Improved mppt algorithm in optical hydrogen storage dc microgrid and three-phase interleaved parallel hydrogen production converter current sharing control method and system

Abstract

The application discloses an improved MPPT algorithm in a light hydrogen storage direct-current microgrid and a three-phase interleaved parallel hydrogen production converter current sharing control method and system, and the method comprises the following steps: obtaining a physical system model according to the hardware circuit parameters of a three-phase interleaved parallel DC-DC converter hydrogen production system of the light hydrogen storage direct-current microgrid; constructing an improved MPPT algorithm according to the output characteristics of a photovoltaic array; obtaining photovoltaic Boost converter control logic according to the improved MPPT algorithm; constructing a small signal model of a main circuit according to the physical system model; obtaining overall control logic according to the control architecture of the three-phase interleaved parallel hydrogen production converter and the photovoltaic Boost converter control logic; constructing a small signal model of a control system according to the overall control logic; obtaining a target small signal model according to the small signal model of the main circuit and the small signal model of the control system, and setting a current sharing control strategy of the three-phase interleaved parallel hydrogen production converter based on the target small signal model.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic maximum power point tracking (MPPT) and low ripple current sharing stability control technology for hydrogen production converters in photovoltaic-hydrogen storage DC microgrids. In particular, it relates to an improved MPPT algorithm and a current sharing control method and system for three-phase interleaved parallel hydrogen production converters in photovoltaic-hydrogen storage DC microgrids. Background Technology

[0002] With the introduction of my country's "dual-carbon" target, new energy sources such as photovoltaics and wind power have experienced explosive growth, and in the future, new energy will gradually replace traditional fossil fuels. However, photovoltaic power generation is affected by environmental factors, exhibiting strong volatility and randomness. Its large-scale grid connection will impact the stability of the power system, leading to frequent curtailment of solar power to ensure grid stability. To address the issue of local consumption of new energy, photovoltaic hydrogen production has been proposed as an effective consumption pathway. Hydrogen energy has advantages such as being pollution-free, clean, and capable of long-term storage, laying the foundation for the development of photovoltaic hydrogen production. Traditional photovoltaic hydrogen storage DC microgrids use the fixed-step incremental conductance method for the photovoltaic power generation portion. However, this maximum power point tracking (MPPT) algorithm, due to its constant step size and other reasons, cannot simultaneously meet the requirements of fast tracking speed and small steady-state fluctuations. Furthermore, while photovoltaic hydrogen production has great potential, it faces numerous challenges. On one hand, the volatility of photovoltaic power generation makes the power supply of DC microgrids unstable, leading to frequent start-ups and shutdowns of electrolyzers, thereby shortening their lifespan. Furthermore, the input current ripple of the electrolyzer also affects hydrogen production efficiency and electrolyzer lifespan. On the other hand, the DC bus voltage boosted by photovoltaic power generation is mismatched with the operating voltage of the electrolyzer, requiring a DC / DC converter for power conversion. Therefore, it is necessary to improve the MPPT algorithm and propose a hydrogen production power supply control strategy that meets the hydrogen production requirements. Summary of the Invention

[0003] To address the aforementioned technical issues, this invention proposes an improved MPPT algorithm and a current sharing control method and system for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid. This invention can track the maximum power output of photovoltaic cells while exhibiting good steady-state performance, meeting the low-ripple, high-current power supply requirements of PEM electrolyzers, and also providing excellent current sharing performance.

[0004] To achieve the above objectives, this invention provides an improved MPPT algorithm and a current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid, comprising:

[0005] Based on the hardware circuit parameters of the hydrogen production system using the three-phase interleaved parallel DC-DC converter of the photovoltaic hydrogen storage DC microgrid, a physical system model is obtained.

[0006] Based on the output characteristics of the photovoltaic array, an improved MPPT algorithm is constructed;

[0007] Based on the improved MPPT algorithm, the control logic of the photovoltaic Boost converter is obtained;

[0008] Based on the physical system model, construct a small-signal model of the main circuit;

[0009] Based on the control architecture of the three-phase interleaved parallel hydrogen production converter and the control logic of the photovoltaic Boost converter, the overall control logic is obtained.

[0010] Based on the overall control logic, a small-signal model of the control system is constructed;

[0011] Based on the small-signal model of the main circuit and the small-signal model of the control system, a target small-signal model is obtained, and a current sharing control strategy for the three-phase interleaved parallel hydrogen production converter is set based on the target small-signal model.

[0012] Optionally, the control method is applied to a three-phase interleaved parallel DC-DC converter hydrogen production system of a photovoltaic hydrogen storage DC microgrid, wherein the three-phase interleaved parallel DC-DC converter hydrogen production system of the photovoltaic hydrogen storage DC microgrid includes a photovoltaic array, a photovoltaic Boost converter, a battery, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC converter, an output-side capacitor of the three-phase interleaved parallel DC-DC converter, and a PEM electrolyzer.

[0013] Optionally, obtaining the physical system model includes:

[0014] Based on the topology of the photovoltaic array, photovoltaic Boost converter, battery, energy storage bidirectional converter, three-phase interleaved parallel DC-DC hydrogen converter, output capacitor and PEM electrolyzer connected in sequence in the hydrogen production system, the electrical parameters of each hardware circuit are obtained.

[0015] Based on the electrical parameters, establish the physical system model.

[0016] Optionally, based on the output characteristics of the photovoltaic array, the improved MPPT algorithm is constructed by including:

[0017] Obtain the output characteristics of the photovoltaic array:

[0018] ;

[0019] Introducing a current-dependent coefficient to affect output characteristics Make corrections;

[0020] The current correlation coefficient, i.e., the variable step size coefficient, is d(k), and the step size change is... ;

[0021] A variable step size coefficient and a step size change amount are set. Based on the relationship between the current operating point's conductance increment and instantaneous conductance, the duty cycle of the photovoltaic Boost converter is adjusted using the variable step size conductance increment method. The duty cycle adjustment amount is determined by the product of the variable step size coefficient and the voltage change amount.

[0022] Optionally, based on the physical system model, constructing the small-signal model of the main circuit includes:

[0023] Based on the hardware circuit parameters of the physical system model, state-space equations are established using Kirchhoff's voltage law and Kirchhoff's current law.

[0024] The average state-space equation is obtained by using the state-space averaging method, and the average state-space equation is linearized by applying a small-signal perturbation to obtain the small-signal model of the main circuit.

[0025] Optionally, based on the control architecture of the three-phase interleaved parallel hydrogen production converter, the overall control logic includes:

[0026] Based on the power output requirements of the photovoltaic Boost converter in the control architecture of the three-phase interleaved parallel hydrogen production converter, the control logic of the photovoltaic Boost converter is set.

[0027] Based on the DC bus voltage stability requirements, the control logic for the energy storage bidirectional converter is set.

[0028] Based on the low-voltage, high-current, and low-ripple power supply requirements of the PEM electrolyzer, the control logic of the three-phase interleaved parallel DC-DC hydrogen converter is set.

[0029] The overall control logic is obtained based on the photovoltaic Boost converter control logic, the energy storage bidirectional converter control logic, and the three-phase interleaved parallel DC-DC hydrogen production converter control logic.

[0030] Optionally, based on the overall control logic, constructing a small-signal model of the control system includes:

[0031] Based on the control variables in the overall control logic, establish the state-space equations of the control system, which include the controller transfer function, the modulation transfer function, and the sampling transfer function;

[0032] The small-signal linearization process is performed on the state-space equations of the control system to obtain the small-signal model of the control system.

[0033] Optionally, the flow sharing control strategy includes:

[0034] Based on the transfer functions of inductor current and duty cycle and output voltage and duty cycle in the target small-signal model, the parameters of the inner current loop PI controller and the outer voltage loop PI controller are designed. Bode plots are drawn using frequency domain analysis. The system stability is verified based on phase margin and gain margin. The current sharing control strategy of the three-phase interleaved parallel hydrogen production converter is determined.

[0035] The present invention also provides an improved MPPT algorithm and a current sharing control system for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid, comprising: an acquisition unit, a first modeling control unit, a second modeling control unit, and a third modeling control unit;

[0036] The acquisition unit is used to acquire the physical system and control logic of the photovoltaic-hydrogen storage DC microgrid hydrogen production system, wherein the photovoltaic-hydrogen storage DC microgrid hydrogen production system includes a photovoltaic Boost converter, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC hydrogen production converter, an output-side capacitor of the three-phase interleaved parallel DC-DC hydrogen production converter, and a PEM electrolyzer connected in sequence; based on the hardware circuit parameters of the photovoltaic-hydrogen storage DC microgrid three-phase interleaved parallel DC-DC converter hydrogen production system, a physical system model is acquired; and an improved MPPT algorithm is constructed based on the output characteristics of the photovoltaic array.

[0037] The first modeling control unit is used to construct a small-signal model of the main circuit based on the physical system model;

[0038] The second modeling control unit is used to obtain the overall control logic based on the control architecture of the three-phase interleaved parallel hydrogen converter; and to construct a small-signal model of the control system based on the overall control logic.

[0039] The third modeling control unit obtains a target small-signal model based on the small-signal model of the main circuit and the small-signal model of the control system, and sets a current sharing control strategy for the three-phase interleaved parallel hydrogen production converter based on the target small-signal model.

[0040] The present invention also provides an electronic device and a computer-readable storage medium, the storage medium storing the control method, the electronic device being able to execute the program of the computer-readable storage medium, and the control method being processed and executed by the electronic device causing the electronic device to perform the control method.

[0041] Compared with the prior art, the present invention has the following advantages and technical effects:

[0042] This invention ensures a good balance between stability and speed in the maximum power point tracking (MPPT) of the photovoltaic (PV) power generation system, meets the low-ripple, high-current power supply requirements of the PEM electrolyzer, and enables current sharing across all phases of the hydrogen production converter. Based on the physical system and control logic of the three-phase interleaved parallel hydrogen production converter system of the PV-hydrogen storage DC microgrid, small-signal models of the main circuit and the control system are constructed separately. These models are then coupled to obtain the final small-signal model of the hydrogen production system. A control strategy for the hydrogen production converter is designed based on this model. Furthermore, an improved variable-step-size conductance incremental method is applied to the Boost converter of the PV power generation system. The control method provided by this invention can improve the stability of the PV power generation system and meet the power supply requirements of the PEM electrolyzer and ensure current sharing across all phases. Attached Figure Description

[0043] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0044] Figure 1 This is a flowchart of an improved MPPT algorithm and a current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to an embodiment of the present invention.

[0045] Figure 2 This is a schematic diagram of a typical application scenario of an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of the equivalent circuit model of a photovoltaic cell according to an embodiment of the present invention;

[0047] Figure 4 This is a flowchart of the improved variable step size MPPT algorithm according to an embodiment of the present invention;

[0048] Figure 5 This is a topology diagram of a three-phase interleaved parallel bidirectional DC-DC converter according to an embodiment of the present invention;

[0049] Figure 6 This is a waveform diagram of the Buck mode D<1 / 3 of the three-phase interleaved parallel hydrogen converter according to an embodiment of the present invention;

[0050] Figure 7 This is a block diagram of the phase-shifting current sharing control algorithm for the hydrogen converter current inner loop according to an embodiment of the present invention;

[0051] Figure 8 This is a control structure diagram of the Buck mode of the three-phase interleaved parallel hydrogen converter according to an embodiment of the present invention;

[0052] Figure 9This is the Bode plot of the current loop after adding a PI controller in an embodiment of the present invention;

[0053] Figure 10 This is a voltage loop Bode diagram after adding a PI controller in an embodiment of the present invention;

[0054] Figure 11 This is a block diagram of a control strategy for a bidirectional energy storage converter according to an embodiment of the present invention;

[0055] Figure 12 This is a dynamic mathematical model diagram of the PEM electrolyzer according to an embodiment of the present invention;

[0056] Figure 13 This is a diagram showing the main waveforms of the MPPT algorithm with a variable step size coefficient of 0.05 / I according to an embodiment of the present invention.

[0057] Figure 14 The variable step size coefficient in this embodiment of the invention is The main waveform diagram of the MPPT algorithm;

[0058] Figure 15 In this embodiment of the invention, the variable step size coefficient is 0.05 / I. 2 Main waveform diagram of the improved MPPT algorithm;

[0059] Figure 16 These are the main simulation waveforms of a conventional Buck converter according to an embodiment of the present invention;

[0060] Figure 17 This is a waveform diagram of the output voltage and output current of a three-phase interleaved parallel hydrogen converter with independent current sharing control in the inner current loop according to an embodiment of the present invention.

[0061] Figure 18 This is a current sharing effect diagram based on the active current inner loop independent current sharing control algorithm of this invention embodiment;

[0062] Figure 19 This is a power curve diagram of a photovoltaic hydrogen storage DC microgrid according to an embodiment of the present invention;

[0063] Figure 20 This is a DC bus voltage diagram of a photovoltaic hydrogen storage DC microgrid according to an embodiment of the present invention;

[0064] Figure 21 This is a schematic diagram of the photovoltaic hydrogen production microgrid hardware experimental platform according to an embodiment of the present invention;

[0065] Figure 22 This is a waveform diagram from a physical experiment of the improved MPPT algorithm according to an embodiment of the present invention;

[0066] Figure 23 The physical experiment of this invention uses the output current waveform of a three-phase interleaved parallel hydrogen converter;

[0067] Figure 24 This is a structural diagram of the control system according to an embodiment of the present invention. Detailed Implementation

[0068] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0069] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0070] This embodiment proposes an improved MPPT algorithm and a current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid. Figure 1 As shown, the specific steps include:

[0071] Based on the hardware circuit parameters of the hydrogen production system using the three-phase interleaved parallel DC-DC converter of the photovoltaic hydrogen storage DC microgrid, a physical system model is obtained.

[0072] Based on the output characteristics of the photovoltaic array, an improved MPPT algorithm is constructed, wherein the improvement of the improved MPPT algorithm is that the variable step size coefficient is set to 0.05 / I. 2 ;

[0073] Based on the improved MPPT algorithm, the control logic of the photovoltaic Boost converter is obtained;

[0074] Based on the physical system model, construct a small-signal model of the main circuit;

[0075] Based on the control architecture of the three-phase interleaved parallel hydrogen production converter and the control logic of the photovoltaic Boost converter, the overall control logic is obtained.

[0076] Based on the overall control logic, a small-signal model of the control system is constructed;

[0077] Based on the small-signal model of the main circuit and the small-signal model of the control system, a target small-signal model is obtained, and a current sharing control strategy for the three-phase interleaved parallel hydrogen production converter is set based on the target small-signal model.

[0078] Specifically, in step S1, the physical system of the hydrogen production system and the photovoltaic power generation system of the three-phase interleaved parallel DC-DC converter of the photovoltaic hydrogen storage DC microgrid is obtained;

[0079] Step S2: Based on the output characteristics of the photovoltaic cell mathematical model of the photovoltaic power generation system, an improved MPPT algorithm is proposed for photovoltaic Boost converter;

[0080] Step S3: Based on the physical system of the hydrogen production system using a three-phase interleaved parallel DC-DC converter in a photovoltaic hydrogen storage DC microgrid, construct a small-signal model of the main circuit.

[0081] Step S4: Obtain the control logic of the three-phase interleaved parallel DC-DC converter hydrogen production system;

[0082] Step S5: Based on the control logic of the hydrogen production system using a three-phase interleaved parallel DC-DC converter, construct a small-signal model of the control system.

[0083] Step S6: After coupling the small-signal model of the main circuit of the hydrogen production system based on the three-phase interleaved parallel DC-DC converter of the photovoltaic hydrogen storage DC microgrid, the small-signal model of the control system is obtained.

[0084] Furthermore, the control method is applied to a three-phase interleaved parallel DC-DC converter hydrogen production system of a photovoltaic hydrogen storage DC microgrid, wherein the three-phase interleaved parallel DC-DC converter hydrogen production system of the photovoltaic hydrogen storage DC microgrid includes a photovoltaic array, a photovoltaic Boost converter, a battery, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC converter, an output-side capacitor of the three-phase interleaved parallel DC-DC converter, and a PEM electrolyzer.

[0085] Specifically, it includes a photovoltaic array, a photovoltaic boost converter, an energy storage converter, a three-phase interleaved parallel bidirectional DC-DC converter, a DC bus, and a PEM electrolytic cell connected in sequence.

[0086] Furthermore, the acquisition of the physical system model includes:

[0087] Based on the topology of the photovoltaic array, photovoltaic Boost converter, battery, energy storage bidirectional converter, three-phase interleaved parallel DC-DC hydrogen converter, output capacitor and PEM electrolyzer connected in sequence in the hydrogen production system, the electrical parameters of each hardware circuit are obtained.

[0088] Based on the electrical parameters, establish the physical system model.

[0089] Specifically, the hardware circuit parameters of the physical system of the photovoltaic-hydrogen storage DC microgrid hydrogen production system, consisting of a photovoltaic array, a photovoltaic Boost converter, a battery, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC hydrogen production converter, an output capacitor of the three-phase interleaved parallel DC-DC hydrogen production converter, and a PEM electrolyzer, are obtained.

[0090] Furthermore, based on the output characteristics of the photovoltaic array, the improved MPPT algorithm is constructed as follows:

[0091] Obtain the output characteristics of the photovoltaic array;

[0092] Introducing a current-dependent coefficient to affect output characteristics Make corrections;

[0093] A variable step size coefficient and a step size change amount are set. Based on the relationship between the current operating point's conductance increment and instantaneous conductance, the duty cycle of the photovoltaic Boost converter is adjusted using the variable step size conductance increment method. The duty cycle adjustment amount is determined by the product of the variable step size coefficient and the voltage change amount.

[0094] Furthermore, based on the physical system model, the small-signal model of the main circuit is constructed as follows:

[0095] Based on the hardware circuit parameters of the physical system model, state-space equations are established using Kirchhoff's voltage law and Kirchhoff's current law.

[0096] The average state-space equation is obtained by using the state-space averaging method, and the average state-space equation is linearized by applying a small-signal perturbation to obtain the small-signal model of the main circuit.

[0097] Specifically, the physical system of the hydrogen production system based on a three-phase interleaved parallel DC-DC converter in a photovoltaic hydrogen storage DC microgrid includes the following small-signal model of the main circuit:

[0098] Based on the physical system hardware circuit parameters of the hydrogen production system of the photovoltaic hydrogen storage DC microgrid three-phase interleaved parallel DC-DC converter, the state space equation corresponding to the main circuit of the photovoltaic hydrogen storage DC microgrid three-phase interleaved parallel DC-DC converter is established using Kirchhoff's laws and the state space averaging method, and the improved MPPT algorithm flowchart is set.

[0099] The state-space equations are linearized using the small-signal perturbation method to obtain the small-signal model of the physical system.

[0100] Furthermore, based on the control architecture of the three-phase interleaved parallel hydrogen production converter, the overall control logic includes:

[0101] Based on the power output requirements of the photovoltaic Boost converter in the control architecture of the three-phase interleaved parallel hydrogen production converter, the control logic of the photovoltaic Boost converter is set.

[0102] Based on the DC bus voltage stability requirements, the control logic for the energy storage bidirectional converter is set.

[0103] Based on the low-voltage, high-current, and low-ripple power supply requirements of the PEM electrolyzer, the control logic of the three-phase interleaved parallel DC-DC hydrogen converter is set.

[0104] The overall control logic is obtained based on the photovoltaic Boost converter control logic, the energy storage bidirectional converter control logic, and the three-phase interleaved parallel DC-DC hydrogen production converter control logic.

[0105] Specifically, the control logic corresponding to each hardware circuit part of the hydrogen production system of the photovoltaic-hydrogen storage DC microgrid three-phase interleaved parallel hydrogen production converter includes: photovoltaic Boost converter control logic, energy storage bidirectional converter control logic, and three-phase interleaved parallel DC-DC hydrogen production converter control logic.

[0106] The photovoltaic Boost converter control logic, energy storage converter control logic, and three-phase interleaved parallel hydrogen production converter control logic include:

[0107] Photovoltaic Boost converter control logic: By setting a variable step size coefficient, the variable step size coefficient is taken as d(k) = 0.05 / I. 2 This maximizes the output power of the photovoltaic system, thereby achieving maximum power point tracking and ensuring optimal stability and speed of the output voltage.

[0108] Energy storage converter control logic: A dual closed-loop PI control strategy for voltage and current is adopted to maintain the stability of the DC bus voltage connected to the high-voltage side capacitor.

[0109] The control logic of the three-phase interleaved parallel DC-DC hydrogen converter adopts a current sharing control strategy based on active method with independent control of the inner current loop.

[0110] Furthermore, based on the overall control logic, the small-signal model of the control system is constructed as follows:

[0111] Based on the control variables in the overall control logic, establish the state-space equations of the control system, which include the controller transfer function, the modulation transfer function, and the sampling transfer function;

[0112] The small-signal linearization process is performed on the state-space equations of the control system to obtain the small-signal model of the control system.

[0113] Specifically, the control logic of the hydrogen production system based on the three-phase interleaved parallel hydrogen production converter of the photovoltaic hydrogen storage DC microgrid constructs a small-signal model of the control system, including:

[0114] Based on the control logic of the hydrogen production system using a three-phase interleaved parallel DC-DC hydrogen production converter connected to a photovoltaic hydrogen storage DC microgrid, the state variables of the control system are determined.

[0115] State-space equations are established based on the state variables of the control system to generate a small-signal model of the control system.

[0116] Furthermore, the flow sharing control strategy includes:

[0117] Based on the transfer functions of inductor current and duty cycle and output voltage and duty cycle in the target small-signal model, the parameters of the inner current loop PI controller and the outer voltage loop PI controller are designed. Bode plots are drawn using frequency domain analysis. The system stability is verified based on phase margin and gain margin. The current sharing control strategy of the three-phase interleaved parallel hydrogen production converter is determined.

[0118] The following is a detailed description of this embodiment with reference to the accompanying drawings:

[0119] Figure 2 This is a schematic diagram of a typical application scenario of an embodiment of the present invention. It includes a photovoltaic array, a photovoltaic boost converter, an energy storage converter, a three-phase interleaved parallel bidirectional DC-DC converter, a DC bus, and a PEM electrolytic cell connected in sequence.

[0120] First, the physical system of the hydrogen production system of the photovoltaic-hydrogen storage DC microgrid three-phase interleaved parallel hydrogen production converter is obtained: the photovoltaic array, photovoltaic Boost converter, energy storage bidirectional converter, three-phase interleaved parallel bidirectional DC-DC converter, and PEM electrolyzer are connected in sequence in the photovoltaic-hydrogen storage DC microgrid hydrogen production system.

[0121] The physical system of a hydrogen production system based on a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid is described. A small-signal model of the main circuit is constructed, and a control strategy for the hydrogen production system is designed based on the small-signal models of the main circuit and control system. The small-signal modeling steps are as follows:

[0122] The state-space equations are linearized using the small-signal perturbation method to obtain the small-signal model of the physical system. Then, a control strategy is designed based on the stability margin of automatic control theory.

[0123] The specific steps of control design are as follows:

[0124] Establish a mathematical model for photovoltaic cells.

[0125] The power electronic equivalent model of a photovoltaic cell consists of an ideal current source device, a diode device, and a resistor device. For example... Figure 3 As shown, It is the photocurrent generated by the photovoltaic cell. It is the equivalent parallel resistance inside the solar cell material. It is the equivalent series resistance, and I is the final output current of the photovoltaic cell. It is the final output voltage of the photovoltaic cell. This is the current flowing through the diode. In practical applications, it can be determined by the short-circuit current. Open circuit voltage Maximum power point Maximum power point Operating voltage at the location With current The mathematical model for photovoltaic cells is established as follows:

[0126] ;

[0127] In equation (1), and The formula is shown below:

[0128] ;

[0129] Equation (1) is based on the reference environmental conditions, i.e., a light intensity of 1000. A mathematical model of a photovoltaic cell at 25℃ is provided. However, in practical applications, the light intensity and ambient temperature differ from the standard test environment. Therefore, the formula needs to be modified. The modified formulas for light intensity and ambient temperature are shown below:

[0130] ;

[0131] ;

[0132] In equations (3) and (4), S represents the actual light intensity, and T represents the actual photovoltaic cell temperature. With corrections to light intensity and temperature, the short-circuit current... Open circuit voltage Maximum operating point Operating voltage at the location With current The relevant modifications were also made, and the modified expressions are shown in equations (5), (6), (7), and (8).

[0133] ;

[0134] ;

[0135] ;

[0136] ;

[0137] ;

[0138] In equation (9) , The values ​​represent the corrected open-circuit voltage and short-circuit current of the photovoltaic array, where N is the number of photovoltaic cells connected in series and M is the number of photovoltaic cells connected in parallel.

[0139] The principle and design of the improved MPPT algorithm allow the photovoltaic cell output characteristics to be expressed as follows:

[0140] ;

[0141] As shown in equation (10), the output characteristics of a photovoltaic cell are related to the current. Traditional variable step size methods typically use... Instead of a fixed step size parameter, a correction is made by multiplying it by a constant coefficient. To reduce the impact of current variations on the output characteristics of photovoltaic cells, a current-related coefficient is introduced. Make corrections.

[0142] Let the variable step size coefficient be The step size change is Then the duty cycle It can be represented as:

[0143] ;

[0144] in, This represents the duty cycle at the previous time step, with the variable step size coefficient being... There are three ways to select them:

[0145] ;

[0146] Simulation and physical experiments were used to compare and analyze the three MPPT methods mentioned above, using steady-state performance and the steady-state fluctuation of the photovoltaic output voltage after external disturbances as evaluation indicators, thereby obtaining the MPPT control strategy with the best stability. The flowchart of the proposed MPPT algorithm in this embodiment is shown below. Figure 4 As shown.

[0147] Analysis of the output characteristics of hydrogen production power supply:

[0148] The hydrogen production power supply uses a three-phase interleaved parallel DC-DC converter, and its circuit topology is as follows: Figure 5As shown in the figure, by shifting the carrier phase by 120°, peak-valley cancellation is achieved to reduce the ripple of the total output current. The three-phase interleaved parallel DC-DC converter adopted has two operating modes: Buck and Boost. There are 8 operating modes in the buck mode, but the 8 operating modes will not appear in the same switching period. According to the value of the duty cycle D, it is divided into three cases: D < 1 / 3, 1 / 3 < D < 2 / 3, 2 / 3 < D. In this embodiment, the Buck mode with D < 1 / 3 is adopted for simulation analysis and physical experiments. When D < 1 / 3, the switching trigger signal and current waveform are as Figure 6 shown.

[0149] From Figure 6 it can be seen that the frequency of the total current output by the three-phase interleaved parallel DC-DC converter is three times that of the single-phase inductor current, which can effectively reduce the inductor volume and improve the power density. According to the volt-second balance and the same change in inductor current within one cycle, the expression for the ripple of its output total current can be deduced as:

[0150] ;

[0151] ;

[0152] In the formula, is the inductance value of each phase ( ), is the switching period, and in this embodiment .

[0153] Small-signal modeling and control strategy design of a three-phase interleaved parallel hydrogen production converter hydrogen production system:

[0154] The design of the three-phase interleaved parallel DC-DC converter should meet the power supply requirements of the electrolyzer and avoid device damage caused by circulating current. A low-ripple current sharing control strategy needs to be designed. When designing the control strategy, the converter needs to be modeled with small signals to provide a theoretical basis for the design of the controller. First, the average state-space equation of the Buck mode of the hydrogen production converter is obtained using the state-space averaging method. After adding small-signal perturbations, canceling the steady-state values, and ignoring the second-order perturbation terms, the differential equation obtained is Laplace-transformed to obtain the small-signal model of the system as shown in Equation (15). In the formula, the "^" indicates the AC small-signal component.

[0155] ;

[0156] Then, by setting the input perturbation amount in the above formula to 0, the transfer functions Gid(s) of the inductor current and the duty cycle and Gvd(s) of the output voltage and the duty cycle are obtained, as shown in Equations (16) and (17).

[0157] ;

[0158] ;

[0159] The hydrogen production power supply control strategy adopts a current sharing control strategy based on active current inner loop independent control. This control strategy shares the voltage outer loop, and the feedback current of the current inner loop comes from the inductor current of each control phase. Its control block diagram is as follows: Figure 7 As shown. To accurately control the output voltage, the converter system control structure is analyzed. The converter control structure is as follows: Figure 8 As shown in the figure, PPS-PWM represents phase shift, and the modulation transfer function is... Transfer function of sampling stage . Figure 7 As the first half of the control structure, the PI of the control algorithm is mainly used to correct the system, quickly tracking the given value while ensuring the steady state of the system.

[0160] First, the current loop controller is designed. After adding the PI controller, the crossover frequency of the open-loop transfer function of the current loop is fc1 = 1 / 20T = 1kHz, and the phase margin is... To reduce overshoot, we take 84° and calculate kip=0.012 and kii=7.6 using equation (16). After adding a PI controller to the voltage loop, fc2=100Hz, and the phase margin is... Take 84°. Combining equations (16) and (17) with relevant knowledge of control theory, the voltage outer loop can be calculated. , . Figure 9 Bode plot of the open-loop transfer function of the current loop after adding a PI controller. Figure 10 The Bode plot shows the open-loop transfer function of the voltage loop after adding the PI controller. Under the proposed phase-shift current sharing control algorithm, both the gain margin and phase margin are greater than zero, and the system is stable.

[0161] Modeling and parameter setting of the photovoltaic hydrogen storage subsystem:

[0162] The energy storage system is primarily designed to maintain stable bus voltage and ensure power self-balancing of the DC microgrid. Therefore, it employs an energy storage converter with constant voltage control using an outer voltage loop and an inner current loop. Its control block diagram is shown below. Figure 11 As shown. This invention constructs a PEM electrolyzer simulation model in MATLAB / Simulink. The model includes an anode model, a cathode model, a proton exchange membrane model, an electrolyzer voltage model, and a hydrogen storage tank model. The mathematical model of the PEM electrolyzer is as follows: Figure 12 As shown.

[0163] Photovoltaic system parameter settings: Irradiance 1350 W / m 2Temperature 25℃, open-circuit voltage 35.8 V, short-circuit current 6.62 A, maximum power point voltage 28.7 V, maximum power point current 5.93 A, number of photovoltaic cells in parallel 16, number in series 10, low-voltage side capacitor 0.001 F, high-voltage side capacitor 0.02 F, inductance 6 mH, parasitic resistance of high and low voltage side capacitors 0.0001Ω. Energy storage system parameter settings: battery capacity 80 Ah, initial state of charge 80%, voltage outer loop PI parameters 2, 100, current inner loop PI parameters 0.02, 10, DC bus side capacitor 1 mF, inductance 5 mH, battery side capacitor 1 uF. Hydrogen production system parameter settings: electrolyzer side capacitor is 1166 uF, inductance L is 1.56 mH, voltage outer loop PI is 3.5, 435, current inner loop PI is 0.012, 7.6, electrolyzer equivalent resistance is 0.0968Ω, and duty cycle is 44 / 800.

[0164] Simulation and physical experiment verification of the control strategy:

[0165] 1. Simulation Verification: To verify the overall performance of the improved MPPT algorithm and the effectiveness of ripple suppression in the triple-interleaved DC-DC converter proposed in this invention, a simulation platform was built based on the parameters of "Modeling and Parameter Design of Photovoltaic Hydrogen Storage Subsystem". Three disturbance factors were set: light intensity, temperature, and DC load. Four operating modes were set, with mode one having a light intensity of 1350 W / m² within 0-0.6 s. 2 Temperature 25℃, DC load 3 kW; Mode 2: Illuminance of 1350 W / m² within 0.6-1 s. 2 Temperature 15℃, DC load 3 kW; Mode 3: Illumination intensity 800 W / m² within 1-1.5 s. 2 Temperature 15℃, DC load unchanged; Mode 4: Illumination intensity 800 W / m² within 1.5-3 seconds. 2 Temperature 15℃, DC load 6 kW. Simulation results are as follows: Figure 13-15 As shown in the figure (k=0.05), the hydrogen production power supply is compared and analyzed with a traditional Buck converter and a three-phase interleaved converter. The output voltage and output current ripple of the two are as follows: Figure 16-17 As shown.

[0166] like Figure 13 As shown, at 0.6 s, the temperature decreases, and the power and voltage curves rise slightly; at 1 s, the irradiance decreases, and the photovoltaic output power decreases significantly. (Comparison) Figure 13 , 14 The waveforms obtained from three different step size coefficients (1, 2, and 3) show that... and steady-state fluctuations Larger The steady-state fluctuation is the largest, but It exhibits minimal steady-state fluctuations, with minimal fluctuations even under varying conditions of illumination, temperature, and DC load. It boasts fast tracking speed and high tracking accuracy, and considering all factors, it offers the best MPPT tracking performance, making it suitable for application in photovoltaic hydrogen storage systems.

[0167] The simulation experiment yielded the output voltage and current ripple of the traditional Buck converter and the three-phase interleaved DC-DC converter, as shown in the figure. Figure 16-17 As shown. By Figure 16-17 It can be seen that the output voltage ripple of a traditional Buck converter is approximately 0.17 V, and the current ripple is about 4 A. In contrast, the output current ripple of a three-phase interleaved parallel DC-DC converter using an independent current sharing control strategy with an inner current loop is only 1.182 A (theoretically calculated to be 1.1775 A), and the peak-to-peak voltage ripple is 0.04 V.

[0168] Simulation experiments show that the three-phase interleaved parallel DC-DC converter with an independent current sharing control strategy using an inner current loop has smaller output current ripple, and the low-voltage side output current waveform under this control strategy is shown in the figure below. Figure 18 Three-phase inductor current The values ​​are 151.6 A, 151.5 A, and 151.9 A, respectively. Using the degree of imbalance as the evaluation index for the flow equalization effect, the calculation formula is as follows:

[0169] ;

[0170] The molecule represents the maximum difference between each pair of inductor currents. Let n be the total output current of the converter, and n be the number of interleaved parallel phases. Substituting the simulation data, we get... This is far less than the 5% required by the national standard GB / T3797-2016, demonstrating good steady-state current sharing performance. (By...) Figures 19-20 It can be seen that the energy storage control strategy adopted in this embodiment effectively maintains the stability of the DC bus voltage and the power self-balancing of the microgrid, with the bus voltage fluctuation controlled within 1V.

[0171] 2. Physical Verification: The improved MPPT algorithm proposed in this embodiment and the three-phase interleaved parallel DC-DC converter capable of stable and efficient hydrogen production were physically verified. The core component of the physical platform was the real-time digital controller RTU-BOX201, which integrates DSP, FPGA, and other main control chips. The physical experimental platform is as follows: Figure 21 As shown.

[0172] The improved variable step-size conductance incremental method tracks and stabilizes at the maximum power point within 3 seconds, significantly improving the tracking speed compared to the traditional MPPT algorithm's 29 seconds. In practical experiments, the tracking speeds of the three variable step-size coefficient variable step-size conductance incremental methods were all within 3 seconds. The MPPT algorithm proposed in this embodiment has an even faster tracking speed. Some parameter settings from the practical experiments are shown in Table 1.

[0173] Table 1

[0174] parameter value unit DC bus voltage 250 V Maximum power point voltage 156 V Photovoltaic power generation 697 W Photovoltaic simulated source open circuit voltage 200 V Electrolytic cell input voltage 10 V Electrolytic cell input current 5 A

[0175] The steady-state photovoltaic output voltage waveforms of the three variable step-size coefficient variable conductance incremental methods are shown in the figure. Figure 22 As shown. The physical experiment selected the one with the best overall performance in the simulation. The variable step-size incremental conductance method and its poor performance A practical experiment was conducted using the variable step-size conductance incremental method. The experimental results are as follows: Figure 22 As shown in the figure, 10,000 sampling points represent 1 second, meaning that samples were taken within 8 seconds. The variable step-size conductance incremental method controls the output voltage fluctuation within 3.3 V, while The output voltage fluctuation of the variable step size incremental conductance method is controlled within 0.8 V. Hardware experiments show that the improved variable step size incremental conductance method proposed in this paper has good steady-state performance.

[0176] The waveform of the input current of the electrolyzer obtained from the actual hydrogen production experiment is as follows: Figure 23 As shown in the figure, the peak-to-peak value of the maximum total output current ripple of the three-phase interleaved DC-DC converter is approximately 0.04 A.

[0177] Therefore, simulation experiments and physical experiments together verify that the improved MPPT algorithm and the current sharing control technology of the three-phase interleaved parallel hydrogen production converter in the photovoltaic hydrogen storage DC microgrid proposed in this invention can achieve both speed and stability in tracking the maximum power of photovoltaic power generation under external disturbances in the hydrogen production system. The output power of the hydrogen production converter using the current sharing control technology meets the requirements of the hydrogen electrolyzer, and the phase-to-phase current sharing error of the converter is better than the national standard requirements, thus verifying the accuracy of the control technology proposed in this invention.

[0178] In addition, this embodiment also provides an improved MPPT algorithm and a current sharing control system for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid, such as Figure 24 As shown, it includes: an acquisition unit, a first modeling control unit, a second modeling control unit, and a third modeling control unit;

[0179] The acquisition unit is used to acquire the physical system and control logic of the photovoltaic-hydrogen storage DC microgrid hydrogen production system, wherein the photovoltaic-hydrogen storage DC microgrid hydrogen production system includes a photovoltaic Boost converter, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC hydrogen production converter, an output-side capacitor of the three-phase interleaved parallel DC-DC hydrogen production converter, and a PEM electrolyzer connected in sequence; based on the hardware circuit parameters of the photovoltaic-hydrogen storage DC microgrid three-phase interleaved parallel DC-DC converter hydrogen production system, a physical system model is acquired; and an improved MPPT algorithm is constructed based on the output characteristics of the photovoltaic array.

[0180] The first modeling control unit is used to construct a small-signal model of the main circuit based on the physical system model;

[0181] The second modeling control unit is used to obtain the overall control logic based on the control architecture of the three-phase interleaved parallel hydrogen converter; and to construct a small-signal model of the control system based on the overall control logic.

[0182] The third modeling control unit obtains a target small-signal model based on the small-signal model of the main circuit and the small-signal model of the control system, and sets a current sharing control strategy for the three-phase interleaved parallel hydrogen production converter based on the target small-signal model.

[0183] This embodiment also provides an electronic device and a computer-readable storage medium, wherein the storage medium stores the control method, the electronic device can execute the program on the computer-readable storage medium, and when the control method is processed and run by the electronic device, the electronic device executes the control method.

[0184] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid, characterized in that, include: Based on the hardware circuit parameters of the hydrogen production system using a three-phase interleaved parallel DC-DC converter in a photovoltaic hydrogen storage DC microgrid, a physical system model is obtained. Based on the output characteristics of the photovoltaic array, an improved MPPT algorithm is constructed; Based on the improved MPPT algorithm, the control logic of the photovoltaic Boost converter is obtained; Based on the physical system model, construct a small-signal model of the main circuit; Based on the control architecture of the three-phase interleaved parallel hydrogen production converter and the control logic of the photovoltaic Boost converter, the overall control logic is obtained. Based on the overall control logic, a small-signal model of the control system is constructed; Based on the small-signal model of the main circuit and the small-signal model of the control system, a target small-signal model is obtained, and a current sharing control strategy for the three-phase interleaved parallel hydrogen production converter is set based on the target small-signal model.

2. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 1, characterized in that, The control method is applied to a three-phase interleaved parallel DC-DC converter hydrogen production system of a photovoltaic hydrogen storage DC microgrid. The three-phase interleaved parallel DC-DC converter hydrogen production system of the photovoltaic hydrogen storage DC microgrid includes a photovoltaic array, a photovoltaic boost converter, a battery, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC converter, an output-side capacitor of the three-phase interleaved parallel DC-DC converter, and a PEM electrolyzer.

3. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 2, characterized in that, The acquisition of the physical system model includes: Based on the topology of the photovoltaic array, photovoltaic Boost converter, battery, energy storage bidirectional converter, three-phase interleaved parallel DC-DC hydrogen converter, output capacitor and PEM electrolyzer connected in sequence in the hydrogen production system, the electrical parameters of each hardware circuit are obtained. Based on the electrical parameters, establish the physical system model.

4. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 1, characterized in that, Based on the output characteristics of the photovoltaic array, the improved MPPT algorithm is constructed as follows: Obtain the output characteristics of the photovoltaic array: ； Introducing a current-related coefficient to the output characteristics Make corrections; The current correlation coefficient, i.e., the variable step size coefficient, is d(k), and the step size change is... ; A variable step size coefficient and step size change amount are set. Based on the relationship between the current operating point's conductance increment and instantaneous conductance, the duty cycle of the photovoltaic Boost converter is adjusted using the variable step size conductance increment method. The duty cycle adjustment amount is determined by the product of the variable step size coefficient and the voltage change amount.

5. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 3, characterized in that, Based on the physical system model, the small-signal model of the main circuit is constructed as follows: Based on the hardware circuit parameters of the physical system model, state-space equations are established using Kirchhoff's voltage law and Kirchhoff's current law. The average state-space equation is obtained by using the state-space averaging method, and the average state-space equation is linearized by applying a small-signal perturbation to obtain the small-signal model of the main circuit.

6. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 2, characterized in that, Based on the control architecture of the three-phase interleaved parallel hydrogen production converter, the overall control logic includes: Based on the power output requirements of the photovoltaic Boost converter in the control architecture of the three-phase interleaved parallel hydrogen production converter, the control logic of the photovoltaic Boost converter is set. Based on the DC bus voltage stability requirements, the control logic for the energy storage bidirectional converter is set. Based on the low-voltage, high-current, and low-ripple power supply requirements of the PEM electrolyzer, the control logic of the three-phase interleaved parallel DC-DC hydrogen converter is set. The overall control logic is obtained based on the photovoltaic Boost converter control logic, the energy storage bidirectional converter control logic, and the three-phase interleaved parallel DC-DC hydrogen production converter control logic.

7. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 2, characterized in that, Based on the overall control logic, the small-signal model of the control system is constructed as follows: Based on the control variables in the overall control logic, establish the state-space equations of the control system, which include the controller transfer function, the modulation transfer function, and the sampling transfer function; The small-signal linearization process is performed on the state-space equations of the control system to obtain the small-signal model of the control system.

8. The improved MPPT algorithm and current sharing control method for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid according to claim 2, characterized in that, The flow sharing control strategy includes: Based on the transfer functions of inductor current and duty cycle and output voltage and duty cycle in the target small-signal model, the parameters of the inner current loop PI controller and the outer voltage loop PI controller are designed. Bode plots are drawn using frequency domain analysis. The system stability is verified based on phase margin and gain margin. The current sharing control strategy of the three-phase interleaved parallel hydrogen production converter is determined.

9. An improved MPPT algorithm and a current sharing control system for a three-phase interleaved parallel hydrogen production converter in a photovoltaic hydrogen storage DC microgrid, used to implement the method as described in any one of claims 1-8, characterized in that, include: Acquisition unit, first modeling control unit, second modeling control unit, and third modeling control unit; The acquisition unit is used to acquire the physical system and control logic of the photovoltaic-hydrogen storage DC microgrid hydrogen production system, wherein the photovoltaic-hydrogen storage DC microgrid hydrogen production system includes a photovoltaic Boost converter, an energy storage bidirectional converter, a three-phase interleaved parallel DC-DC hydrogen production converter, an output-side capacitor of the three-phase interleaved parallel DC-DC hydrogen production converter, and a PEM electrolyzer connected in sequence; based on the hardware circuit parameters of the photovoltaic-hydrogen storage DC microgrid three-phase interleaved parallel DC-DC converter hydrogen production system, a physical system model is acquired; and an improved MPPT algorithm is constructed based on the output characteristics of the photovoltaic array. The first modeling control unit is used to construct a small-signal model of the main circuit based on the physical system model; The second modeling control unit is used to obtain the overall control logic based on the control architecture of the three-phase interleaved parallel hydrogen converter; and to construct a small-signal model of the control system based on the overall control logic. The third modeling control unit obtains a target small-signal model based on the small-signal model of the main circuit and the small-signal model of the control system, and sets a current sharing control strategy for the three-phase interleaved parallel hydrogen production converter based on the target small-signal model.

10. An electronic device and a computer-readable storage medium, characterized in that, The readable storage medium stores the control method according to any one of claims 1-8, and the electronic device can execute a computer-readable storage medium program. When the control method is processed and executed by the electronic device, the electronic device performs the control method according to any one of claims 1-8.

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