A hydrogen-electrochemical energy storage system and power allocation method based on power fluctuation

Abstract

The present invention belongs to the technical field of electrochemical energy storage, and discloses a hydrogen-electrochemical energy storage system and a power allocation method based on power fluctuations. The method includes: S1. Obtain the SOC of the electrochemical energy storage device; if 0.1 < SOC < 0.9, then jump to step S2, otherwise no power allocation is performed; S2. Calculate the output power error of renewable energy \(P_{s}=|P_{p}-P_{w}|\) and the output power error ratio of renewable energy \(P_{d}=P_{s} / P_{p}\); if \(P_{d}\) is less than the set threshold, no power allocation is performed; otherwise, further judge the magnitude of SOC: if 0.3 < SOC < 0.7, then jump to step S3; S3. Call the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model to obtain the optimal hydrogen production power \(P_{H}\) and the actual optimal battery charge and discharge power \(P_{B}\). The present invention makes up for the problem of insufficient response characteristics of the electrolytic hydrogen production device, maximizes the consumption of renewable energy on the premise of minimizing the impact on the life of the hydrogen production device, and ensures the economy of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and particularly relates to a hydrogen-electrochemical energy storage system based on power fluctuations and a power allocation method. Background Art

[0002] With the rapid development of electrolytic hydrogen production technology, demonstration projects applying it to the consumption of renewable energy are emerging continuously. Power-to-Gas, that is, converting renewable energy power generation into hydrogen, has gradually become an important direction for the development and application of renewable energy internationally. For example, the Power-to-Gas project of E.ON Group in Germany in 2012 and the Power-to-Gas project in the Toronto area in 2014. In China, it is still in its infancy. For example, in 2017, a 10MW-level demonstration project using wind power to produce hydrogen began to be built in Guyuan, Hebei. It can be foreseen that in the future, with the proposal and realization of the dual-carbon goal, the development scale of electrolytic hydrogen production will become larger and larger. However, in renewable energy hydrogen production systems, the alkaline electrolyzer hydrogen production method is mostly used; renewable energy usually has strong volatility, while the response of the electrolyzer is relatively slow; when this type of hydrogen production scheme is applied to the renewable energy power generation side, the frequent fluctuations of the power input will cause losses to the service life of the electrolyzer, resulting in a decline in the economy of the hydrogen production system and a reduction in the hydrogen production volume.

[0003] Therefore, to solve these problems, it is necessary to study the optimized operation scheme of the renewable energy hydrogen production system. Summary of the Invention

[0004] The purpose of the present invention is to provide a hydrogen-electrochemical energy storage system based on power fluctuations and a power allocation method to solve the technical problem that the power fluctuations of new energy seriously affect the service life of the hydrogen production device.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuations, including the following steps:

[0007] S1. Obtain the SOC of the electrochemical energy storage device; and judge the magnitude of the SOC. If SOC ≤ 0.1 or SOC ≥ 0.9, no power allocation is performed; if 0.1 < SOC < 0.9, then jump to step S2;

[0008] S2. Obtain the planned output P p and the actual output P w of the renewable energy; calculate the output error P s of the renewable energy = |P p -P w| and the output error ratio P d=P s / P p ; Determine the magnitude of P d . If P d is less than or equal to the set threshold, no power allocation is performed; if P d is greater than the set threshold, further determine the magnitude of SOC:

[0009] Does it satisfy 0.3 < SOC < 0.7? If so, jump to step S3;

[0010] S3. Invoke the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model to obtain the optimal hydrogen production power P H and the actual optimal battery charge / discharge power P B .

[0011] A further improvement of the present invention lies in that: the threshold value in step S2 is 25%.

[0012] A further improvement of the present invention lies in that: in step S2, further determine the magnitude of SOC:

[0013] If it does not satisfy 0.3 < SOC < 0.7, then further determine the capacity E of the hydrogen storage tank H Is it greater than 0.9? If the judgment result is no, perform power allocation according to case 3; if the judgment result is yes, perform power allocation according to case 4;

[0014] Case 3: Battery SOC ≤ 0.3. If (P p -P w ) < 0, P B +P H =P S and enter step S3 for optimal control. If (P p -P w ) > 0, P B =0, P H =0; Battery SOC ≥ 0.7. If (P p -P w ) < 0, P H =P el ; If (P p -P w ) > 0, P B =Pe; P el is the rated power of the electrolyzer, in MW; Pe is the rated charge / discharge power of the energy storage;

[0015] Case 4: Battery SOC ≤ 0.3. If (P p -P w ) < 0, P B =P e , if (P p -Pw ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.7, if (P p -P w ) < 0, P B = 0, P H = 0, if (P p -P w ) > 0, P B = -P e .

[0016] A further improvement of the present invention lies in that: the objective function of the pre-established hydrogen-electrochemical energy storage coupling model in step S3 is specifically:

[0017] min{F1 + F2 + F3 - I1 - I2} (1)

[0018] wherein, F1 is the cost of the hydrogen production system, F2 is the penalty cost for abandoned wind, F3 is the cost of purchasing electricity, I1 is the income from hydrogen production, and I2 is the income from energy storage grid connection.

[0019] A further improvement of the present invention lies in that: in step S3:

[0020] The expression of the cost F1 of the hydrogen production system is:

[0021] F1 = f1 + f2 (2)

[0022] f1 is the investment cost of the hydrogen production system, and f2 is the operation and maintenance cost of the hydrogen production system;

[0023] f1 = (C el *P el + C tan *E tan )*f sc (3)

[0025] wherein, C el is the cost per unit of electrolyzer power, unit: yuan / MW; P el is the rated power of the electrolyzer, unit: MW; C tan is the cost per unit of hydrogen storage tank capacity, unit: yuan / MWh; E tan is the rated capacity of the electrolyzer, unit: MWh; f sc represents the daily discount value;

[0026]

[0027] wherein, V el is the operation and maintenance cost of the electrolyzer system, unit: yuan; P el is the rated power of the electrolyzer, unit: MW; V his the storage and transportation cost of the produced hydrogen, unit: yuan / MWh; is the mass of the produced hydrogen, unit: t;

[0028]

[0029] Among them, r is the social discount rate; LP is the designed service life of the energy storage system; N is the operation cycle of the hydrogen energy storage system.

[0030] A further improvement of the present invention lies in: in step S3:

[0031] The expression of the curtailment penalty cost F2 is:

[0032]

[0033] Among them, C w is the curtailment penalty cost, yuan / MW; P w is the theoretical wind power output, MM; P i is the actual wind power output, MW; P w ' is the power consumption of the hybrid energy storage.

[0034] A further improvement of the present invention lies in: in step S3:

[0035] The expression of the power purchase cost F3 is:

[0036]

[0037] Among them, E i represents the power purchase electricity quantity; e i represents the power purchase electricity price.

[0038] A further improvement of the present invention lies in: in step S3:

[0039] The expression of the hydrogen production income I1 is:

[0040] I1 = M (H2) ×C h (8)

[0041] In the formula, c h represents the selling price per unit of hydrogen, unit: yuan / kg;

[0042] The expression of the energy storage grid connection income I2 is:

[0043] I2 = E deal *e deal +E surplus *B i (9)

[0044] In the formula, E deal 、E surplusThey are the electricity fed into the grid by energy storage and the electricity charged to energy storage respectively; e deal , B i They are the electricity price for energy storage fed into the grid and the policy subsidy respectively.

[0045] A further improvement of the present invention lies in that: the constraint conditions in step S3 include:

[0046] (a) Renewable energy constraints

[0047] i. Power deviation constraint

[0048] |P grid (t) - P ref (t)| ≤ γ max %C v (13)

[0049] In the formula: P grid (t) is the grid-connected power of the power station at time t; P ref (t) is the planned output at time t, and γ max % is the specified maximum deviation rate; C v is the installed capacity of renewable energy;

[0050] ii. Renewable energy capacity constraint

[0051] 0 ≤ P grid (t) ≤ C v (14)

[0052] iii. Line capacity ratio constraint

[0053]

[0054] Among them, P line represents the line transmission power, MW; P line-max represents the upper limit of the line transmission power, MW; K max represents the upper limit of the line capacity ratio;

[0055] b) Hydrogen energy storage related constraints

[0056] i. Minimum start-stop time constraint of the electrolyzer

[0057]

[0058] In the formula, T on , T off are the minimum start-up and shutdown times of the electrolyzer respectively; u t is the start-stop state of the electrolyzer at time t, 1 represents start-up, and 0 represents shutdown;

[0059] ii. Upper and lower power limit constraints of the electrolyzer

[0060] Pel-min ≤P el ≤P el-max (17)

[0061] Wherein, P el-min and P el-max represent the lower limit and upper limit of the electrolyzer power respectively;

[0062] iii. Fluctuating input limit constraint

[0063] P el ≥20%P el-rated (18)

[0064] P el-rated represents the rated power;

[0065] P el ≤P el-rated (19)

[0066] iv. Constraints on the upper and lower limits of the hydrogen storage capacity

[0067] 0 ≤ E H ≤ E max (20)

[0068] Wherein E H is the capacity of the hydrogen storage tank; E max is the limit value of the hydrogen storage tank capacity;

[0069] v. Ramp rate constraint

[0070] r di ≤ P tan - P tan-1 ≤ r ri (21)

[0071] r di 、r ri represent the lower limit and upper limit constraints of the output of the hydrogen production device respectively;

[0072] c) Electrochemical energy storage related constraints

[0073] i. Energy storage SOC constraint

[0074] SOC min ≤ SOC(i) ≤ SOC max

[0075]

[0076] SOC min and SOC max represent the upper and lower limits of the energy storage SOC; represents the rated capacity of the energy storage; η charge and ηdischarge respectively represent the charge and discharge efficiency;

[0077] ii. Charge and discharge quantity conservation constraint

[0078] E qd_ESS = E el_ESS (23)

[0079] E qd_ESS represents the electricity quantity obtained through curtailed electricity consumption; E el_ESS represents the electricity quantity delivered to the hydrogen energy storage.

[0080] A further improvement of the present invention lies in that: in the step of calling the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model in step S3, specifically, the multi-objective solution algorithm NSGA-III and the TOPSIS algorithm are applied for solution.

[0081] In a second aspect, the present invention provides a hydrogen-electrochemical energy storage system based on power fluctuations, including: an electrochemical energy storage device, a hydrogen energy storage device, an inverter, a rectifier, and a converter; the hydrogen energy storage device includes an electrolyzer and a hydrogen storage tank;

[0082] Renewable energy is connected to the power grid, the rectifier, and the converter through the inverter;

[0083] The output end of the rectifier is connected to the electrolyzer, the output end of the converter is connected to the electrochemical energy storage device, and the output end of the electrochemical energy storage device is also connected to the electrolyzer; the hydrogen outlet of the electrolyzer is connected to the hydrogen storage tank;

[0084] When the hydrogen-electrochemical energy storage system based on power fluctuations performs power allocation, it specifically includes the following steps:

[0085] S1. Obtain the SOC of the electrochemical energy storage device; and judge the magnitude of the SOC. If SOC ≤ 0.1 or SOC ≥ 0.9, no power allocation is performed; if 0.1 < SOC < 0.9, then jump to step S2;

[0086] S2. Obtain the planned output P p and the actual output P w of the renewable energy; calculate the output error P s = |P p - P w| and the output error ratio P d = P s / P p ; judge the magnitude of P d . If P d is less than or equal to the set threshold, no power allocation is performed; if P d is greater than the set threshold, further judge the magnitude of the SOC:

[0087] Check if 0.3 < SOC < 0.7. If yes, jump to step S3; if not, further check the capacity E of the hydrogen storage tank H Check if it is greater than 0.9. If the judgment result is no, perform power allocation according to case 3; if the judgment result is yes, perform power allocation according to case 4;

[0088] Case 3: Battery SOC ≤ 0.3. If (P p -P w ) < 0, P B +P H = P S and enter step S3 for optimal control. If (P p -P w ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.7. If (P p -P w ) < 0, P H = P el ; If (P p -P w ) > 0, P B = Pe; P el is the rated power of the electrolyzer, with the unit of MW; Pe is the rated charge / discharge power of the energy storage;

[0089] Case 4: Battery SOC ≤ 0.3. If (P p -P w ) < 0, P B = P e , if (P p -P w ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.7. If (P p -P w ) < 0, P B = 0, P H = 0, if (P p -P w ) > 0, P B = -P e ;

[0090] S3. Call the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model to obtain the optimal hydrogen production power P H and the actual optimal battery charge / discharge power P B .

[0091] Compared with the prior art, the present invention has the following beneficial effects:

[0092] Based on the characteristics of fast response speed, flexible configuration, and bidirectional power output of electrochemical energy storage, the present invention proposes a hydrogen-electrochemical energy storage system based on a hydrogen storage system and provides its power regulation method to make up for the insufficient response characteristics of electrolytic hydrogen production devices, maximize the consumption of renewable energy with the least impact on the service life of hydrogen production devices, and ensure the economy of the system.

[0093] The present invention uses electrochemical energy storage as an auxiliary device, which can effectively alleviate the impact of the volatility of new energy on the service life of hydrogen production devices and improve the hydrogen production efficiency and service life of hydrogen production devices;

[0094] The power allocation method of the hydrogen-electrochemical energy storage coupling system adopted by the present invention can effectively reduce the volatility of hydrogen production power, improve the hydrogen production efficiency of hydrogen production devices, improve the consumption rate of wind power / photovoltaic power, and can effectively perform peak shaving on the power generation side. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] The accompanying drawings forming a part of this invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0096] Figure 1 is a structural block diagram of a hydrogen-electrochemical energy storage system based on power fluctuation of the present invention;

[0097] Figure 2 is a schematic flow chart of the power allocation method of a hydrogen-electrochemical energy storage system based on power fluctuation of the present invention;

[0098] Figure 3 is a flow chart of the NSGA-III algorithm. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0099] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0100] The following detailed descriptions are all exemplary descriptions and are intended to provide further details of the present invention. Unless otherwise specified, all technical terms adopted by the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. The terms used in the present invention are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0101] SOC: State of Charge of the battery, which is used to reflect the remaining capacity of the battery. Numerically, it is defined as the ratio of the remaining capacity to the battery capacity, usually expressed as a percentage. Its value range is 0 to 1. When SOC = 0, it means the battery is fully discharged, and when SOC = 1, it means the battery is fully charged; The objective function of the present invention includes the use of electrochemically stored energy for electrolytic hydrogen production in the design; The described EMD is the Empirical Mode Decomposition method, which decomposes signals based on the time-scale characteristics of the data itself without the need to preset any basis functions.

[0102] Embodiment 1

[0103] Please refer to Figure 1 As shown in the figure, the present invention provides a hydrogen - electrochemically stored energy system based on power fluctuations, including: an electrochemically stored energy device, a hydrogen storage device (electrolyzer, hydrogen storage tank), an inverter, a rectifier, and a converter; Renewable energy is connected to the power grid, rectifier, and converter through an inverter; The output end of the rectifier is connected to the electrolyzer, the output end of the converter is connected to the electrochemically stored energy device, and the output end of the electrochemically stored energy device is also connected to the electrolyzer; The hydrogen outlet of the electrolyzer is connected to the hydrogen storage tank.

[0104] The present invention provides a power allocation method for a hydrogen - electrochemically stored energy system based on power fluctuations, which is specifically implemented according to Embodiment 2.

[0105] Embodiment 2

[0106] When the input power of renewable energy is greater than the power required for grid connection, curtailment of light will occur. However, different control strategies are selected according to the magnitude of the curtailment power and the quality of wind power. When the input power of wind power is large, hydrogen production is prioritized; when the input power of wind power is small, grid connection is prioritized. In addition, when the SOC of the energy storage battery is not within the normal range, SOC reset is performed; The specific working flowchart is as Figure 2 shown. Please refer to Figure 2 As shown in the figure, a power allocation method for a hydrogen - electrochemically stored energy system based on power fluctuations according to the present invention includes the following steps:

[0107] S1. Obtain the SOC of the electrochemically stored energy device; and judge the magnitude of the SOC. If the electrochemically stored energy SOC ≤ 0.1, it is Case 1, and the electrochemically stored energy device only charges and does not discharge, Pcharge = -P Bmax , and no power allocation is performed; if the electrochemically stored energy SOC ≥ 0.9, it is Case 2, and the electrochemically stored energy device only discharges and does not charge, Pdischarge = P Bmax , and no power allocation is performed; if 0.1 < SOC < 0.9, jump to step S2; where, P charge represents the charging power, and P Bmax represents the maximum charge - discharge power;

[0108] S2. Obtain the planned output P of renewable energyp and the actual output P w ; calculate the output error P of renewable energy s = |P p - P w| and the output error ratio P of renewable energy d = P s / P p ; judge the magnitude of P d . If P d is less than the set threshold, power allocation is not performed. The threshold can be 25% or other values, which can be set according to local conditions; if P d is greater than the set threshold, further judge the magnitude of SOC:

[0109] whether it satisfies 0.3 < SOC < 0.7. If so, jump to step S3; if not, further judge whether the capacity E of the hydrogen storage tank H is greater than 0.9. If the judgment result is no, perform power allocation according to case 3; if the judgment result is yes, perform power allocation according to case 4;

[0110] Case 3: Battery SOC ≤ 0.3. If (P p - P w ) < 0, P B + P H = P S and enter step S3 for optimization control. If (P p - P w ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.7. If (P p - P w ) < 0, P H = P el ; If (P p - P w ) > 0, P B = Pe; P el is the rated power of the electrolyzer, with the unit of MW; Pe is the rated power of energy storage charging / discharging;

[0111] Case 4: Battery SOC ≤ 0.3. If (P p - P w ) < 0, P B = P e , if (P p - P w ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.7. If (P p - P w ) < 0, P B = 0, PH = 0, if (P p - P w ) > 0, P B = -P e ;

[0112] S3. Call the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model to obtain the optimal hydrogen production power P H and the actual power of the optimal battery charge and discharge P B ;

[0113] Taking wind power as an example in the present invention: the prediction deviation of wind power should be less than or equal to 25% (i.e., Pd = (actual output - theoretical output) / actual output <= 25%); when the quality of renewable energy is poor, the EMD decomposition method is enabled; when the dispatching requires curtailment of wind, try to select the electrochemcial energy storage to connect to the grid and the wind power hydrogen production strategy; adopt the empirical mode (EMD) decomposition method to allocate the high-frequency fluctuation signals to the electrochemcial energy storage, and allocate the medium and low-frequency energy signals to the electrolyzer system for hydrogen production. The produced hydrogen is stored using a hydrogen storage tank and then locally consumed through the chemical industry, hydrogen fuel cell vehicles, etc. Pe is the rated power of the energy storage charge / discharge; Pel is the rated power of the hydrogen energy storage charge / discharge; P H 、P B are the obtained optimal hydrogen production and actual power of battery charge and discharge.

[0114] With the goal of maximizing the consumption of renewable energy and minimizing the total cost of the hydrogen production system, fully considering the impact on the service life of the electrolytic hydrogen production system, and at the same time considering the characteristic parameters such as the ramp rate, hydrogen production efficiency, electrochemcial energy storage charge and discharge, and the constraint conditions such as the operating state, a hydrogen-electrochemical energy storage coupling model is established. The establishment process of the hydrogen-electrochemical energy storage coupling model includes:

[0115] S31. Objective function

[0116] The total cost of the wind power hydrogen production system consists of the hydrogen production system cost, curtailment penalty cost, power purchase cost, hydrogen production income, and energy storage grid connection subsidy. The present invention takes the minimization of the total cost of the renewable energy hydrogen production system within one day as the objective function. The objective function is specifically described by Equation (1).

[0117] min{F1 + F2 + F3 - I1 - I2} (1)

[0118] 1) Hydrogen production system cost F1

[0119] The hydrogen production system includes an electrolyzer and hydrogen storage equipment. The hydrogen production system cost F1 consists of the investment cost (f1) and the operation and maintenance cost (f2), that is

[0120] F1 = f1 + f2 (2)

[0121] The investment cost f1 is calculated by Equation (3).

[0122] f1 = (C el *P el +C tan *E tan )*f sc (3)

[0123] Wherein, C el is the power cost per unit electrolyzer, unit: yuan / MW; P el is the rated power of the electrolyzer, unit: MW; C tan is the cost per unit hydrogen storage tank capacity, unit: yuan / MWh; E tan is the rated capacity of the electrolyzer, unit: MWh; f sc represents the daily present value.

[0124] The operation and maintenance cost f2 includes the operation and maintenance cost of the electrolyzer and the storage and transportation costs of the produced hydrogen, and is calculated by Equation (4).

[0125]

[0126] Wherein, V el is the operation and maintenance cost of the electrolyzer system, unit: yuan; P el is the rated power of the electrolyzer, unit: MW; V h is the storage and transportation cost of the produced hydrogen, unit: yuan / MWh; is the mass of the produced hydrogen, unit: t.

[0127]

[0128] Wherein, r is the social present value; LP is the designed service life of the energy storage system; N is the operation cycle of the hydrogen energy storage system.

[0129] 2) Penalty cost for curtailed wind power F2

[0130]

[0131] Wherein, C w is the penalty cost for curtailed wind power, (yuan / MW); P w is the theoretical output of wind power, (MW); P i is the actual output of wind power (MW); P w ' is the power absorbed by the hybrid energy storage.

[0132] 3) Power purchase cost F3

[0133] When there is a large amount of new energy generated, it is difficult for the power grid to absorb this part of the wind energy. Therefore, it can be converted into hydrogen through electrolysis for absorption. Since this part of the wind energy is difficult to be absorbed by the power grid, it can be obtained by purchasing at a relatively low price. The specific calculation method is as follows:

[0134]

[0135] Among them, E i represents the purchased electricity quantity; e i represents the purchased electricity price;

[0136] 4) Hydrogen production income I1

[0137] I1 = M (H2) × C h (8)

[0138] In the formula, c h represents the selling price per unit of hydrogen, in yuan / kg.

[0139] 5) Energy storage grid connection income I2

[0140] I2 = E deal * e deal + E surplus * B i (9)

[0141] E deal 、E surplus are the energy storage grid connection electricity quantity and the energy storage charging electricity quantity respectively; e deal 、B i are the energy storage grid connection electricity price and the policy subsidy respectively.

[0142] The objective function is to maximize the efficiency utilization of the alkaline electrolyzer while satisfying the maximum absorption of renewable energy, which is expressed by the minimum of the wind and light abandonment amount and the hydrogen production power consumption per unit of hydrogen, that is:

[0143] min{P q}+ min{E dh} (10)

[0144] P q represents the curtailment rate, %, and the maximum absorption of new energy is expressed by the wind and light curtailment rates. When the curtailment rate is smaller, it means the larger the absorption amount of new energy. E dh represents the hydrogen production power consumption per unit of hydrogen production.

[0145]

[0146] P wq represents the renewable energy curtailment power, kW; P w ' represents the absorption power of the electrochemical energy storage and hydrogen energy storage, kW.

[0147]

[0148]

[0149] E dh represents the hydrogen production power consumption per unit hydrogen, kW / kg; related to the hydrogen production efficiency; P in represents the hydrogen production input power, kW; E in represents the hydrogen production power consumption, kWh; represents the hydrogen production, kg.

[0150] After mechanism modeling, it can be obtained that: the efficiency of the electrolyzer increases rapidly with the increase of the input power, and then gradually decreases. Before the optimal efficiency point P, the hydrogen production power is small and the hydrogen purity is low; after point P, as the input power approaches the rated power, the marginal cost of hydrogen production increases synchronously, resulting in poor economy. Therefore, the optimal hydrogen production power should be in the right half of the optimal efficiency point P and change dynamically with the curtailed power.

[0151] S32. Constraint conditions

[0152] (a) Renewable energy constraint

[0153] i. Power deviation constraint

[0154] |P grid (t) - P ref (t)| ≤ γ max %C v (13)

[0155] In the formula: P grid (t) is the grid-connected power of the power station at time t; P ref (t) is the planned output at time t, obtained from scenario analysis, γ max % is the specified maximum deviation rate; C v is the installed capacity of renewable energy. According to the Technical Regulations for Grid Connection of Photovoltaic Power Stations of State Grid Corporation of China, the grid-connected power of the PV-battery energy storage system should be consistent with the dispatching curve, and power deviation within a certain ratio is allowed.

[0156] ii. Renewable energy capacity constraint

[0157] 0 ≤ P grid (t) ≤ C v (14)

[0158] iii. Line capacity ratio constraint

[0159] The capacity of the transmission circuit has an upper limit. When the transmitted power is greater than the upper limit of the line capacity ratio, the excess power needs to be curtailed.

[0160]

[0161] Among them, P line represents the line transmission power, MW; P line-max represents the upper limit of the line transmission power, MW; K max represents the upper limit of the line capacity ratio.

[0162] b) Constraints related to hydrogen energy storage

[0163] 1. Minimum start-stop time constraint of electrolyzer

[0164]

[0165] In the formula, T on , T off are respectively the minimum start-up and shutdown times of the electrolyzer; u t is the start-stop state of the electrolyzer at time t, 1 represents start-up, and 0 represents shutdown.

[0166] 2. Power upper and lower limit constraints of electrolyzer

[0167] P el-min ≤P el ≤P el-max (17)

[0168] In the formula, P el-min and P el-max represent the lower limit and upper limit of the electrolyzer power respectively.

[0169] 3. Fluctuating input limit constraint

[0170] Since the fluctuating input will have a serious impact on the life of the hydrogen production device, when the fluctuating input exceeds the tolerance range of the electrolyzer, it is necessary to stabilize the input power within the allowable range with the cooperation of electrochemistry.

[0171] P el ≥20%P el-rated (18)

[0172] P el-rated represents the rated power. When the input power is less than 20%P el-rated due to fluctuations, some sub-electrolyzers will operate intermittently, causing the operating temperature of the electrolyzer to be lower than the rated state, with low efficiency and the risk of hydrogen-oxygen intermixing and explosion.

[0173] P el ≤P el-rated (19)

[0174] The electrolyzer is designed with a rated power. After exceeding the rated power (overload power) for a period of time, it will have an irreversible impact on the life of the electrolyzer. Therefore, it is necessary to avoid long-term overload conditions.

[0175] 4. Constraints on the upper and lower limits of hydrogen storage

[0176] 0 ≤ E H ≤ E max (20)

[0177] In the formula, E H is the capacity of the hydrogen storage tank; E max is the limit value of the hydrogen storage tank capacity.

[0178] 5. Ramp rate constraint (judge whether the condition is met. If not, generate power together)

[0179] The output change of the hydrogen production device has an upper limit. When the output change exceeds the allowable range, an electrochemical assisted hydrogen production device is required to absorb the curtailed wind power.

[0180] r di ≤ P tan - P tan-1 ≤ r ri (21)

[0181] r di 、r ri represent the lower limit and upper limit constraints of the output of the hydrogen production device respectively;

[0182] c) Constraints related to electrochemical energy storage

[0183] i. SOC constraint of energy storage

[0184] SOC min ≤ SOC(i) ≤ SOC max

[0185]

[0186] SOC min and SOC max represent the upper and lower limits of the energy storage SOC; represents the rated capacity of the energy storage; η charge and η discharge represent the charge and discharge efficiencies respectively.

[0187] ii. Charge and discharge quantity conservation constraint

[0188] Within a cycle with as the time unit, the electricity obtained by the electrochemical energy storage through absorbing curtailed electricity should be consistent with the total amount of electricity delivered to the hydrogen energy storage, so that the SOC of the electrochemical energy storage is maintained at 50%.

[0189] Eqd_ESS = E el_ESS (23)

[0190] E qd_ESS represents the amount of electricity obtained through curtailment consumption; E el_ESS represents the amount of electricity delivered to the hydrogen energy storage.

[0191] S33. Solution strategy - multi-objective optimization: In the renewable energy hydrogen production system proposed by the invention, with the objectives of minimizing the total cost of the hydrogen production system, minimizing the amount of curtailed wind and solar power, and minimizing the power consumption per unit of hydrogen production, the multi-objective solution algorithms NSGA-III and TOPSIS algorithms are applied to solve (multiple Ps are calculated through the NSGA-III algorithm B and P H , and then the optimal solutions P B and P H ) are selected through TOPSIS. Please refer to Figure 3 As shown, the NSGA-III algorithm selects the next-generation population based on the reference point, not only retaining the advantages of the NSGA-II algorithm but also maintaining the width and uniformity of the non-dominated solutions, greatly improving the convergence of the algorithm.

[0192] In addition, for the case of large power fluctuations, filtering means are used to improve the power fluctuations delivered to the electrolyzer. When the hydrogen production power of the electrolyzer is lower than the limit value, it will lead to low hydrogen production efficiency and poor safety. At this time, the electric energy stored in the electrochemical energy storage is used for hydrogen production to keep the hydrogen production efficiency in a better range. That is, when in the above discussion, E H > 0.9, the electrolytic hydrogen production power is 0. Finally, the constraints of the electrolyzer and the electrochemical energy storage are kept satisfied.

[0193] The present invention introduces an electrochemical energy storage as an auxiliary regulating device, and uses the characteristics of fast and accurate regulation of the electrochemical energy storage to propose a power allocation method for a hydrogen-electrochemical energy storage coupling system; with the objectives of maximizing the utilization of renewable energy and the highest efficiency of the alkaline electrolyzer, fully considering the characteristic parameters and operating conditions such as the operating life, ramp rate, charge and discharge of the electrochemical energy storage of the electrolytic hydrogen production system, a power allocation strategy for the hydrogen-electrochemical energy storage coupling system is proposed.

[0194] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0195] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device generate means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0196] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0197] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuations, characterized in that It includes the following steps: S1. Obtain the SOC of the electrochemical energy storage device; and judge the magnitude of the SOC. If SOC ≤ 0.1 or SOC ≥ 0.9, no power allocation is performed; if 0.1 < SOC < 0.9, then jump to step S2; S2. Obtain the planned output power P of renewable energy p and the actual output power P w ; Calculate the output power error P of renewable energy s = |P p - P w| and the output power error ratio P of renewable energy d = P s / P p ; Judge the magnitude of P d . If P d is less than or equal to the set threshold, no power allocation is performed; if P d is greater than the set threshold, further judge the magnitude of SOC: Judge whether 0.3 < SOC < 0.7 is satisfied. If yes, then jump to step S3; S3. Call the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model, and obtain the optimal hydrogen production power P H and the actual optimal battery charge and discharge power P B ; In step S2, further judge the magnitude of the SOC: If 0.3 < SOC < 0.7 is not satisfied, then further judge the capacity E of the hydrogen storage tank H Whether it is greater than 0.

9. If the judgment result is no, then perform power allocation according to case 3; if the judgment result is yes, then perform power allocation according to case 4; Case 3: Battery SOC ≤ 0.

3. If (P p -P w ) < 0, P B +P H =P s and enter step S3 for optimization control. If (P p -P w ) > 0, P B =0, P H =0; When battery SOC ≥ 0.7, if (P p -P w ) < 0, P H =P el ; if (P p -P w ) > 0, P B =Pe; P el is the rated power of the electrolyzer, with the unit of MW; Pe is the rated charge / discharge power of the energy storage; Case 4: Battery SOC ≤ 0.

3. If (P p -P w ) < 0, P B = P e . If (P p -P w ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.

7. If (P p -P w ) < 0, P B = 0, P H = 0. If (P p -P w ) > 0, P B = -P e ; The objective function of the pre-established hydrogen-electrochemical energy storage coupling model in step S3 is specifically: (1) Among them, F1 is the cost of the hydrogen production system, F F2 is the penalty cost for curtailed wind, F3 is the electricity purchase cost, I1 is the hydrogen production revenue, I F2 is the revenue from energy storage feeding into the grid.

2. A power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuations according to claim 1, characterized in that In step S3: The expression of the hydrogen production system cost F1 is: (2) f 1 is the investment cost of the hydrogen production system, f2 is the operation and maintenance cost of the hydrogen production system; (3) Among them, C el is the power cost per unit electrolytic cell, unit: yuan / MW; P el is the rated power of the electrolytic cell, unit: MW; C tan is the cost per unit hydrogen storage tank capacity, unit: yuan / MWh; E tan is the rated capacity of the electrolytic cell, unit: MWh; f sc represents the daily discounted value; (4) Among them, is the operation and maintenance cost of the electrolyzer system, unit: yuan; P el is the rated power of the electrolyzer, unit: MW; is the storage and transportation cost of the produced hydrogen, unit: yuan / MWh; is the mass of the produced hydrogen, unit: t; (5) Where r is the social discount rate; LP is the designed service life of the energy storage system; N is the operation cycle of the hydrogen energy storage system.

3. A power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuation according to claim 1, characterized in that In step S3: Wind curtailment penalty cost F The expression of 2 is as follows: (6) Among them, C w is the curtailment penalty cost, yuan / MW; is the power consumption of the hybrid energy storage.

4. A power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuations according to claim 1, characterized in that, In step S3: The expression of the electricity purchase cost F3 is: (7) Among them, E i represents the electricity purchase quantity; e i represents the electricity purchase price.

5. The power allocation method of a hydrogen-electrochemical energy storage system based on power fluctuation according to claim 2, wherein, In step S3: The expression of the hydrogen production income I1 is: I 1 =M （H2） ×C h (8) In the formula, represents the selling price of unit hydrogen, in yuan per kilogram; Energy storage grid connection revenue I The expression of 2 is: (9) Wherein, E deal and E surplus are the electricity quantity of energy storage fed into the grid and the electricity quantity of energy storage charging respectively; e deal and B i are the electricity price of energy storage fed into the grid and the policy subsidy respectively.

6. A power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuation according to claim 1, characterized in that The constraint conditions in step S3 include: (a) Renewable energy constraints i. Power offset constraint (13) Where: is the grid-connected power of the power station at time t; is the planned output at time t, is the specified maximum deviation rate; is the installed capacity of renewable energy; ii. Renewable energy capacity constraint (14) iii. Line capacity ratio constraint (15) Among them, represents the line transmission power, MW; P line-max represents the upper limit of the line transmission power, MW; represents the upper limit of the line capacity ratio; b) Hydrogen energy storage related constraints i. Minimum start-stop time constraint of the electrolyzer (16) where and are the minimum start-up and shutdown times of the electrolyzer, respectively; is the start-stop state of the electrolyzer at time t, where 1 represents start-up and 0 represents shutdown; ii. Power upper and lower limit constraints of the electrolyzer (17) In the formula, and represent the lower limit and upper limit of the electrolyzer power respectively; iii. Fluctuating input limit constraint (18) Represents the rated power; (19) iv. Hydrogen storage capacity upper and lower limit range constraint (20) wherein is the capacity of the hydrogen storage tank; is the capacity limit of the hydrogen storage tank; v. Ramping rate constraint (21) , respectively represent the lower and upper output limit constraints of the hydrogen production device; c) Electrochemical energy storage related constraints i. Energy storage SOC constraint (22) and represent the upper and lower limits of the energy storage SOC; represents the rated capacity of the energy storage; and represent the charge and discharge efficiency respectively; ii. Charge and discharge quantity conservation constraint (23) represents the electricity quantity obtained through curtailment for consumption; represents the electricity quantity delivered to the hydrogen energy storage.

7. A power allocation method for a hydrogen-electrochemical energy storage system based on power fluctuations according to claim 1, characterized in that In the step of calling the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model in step S3, specifically, the multi-objective solution algorithms NSGA-III and TOPSIS algorithms are applied for solution.

8. A hydrogen-electrochemical energy storage system based on power fluctuations, characterized in that It includes: An electrochemical energy storage device, a hydrogen energy storage device, an inverter, a rectifier, and a converter; the hydrogen energy storage device includes an electrolyzer and a hydrogen storage tank; Renewable energy is connected to the power grid, rectifier, and converter through an inverter; The output end of the rectifier is connected to the electrolyzer, the output end of the converter is connected to the electrochemical energy storage device, and the output end of the electrochemical energy storage device is also connected to the electrolyzer; the hydrogen outlet of the electrolyzer is connected to the hydrogen storage tank; When the hydrogen-electrochemical energy storage system based on power fluctuation performs power allocation, it specifically includes the following steps: S1. Obtain the SOC of the electrochemical energy storage device; and judge the magnitude of the SOC. If SOC ≤ 0.1 or SOC ≥ 0.9, no power allocation is performed; if 0.1 < SOC < 0.9, then jump to step S2; S2. Obtain the planned output power P of renewable energy p and the actual output power P w ; Calculate the output power error P of renewable energy s =|P p -P w| and the output power error ratio P of renewable energy d =P s / P p ; Judge the magnitude of P d . If P d is less than or equal to the set threshold, no power allocation is performed; if P d is greater than the set threshold, further judge the magnitude of SOC: Whether it satisfies 0.3 < SOC < 0.

7. If yes, jump to step S3; if not, further judge the capacity E of the hydrogen storage tank H Whether it is greater than 0.

9. If the judgment result is no, perform power allocation according to case 3; if the judgment result is yes, perform power allocation according to case 4; Case 3: Battery SOC ≤ 0.

3. If (P p -P w ) < 0, P B +P H =P s and enter step S3 for optimization control. If (P p -P w ) > 0, P B =0, P H =0; When battery SOC ≥ 0.7, if (P p -P w ) < 0, P H =P el ; if (P p -P w ) > 0, P B =Pe; P el is the rated power of the electrolyzer, with the unit of MW; Pe is the rated charge / discharge power of the energy storage; Case 4: Battery SOC ≤ 0.3, if (P p -P w ) < 0, P B = P e , if (P p -P w ) > 0, P B = 0, P H = 0; Battery SOC ≥ 0.7, if (P p -P w ) < 0, P B = 0, P H = 0, if (P p -P w ) > 0, P B = -P e； If 0.3 < SOC < 0.7, then jump to step S3; S3. Call the constraint conditions to solve the objective function of the pre-established hydrogen-electrochemical energy storage coupling model to obtain the optimal hydrogen production power P H and the actual power P B ; The objective function of the pre-established hydrogen-electrochemical energy storage coupling model is specifically: (1) Among them, F1 is the cost of the hydrogen production system, F F2 is the penalty cost for curtailed wind, F3 is the cost of purchasing electricity, I1 is the income from hydrogen production, I F2 is the income from energy storage feeding into the grid.

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