A control strategy for a photovoltaic direct-current coupling hydrogen production system based on Pso

Abstract

The present application belongs to the field of photovoltaic direct current coupling hydrogen production system control, especially relates to a photovoltaic direct current coupling hydrogen production system control strategy based on Pso. The present application comprises: determining the structure of photovoltaic hydrogen production direct coupling system, establishing photovoltaic array model and PEM electrolytic cell chamber model; analyzing the working characteristics of photovoltaic array and PEM electrolytic cell array, making the photovoltaic array output with maximum power, and making the electrolytic cell track the output of the photovoltaic array; determining the control target of the photovoltaic direct current coupling hydrogen production system, segmenting the working curve of the electrolytic cell chamber, constructing the objective function, setting the constraint condition, and establishing the mathematical model of the photovoltaic direct current coupling hydrogen production system control optimization; setting the control variable, optimizing the objective function value based on the particle swarm optimization algorithm, and obtaining the optimal control strategy of the photovoltaic direct current coupling hydrogen production system. The present application makes the energy conversion rate and hydrogen production efficiency of the photovoltaic direct current coupling hydrogen production system significantly improved through the particle swarm optimization algorithm.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic DC-coupled hydrogen production system control, and particularly relates to a control strategy for a photovoltaic DC-coupled hydrogen production system based on Pso. Background Technology

[0002] The photovoltaic DC-coupled hydrogen production system directly connects the photovoltaic array to the PEM electrolyzer array to improve the system's energy conversion rate, reduce system costs, and increase hydrogen production efficiency.

[0003] For photovoltaic DC-coupled hydrogen production systems, firstly, in order to maximize the photoelectric conversion efficiency of the photovoltaic array, the photovoltaic array should always operate at maximum power. Secondly, since the photovoltaic array is directly connected to the PEM electrolyzer array, it is also necessary to consider the matching problem between the output of the photovoltaic array and the PEM electrolyzer array when weather conditions change.

[0004] In addition, factors such as the efficiency of hydrogen production by electrolyzers and techno-economic issues must also be considered.

[0005] In actual operating conditions, the intensity of sunlight and the ambient temperature change constantly over time, which can easily lead to a mismatch between the maximum power point of the photovoltaic array and the operating point of the electrolyzer array, resulting in a direct coupling mismatch problem. In recent years, there has been limited analysis of the regulation strategies for photovoltaic DC-coupled hydrogen production systems. These strategies have not fully explored the operating characteristics of the electrolyzer itself, lacked sufficient analysis of other operating points of the electrolyzer, and underestimated the hydrogen production efficiency of the electrolyzer. This results in the system's inability to adapt to the randomness and volatility of solar energy, failing to achieve optimal control. Therefore, the optimized control of photovoltaic DC-coupled hydrogen production systems urgently needs to be addressed. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides a control strategy for a photovoltaic-DC coupled hydrogen production system based on PSO (Particle Swarm Optimization). The aim is to significantly improve the energy conversion rate and hydrogen production efficiency of the photovoltaic-DC coupled hydrogen production system through particle swarm optimization.

[0007] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0008] A control strategy for a PSO-based photovoltaic DC-coupled hydrogen production system includes the following steps:

[0009] Step S1: Determine the structure of the photovoltaic hydrogen production direct coupling system, and establish the photovoltaic array model and the PEM electrolyzer cell model;

[0010] Step S2: Analyze the operating characteristics of the photovoltaic array and the PEM electrolytic cell array to enable the photovoltaic array to output maximum power and the electrolytic cell to track the output of the photovoltaic array;

[0011] Step S3: Determine the control objective of the photovoltaic DC-coupled hydrogen production system, perform piecewise linearization on the working curve of the electrolyzer chamber, construct the objective function, set constraints, and establish a mathematical model for the control optimization of the photovoltaic DC-coupled hydrogen production system;

[0012] Step S4: Set control variables, optimize the objective function value based on particle swarm optimization algorithm, and obtain the optimal control strategy for photovoltaic DC coupled hydrogen production system.

[0013] Furthermore, as described in step S1, determining the structure of the photovoltaic hydrogen production direct coupling system and establishing a photovoltaic array model and a PEM electrolyzer cell model includes:

[0014] Step S11: Determine the structure of the photovoltaic hydrogen production direct coupling system, including the photovoltaic array and the PEM electrolyzer array;

[0015] Step S12: Establish the mathematical model of the photovoltaic array, as shown in formula (1):

[0016]

[0017] Where I is the photovoltaic output current, U is the photovoltaic output voltage, and I L For photocurrent, I d R is the reverse saturation current of the diode. sh For shunt resistor, I sh R is the current flowing through the resistor. s Let q be the parasitic resistance, q be the unit charge, K be the Boltzmann constant, n be the diode quality factor, and T be the voltage drop factor. pv This refers to the operating temperature of photovoltaic cells.

[0018] Considering R s The value of R is close to 0 and s Approaching infinity, let I L =I sc C1I sc =I0, The simplified engineering model is shown in formula (2):

[0019]

[0020] Among them, I sc For the battery's short-circuit current, U oc For the battery's open-circuit voltage, I mp The current at the battery's maximum power point, U mp Let C1 and C2 be the voltage at the battery's maximum power point, and C1 and C2 be intermediate coefficients, whose expressions are shown in formula (3):

[0021]

[0022] The model of a photovoltaic array composed of multiple photovoltaic cells is shown in formula (4):

[0023]

[0024] Among them, I pv U is the output current of the photovoltaic array. pv N is the output voltage of the photovoltaic array. p and N s These represent the number of modules connected in parallel and the number connected in series in the photovoltaic array, respectively.

[0025] Step S13: Establish the mathematical model of the PEM electrolytic cell. The expression for the total voltage of the PEM electrolytic cell is shown in formula (5):

[0026] U el =U rev +U ohm +U act +U diff (5)

[0027] Among them, U et U is the total voltage of the electrolytic cell. rev For reversible voltage, U ohm U is the ohmic overpotential generated by the resistor. act U is the overpotential generated by the electrochemical reaction. diff This refers to the diffusion overpotential caused by mass transfer and diffusion.

[0028] The reversible voltage is obtained from the Nernst equation, and its expression is shown in formula (6):

[0029]

[0030] in, These are the partial pressures of hydrogen and oxygen, respectively. Let F be the water activity, F be the Faraday constant, R be the gas constant, and T be the T. el This refers to the operating temperature of the electrolytic cell.

[0031] The expression for the ohmic overpotential is shown in equation (7):

[0032]

[0033] Where δ is the membrane electrode thickness, i is the current density, and α is the membrane conductivity;

[0034] The activation overpotential is divided into anodic and cathodic polarization overpotentials, and their expressions are shown in formula (8):

[0035]

[0036] Among them, U act,an U is the anodic polarization overpotential. act,cn For cathode polarization overpotential, i an i is the anode exchange current density. cn This represents the cathode exchange current density.

[0037] Furthermore, step S2 involves analyzing the operating characteristics of the photovoltaic array and the PEM electrolytic cell array to ensure the photovoltaic array outputs maximum power and the electrolytic cell can track the output of the photovoltaic array; this includes:

[0038] Step S21: Adjust the operating point of the photovoltaic array in real time using the maximum power point tracking method so that it always operates near the maximum power point;

[0039] Step S22: Solve for the MPP curve expression. The output power of the photovoltaic array is as follows:

[0040]

[0041] In the above formula, U pv I is the output voltage of the photovoltaic array. pv N is the output current of the photovoltaic array. p and N s These represent the number of modules connected in parallel and the number connected in series in the photovoltaic array, respectively; I sc This is the short-circuit current of the battery; when the operating point is at the maximum power point, The expression formula (10) is shown below:

[0042]

[0043] In the above formula, T pv U is the operating temperature of the photovoltaic cell, d is the sign of the differential, q is the unit charge, and U is the value of the derivative. pv N is the output voltage of the photovoltaic array. p and N s These represent the number of modules connected in parallel and the number connected in series in the photovoltaic array, I. O As an intermediate variable, its calculation formula is shown in equation (11):

[0044] I o =C1I sc (11)

[0045] make The maximum power output curve of the photovoltaic array is shown in formula (12):

[0046]

[0047] In the above formula, U mp This is the voltage at the battery's maximum power point;

[0048] Step S23: The model of the PEM electrolytic cell array composed of electrolytic cell chambers is shown in formula (13):

[0049]

[0050] Where, n p n s These represent the parallel and series numbers of electrolytic cell chambers in the electrolytic cell array, respectively. el For the current flowing through a single electrolytic cell, U el U is the operating voltage of the electrolytic cell chamber. stack I is the voltage of the electrolytic cell array. stack This refers to the current in the electrolytic cell array.

[0051] The number of cells in series electrolytic cells is related to the lateral movement of the working curve, while the number of cells in parallel electrolytic cells is related to the inclination of the working curve. When making adjustments, first adjust the number of cells in series to make the working point approach the MPP, and then adjust the number of cells in parallel to improve the overall tracking accuracy so that the working curve coincides with the MPP curve.

[0052] Furthermore, step S21, which involves adjusting the operating point of the photovoltaic array in real time using the maximum power point tracking method to ensure it always operates near the maximum power point, includes:

[0053] (1) Maximum power point tracking methods for photovoltaic systems include: constant voltage tracking, disturbance observation method, incremental conductance method, optimal gradient method, hysteresis comparison method, intermittent scanning method, fuzzy control method, real-time monitoring method and neural network prediction method;

[0054] (2) Record the voltage and current values ​​of the photovoltaic array in the previous control cycle as U. b I b At the current moment, the voltage and current values ​​of the photovoltaic array are U. n I n The difference between voltage and current is calculated as dU = U. n- U b dI=I n- I b ;

[0055] (3) If the voltage difference is not zero, determine the change in conductance. With negative conductivity The magnitudes of the conductances are related; if they are equal, the maximum power point is reached; if the change in conductance is large, the operating voltage is increased; if the change in conductance is small, the operating voltage is decreased.

[0056] (4) If the voltage difference dU is 0, then jump to 2) to perform the next cycle detection until the voltage difference is detected to be non-zero, so that the photovoltaic array can intelligently output maximum power under various light intensities and temperature environments.

[0057] Further, step S3 describes: determining the control objective of the photovoltaic-DC coupled hydrogen production system, segmenting and linearizing the working curve of the electrolyzer chamber, constructing the objective function, setting constraints, and establishing a mathematical model for the control optimization of the photovoltaic-DC coupled hydrogen production system; including:

[0058] Step S31: The working curve of the electrolytic cell chamber is divided into several sub-blocks using the unequal division method. The curve in each sub-block is linearized. The segmentation position is determined according to the correlation coefficient to achieve optimization. The straight lines fitted by each sub-block are combined to form a piecewise function.

[0059] Step S32: Determine the control objective of the photovoltaic DC-coupled hydrogen production system and construct the objective function, as shown in formula (14):

[0060]

[0061] Where w1 and w2 are coefficients, q H2 denoted as the hydrogen production rate of the PEM electrolyzer array, and abs is the absolute value function.

[0062] According to electrochemical principles, the actual hydrogen production rate of a single PEM electrolyzer is shown in formula (15):

[0063]

[0064] in, The hydrogen production rate of a single electrolyzer. Let A be the molar volume of hydrogen, A be the active area of ​​the electrolyzer, and η be the molar volume of hydrogen. F Here, f is the Faraday efficiency, f1 and f2 are parameters related to the Faraday efficiency, and F is the Faraday electromagnetic constant;

[0065] For an electrolyzer array consisting of series and parallel electrolyzer cells, the hydrogen production rate is shown in formula (16):

[0066]

[0067] In the above formula, n p n s These represent the number of parallel and series connections of the electrolytic cell chambers in the electrolytic cell array, respectively; VH2 is the molar volume of hydrogen; I... el

[0068] This is the operating current of the electrolytic cell chamber;

[0069] Step S33: Set the curve fitting correlation constraints as shown in formula (17): (17)

[0071] Where i is the number of sub-blocks into which the electrolytic cell array's working curve is divided. This represents the lower limit of a strong correlation. The correlation coefficient, These represent the sum of squared residuals and the mean square error of the fitted lines within the sub-blocks, respectively, satisfying the upper and lower limits of the fitting strength constraints. This represents the upper limit of the sum of squared residuals. This represents the upper limit of the mean square error.

[0072] The rounding deviation constraint for setting the number of series and parallel cells in the electrolytic cell is shown in formula (18):

[0073]

[0074] Where, △n p,i , △n s,i This represents the difference between the theoretical and actual values ​​of the number of electrolytic cell chambers connected in series and parallel. n is the theoretical value obtained through mathematical relations. p,i n s,i This is the actual value;

[0075] The number of electrolytic cell chambers connected in series and parallel is constrained as shown in formula (19):

[0076]

[0077] Where, n p.max n s.max This represents the maximum number of electrolytic cells connected in parallel or in series.

[0078] The safety operation constraints for the PEM electrolyzer are set as shown in formula (20):

[0079] 0.25P el (t)≤P el (t)≤1.1P el (t) (20)

[0080] Among them, P el (t) represents the rated power of the electrolytic cell;

[0081] The response rate constraint condition of the PEM electrolyzer is set as shown in formula (21):

[0082]

[0083] Among them, △P el (t) represents the rate of change of hydrogen production power in the electrolyzer. The response speed for adjusting the hydrogen production power of the electrolyzer is adjusted downwards and upwards.

[0084] Furthermore, step S4 describes: setting control variables, optimizing the objective function value based on the particle swarm optimization algorithm, and obtaining the optimal control strategy for the photovoltaic DC-coupled hydrogen production system, including:

[0085] Step S41: Using the number of series connections n in the electrolytic cell array structure s Parallel number n p The operating point of the electrolytic cell chamber is used as a control variable to initialize the population parameters;

[0086] Step S42: Based on the PSO optimization algorithm, optimize the objective function value of each particle to obtain the initial individual historical best position and the population historical best position;

[0087] Update the velocity and position of each particle as shown in Equation (22):

[0088]

[0089] Where X represents the particle position, V represents the particle search position, ω is the inertia factor, c1 and c2 are learning factors, rand() is a random function, and X bcst G represents the optimal position in the particle's history, i.e., the optimal point within each particle swarm. bcst The optimal position for the population is the optimal point for all particles in the swarm.

[0090] Step S43: Calculate the objective function value for each particle and update the historical best position and global best position for each particle. When the maximum number of iterations is reached, stop the iteration and output the global best value. Through iterative calculation, obtain the optimal control strategy for the photovoltaic DC-coupled hydrogen production system.

[0091] Furthermore, the control variables include the number of series connections, the number of parallel connections, and the operating point of the electrolytic cell array structure.

[0092] A control device for a photovoltaic DC-coupled hydrogen production system based on PSO, comprising:

[0093] Photovoltaic array modules are used to convert solar energy into electrical energy;

[0094] PEM electrolyzer cell module is used to produce hydrogen using the electrical energy generated by the photovoltaic array module;

[0095] The MPPT control module is used to control the output voltage and current of the photovoltaic array so that the photovoltaic array can output maximum power.

[0096] PEM electrolyzer array module is used to integrate PEM electrolyzer cell module and improve the overall energy utilization of the system by matching the output of photovoltaic array module;

[0097] The PEM electrolyzer external characteristic module uses a piecewise linearization method to fit the PEM electrolyzer external characteristics in order to quickly match the maximum power point of photovoltaic output, since the external characteristics of the PEM electrolyzer have nonlinear features.

[0098] The optimization model module is used to create an optimization model for the system, including the system optimization objective and constraints.

[0099] The solution module is used to solve the system optimization model based on the power output of the photovoltaic array module and the external characteristics module of the PEM electrolyzer, so as to obtain the optimal state of the PEM electrolyzer array.

[0100] A computer device includes a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein the processor executes the computer program to implement the steps of a control strategy for a PSO-based photovoltaic DC-coupled hydrogen production system.

[0101] A computer storage medium storing a computer program, wherein when the computer program is executed by a processor, the steps of any of the control strategies for a PSO-based photovoltaic DC-coupled hydrogen production system are disclosed.

[0102] The present invention has the following beneficial effects and advantages:

[0103] This invention takes the coincidence of the working curve of the electrolyzer array with the maximum power curve of the photovoltaic array, the highest hydrogen production efficiency, and the maximum energy conversion rate of the system as the control objectives, and the number of series connections, the number of parallel connections, and the working point of the electrolyzer cells as control variables. It proposes a control strategy based on particle swarm optimization algorithm to achieve real-time matching between the photovoltaic array and the electrolyzer array.

[0104] The photovoltaic DC-coupled hydrogen production system control strategy provided by this invention is applicable to scenarios where the photovoltaic array and the electrolyzer array are directly connected. It uses the maximum power point tracking control method to make the photovoltaic array work at maximum power, fully analyzes the working characteristics of the electrolyzer to determine the optimal control target, and realizes real-time matching between the photovoltaic array and the electrolyzer array based on the particle swarm optimization algorithm.

[0105] This invention solves the problem of low energy conversion efficiency in photovoltaic DC-coupled systems by using a maximum power point tracking control method to enable the photovoltaic array to operate at maximum power and by fully analyzing the operating characteristics of the electrolytic cell to enable it to track the output of the photovoltaic array.

[0106] This invention also solves the problem of low matching degree between MPP curve and electrolytic cell array working curve. It adopts the unequal division method to divide the working curve of electrolytic cell chamber into several sub-blocks, linearizes the curve in each sub-block, and synthesizes the straight lines fitted by each sub-block into a piecewise function.

[0107] This invention also solves the problem of low system efficiency caused by only considering the fixed operating point of the electrolytic cell, and analyzes the control strategies for different operating points of the electrolytic cell. Attached Figure Description

[0108] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0109] Figure 1 This is a flowchart of the control strategy of the present invention;

[0110] Figure 2 This is a structural diagram of a photovoltaic hydrogen production direct coupling system in an embodiment of the present invention;

[0111] Figure 3 This is a flowchart of the incremental conductance method in an embodiment of the present invention;

[0112] Figure 4 This is a flowchart of the particle swarm optimization algorithm in an embodiment of the present invention. Detailed Implementation

[0113] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0114] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0115] The following reference Figures 1-4 The technical solutions of some embodiments of the present invention are described below.

[0116] Example 1

[0117] This invention provides an embodiment of a control strategy for a photovoltaic DC-coupled hydrogen production system based on PSO. For example... Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the present invention. In scenarios where the photovoltaic array and the electrolyzer array are directly connected, the present invention optimizes the real-time operation strategy of the hydrogen production system based on a particle swarm optimization algorithm, thereby maximizing the energy conversion rate of the photovoltaic DC-coupled hydrogen production system and achieving the highest hydrogen production efficiency.

[0118] like Figure 1 As shown in the figure, an embodiment of the present invention provides a control strategy for a photovoltaic DC-coupled hydrogen production system based on Pso, which includes the following steps:

[0119] Step S1: Determine the structure of the photovoltaic hydrogen production direct coupling system, and establish the photovoltaic array model and the PEM electrolyzer cell model;

[0120] Step S2: Analyze the operating characteristics of the photovoltaic array and the PEM electrolyzer array to ensure that the photovoltaic array outputs maximum power, and analyze the operating characteristics of the electrolyzer to enable it to track the output of the photovoltaic array;

[0121] Step S3: Determine the control objective of the photovoltaic DC-coupled hydrogen production system, perform piecewise linearization on the working curve of the electrolyzer chamber, construct the objective function, set constraints, and establish a mathematical model for the control optimization of the photovoltaic DC-coupled hydrogen production system;

[0122] Step S4: Set control variables, using the number of series and parallel connections in the electrolyzer array structure and the operating point of the electrolyzer cell as control variables, and optimize the objective function value based on the particle swarm optimization algorithm to obtain the optimal control strategy for the photovoltaic DC-coupled hydrogen production system.

[0123] In this embodiment, step S1 above, which involves determining the structure of a photovoltaic hydrogen production direct coupling system and establishing a photovoltaic array model and a PEM electrolyzer cell model, specifically includes:

[0124] Step S11: Determine the structure of the photovoltaic hydrogen production direct coupling system, mainly including the photovoltaic array and the PEM electrolyzer array, such as... Figure 2 As shown;

[0125] Step S12: Establish the mathematical model of the photovoltaic array. The photovoltaic array is composed of several photovoltaic cells connected in series and parallel. The equivalent model of the photovoltaic cell adopts the equivalent circuit of a single diode with series and parallel resistors. The mathematical model is shown in formula (1):

[0126]

[0127] Where I is the photovoltaic output current, U is the photovoltaic output voltage, and I L For photocurrent, I d R is the reverse saturation current of the diode. sh For shunt resistor, I sh R is the current flowing through the resistor. s Let q be the parasitic resistance, q be the unit charge, K be the Boltzmann constant, n be the diode quality factor, and T be the voltage drop factor. pv This refers to the operating temperature of photovoltaic cells.

[0128] For ease of engineering application, considering R s The value of R is close to 0 and s Approaching infinity, let I L =I sc C １I sc =I0, The simplified engineering model is shown in formula (2):

[0129]

[0130] Among them, I sc For the battery's short-circuit current, U oc For the battery's open-circuit voltage, I mp The current at the battery's maximum power point, U mp The voltage at the battery's maximum power point is given by the manufacturer. These parameters can be obtained directly from the manufacturer. C1 and C2 are intermediate coefficients, and their expressions are shown in formula (3).

[0131]

[0132] The model of a photovoltaic array composed of multiple photovoltaic cells is shown in formula (4):

[0133]

[0134] Among them, I pv U is the output current of the photovoltaic array. pv N is the output voltage of the photovoltaic array. p and N s These represent the number of modules connected in parallel and the number connected in series in the photovoltaic array, respectively.

[0135] Step S13: Establish the mathematical model of the PEM electrolytic cell. The expression for the total voltage of the PEM electrolytic cell is shown in formula (5):

[0136] U el =U rev +U ohm +U act +U diff (5)

[0137] Among them, U et U is the total voltage of the electrolytic cell. rev For reversible voltage, U ohm U is the ohmic overpotential generated by the resistor. act U is the overpotential generated by the electrochemical reaction. diff The diffusion overpotential caused by mass transfer diffusion accounts for a small proportion and can usually be ignored.

[0138] The reversible voltage is obtained from the Nernst equation, and its expression is shown in formula (6):

[0139]

[0140] in, These are the partial pressures of hydrogen and oxygen, respectively. Let F be the water activity, F be the Faraday constant, R be the gas constant, and T be the T. el This refers to the operating temperature of the electrolytic cell.

[0141] The expression for the ohmic overpotential is shown in equation (7):

[0142]

[0143] Where δ is the membrane electrode thickness, i is the current density, and α is the membrane conductivity;

[0144] The activation overpotential is divided into anodic and cathodic polarization overpotentials, and their expressions are shown in formula (8):

[0145]

[0146] Among them, U act,an U is the anodic polarization overpotential. act,cn For cathode polarization overpotential, i an i is the anode exchange current density. cn This represents the cathode exchange current density.

[0147] After step S1 above, the structure of the photovoltaic hydrogen production direct coupling system was determined, and the photovoltaic array model and the PEM electrolyzer cell model were established.

[0148] In this embodiment, step S2 above, which involves analyzing the operating characteristics of the photovoltaic array and the PEM electrolyzer array to ensure that the photovoltaic array outputs maximum power and analyzing the operating characteristics of the electrolyzer to enable it to track the output of the photovoltaic array, specifically includes:

[0149] Step S21: To improve the efficiency of photoelectric conversion, the operating point of the photovoltaic array is adjusted in real time using the maximum power point tracking method so that it always operates near the maximum power point;

[0150] 1) Commonly used maximum power point tracking (MPPT) methods for photovoltaic (PV) systems include: constant voltage tracking, perturbation observation method, incremental conductance method, optimal gradient method, hysteresis comparison method, intermittent scanning method, fuzzy control method, real-time monitoring method, and neural network prediction method. This invention uses the incremental conductance method to illustrate the process of adjusting the operating point of a PV system to track its maximum power point.

[0151] 2) Record the voltage and current values ​​of the photovoltaic array in the previous control cycle as U. b I b At the current moment, the voltage and current values ​​of the photovoltaic array are U. n I n The difference between voltage and current is calculated as dU = U. n- U b dI=I n- Ib ;

[0152] 3) If the voltage difference is not zero, determine the change in conductance. With negative conductivity The magnitudes of the conductances are related; if they are equal, the maximum power point is reached; if the change in conductance is large, the operating voltage is increased; if the change in conductance is small, the operating voltage is decreased.

[0153] 4) If the voltage difference dU is 0, then jump to 2) to perform the next cycle detection until a non-zero voltage difference is detected, enabling the photovoltaic array to intelligently output maximum power under various light intensities and temperature environments, such as... Figure 3 As shown, Figure 3 The following is the algorithm flow of the incremental conductance method in the embodiments of the present invention.

[0154] Step S22: Solve for the MPP curve expression. The output power of the photovoltaic array is as shown in formula (9).

[0155]

[0156] In the above formula, U pv I is the output voltage of the photovoltaic array. pv N is the output current of the photovoltaic array. p and N s These represent the number of modules connected in parallel and the number connected in series in the photovoltaic array, respectively; I sc This is the short-circuit current of the battery.

[0157] When the operating point is at the maximum power point The expression formula (10) is shown below:

[0158]

[0159] In the above formula, T pv U is the operating temperature of the photovoltaic cell, d is the sign of the differential, q is the unit charge, and U is the value of the derivative. pv N is the output voltage of the photovoltaic array. p and N s These represent the number of modules connected in parallel and the number connected in series in the photovoltaic array, I. O As an intermediate variable, its calculation formula is shown in equation (11):

[0160] I o =C1I sc (11)

[0161] make The maximum power output curve of the photovoltaic array is shown in formula (12):

[0162]

[0163] In the above formula, U mp This is the voltage at the battery's maximum power point.

[0164] Step S23: The model of the PEM electrolytic cell array composed of electrolytic cell chambers is shown in formula (13):

[0165]

[0166] Where, n p n s These represent the parallel and series numbers of electrolytic cell chambers in the electrolytic cell array, respectively. el For the current flowing through a single electrolytic cell, U el U is the operating voltage of the electrolytic cell chamber. stack I is the voltage of the electrolytic cell array. stack This represents the current in the electrolytic cell array.

[0167] The number of cells in series electrolytic cells is related to the lateral movement of the working curve, while the number of cells in parallel electrolytic cells is related to the inclination of the working curve. When adjusting, the number of cells in series should be adjusted first to make the working point closer to the MPP curve, and then the number of cells in parallel should be adjusted to improve the overall tracking accuracy so that the working curve coincides with the MPP curve.

[0168] After step S2 above, the photovoltaic array is kept near the maximum power point by using the maximum power point tracking method, and the working characteristics of the electrolytic cell are fully analyzed so that it can track the output of the photovoltaic array.

[0169] In this embodiment, step S3 above involves: determining the control objective of the photovoltaic-DC coupled hydrogen production system, performing piecewise linearization on the working curve of the electrolyzer chamber, constructing the objective function, setting constraints, and establishing a mathematical model for the control optimization of the photovoltaic-DC coupled hydrogen production system. Specifically, this includes:

[0170] Step S31: The working curve of the electrolytic cell chamber is divided into several sub-blocks using the unequal division method. The curve in each sub-block is linearized. The segmentation position is determined according to the correlation coefficient to achieve optimization. The straight lines fitted by each sub-block are combined to form a piecewise function.

[0171] Step S32: Determine the control objective of the photovoltaic DC-coupled hydrogen production system to ensure that the working curve of the electrolyzer array coincides as much as possible with the maximum power output curve of the photovoltaic array, and that the hydrogen production efficiency reaches its maximum, so as to maximize the energy conversion rate of the photovoltaic DC-coupled hydrogen production system; construct the objective function as shown in formula (14):

[0172]

[0173] Where w1 and w2 are coefficients, q H2Let be the hydrogen production rate of the PEM electrolyzer array, and abs be the absolute value function.

[0174] According to electrochemical principles, the actual hydrogen production rate of a single PEM electrolyzer is shown in formula (15):

[0175]

[0176] in, The hydrogen production rate of a single electrolyzer. Let A be the molar volume of hydrogen, A be the active area of ​​the electrolyzer, and η be the molar volume of hydrogen. F Here, f is the Faraday efficiency, f1 and f2 are parameters related to the Faraday efficiency, and F is the Faraday electromagnetic constant.

[0177] For an electrolyzer array consisting of series and parallel electrolyzer cells, the hydrogen production rate is shown in formula (16):

[0178]

[0179] In the above formula, n p n s These represent the number of parallel and series connections of the electrolytic cell chambers in the electrolytic cell array, respectively; VH2 is the molar volume of hydrogen; I... el This is the operating current of the electrolytic cell chamber.

[0180] Step S33: Set the curve fitting correlation constraints as shown in formula (17):

[0181]

[0182] Where i is the number of sub-blocks into which the electrolytic cell array's working curve is divided. This represents the lower limit of a strong correlation. R is the correlation coefficient. i , These represent the correlation coefficient, sum of squared residuals, and mean square error of the fitted straight line within the sub-block, respectively, and must satisfy the upper and lower limits of the fitting strength constraints. This represents the upper limit of the sum of squared residuals. This represents the upper limit of the mean square error.

[0183] The rounding deviation constraint for setting the number of series and parallel cells in the electrolytic cell is shown in formula (18):

[0184]

[0185] Where, △n p,i , △n s,i This represents the difference between the theoretical and actual values ​​of the number of electrolytic cell chambers connected in series and parallel. n is the theoretical value obtained through mathematical relations. p,i ns,i This is the actual value;

[0186] The number of electrolytic cell chambers connected in series and parallel is constrained as shown in formula (19):

[0187]

[0188] Where, n p.max n s.max This represents the maximum number of electrolytic cells connected in parallel or in series.

[0189] The safety operation constraints for the PEM electrolyzer are set as shown in formula (20):

[0190] 0.25P el (t)≤P el (t)≤1.1P el (t) (20)

[0191] Among them, P el (t) represents the rated power of the electrolytic cell;

[0192] The response rate constraint condition of the PEM electrolyzer is set as shown in formula (21):

[0193]

[0194] Among them, △P el (t) represents the rate of change of hydrogen production power in the electrolyzer. The response speed for adjusting the hydrogen production power of the electrolyzer is adjusted downwards and upwards.

[0195] After step S3 above, the control objective of the photovoltaic DC-coupled hydrogen production system was determined, the working curve of the electrolyzer chamber was piecewise linearized, and a mathematical model for the control optimization of the photovoltaic DC-coupled hydrogen production system was established.

[0196] In the embodiment, step S4 above: using the number of series connections n of the electrolytic cell array structure s Parallel number n p The operating point of the electrolyzer chamber is used as the control variable, and the objective function value is optimized based on the particle swarm optimization algorithm to obtain the optimal control strategy for the photovoltaic DC-coupled hydrogen production system, such as... Figure 4 As shown, it specifically includes:

[0197] Step S41: Using the number of series connections n in the electrolytic cell array structure s Parallel number n p The operating point of the electrolytic cell chamber is used as a control variable to initialize the population parameters;

[0198] Step S42: Based on the PSO optimization algorithm, optimize the objective function value of each particle to obtain the initial individual historical best position and the population historical best position;

[0199] Update the velocity and position of each particle as shown in Equation (22):

[0200]

[0201] Where X represents the particle position, V represents the particle search position, ω is the inertia factor, c1 and c2 are learning factors, rand() is a random function, and X bcst G represents the optimal position in the particle's history, i.e., the optimal point within each particle swarm. bcst The optimal position for the population is the optimal point for all particles in the swarm.

[0202] Step S43: Calculate the objective function value for each particle and update the historical best position and global best position for each particle. When the maximum number of iterations is reached, stop the iteration and output the global best value. Through iterative calculation, the optimal control strategy for the photovoltaic DC-coupled hydrogen production system is obtained. The control flow is as follows: Figure 4 As shown.

[0203] After step S4 above, control variables were set, the objective function value was optimized based on the particle swarm optimization algorithm, and the optimal control strategy for the photovoltaic DC-coupled hydrogen production system was proposed.

[0204] Example 2

[0205] The present invention provides another embodiment of a control device for a photovoltaic DC-coupled hydrogen production system based on PSO, comprising:

[0206] Photovoltaic array modules are used to convert solar energy into electrical energy;

[0207] The PEM electrolyzer cell module is used to produce hydrogen using electricity generated by the photovoltaic array module.

[0208] The MPPT control module is used to control the output voltage and current of the photovoltaic array so that the photovoltaic array can output maximum power.

[0209] The PEM electrolyzer array module is used to integrate the PEM electrolyzer cell module and improve the overall energy utilization of the system by matching the output of the photovoltaic array module.

[0210] The PEM electrolyzer external characteristic module uses a piecewise linearization method to fit the external characteristics of the PEM electrolyzer to quickly match the maximum power point of photovoltaic output, since the external characteristics of the PEM electrolyzer have nonlinear features.

[0211] The optimization model module is used to create an optimization model for the system, including the system optimization objectives, constraints, and so on.

[0212] The solution module is used to solve the system optimization model based on the power output of the photovoltaic array module and the external characteristics module of the PEM electrolyzer, so as to obtain the optimal state of the PEM electrolyzer array.

[0213] Example 3

[0214] Based on the same inventive concept, embodiments of the present invention also provide a computer device, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the computer program, it implements the steps of any of the control strategies for a PSO-based photovoltaic DC-coupled hydrogen production system described in Embodiment 1 or 2.

[0215] Example 4

[0216] Based on the same inventive concept, this embodiment of the invention also provides a computer storage medium storing a computer program, which, when executed by a processor, implements the steps of any of the control strategies for a PSO-based photovoltaic DC-coupled hydrogen production system described in Embodiment 1 or 2.

[0217] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied 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.

[0218] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0219] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0220] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0221] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A control strategy for a Pso-based photovoltaic direct-coupled hydrogen system, characterized by: Comprising the following steps: Step S1: determine the structure of the photovoltaic hydrogen production directly coupled system, establish a photovoltaic array model and a PEM electrolytic cell chamber model, comprising: step S11: determine the structure of the photovoltaic hydrogen production directly coupled system, comprising a photovoltaic array and a PEM electrolytic cell array; step S12: establish a mathematical model of the photovoltaic array; the model of the photovoltaic array composed of multiple photovoltaic cells is shown in formula (4): where I pv is the output current of the photovoltaic array, U pv is the output voltage of the photovoltaic array, N p and N s are the parallel and series numbers of the components in the photovoltaic array, respectively, I sc is the short-circuit current of the cell, U oc is the open-circuit voltage of the cell, and C1 and C2 are intermediate coefficients. Step S13: establish a mathematical model of the PEM electrolytic cell chamber, and the total voltage expression of the PEM electrolytic cell chamber is shown in formula (5): U el = U rev + U ohm + U act + U diff (5) where U et is the total voltage of the cell, U rev is the reversible voltage, U ohm is the ohmic overpotential due to resistance, U act is the overpotential due to electrochemical reactions, U diff is the diffusion overpotential due to mass transfer diffusion; the reversible voltage is obtained from the Nernst equation, as shown in equation (6): wherein the partial pressure of hydrogen and oxygen, respectively, is the water activity, F is the Faraday constant, R is the gas constant, T el is the electrolyzer operating temperature; the expression for the ohmic overpotential is given by equation (7): Wherein, δ is the thickness of the membrane electrode, i is the current density, and α is the conductivity of the membrane; The activation overpotential is divided into anode and cathode polarization overpotential, and its expression is shown in formula (8): where U act,an is the anodic overpotential, U act,cn is the cathodic overpotential, i an is the anodic exchange current density, i cn is the cathodic exchange current density; Step S2: analyze the working characteristics of the photovoltaic array and the PEM electrolytic cell array, so that the photovoltaic array outputs maximum power, and the electrolytic cell can track the output of the photovoltaic array; comprising: step S21: adjust the working point of the photovoltaic array in real time through the maximum power point tracking method, so that it always works near the maximum power point; step S22: solve the expression of the MPP curve, and the output power of the photovoltaic array is as follows: In the above equation, U pv is the output voltage of the photovoltaic array, I pv is the output current of the photovoltaic array, N p and N s are the number of parallel and series components in the photovoltaic array, respectively; I sc is the short-circuit current of the cell; when the operating point is at the maximum power point, the voltage U is given by the expression formula (10): In the above formula, T pv is the operating temperature of the photovoltaic cell, d is the differential symbol, q is the unit charge, U pv is the output voltage of the photovoltaic array, N p and N s are the parallel number and series number of components in the photovoltaic array, respectively, I O is an intermediate variable, and its calculation formula is as follows: I o = C1I sc (11) Let The maximum power curve of the photovoltaic array output is shown in formula (12): In the above formula, U mp is the voltage at the maximum power point of the battery; Step S23: the model of the PEM electrolytic cell array composed of electrolytic cell chambers is shown in formula (13): wherein, n p , n s are the parallel and series numbers of electrolytic cell chambers in the electrolytic cell array, I el is the current flowing through a single electrolytic cell, U el is the working voltage of the electrolytic cell chamber, U stack is the voltage of the electrolytic cell array, I stack is the current of the electrolytic cell array; the number of series electrolytic cell chambers is related to the lateral movement of the working curve, and the number of parallel electrolytic cell chambers is related to the degree of inclination of the working curve; when adjusting, the series number is first adjusted to make the working point approach the MPP, and then the parallel number is adjusted to improve the overall tracking precision so that the working curve coincides with the MPP curve; Step S3: determine the control target of the photovoltaic direct current coupled hydrogen production system, segmentally linearize the working curve of the electrolytic cell chamber, construct an objective function, set a constraint condition, and establish a mathematical model of the control optimization of the photovoltaic direct current coupled hydrogen production system; comprising: step S31: the working curve of the electrolytic cell chamber is divided into several sub-blocks by using the uneven division method, the curve in each sub-block is linearized, the segmentation position is determined according to the correlation coefficient so as to achieve optimization, the straight lines fitted out of the sub-blocks are synthesized to form a segmented function; step S32: determine the control target of the photovoltaic direct current coupled hydrogen production system, and construct an objective function, as shown in formula (14): f = min(wl(abs(U pv -U stack )+ abs(I pv -I stack )- w2(qH2)) (14) where w1, w2 are coefficients, q H2 is the hydrogen production rate of the PEM cell array, and abs is the absolute value function. According to the electrochemical principle, the actual hydrogen production rate of a single PEM electrolytic cell is shown in formula (15): wherein, is the hydrogen production rate of a single electrolyzer, is the molar volume of hydrogen, A is the active area of the electrolyzer, η F is the Faraday efficiency, f1, f2 are Faraday efficiency related parameters, F is the Faraday electromagnetic constant; For the electrolytic cell array composed of electrolytic cell chambers in series and parallel, the hydrogen production rate is shown in formula (16): In the above formula, n p , n s are respectively the parallel number and series number of electrolytic cell cells in the electrolytic cell array, VH2 is the molar volume of hydrogen gas, I el is the working current of the electrolytic cell cell. Step S33: Set the curve fitting correlation constraint condition as shown in equation (17): Wherein, i is the number of electrolytic cell array working curve sub-block division, is the lower limit value of strong correlation, is the correlation coefficient, respectively, the residual sum of squares and the mean square error of the fitting straight line in the sub-block, satisfying the upper and lower limit constraints of the fitting strength, is the upper limit value of the residual sum of squares, is the upper limit value of the mean square error; The integral deviation constraint condition of the number of electrolytic cell chambers in series and parallel is shown in formula (18): where Δn p,i , Δn s,i is the difference between the theoretical and actual number of cells in series and parallel, is the theoretical value obtained by a mathematical relationship, n p,i , n s,i is the actual value; The quantity constraint condition of the number of electrolytic cell chambers in series and parallel is shown in formula (19): wherein n p.max , n s.max is the maximum value of the number of parallel and series connections of the electrolytic cells. The safe operation constraint condition of the PEM electrolytic cell is shown in formula (20): 0.25P el (t)≤P el (t)≤1.1P el (t) (20) Among them, P el (t) represents the rated power of the electrolytic cell; The response speed constraint condition of the PEM electrolytic cell is shown in formula (21): wherein ΔP el (t) is the rate of change of the power of the electrolyser for producing hydrogen, is the response speed of the power of the electrolyser for producing hydrogen to the down-regulation and up-regulation; Step S4: set the control variable, optimize the objective function value based on the particle swarm optimization algorithm, and obtain the optimal control strategy of the photovoltaic direct current coupled hydrogen production system.

2. The control strategy for a Pso-based photovoltaic direct coupling hydrogen production system according to claim 1, characterized in that: The step S21 adjusts the working point of the photovoltaic array in real time through the maximum power point tracking method, so that it always works near the maximum power point, comprising: (1) the maximum power point tracking method of the photovoltaic system comprises: constant voltage tracking, perturbation and observation method, conductance increment method, optimal gradient method, hysteresis comparison method, intermittent scanning method, fuzzy control method, real-time monitoring method and neural network prediction method; (2) record the voltage and current values of the photovoltaic array in the previous control period as U b , b , the voltage and current values of the photovoltaic array at the current moment as U n , n , calculate the difference values of the voltage and current as dU = U n- U b , dI = I n- I b ; (3) If the voltage difference is not 0, judge the conductance change and the size relation with the negative conductance value ; if equal, reach the maximum power point, if the conductance change is larger, increase the working voltage, if the conductance change is smaller, reduce the working voltage; (4) If the voltage difference dU is 0, jump to 2) to detect the next cycle until the voltage difference is not zero, so that the photovoltaic array can intelligently output maximum power under various light intensity and temperature environments.

3. The control strategy for a Pso-based photovoltaic DC-coupled hydrogen generation system according to claim 1, characterized in that: Step S4 The setting control variable, the objective function value is optimized based on the particle swarm optimization algorithm, and the optimal control strategy of the photovoltaic direct-current coupled hydrogen production system is obtained, including: Step S41: taking the series number n of the electrolytic cell array structure s , the parallel number n p , and the working point of the electrolytic cell chamber as control variables, initializing the population parameters; Step S42: Based on the PSO optimization algorithm, the objective function value of each particle is optimized to obtain the initial individual historical optimal position and the population historical optimal position; Update the speed and position of each particle, as shown in formula (22): where X represents the particle position, V represents the particle search position, ω is an inertia factor, c1 and c2 are learning factors, rand() is a random function, X bcst is the particle historical optimal position, i.e., the optimal point within each particle group, G bcst is the population optimal position, i.e., the optimal point of all particle groups; Step S43: Calculate the objective function value of each particle, and update the historical optimal position of each particle and the global optimal position, when the maximum iteration number is reached, stop iteration, output the global optimal value, and obtain the optimal control strategy of the photovoltaic direct-current coupled hydrogen production system through iterative calculation.

4. The control strategy for a Pso-based photovoltaic DC-coupled hydrogen generation system according to claim 1, characterized in that: The control variable includes the series number and parallel number of the electrolytic cell array structure, and the working point of the electrolytic cell chamber.

5. The Pso-based photovoltaic direct-current coupled hydrogen production system control strategy according to claim 1, characterized in that it comprises: A photovoltaic array module for converting solar energy into electrical energy; A PEM electrolytic cell chamber module for producing hydrogen gas using the electrical energy generated by the photovoltaic array module; An MPPT control module for controlling the output voltage and current of the photovoltaic array to enable the photovoltaic array to output maximum power; A PEM electrolytic cell array module for integrating the PEM electrolytic cell chamber module to improve the overall energy utilization rate of the system by matching the output of the photovoltaic array module; A PEM electrolytic cell external characteristic module, since the external characteristics of the PEM electrolytic cell have nonlinear characteristics, in order to quickly match the maximum power point of the photovoltaic output, the external characteristics of the PEM electrolytic cell are fitted using the piecewise linearization method; An optimization model module for the optimization model of the system, including the system optimization target and the constraint condition; A solving module for solving the system optimization model based on the PEM electrolytic cell external characteristic module according to the power output of the photovoltaic array module to obtain the optimal state of the PEM electrolytic cell array.

6. A computer device comprising a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, characterized in that, The processor executes the computer program to realize the steps of the Pso-based photovoltaic direct-current coupled hydrogen production system control strategy according to any one of claims 1-4.

7. A computer storage medium, characterized by: The computer storage medium has a computer program stored thereon, and the computer program is executed by the processor to realize the steps of the Pso-based photovoltaic direct-current coupled hydrogen production system control strategy according to any one of claims 1-4.

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