Hybrid energy storage system two-stage planning method considering electro-hydrogen coupling

Abstract

The invention discloses a hybrid energy storage system two-stage planning method considering electro-hydrogen coupling. The method comprises the steps that output models of all devices of a hybrid energy storage system are established; establishing a first-stage energy-abundance period capacity optimization configuration model; establishing a second-stage dead energy period capacity optimization configuration model; establishing load power loss rate and energy excess rate evaluation indexes; and solving the two-stage planning model of the micro-grid hybrid energy storage system. The method can be used for stabilizing new energy fluctuation and improving the operation stability of a power system.

Description

Technical Field

[0001] The present invention belongs to the technical field of microgrid energy storage system planning, and in particular relates to a two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling. Background Art

[0002] Planning energy storage devices in microgrids can improve the stability and security of the power grid. Compared with traditional battery energy storage, existing energy storage systems are developing in the direction of multiple energy storage such as gas storage, hydrogen storage, cold storage, and heat storage. Among the many energy storage methods, hydrogen energy storage has the advantages of long-term storage, large storage scale, environmental protection, and no pollution, and is not restricted by the geographical environment. It has received widespread attention. Using battery energy storage and hydrogen energy storage in microgrids as hybrid energy storage, the various components of the system coordinate with each other, which can greatly improve the absorption capacity of the microgrid system. At present, some research has been done at home and abroad on the planning and configuration of hydrogen energy storage in microgrids.

[0003] Reference [1]: Zuo Guanlin, Guo Hongxia, Lin Wenzhi, et al. Optimal configuration of microgrid considering low-carbon hydrogen production [J]. Electric Power Automation Equipment, 2023, 43(2): 9-18. Taking into account both the system economy and the amount of wind and solar power consumption, a robust planning model for the electric-hydrogen energy system considering the electric-hydrogen coupling and carbon trading mechanism was established. A "electricity-hydrogen-electricity" energy closed-loop structure was constructed through hydrogen fuel cells, realizing the temporal and spatial transfer of loads.

[0004] Reference [2]: Si Yang, Chen Laijun, Chen Xiaotao, et al. Optimal configuration of hydrogen energy storage capacity of wind-hydrogen hybrid system based on distributed blue rods [J]. Electric Power Automation Equipment, 2021, 41(10): 3-10. Taking into account the economy and reliability of the microgrid system, the hydrogen storage system is used for the capacity optimization configuration problem of the isolated DC microgrid, and an operation strategy considering the electric-hydrogen coupled microgrid is proposed, and the proposed control strategy is verified through semi-physical simulation.

[0005] Reference [3]: Sun Huijuan, Que Weixin, Peng Chunhua. Confidence gap robust planning of electric-hydrogen energy system considering electric-hydrogen coupling and carbon trading [J]. Power System Technology, 2023. A long-term capacity optimization method is proposed to optimize the microgrid capacity by analyzing the dynamic efficiency of the hydrogen storage system and establishing a model.

[0006] The above-mentioned literature improves the stability of the power system and reduces the amount of wind and solar power curtailment in the region by introducing hydrogen energy storage with long-term storage capacity in traditional microgrids. However, it is not enough to rely solely on hydrogen energy storage with long-term regulation capabilities. Few literatures use hydrogen energy storage and electrochemical energy storage to carry out planning research in microgrids based on the energy regulation needs at different time scales. Furthermore, although the "electricity-hydrogen-electricity" energy closed-loop structure has achieved long-term energy transfer, it has failed to fully tap the economic value of renewable energy hydrogen conversion, and the economic efficiency of microgrids still has room for improvement. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling, which can be used to smooth out fluctuations in new energy and improve the operating stability of the power system.

[0008] The technical solution adopted by the present invention is:

[0009] A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling includes the following steps:

[0010] Step 1: Establish the output model of each device of the hybrid energy storage system;

[0011] Step 2: Establish the capacity optimization configuration model for the first phase of abundant energy period;

[0012] Step 3: Establish the capacity optimization configuration model for the second phase of the lean period;

[0013] Step 4: Establish evaluation indicators of load power failure rate and energy surplus rate;

[0014] Step 5: Solve the two-stage planning model of the microgrid hybrid energy storage system.

[0015] In step 1, the output model of each device of the hybrid energy storage system includes:

[0016] (1) Battery:

[0017] The battery can effectively smooth out the fluctuations in the microgrid caused by the instability of photovoltaic and wind power output in the short term. The battery can be charged and discharged according to the actual situation. The operating temperature of the energy storage battery is generally the same as the room temperature, so the effect of temperature on the charging and discharging of the battery can be ignored.

[0018] The battery capacity characteristics satisfy the following relationship:

[0019]

[0020] In formula (1): E t+1 is the battery capacity at time t+1; α is the battery self-discharge rate; E t is the battery capacity at time t; Pch (t), P dis (t) are the charging and discharging power of the battery respectively; η ch , η dis are the battery charging and discharging efficiencies respectively; △t is the time interval.

[0021] (2) Electrolyzer:

[0022] The electrolyzer converts water into hydrogen and oxygen (power to hydrogen, P2H) through water electrolysis technology. The commonly used methods are alkaline water electrolysis of hydrogen and proton exchange membrane water electrolysis of hydrogen. Among them, the alkaline electrolyzer has a fast reaction speed and a more mature technology. Its hydrogen production can be expressed as:

[0023] M el (t) = η el P el (t) (2);

[0024] Where: M el (t), P el (t) are the hydrogen production and power of the electrolyzer at time t; η el is the hydrogen production efficiency of the electrolyzer.

[0025] (3) Hydrogen compressor:

[0026] The pressure of hydrogen produced by electrolysis is generally 14 bar. In order to achieve large-scale storage, hydrogen needs to be compressed to 200 bar before being stored in a hydrogen storage tank. The working power of the hydrogen compressor is related to the pressure difference before and after compression and the properties of the gas. Its configuration capacity is determined by the capacity of the electrolyzer. In order to simplify the model, the present invention considers the configuration relationship between the hydrogen compressor and the electrolyzer as a linear relationship:

[0027] P cp =kP el (3)

[0028] Where: P cp is the power of hydrogen compressor, P el is the electrolytic cell power, and k is the proportionality coefficient.

[0029] (4) Fuel cells:

[0030] The fuel cell uses the widely used proton exchange membrane battery as an electric-hydrogen coupling element to convert hydrogen into electrical energy and feed it back to the grid. The output power of the fuel cell is related to the amount of hydrogen input, as shown in the following formula:

[0031] P FC (t) = η FC M FC (t) (4);

[0032] Where: PFC (t) is the fuel cell output power; η FC is the hydrogen-to-electricity conversion efficiency of the fuel cell; M FC (t) represents the hydrogen consumption of the fuel cell at time t.

[0033] (5) Hydrogen storage tank:

[0034] The hydrogen storage capacity S of the hydrogen storage tank at time t+1 H (t+1) and the hydrogen storage amount S at time t H (t) is related to the hydrogen output of the hydrogen compressor or the hydrogen consumption of the fuel cell at time t, as shown in the following formula:

[0035]

[0036] Where: S H (t+1) is the hydrogen storage capacity at time t; S H (t) and the hydrogen output of the hydrogen compressor at time t.

[0037] In step 2, the first stage capacity optimization configuration model for the abundant energy period converts the surplus energy of the electrolyzer in the abundant energy period into hydrogen and stores it for backup during the lean energy period, and fully taps the economic value of renewable energy hydrogen conversion under the premise of meeting the power supply reliability constraints.

[0038] The optimal configuration model for the capacity during the abundant energy period includes the investment cost of the battery C BESS，inv , Maintenance cost C BESS，ope and hydrogen production and storage costs C H,st , Hydrogen sales revenue The objective function in the model is shown in formula (6):

[0039]

[0040] In the formula: f1 represents the objective function 1.

[0041] In step 3, the second stage of the lean period capacity optimization configuration model is that the hydrogen fuel cell, photovoltaic and wind turbines work together to meet the load power demand during the lean period. The optimization goal during the lean period is to make the hydrogen fuel cell investment cost C FC,inv , Operation and maintenance costs C FC,ope and fuel cell start-stop cost C FC,on Minimum, as shown in formula (7):

[0042] f2=min(C FC,inv +C FC,ope +C FC,on )(7);

[0043] Where: f2 represents the objective function 2.

[0044] In step 4, the microgrid may experience wind and solar power abandonment and load power failure during operation. In order to analyze the wind and solar power abandonment and load power failure of the microgrid, the load power failure rate σ is introduced. SLD and energy excess rate σ EED To characterize the reliability of the microgrid, the expressions are as follows:

[0045]

[0046] Where: P SLD (t) is the power shortage of the microgrid at time t; P rem (t) is the energy abandoned by the microgrid at time t, P LOAD (t) is the load power at time t; P G (t) is the power output at time t.

[0047] In order to absorb wind and solar resources as much as possible and meet the reliability requirements of microgrid operation, it is necessary to constrain the microgrid load power failure rate and energy surplus rate, as shown in the following formula:

[0048]

[0049] Where: SLD,max , σ EER,max They are the maximum load power failure rate and energy surplus rate allowed by the microgrid respectively.

[0050] In step 5, the solution process of the two-stage planning model of the microgrid hybrid energy storage system is:

[0051] First, net energy data is generated at intervals of one day. The capacity optimization configuration model in the abundant energy period solves the preliminary configuration capacity of each part and the hydrogen production and storage capacity according to the abundant energy sequence; the capacity optimization configuration model in the dry energy period calculates the hydrogen demand of the microgrid in the dry energy period and the preliminary planning capacity of the hydrogen fuel cell according to the energy deficiency sequence;

[0052] Secondly, according to the feasibility constraints of hydrogen production and demand, the relationship between hydrogen production and storage in the abundant energy period and hydrogen production in the dry energy period is compared, and the initial configuration capacity is iteratively updated according to different situations to obtain the planned capacity of each part of the hydrogen storage system;

[0053] Finally, the configured power and capacity of the battery when meeting the microgrid load power failure rate are calculated at intervals of 1 hour.

[0054] Step 5 includes the following process steps:

[0055] Step 5.1: Input the source and load data of the pre-planning area with a time interval of △t (take 1h), and generate the net energy data according to the following formula.

[0056]

[0057] Where: E net (t) is the net energy sequence of the microgrid; E G (t) is the electric energy output by the power supply at time t; E load (t) is the electric energy consumed by the load at time t; is the abundant energy at time t; is the electrical energy shortage at time t.

[0058] Step 5.2: Calculate the maximum continuous surplus energy of the microgrid according to the following formula, and use the last moment of the period with the maximum continuous surplus energy as the initial moment of the hydrogen storage tank.

[0059]

[0060] Where: T + Represents a collection of sequence rich energy sequence time periods.

[0061]

[0062] Where: S tank (0) is the energy storage of the hydrogen storage tank at the initial moment; Represent the 0th to Nth maximum continuous surplus energies respectively.

[0063] Step 5.3: The capacity optimization configuration model in the abundant energy period is used to solve the initial rated power P of the electrolyzer EL , initial battery capacity S B The initial capacity of the hydrogen storage tank S H ; The capacity optimization configuration model during the off-season calculates the rated power of the hydrogen fuel cell according to formula (13) And solve the optimized operation mode in step 5.2-step 5.3 to obtain the hydrogen demand when the microgrid has no continuous energy shortage for M hours during the dry season.

[0064]

[0065] Where: is the rated power of the hydrogen fuel cell; P load (t) represents the load power at time t.

[0066] Step 5.4: Simulate the hydrogen storage state of the hydrogen storage tank according to formula (5), where the operating power P el (t) is less than the rated power P EL ; Step 5.5: Check whether the feasibility constraint of hydrogen production and demand is met according to formula (14). If so, it means that the microgrid energy supply exceeds the demand. Then solve whether the energy surplus rate meets the constraint according to formula (8). If so, the rated power of the electrolyzer is If it is not satisfied, the microgrid has wind and solar power abandonment. In order to minimize wind and solar power abandonment, the electrolyzer power and hydrogen storage tank capacity can be increased to convert excess energy into hydrogen and sell it to obtain a certain amount of hydrogen sales revenue, that is, P in step 5.3 EL '=P EL +△p,P EL ' represents the updated electrolytic cell power, P EL represents the original electrolytic cell power, and △p represents the increased electrolytic cell power.

[0067] Until the energy surplus rate index σ in step 5.4 is met EER ≤σ EER,max until;

[0068]

[0069] Where: S H (t) represents the capacity of the hydrogen storage tank at time t. load (t+1) represents the load power at time t+1. G (t+1) represents the power output at time t+1.

[0070] Step 5.6: If the operation constraints shown in equation (14) are not satisfied, then P EL '=P EL +△p, repeat steps 5.3-5.5 until the operation constraints are met, and the iteration stop condition is ).

[0071] If the iteration stops and the energy demand is still not satisfied, it means that the microgrid energy supply is insufficient. At this time, the installed capacity of the power supply should be increased to change the surplus energy sequence. Repeat steps 5.1 to 5.6 until the operation constraints are met.

[0072] Step 5.7: Calculate the microgrid load power failure rate after the iteration of step 5.6 stops at a time interval of 1h. If the load power failure rate σ SLD >σ SLD,max , then return to step 5.3 to increase the battery configuration capacity in the first stage, that is, S B '=S B +△s,S B ' represents the updated hydrogen storage tank capacity; S B represents the original hydrogen storage tank capacity; △s represents the newly added hydrogen storage tank capacity; until σ is satisfied SLD ≤σ SLD,max The iteration ends when the planned capacity of each part is obtained.

[0073] The flow chart of the above steps is as follows Figure 2 shown.

[0074] The present invention provides a two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling, and the technical effects are as follows:

[0075] 1) In step 1 of the present invention, mathematical models of the battery, electrolyzer, hydrogen compressor, hydrogen storage tank, and hydrogen fuel are established, and the connection between the input and output of each part is established through mathematical relationships.

[0076] 2) In step 2 of the present invention, an optimization configuration model for the abundant energy period is established with battery cost, hydrogen energy storage cost, start-stop cost and hydrogen sales revenue as objective functions. In the model, the surplus energy of the microgrid is converted into hydrogen through an electrolyzer and stored for backup during the lean period, and the economic value of renewable energy hydrogen conversion is fully explored under the premise of meeting the power supply reliability constraints.

[0077] 3) In step 3 of the present invention, a lean period capacity optimization configuration model is established, which aims to maintain the supply and demand balance of the microgrid by discharging the electrolyzer during the lean period. The model optimization goal is to minimize the hydrogen fuel cell investment cost, operation and maintenance cost, and fuel cell start-up and shutdown cost while supporting the power shortage.

[0078] 4) In step 4 of the present invention, the load power failure rate and the energy surplus rate are introduced to characterize the reliability of the microgrid, so as to analyze the wind and solar power abandonment and load power failure at all times during the iterative solution process. By setting constraints, the microgrid can absorb wind and solar power resources as much as possible and meet the requirements of microgrid operation reliability.

[0079] 5) In step 5 of the present invention, the relationship between hydrogen production and storage in the abundant energy period and hydrogen production in the lean energy period is compared according to the feasibility constraint of hydrogen production-hydrogen demand, and the preliminary configuration capacity is iteratively updated according to different situations to obtain the planned capacity of each part of the hydrogen storage system, and the configuration power and capacity of the battery when meeting the microgrid load power failure rate are calculated at intervals of 1 hour. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0081] Figure 1 It is a schematic diagram of the process of the present invention.

[0082] Figure 2 Flowchart for solving the two-stage model of a hybrid energy storage system.

[0083] Figure 3 This is the structural diagram of the electricity-hydrogen coupled microgrid.

[0084] Figure 4 This is the annual wind power output curve of the microgrid.

[0085] Figure 5 This is the annual photovoltaic output curve of the microgrid.

[0086] Figure 6 This is the hourly load power curve.

[0087] Figure 7 This is a schematic diagram of the system output on a typical day in scenario 2.

[0088] Figure 8 This is a schematic diagram of the battery's operation throughout the year.

[0089] Fig. 9 This is a schematic diagram of the electrolytic cell's operation throughout the year. DETAILED DESCRIPTION

[0090] A two-stage planning method for hybrid energy storage system considering electric-hydrogen coupling is proposed. The hybrid energy storage system is constructed by using the complementary principle of electrochemical energy storage and hydrogen energy storage. The hydrogen storage system ensures that the microgrid has no continuous energy loss of more than 1 day. Under the premise of meeting the load power failure rate, the economic value of renewable energy is fully exploited. The excess electricity is converted into hydrogen through the electrolyzer and sold to obtain a certain income. The battery ensures that the microgrid has no continuous energy loss of more than M hours to meet the reliability requirements of the microgrid. A two-stage capacity planning model for hybrid energy storage of microgrid is established with the goal of minimizing the annualized total cost of the system, and it is proposed to solve the constructed model through the coupling relationship between the hydrogen production of the first stage model and the hydrogen demand of the second stage model.

[0091] The steps include:

[0092] Step 1: Establish mathematical models of batteries, electrolyzers, hydrogen compressors, hydrogen storage tanks, and hydrogen fuel.

[0093] Step 2: Establish a capacity optimization configuration model for the first phase of abundant energy.

[0094] Step 3: Establish the optimal configuration model for the second phase of the dry season.

[0095] Step 4: Establish evaluation indicators for load power failure rate and energy surplus rate.

[0096] Step 5: Solve the constructed two-level planning model according to the coupling relationship between the two-stage models.

[0097] Furthermore, the device models built in step 1 include:

[0098] (1) Battery:

[0099] The battery capacity characteristics satisfy the following relationship:

[0100]

[0101] Where: α is the battery self-discharge rate; E t is the battery capacity at time t; E t+1 is the battery capacity at time t+1; Pch (t), P dis (t) are the battery charge / discharge power; η ch , η dis are the battery charge / discharge efficiency; S B is the rated capacity of the battery; △t is the time interval.

[0102] (2) Electrolyzer:

[0103] The electrolyzer converts water into hydrogen and oxygen (power to hydrogen, P2H) through water electrolysis technology. The commonly used methods are alkaline water electrolysis of hydrogen and proton exchange membrane water electrolysis of hydrogen. Among them, the alkaline electrolyzer has a fast reaction speed and a more mature technology. Its hydrogen production can be expressed as:

[0104] M el (t) = η el P el (t) (2);

[0105] Where: M el (t), P el (t) are the hydrogen production and power of the electrolyzer at time t; η el is the hydrogen production efficiency of the electrolyzer.

[0106] (3) Hydrogen compressor:

[0107] The pressure of hydrogen produced by electrolysis is generally 14 bar. In order to achieve large-scale storage, hydrogen needs to be compressed to 200 bar before being stored in a hydrogen storage tank. The working power of the hydrogen compressor is related to the pressure difference before and after compression and the properties of the gas. Its configuration capacity is determined by the capacity of the electrolyzer. In order to simplify the model, the present invention considers the configuration relationship between the hydrogen compressor and the electrolyzer as a linear relationship.

[0108] (4) Fuel cells:

[0109] The fuel cell uses the widely used proton exchange membrane battery as an electric-hydrogen coupling element to convert hydrogen into electrical energy and feed it back to the grid. The output power of the fuel cell is related to the amount of hydrogen input, as shown in the following formula:

[0110] P FC (t) = η FC M FC (t) (4);

[0111] Where: P FC (t) is the fuel cell output power; η FC is the hydrogen-to-electricity conversion efficiency of the fuel cell.

[0112] (5) Hydrogen storage tank:

[0113] The hydrogen storage capacity S of the hydrogen storage tank at time t+1 H (t+1) and the hydrogen storage amount S at time t H (t) is related to the hydrogen output of the hydrogen compressor or the hydrogen consumption of the fuel cell at time t, as shown in the following formula:

[0114]

[0115] Where: S H (t+1) is the hydrogen storage capacity at time t; S H (t) and the hydrogen output of the hydrogen compressor at time t.

[0116] Furthermore, the objective function and constraints of the high-energy period optimization configuration model built in step 2 are as follows:

[0117] The first stage of the abundant energy period planning configuration model is based on the investment cost of the battery C BESS，inv , Maintenance cost C BESS，ope and hydrogen production and storage costs C H,st 、Abandoned energy cost C cur Revenue from hydrogen sales Minimum is the goal.

[0118]

[0119] The specific parts of formula (6) are as follows:

[0120]

[0121] Where: w B is the unit capacity investment cost of the battery; B , γ B are the maintenance cost and replacement cost of battery unit capacity respectively; S H is the capacity of the hydrogen storage station; w H (k),ω H (k) are the unit capacity investment cost and maintenance cost of electrolyzer, hydrogen compressor and hydrogen storage tank respectively; m H is the selling price of hydrogen; M sell (t) is the hydrogen sales volume at time t; μ CRF is the capital recovery factor.

[0122] The first phase of the high energy period planning configuration model includes the following constraints:

[0123] (1) The microgrid meets the following power balance constraints when producing and storing hydrogen during the abundant energy period:

[0124] P WT (t)+P PV (t)+P dis (t) = P ch (t)+P load(t)+P el (t)+P rem (t) (16);

[0125] Where: P WT (t), P PV (t), P load (t), P el (t) are the power of wind turbine, photovoltaic, load and electrolyzer at time t; P rem (t) is the energy abandoned by the microgrid at time t.

[0126] (2) The output and capacity constraints of each device are as follows:

[0127]

[0128] Where: Respectively represent the maximum power of the electrolyzer and hydrogen compressor; Indicates the rated capacity of the hydrogen storage tank.

[0129] (3) Hydrogen production-hydrogen demand constraints:

[0130] The amount of hydrogen produced by the electrolyzer during the abundant energy period is equal to the sum of the hydrogen sold and the hydrogen required by the hydrogen fuel cell during the dry energy period. The hydrogen required by the hydrogen fuel cell can be calculated from the source and load power during the dry energy period, as shown in the following formula:

[0131]

[0132] Where: is the amount of hydrogen produced by the electrolyzer during the abundant energy period; The amount of hydrogen required for hydrogen fuel cells during the lean period; Microgrid hydrogen sales volume; P G (t) represents the total output of wind turbine and photovoltaic at time t.

[0133] Furthermore, the objective function and constraints of the dry season optimization configuration model constructed in step 3 are as follows:

[0134] During the lean period, hydrogen fuel cells, photovoltaics and wind turbines work together to meet the load power demand. The optimization goal during the lean period is to reduce the investment cost of hydrogen fuel cells to C while supporting the power shortage. FC,inv , Operation and maintenance costs C FC,ope and fuel cell start-stop cost C FC,on minimum, as shown below.

[0135] f2=min(C FC,inv +C FC,ope +C FC,on ) (7);

[0136]

[0137] Where: w FC is the unit power investment cost of the fuel cell; is the rated power of the fuel cell; ω FC is the fuel cell unit power operation and maintenance cost; is the startup cost of a single fuel cell; N FC is the planned number of fuel cells; λ(t) is the startup state of the fuel cell, λ(t)=1 indicates startup, λ(t)=0 indicates shutdown; ε(t) is the operating state of the fuel cell, ε(t)=1 indicates operation, ε(t)=0 indicates shutdown.

[0138] (1) When there is a long-term power shortage, the power balance constraints satisfied by the system are as follows:

[0139] P WT (t)+P PV (t)+P FC (t)+P SLD (t) = P load (t) (20);

[0140] Where: P SLD (t) is the power deficit of the microgrid at time t.

[0141] (2) The fuel cell meets the following maximum power constraints:

[0142]

[0143] Where: Rated power for hydrogen fuel cells.

[0144] Furthermore, the load power failure rate and energy surplus rate evaluation indicators established in step 4 are as follows:

[0145] Introducing load power failure rate σ SLD and energy excess rate σ EED To characterize the reliability of the microgrid, the expressions are as follows:

[0146]

[0147] Where: P SLD (t) is the power shortage of the microgrid at time t; P rem (t) is the energy abandoned by the microgrid at time t, P LOAD (t) is the load power at time t; P G (t) is the power output at time t.

[0148] Furthermore, the solution flow chart of the two-stage planning model in step 5 is as follows: Figure 2 As shown, Figure 2 The following specific steps are included:

[0149] Step 5.1: Input the source and load data of the area with a time interval of △t, where △t is 1h, and calculate the net energy data according to the following formula.

[0150]

[0151] Where: E G (t) is the electric energy output by the power supply at time t; E load (t) is the electric energy consumed by the load at time t; is the abundant energy at time t; is the electric energy shortage at time t; E net (t) is the net energy sequence of the microgrid.

[0152] Step 5.2: Calculate the maximum continuous surplus energy of the microgrid according to the following formula, and use the last moment of this period as the initial moment of the hydrogen storage tank.

[0153]

[0154] Where: is the rich energy sequence; S tank (0) is the energy storage of the hydrogen storage tank at the initial moment.

[0155] Step 5.3: Optimal configuration model in the abundant energy period to solve the initial rated power P of the electrolyzer EL , initial battery capacity S B The initial capacity of the hydrogen storage tank S H The optimal configuration model for the dry season calculates the rated power of the hydrogen fuel cell according to formula (13): And solve the optimization operation model formula in step 5.2-step 5.3 to obtain the hydrogen demand when the microgrid has no continuous M hours of energy shortage during the dry season.

[0156]

[0157] Where: Rated power for hydrogen fuel cells.

[0158] Step 5.4: Simulate the hydrogen storage state of the hydrogen storage tank according to formula (5), where the operating power P el (t) is less than the rated power P EL .

[0159] Step 5.5: Check whether the feasibility constraint of hydrogen production and demand is met according to formula (14). If so, it means that the energy supply of the microgrid exceeds the demand. Then solve whether the energy surplus rate meets the constraint according to formula (8). If so, the rated power of the electrolyzer is If it is not satisfied, the microgrid has wind and solar power abandonment. In order to minimize wind and solar power abandonment, the electrolyzer power and hydrogen storage tank capacity can be increased to convert excess energy into hydrogen and sell it to obtain a certain amount of hydrogen sales revenue, that is, P in step 5.3 EL =P EL +△p, until the energy surplus rate index σ in step 5.4 is met EER ≤σ EER,max until.

[0160]

[0161] Step 5.6: If the operation constraints shown in equation (14) are not satisfied, then P EL =P EL +△p, repeat steps 5.3-5.5 until the operation constraints are met, and the iteration stop condition is If the iteration stops and the energy demand is still not satisfied, it means that the microgrid energy supply is insufficient. At this time, the installed capacity of the power supply should be increased to change the surplus energy sequence. Repeat steps 5.1-5.6 until the operation constraints are met.

[0162] Step 5.7: Calculate the microgrid load power failure rate after the iteration of step 5.6 stops at a time interval of 1h. If the load power failure rate σ SLD >σ SLD,max , then return to step 5.3 to increase the battery configuration capacity in the first stage, that is, S B =S B +△s, until σ is satisfied SLD ≤σ SLD,max The iteration ends when the planned capacity of each part is obtained.

[0163] Verification example:

[0164] The microgrid structure involved in the present invention is as follows Figure 3 As shown. The load is provided by wind farms and photovoltaic power generation. The surplus electricity is converted into hydrogen through the electrolyzer and stored in the hydrogen storage tank for use during the system's energy-sluggish period. On the other hand, it is sold to the hydrogen energy market to obtain certain income. The hybrid energy storage system in the microgrid consists of battery energy storage and a hydrogen energy storage system consisting of an electrolyzer, a hydrogen compressor, a hydrogen storage tank and a hydrogen fuel cell.

[0165] In order to verify the effectiveness of the planning model proposed in this paper, a microgrid in a certain area in Northwest China was selected to plan the hybrid energy storage system. The maximum output of the photovoltaic power station in this area is 6.47MW, the maximum output of the wind turbine is 25.2MW, and the average hourly load power is 6.92MW. The wind turbine, photovoltaic and load power curves are shown in Figure 2. Figures 4 to 6 The parameter settings in the model are shown in Table 1.

[0166] Table 1 Other parameters in the model

[0167]

[0168]

[0169] The CPLEX solver is called by the method described in step 5 to iteratively update the model, and the following capacity configuration results and various costs are obtained as shown in Table 2.

[0170] Table 2 Iterative solution results

[0171]

[0172] It can be seen from Table 2 that the configuration capacity and the cost of each part obtained through the two-stage iterative solution are within a reasonable range, and the load power failure rate and energy surplus rate in the evaluation indicators also meet the requirements.

[0173] The 167th day of summer is selected as a typical day in the annual operation curve to verify the operation status. Figure 7 The annual operation of the battery and hydrogen storage tank in the hybrid energy storage system is shown in Figure 8 , Fig. 9 As shown. Figure 7 It can be seen that the battery can adjust the power of the microgrid by frequent charging and discharging. When the battery power is insufficient for regulation, the hydrogen storage system participates in the regulation, and the charging and discharging together maintain the balance of supply and demand of the microgrid. Figure 8 and Fig. 9 It also further shows that batteries have advantages in short-term energy storage. The energy storage state change cycle of hydrogen storage tanks is relatively long, maintaining a high energy storage state in summer and autumn, and a low level in spring and winter, which shows that hydrogen storage tanks have an advantage in long-term energy storage.

[0174] The present invention provides a two-stage planning method for a hybrid energy storage system that takes into account the coupling of electricity and hydrogen. The hybrid energy storage system is constructed by utilizing the complementary principle of electrochemical energy storage and hydrogen energy storage. In the first stage planning model for the abundant energy period, a large amount of hydrogen is produced as a backup for the lean energy period. The hydrogen storage system in the planning model ensures that the microgrid has no continuous energy loss for more than 24 hours, fully taps the economic value of renewable energy on the premise of meeting the load power failure rate, converts excess electricity into hydrogen through an electrolyzer and sells it to obtain a certain income, and the storage battery ensures that the microgrid has no continuous energy loss for more than M hours to meet the reliability requirements of the microgrid. The model takes the annual total cost as the target, and iteratively solves the coupling relationship between the hydrogen production in the abundant energy period and the hydrogen storage in the lean energy period to obtain the final planning capacity of the hybrid energy storage system. The present invention can be used to smooth out the fluctuations of new energy and improve the operational stability of the power system.

Claims

1. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling, characterized in that The following steps are involved: Step 1: Establish the output model of each device of the hybrid energy storage system; Step 2: Establish the capacity optimization configuration model for the first phase of abundant energy period; Step 3: Establish the capacity optimization configuration model for the second phase of the lean period; Step 4: Establish evaluation indicators of load power failure rate and energy surplus rate; Step 5: Solve the two-stage planning model of the microgrid hybrid energy storage system.

2. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling according to claim 1, characterized in that: In step 1, the output model of each device of the hybrid energy storage system includes: (1) Battery: The battery capacity characteristics satisfy the following relationship: In formula (1): E t+1 is the battery capacity at time t+1; α is the battery self-discharge rate; E t is the battery capacity at time t; P ch (t), P dis (t) are the charging and discharging power of the battery respectively; η ch , η dis are the charging and discharging efficiencies of the battery respectively; △t is the time interval; (2) Electrolyzer: The hydrogen production of the electrolyzer can be expressed as: M el (t)=η el P el (t) (2); Where: M el (t), P el (t) are the hydrogen production and power of the electrolyzer at time t; η el is the hydrogen production efficiency of the electrolyzer; (3) Hydrogen compressor: Consider the configuration relationship between the hydrogen compressor and the electrolyzer as a linear relationship: P cp =kP el (3) Where: P cp is the hydrogen compressor power, P el is the electrolytic cell power, k is the proportionality coefficient; (4) Fuel cells: The output power of the fuel cell is related to the amount of hydrogen input, as shown in the following formula: P FC (t)=η FC M FC (t) (4); Where: P FC (t) is the fuel cell output power; η FC is the hydrogen-to-electricity conversion efficiency of the fuel cell; M FC (t) represents the hydrogen consumption of the fuel cell at time t; (5) Hydrogen storage tank: The hydrogen storage capacity S of the hydrogen storage tank at time t+1 H (t+1) and the hydrogen storage amount S at time t H (t) is related to the hydrogen output of the hydrogen compressor or the hydrogen consumption of the fuel cell at time t, as shown in the following formula: Where: S H (t+1) is the hydrogen storage capacity at time t; S H (t) and the hydrogen output of the hydrogen compressor at time t.

3. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling according to claim 1, characterized in that: In step 2, the first phase of the high energy period capacity optimization configuration model includes the investment cost C of the battery BESS，inv , Maintenance cost C BESS，ope and hydrogen production and storage costs C H,st , Hydrogen sales revenue The objective function in the model is shown in formula (6): In the formula: f1 represents the objective function 1.

4. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling according to claim 1, characterized in that: In step 3, the second stage of the lean period capacity optimization configuration model is that the hydrogen fuel cell, photovoltaic and wind turbines work together to meet the load power demand during the lean period. The optimization goal during the lean period is to make the hydrogen fuel cell investment cost C FC,inv , Operation and maintenance costs C FC,ope and fuel cell start-stop cost C FC,on Minimum, as shown in formula (7): f2=min(C FC,inv +C FC,ope +C FC,on )(7); Where: f2 represents the objective function 2.

5. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling according to claim 1, characterized in that: In step 4, the load power failure rate σ is introduced SLD and energy excess rate σ EED To characterize the reliability of the microgrid, the expressions are as follows: Where: P SLD (t) is the power shortage of the microgrid at time t; P rem (t) is the energy abandoned by the microgrid at time t, P LOAD (t) is the load power at time t; P G (t) is the power output at time t; In order to absorb wind and solar resources as much as possible and meet the reliability requirements of microgrid operation, the load power failure rate and energy surplus rate of the microgrid are constrained as shown in the following formula: Where: SLD,max , σ EER,max They are the maximum load power failure rate and energy surplus rate allowed by the microgrid respectively.

6. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling according to claim 1, characterized in that: In step 5, the solution process of the two-stage planning model of the microgrid hybrid energy storage system is: First, net energy data is generated at intervals of one day. The capacity optimization configuration model in the abundant energy period solves the preliminary configuration capacity of each part and the hydrogen production and storage capacity according to the abundant energy sequence; the capacity optimization configuration model in the dry energy period calculates the hydrogen demand of the microgrid in the dry energy period and the preliminary planning capacity of the hydrogen fuel cell according to the energy deficiency sequence; Secondly, according to the feasibility constraints of hydrogen production and demand, the relationship between hydrogen production and storage in the abundant energy period and hydrogen production in the dry energy period is compared, and the initial configuration capacity is iteratively updated according to different situations to obtain the planned capacity of each part of the hydrogen storage system; Finally, the configured power and capacity of the battery when meeting the microgrid load power failure rate are calculated at intervals of 1 hour.

7. A two-stage planning method for a hybrid energy storage system considering electric-hydrogen coupling according to claim 6, characterized in that: Step 5 includes the following process steps: Step 5.1: Input the source and load data of the pre-planning area with a time interval of △t, and generate the net energy data according to the following formula; Where: E net (t) is the net energy sequence of the microgrid; E G (t) is the electric energy output by the power supply at time t; E load (t) is the electric energy consumed by the load at time t; is the abundant energy at time t; is the power shortage at time t; Step 5.2: Calculate the maximum continuous surplus energy of the microgrid according to the following formula, and use the last moment of the period with the maximum continuous surplus energy as the initial moment of the hydrogen storage tank; Where: T + Represents the set of sequence rich energy sequence time periods; Where: S tank (0) is the energy storage of the hydrogen storage tank at the initial moment; Respectively represent the 0th to Nth maximum continuous surplus energy; Step 5.3: The capacity optimization configuration model in the abundant energy period is used to solve the initial rated power P of the electrolyzer EL , initial battery capacity S B The initial capacity of the hydrogen storage tank S H ; The capacity optimization configuration model during the off-season calculates the rated power of the hydrogen fuel cell according to formula (13) And solve the optimized operation mode in step 5.2-step 5.3 to obtain the hydrogen demand when the microgrid has no continuous M hours of energy shortage during the dry season; Where: is the rated power of the hydrogen fuel cell; P load (t) represents the load power at time t; Step 5.4: Simulate the hydrogen storage state of the hydrogen storage tank according to formula (5), where the operating power P el (t) is less than the rated power P EL ; Step 5.5: According to formula (14), check whether the feasibility constraint of hydrogen production-demand is met. If it is met, it means that the energy supply of the microgrid exceeds the demand. Then, according to formula (8), solve whether the energy surplus rate meets the constraint. If it is met, the rated power of the electrolyzer is If it is not satisfied, the microgrid has wind and solar power abandonment. In order to minimize wind and solar power abandonment, the electrolyzer power and hydrogen storage tank capacity can be increased to convert excess energy into hydrogen and sell it to obtain a certain amount of hydrogen sales revenue, that is, P in step 5.3 EL '=P EL +△p,P EL ' represents the updated electrolytic cell power, P EL represents the original electrolytic cell power, △p represents the increased electrolytic cell power; Until the energy surplus rate index σ in step 5.4 is met EER ≤σ EER,max until; Where: S H (t) represents the capacity of the hydrogen storage tank at time t; P load (t+1) represents the load power at time t+1; P G (t+1) represents the power output at time t+1; Step 5.6: If the operation constraints shown in equation (14) are not satisfied, then P EL '=P EL +△p, repeat steps 5.3-5.5 until the operation constraints are met, and the iteration stop condition is If the iteration stops and the energy demand is still not satisfied, it means that the microgrid energy supply is insufficient. At this time, the installed capacity of the power supply should be increased to change the surplus energy sequence. Repeat steps 5.1 to 5.6 until the operation constraints are met; Step 5.7: Calculate the microgrid load power failure rate after the iteration of step 5.6 stops at a time interval of 1h. If the load power failure rate σ SLD >σ SLD,max , then return to step 5.3 to increase the battery configuration capacity in the first stage, that is, S B '=S B +△s,S B ' represents the updated hydrogen storage tank capacity; S B represents the original hydrogen storage tank capacity; △s represents the newly added hydrogen storage tank capacity; until σ is satisfied SLD ≤σ SLD,max The iteration ends when the planned capacity of each part is obtained.

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