then for the day with the maximum amount of feeder / busbar power turnover, the ideal amount of energy storage absorbed is the amount of power turnover on that day: Among them, P load-l (t) is the feeder / bus load power; P pv-l (t) is the feeder / bus photovoltaic output.

8. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 4 is characterized by: The energy storage power station operation condition constraints in step 3.2 include: energy storage power station power constraints, energy storage power station capacity constraints and energy storage power station operation constraints.

9. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 8, characterized in that: The power balance constraints in step 3.2 include: substation power balance constraints, single-household power balance constraints, 10 kV feeder / bus power balance constraints, substation or feeder interaction power constraints, and main grid interconnection branch power constraints.

10. The three-level hierarchical energy storage configuration method for rural distribution network based on daily balance mechanism as claimed in claim 4, characterized in that: The planning goal of the economic storage allocation condition setting in step 3.3 is specifically: min C = C Ess +C f +C buy +C loss (twenty two), In the formula, C Ess is the investment cost of the energy storage device; n is the number of energy storage devices; ξ is the discount rate; y is the service life of ESS; is the investment cost per unit capacity of the energy storage device; The rated capacity of the i-th energy storage device; is the investment cost per unit power of the energy storage device; The rated power of the i-th energy storage device; C f is the operation and maintenance cost of the energy storage device; T is 8760h per year; The operation and maintenance cost per unit charge and discharge capacity of the energy storage device; is the charging and discharging power of ESS at time t; C buy The electricity purchase cost for the main grid; n cp The number of main network liaison branches; P is the real-time electricity price of the main grid at that moment; grid,t is the power on the main network connection branch at time t; C loss is the network loss cost of the distribution network; C l Represents unit network loss cost; N z is the total number of branches; I i is the current value flowing through branch i during period t; r i is the resistance value of branch i.

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