Photovoltaic direct-current off-grid hydrogen production system and control method thereof

Abstract

The application provides a photovoltaic direct-current off-grid hydrogen production system and a control method thereof. The method is applied to a hydrogen production direct-current power supply in the photovoltaic direct-current off-grid hydrogen production system and comprises the following steps: receiving an output electrical parameter instruction; determining an input voltage of the hydrogen production direct-current power supply; determining a maximum limiting amplitude according to a corresponding relationship between the input voltage and the maximum limiting amplitude; determining a working state of the hydrogen production direct-current power supply according to the output electrical parameter instruction, the maximum limiting amplitude and a current output electrical parameter of the hydrogen production direct-current power supply, and controlling an actual output electrical parameter of the hydrogen production direct-current power supply in the corresponding working state; wherein the working state comprises an MPPT mode and a non-MPPT mode; thus, the hydrogen production direct-current power supply adopts an adaptive adjustment control strategy, the photovoltaic array MPPT function is tracked, and the stability of the photovoltaic direct-current off-grid hydrogen production system is ensured.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic off-grid hydrogen production technology, and more specifically, it relates to a photovoltaic DC off-grid hydrogen production system and its control method. Background Technology

[0002] The photovoltaic DC off-grid hydrogen production system includes a photovoltaic array, a hydrogen production DC power supply, an electrolyzer, and a hydrogen production system controller. The main power circuit has no grid connection and no energy storage devices such as batteries are connected. Traditional hydrogen production DC power supplies employ a control scheme where the power supply performs MPPT (Multi-Level Testing), calculates / detects output electrical parameters, and receives power output parameter commands from the hydrogen production system controller. When the output electrical parameter is greater than or equal to the corresponding command value, the power supply exits MPPT and executes and controls its output electrical parameters according to the command; if it is less than the command value, the power supply continues to perform MPPT.

[0003] However, when a sudden drop in photovoltaic power occurs, the photovoltaic power change is usually <10ms and the MPPT period is usually >100ms. Therefore, the hydrogen production DC power supply cannot detect and respond to the photovoltaic power change in time. This will cause the input voltage of the hydrogen production DC power supply to oscillate, or even cause the voltage to drop sharply below the operating voltage of the hydrogen production DC power supply. Ultimately, this will cause power failure shutdown or power outage shutdown, triggering abnormalities in the hydrogen production system, and posing safety risks. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a photovoltaic DC off-grid hydrogen production system and its control method, which realizes the adaptive adjustment control strategy of the hydrogen production DC power supply, and ensures the stability of the photovoltaic DC off-grid hydrogen production system while having the MPPT tracking function of the photovoltaic array.

[0005] The first aspect of this application discloses a control method for a photovoltaic DC off-grid hydrogen production system applied to the hydrogen production DC power supply in the photovoltaic DC off-grid hydrogen production system, including:

[0006] Receive output electrical parameter commands;

[0007] Determine the input voltage of the hydrogen production DC power supply, and determine the maximum amplitude limit based on the correspondence between the input voltage and the maximum amplitude limit;

[0008] Based on the output electrical parameter command, the maximum amplitude limit value, and the current output electrical parameters of the hydrogen production DC power supply, determine the operating state of the hydrogen production DC power supply and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding operating state;

[0009] The operating states include: MPPT mode and non-MPPT mode.

[0010] Optionally, before determining the operating state of the hydrogen production DC power supply based on the output electrical parameter command, the maximum limiting value, and the current output electrical parameters of the hydrogen production DC power supply, the method further includes:

[0011] Determine the current output electrical parameters of the hydrogen production DC power supply.

[0012] Optionally, the maximum limiting value is the maximum output electrical parameter, and / or the duty cycle limiting value or the conduction angle limiting value.

[0013] Optionally, the operating state of the hydrogen production DC power supply is determined based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, including:

[0014] Determine whether the current output electrical parameters of the hydrogen production DC power supply are greater than or equal to the value of the output electrical parameter command;

[0015] If so, the hydrogen production DC power supply enters the non-MPPT mode;

[0016] If not, the hydrogen-generating DC power supply enters MPPT mode.

[0017] Optionally, the actual output electrical parameters for controlling the hydrogen production DC power supply in the corresponding operating state include:

[0018] When the hydrogen production DC power supply enters the non-MPPT mode, the output electrical parameter command is executed as a control command so that the actual output electrical parameters of the hydrogen production DC power supply in the non-MPPT mode are the values ​​of the output electrical parameter command.

[0019] Optionally, after determining the operating state of the hydrogen-producing DC power supply based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen-producing DC power supply, and the actual output electrical parameters for controlling the hydrogen-producing DC power supply to be in the corresponding operating state, the method further includes:

[0020] Determine whether the input voltage of the hydrogen production DC power supply is less than a preset voltage threshold;

[0021] If so, the maximum amplitude value is used as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

[0022] Optionally, the maximum amplitude limit value is the maximum output electrical parameter;

[0023] Using the maximum limit value as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode includes: using the maximum output electrical parameters as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

[0024] Optionally, the maximum limiting value is either the duty cycle limiting value or the conduction angle limiting value;

[0025] Using the maximum limiting value as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode includes: using the duty cycle limiting value or the conduction angle limiting value as a control command to control the on / off switching of the power electronic switching devices in the hydrogen production DC power supply, thereby controlling the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

[0026] Optionally, the maximum limiting value is either the duty cycle limiting value or the conduction angle limiting value;

[0027] Based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, after determining the operating state of the hydrogen production DC power supply and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding operating state, the method further includes:

[0028] If the calculated duty cycle or conduction angle of the power electronic switching device exceeds the corresponding duty cycle limit or conduction angle limit, then the power electronic switching device of the hydrogen production DC power supply shall be controlled according to the duty cycle limit or conduction angle limit.

[0029] If the calculated duty cycle or conduction angle of the power electronic switching device does not exceed the corresponding duty cycle limit or conduction angle limit, then the calculation result of the duty cycle or conduction angle shall be executed.

[0030] Optionally, based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, the operating state of the hydrogen production DC power supply, and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding operating state, are determined, including:

[0031] The smaller value between the output electrical parameter command and the maximum amplitude limit is taken as the target output value;

[0032] Based on the current output electrical parameters of the hydrogen-generating DC power supply and the target output value, the operating state of the hydrogen-generating DC power supply is determined, as well as the actual output electrical parameters for controlling the hydrogen-generating DC power supply to be in the corresponding operating state.

[0033] Optionally, the operating state of the hydrogen-generating DC power supply is determined based on its current output electrical parameters and the target output value. The actual output electrical parameters for controlling the hydrogen-generating DC power supply to operate in the corresponding state include:

[0034] Determine whether the current output electrical parameter is greater than or equal to the target output value;

[0035] If so, the hydrogen-generating DC power supply enters non-MPPT mode, and the target output value is used as a control command to control the actual output electrical parameters of the hydrogen-generating power supply in non-MPPT mode.

[0036] If not, the hydrogen-generating DC power supply enters MPPT mode.

[0037] Optionally, the maximum output electrical parameter, output electrical parameter command, current output electrical parameter, and actual output electrical parameter can all be at least one of voltage, current, and power.

[0038] The second aspect of this application discloses a photovoltaic DC off-grid hydrogen production system, including: a photovoltaic array, a hydrogen production DC power supply, an electrolyzer, and a hydrogen production system controller;

[0039] The output terminal of the photovoltaic array is connected to the input terminal of the hydrogen production DC power supply;

[0040] The output terminal of the hydrogen production DC power supply is connected to the electrolytic cell;

[0041] The hydrogen production DC power supply is communicatively connected to the hydrogen production system controller.

[0042] The hydrogen-producing DC power supply is used to execute the control method of the photovoltaic DC off-grid hydrogen production system as described in any of the first aspects of this application.

[0043] Optionally, a photovoltaic DC power supply may also be provided between the photovoltaic array and the hydrogen production DC power supply.

[0044] As can be seen from the above technical solution, the control method of the photovoltaic DC off-grid hydrogen production system provided by the present invention is applied to the hydrogen production DC power supply in the photovoltaic DC off-grid hydrogen production system, including: receiving output electrical parameter commands; determining the input voltage of the hydrogen production DC power supply; determining the maximum limit value according to the correspondence between the input voltage and the maximum limit value; determining the working state of the hydrogen production DC power supply and the actual output electrical parameters of the hydrogen production DC power supply under the corresponding working state according to the output electrical parameter commands, the maximum limit value and the current output electrical parameters of the hydrogen production DC power supply; wherein, the working state includes: MPPT mode and non-MPPT mode; thereby realizing the adaptive adjustment control strategy of the hydrogen production DC power supply, ensuring the stability of the photovoltaic DC off-grid hydrogen production system while having the MPPT tracking function of the photovoltaic array. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of a control method for a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0047] Figure 2 This is a flowchart of another control method for a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0048] Figure 3 This is a flowchart of another control method for a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0049] Figure 4 This is a flowchart of another control method for a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0050] Figure 5 This is a flowchart of another control method for a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0051] Figure 6 This is a flowchart of another control method for a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0052] Figure 7 This is a schematic diagram of a photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention;

[0053] Figure 8 This is a schematic diagram of another photovoltaic DC off-grid hydrogen production system provided in an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0056] This application provides a control method for a photovoltaic DC off-grid hydrogen production system to address the problems in the prior art where photovoltaic power surges are typically <10ms and MPPT cycles are typically >100ms. When a sudden drop in photovoltaic power occurs, the hydrogen production DC power supply cannot promptly detect and respond to the surge, leading to oscillations in the input voltage of the hydrogen production DC power supply, or even a sharp drop in voltage below the operating voltage of the hydrogen production DC power supply. This ultimately causes power failure shutdown or power outage shutdown, triggering abnormalities in the hydrogen production system, and posing safety risks.

[0057] This photovoltaic DC off-grid hydrogen production system includes a photovoltaic array, a hydrogen production DC power supply, an electrolyzer, and a hydrogen production system controller. The main power circuit has no grid connection and no energy storage devices such as batteries connected. The control method of this photovoltaic DC off-grid hydrogen production system is applied to the hydrogen production DC power supply within the system.

[0058] See Figure 1 Control methods for photovoltaic DC off-grid hydrogen production systems include:

[0059] S101, Receive output electrical parameter command.

[0060] It should be noted that in this photovoltaic DC off-grid hydrogen production system, after the photovoltaic array is irradiated by light, the photovoltaic array outputs a DC voltage; the hydrogen production DC power supply starts up after receiving a start-up command from the hydrogen production system controller. After the hydrogen production DC power supply is started up, the hydrogen production system controller will control the operating status of the hydrogen production DC power supply; for example, the hydrogen production system controller will send output electrical parameter commands to the hydrogen production DC power supply, so that the hydrogen production DC power supply controller will perform corresponding actions according to the output electrical parameter commands.

[0061] The hydrogen production DC power supply in this application has an adaptive adjustment function; therefore, the hydrogen production DC power supply will not only perform corresponding actions according to the output electrical parameter command, but will perform subsequent steps after receiving the output electrical parameter command, so that the hydrogen production DC power supply can ensure the stability of the photovoltaic DC off-grid hydrogen production system while having the MPPT tracking function of the photovoltaic array.

[0062] In practical applications, electrical parameters can be one of power, current, and voltage, or combinations thereof, which will not be elaborated here, but are all within the scope of protection of this application.

[0063] S102. Determine the input voltage of the hydrogen production DC power supply; and determine the maximum limit value based on the correspondence between the input voltage and the maximum limit value.

[0064] It should be noted that the input voltage of the hydrogen production DC power supply affects its output. Therefore, it is necessary to determine the input voltage and the maximum limit value, and then perform the subsequent step S103.

[0065] Specifically, the input voltage of the hydrogen-generating DC power supply can be determined by detecting the input voltage of the hydrogen-generating DC power supply through a detection unit. Alternatively, the input voltage of the hydrogen-generating DC power supply can be determined through corresponding calculations.

[0066] The specific working process of step S102 will not be described in detail here. As long as the input voltage of the hydrogen production DC power supply can be determined, it is within the protection scope of this application.

[0067] It should be noted that the maximum limiting value varies depending on the input voltage. This correspondence between the input voltage and the maximum limiting value can be preset; the specific details will not be elaborated here, but will depend on the actual situation, and all are within the scope of protection of this application.

[0068] In practical applications, the maximum limiting value is the maximum output electrical parameter, and / or the duty cycle limiting value or the conduction angle limiting value; of course, other values ​​are also possible, which will not be elaborated here, depending on the actual situation, and all are within the protection scope of this application.

[0069] S103. Based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, determine the operating state of the hydrogen production DC power supply and the actual output electrical parameters that control the hydrogen production DC power supply to be in the corresponding operating state.

[0070] The working status includes: MPPT mode and non-MPPT mode.

[0071] It should be noted that the current output electrical parameters of the hydrogen production DC power supply can be obtained by detection unit or by corresponding calculation. The process of obtaining the current output parameters of the hydrogen production DC power supply will not be described in detail here, but is within the scope of protection of this application.

[0072] Specifically, the operating state can be determined based on the relationship between the output electrical parameter command, the maximum limit value, and the current output electrical parameter of the hydrogen production DC power supply. Of course, it is also possible to determine the operating state based on the relationship between any two of these parameters. For example, if the current output electrical parameter of the hydrogen production DC power supply is less than the value of the output electrical parameter command, the hydrogen production DC power supply enters MPPT mode; if the current output electrical parameter of the hydrogen production DC power supply is greater than or equal to the value of the output electrical parameter command, the hydrogen production DC power supply exits MPPT mode.

[0073] Of course, the working state can also be determined based on the relationship between the current output electrical parameters of the hydrogen production DC power supply and the value range of the output electrical parameter command. The specific working process and principle will not be elaborated here, but are all within the protection scope of this application.

[0074] The operating state is determined based on the relationship between the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply. This will not be elaborated further here, but can be determined according to the actual situation, and all are within the protection scope of this application.

[0075] It should be noted that after adjusting the working state of the hydrogen production DC power supply, it is also necessary to control the actual output electrical parameters of the hydrogen production DC power supply under the corresponding working state, so as to adjust the actual output electrical parameters of the hydrogen production DC power supply under different working states.

[0076] Adjusting its actual output electrical parameters is to make the actual output electrical parameters match the working state, so as to realize the adaptive adjustment control strategy of the hydrogen production DC power supply.

[0077] In this embodiment, the system receives an output electrical parameter command; determines the input voltage of the hydrogen production DC power supply; and determines the maximum limit value based on the correspondence between the input voltage and the maximum limit value. Based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, the system determines the operating state of the hydrogen production DC power supply and the actual output electrical parameters controlling the hydrogen production DC power supply to operate in the corresponding operating state. The operating states include MPPT mode and non-MPPT mode. This enables the hydrogen production DC power supply to adopt an adaptive control strategy, ensuring the stability of the photovoltaic DC off-grid hydrogen production system while possessing the MPPT tracking function of the photovoltaic array.

[0078] In practical applications, see Figure 2 Before step S103, which determines the operating state of the hydrogen production DC power supply based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, and before determining the actual output electrical parameters for controlling the hydrogen production DC power supply to operate in the corresponding state, the method further includes:

[0079] S201. Determine the current output electrical parameters of the hydrogen production DC power supply.

[0080] It should be noted that the current output electrical parameters of the hydrogen-generating DC power supply are a factor in determining the operating status of the hydrogen-generating DC power supply; therefore, the current output electrical parameters of the hydrogen-generating DC power supply can be determined before determining the operating status.

[0081] However, there are various ways to determine the current output electrical parameters of the hydrogen production DC power supply, such as detection by a detection unit or calculation, which will not be elaborated here. The appropriate method depends on the actual situation and is within the scope of protection of this application.

[0082] Specifically, when the current output electrical parameter is the output voltage, the output voltage can be detected by a voltage sensor; when the current output electrical parameter is the output current, the output current can be detected by a current sensor; the same applies when the current output electrical parameter is the output power. These will not be elaborated on here, and all are within the scope of protection of this application.

[0083] In practical applications, see Figure 3 The step S103, which involves determining the operating state of the hydrogen production DC power supply based on the output electrical parameter command, the maximum limiting value, and the current output electrical parameters of the hydrogen production DC power supply, includes:

[0084] S301. Determine whether the current output electrical parameters of the hydrogen production DC power supply are greater than or equal to the value of the output electrical parameter command.

[0085] It should be noted that if the current output electrical parameters of the hydrogen production DC power supply are greater than or equal to the value of the output electrical parameter command, it means that the current output of the hydrogen production DC power supply exceeds the required value, and therefore step S302 is executed.

[0086] S302, the hydrogen production DC power supply enters non-MPPT mode.

[0087] In practical applications, the actual output electrical parameters of the hydrogen production DC power supply in the corresponding operating state involved in step S103 include:

[0088] When the hydrogen production DC power supply enters non-MPPT mode, the output electrical parameter command is executed as a control command so that the actual output electrical parameters of the hydrogen production DC power supply in the non-MPPT mode are the values ​​of the output electrical parameter command.

[0089] It should be noted that if the current output electrical parameters of the hydrogen production DC power supply are less than the value of the output electrical parameter command, it means that the current output of the hydrogen production DC power supply cannot meet the demand value, and step S303 is executed to allow the hydrogen production DC power supply to output at its maximum capacity.

[0090] S303, the hydrogen production DC power supply enters MPPT mode.

[0091] In practical applications, see Figure 4 After determining the operating state of the hydrogen production DC power supply and the actual output parameters for controlling the hydrogen production DC power supply to operate in the corresponding state based on the output electrical parameter command, the maximum amplitude limit value, and the current output electrical parameters of the hydrogen production DC power supply in step S103, the method further includes:

[0092] S401. Determine whether the input voltage of the hydrogen production DC power supply is less than the preset voltage threshold.

[0093] As explained above, it is necessary to determine the relationship between the input voltage and the voltage threshold of the hydrogen production DC power supply in order to adjust the output of the hydrogen production DC power supply.

[0094] Specifically, when the input voltage of the hydrogen production unit is lower than the preset voltage threshold, the maximum output value corresponding to the input voltage is used as the control command to control the actual output electrical parameters; that is, when the input voltage decreases, the output of the hydrogen production DC power supply needs to be adjusted to ensure the stability of the photovoltaic DC off-grid hydrogen production system.

[0095] It should be noted that if the input voltage is lower than the preset voltage threshold, and the output continues in the current mode, such as MPPT mode, the photovoltaic DC off-grid hydrogen production system will become unstable. Therefore, the output of the hydrogen production DC power supply should be adjusted so that the maximum output value corresponding to the input voltage is used as the control command to control the actual output electrical parameters. The maximum output value corresponding to this input voltage is less than the output parameters in MPPT mode.

[0096] Therefore, if the input voltage of the hydrogen production DC power supply is less than the preset voltage threshold, it indicates that the input voltage of the hydrogen production DC power supply is small, that is, the photovoltaic output voltage is small, and there may be a sudden drop in photovoltaic power. At this time, it is necessary to adjust the actual output electrical parameters of the hydrogen production DC power supply to avoid the oscillation of the photovoltaic off-grid hydrogen production system and execute step S402.

[0097] S402, using the maximum limit value as a control command, controls the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

[0098] Specifically, there are several ways to implement the maximum amplitude limit as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode. The following explains two implementation methods:

[0099] 1) If the maximum limit value is the maximum output electrical parameter, then based on the input voltage, the maximum output electrical parameter is obtained according to the pre-set relationship between the input voltage and the maximum output electrical parameter; the maximum output electrical parameter is used as the control command to control the hydrogen production DC power supply to be in non-MPPT mode.

[0100] Specifically, the working process of a photovoltaic DC off-grid hydrogen production system will be explained as an example:

[0101] 1. When the photovoltaic array is illuminated by light, it outputs DC voltage.

[0102] 2. The hydrogen production DC power supply starts up after receiving the start command from the hydrogen production system controller.

[0103] 3. The hydrogen production DC power supply receives output electrical parameter commands from the hydrogen production system controller, such as one of the following: output voltage command Uref, current command Iref, or power command Pref.

[0104] 4. The hydrogen-generating DC power supply executes MPPT and calculates / detects the current output electrical parameters, such as output voltage Ufdb, current Ifdb, or power Pfdb. The current output electrical parameter is consistent with the type of the output parameter command.

[0105] It should be noted that this hydrogen production DC power supply can also directly perform the step of outputting electrical parameters.

[0106] 5. If the current output electrical parameter is greater than or equal to the value of the output electrical parameter command, then the actual output electrical parameter of the hydrogen production DC power supply shall be executed and controlled according to the output electrical parameter command; if the current output electrical parameter is less than the value of the output electrical parameter command, then the hydrogen production DC power supply shall continue to execute MPPT.

[0107] Specifically, the output voltage Ufdb is compared with the value of the output voltage command Uref, the output current Ifdb is compared with the value of the output current command Iref, and the output power Pfdb is compared with the value of the output power command Pref.

[0108] 6. Determine the input voltage Vpv of the hydrogen production DC power supply and its threshold value.

[0109] 6.1 When the input voltage Vpv of the hydrogen production DC power supply is lower than the threshold, the control strategies 6.1.1 and / or 6.1.2 shall be executed first, and then 6.1.3 shall be executed.

[0110] Among them, 6.1.1, according to the pre-set correspondence between the input voltage Vpv and the maximum output electrical parameters (maximum output voltage Umax, maximum output current Imax, or maximum output power Pmax), execute and control the actual output electrical parameters of the hydrogen production DC power supply according to the maximum output electrical parameters.

[0111] 6.1.2. Based on the pre-set correspondence between the input voltage Vpv and the duty cycle or conduction angle of the power electronic switching device, obtain the duty cycle limit value duty_limit or the conduction angle limit value ang_limit; control the power electronic switching device of the hydrogen production DC power supply according to the duty cycle limit value duty_limit or the conduction angle limit value ang_limit to realize the control of the actual output electrical parameters of the hydrogen production DC power supply.

[0112] If both steps 6.1.2 and 6.1.1 exist, and the actual output electrical parameters are different in the two steps, then the method that can reduce the actual output electrical parameters should be chosen.

[0113] 6.1.3 Continue with steps 3 through 6.

[0114] 6.2 When the input voltage Vpv of the hydrogen production DC power supply is greater than or equal to the threshold, continue to execute steps 3 to 6.

[0115] It should be noted that if the hydrogen production DC power supply is currently in MPPT mode and needs to enter a non-MPPT mode, the hydrogen production DC power supply must first exit MPPT mode before performing the corresponding action. The above voltage thresholds are usually selected as ≤ the minimum value of the full-load MPPT point.

[0116] 2) If the maximum limiting value is the duty cycle limiting value or the conduction angle limiting value, then based on the input voltage and the pre-set correspondence between the input voltage and the duty cycle or conduction angle of the power electronic switching device, the duty cycle limiting value or the conduction angle limiting value is obtained; the duty cycle limiting value or the conduction angle limiting value is used as a control command to control the on and off of the power electronic switching device in the hydrogen production DC power supply, thereby controlling the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

[0117] In practical applications; after determining the operating state of the hydrogen-generating DC power supply and the actual output parameters controlling the hydrogen-generating DC power supply to operate in the corresponding state based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen-generating DC power supply in step S103, the process further includes:

[0118] If the calculated duty cycle or conduction angle of the power electronic switching device exceeds the corresponding duty cycle limit or conduction angle limit, then the power electronic switching device of the hydrogen production DC power supply shall be controlled according to the duty cycle limit or conduction angle limit.

[0119] If the calculated duty cycle or conduction angle of the power electronic switching device does not exceed the corresponding duty cycle limit or conduction angle limit, then the calculation result of the duty cycle or conduction angle shall be executed.

[0120] Specifically, the working process of a photovoltaic DC off-grid hydrogen production system will be explained as an example:

[0121] 1. When the photovoltaic array is illuminated by light, it outputs DC voltage.

[0122] 2. The hydrogen production DC power supply starts up after receiving the start command from the hydrogen production system controller.

[0123] 3. The hydrogen production DC power supply receives power output commands (Uref for voltage, Iref for current, and Pref for power) from the hydrogen production system controller.

[0124] 4. Calculate / detect the input voltage Vpv of the hydrogen production DC power supply, and obtain the duty cycle limit value duty_limit or the conduction angle limit value ang_limit based on the pre-set correspondence between the input voltage Vpv and the duty cycle or conduction angle of the power electronic switching device.

[0125] 5. Calculate / detect the current output electrical parameters.

[0126] 6. When the current output electrical parameter is greater than or equal to the output electrical parameter command, execute and control the actual output electrical parameter of the hydrogen production DC power supply according to the output electrical parameter command; otherwise, the hydrogen production DC power supply continues to execute MPPT.

[0127] 7. During the entire operation of the hydrogen production DC power supply, if the calculated duty cycle or conduction angle of the power electronic switching device exceeds the corresponding duty cycle limit value (duty_limit) or conduction angle limit value (ang_limit), the power electronic switching device of the hydrogen production DC power supply shall be controlled according to the duty cycle limit value (duty_limit) or conduction angle limit value (ang_limit); if it does not exceed the limit, the calculated duty cycle or conduction angle shall be executed.

[0128] 8. Repeat steps 3 through 8.

[0129] Note: The relationship between the input voltage Vpv of the hydrogen production DC power supply and the duty cycle limit value duty_limit can be represented by a function:

[0130] duty_limit = function(Vpv);

[0131] Here, the function is a monotonically non-decreasing function, meaning that a unique Vpv value corresponds to a unique duty_limit value. For example:

[0132] The duty_limit is set to (Vpv-800) / 1300, with an upper limit of 1 and a lower limit of 0.

[0133] Similarly, the input voltage Vpv and the maximum current ang_limit of the hydrogen production DC power supply can also be characterized as a monotonically non-decreasing function.

[0134] Note: The definition of a monotonically non-decreasing function is: for any two independent variables x1 and x2, if f(x1)≥f(x2) when x1>x2, then f(x) is a monotonically non-decreasing function.

[0135] In practical applications, see Figure 5 Step S103 determines the operating state of the hydrogen production DC power supply and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding operating state based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, including:

[0136] S501. Take the smaller value between the output electrical parameter command value and the maximum limit value as the target output value.

[0137] S502. Based on the current output electrical parameters and target output value of the hydrogen production DC power supply, determine the working state of the hydrogen production DC power supply and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding working state.

[0138] In other words, the operating state of the hydrogen-generating DC power supply is determined based on the smaller of the current output electrical parameters of the hydrogen-generating DC power supply and the value of the output electrical parameter command and the maximum limit value corresponding to the input voltage; that is, when determining the operating state of the hydrogen-generating DC power supply, the smaller of the value of the output electrical parameter command and the maximum limit value corresponding to the input voltage is one of the factors.

[0139] Specifically, the operating state can be determined based on the relationship between the current output electrical parameters of the hydrogen production DC power supply and the target output value. For example, if the current output electrical parameters of the hydrogen production DC power supply are less than the target output value, the hydrogen production DC power supply enters MPPT mode; if the current output electrical parameters of the hydrogen production DC power supply are greater than or equal to the target output value, the hydrogen production DC power supply exits MPPT mode, and the target output value is used as the control command to control the actual output electrical parameters of the hydrogen production power supply.

[0140] Of course, the working state can also be determined based on the relationship between the current output electrical parameters of the hydrogen production DC power supply and the target output value. The specific working process and principle will not be elaborated here, but are all within the scope of protection of this application.

[0141] See Figure 6 In practical applications, step S502, which involves determining the operating state of the hydrogen-generating DC power supply based on its current output electrical parameters and target output value, includes:

[0142] S601. Determine whether the current output electrical parameter is greater than or equal to the target output value.

[0143] If the output electrical parameters are greater than or equal to the target output value, it indicates that the current output of the hydrogen production DC power supply exceeds the demand, and step S602 is executed.

[0144] S602, the hydrogen production DC power supply enters non-MPPT mode, and uses the target output value as a control command to control the actual output electrical parameters of the hydrogen production power supply in non-MPPT mode.

[0145] If the current output electrical parameters are less than the target output value, it means that the current output of the hydrogen production DC power supply does not meet the requirements. Execute step S603 to allow the hydrogen production DC power supply to output at its maximum capacity.

[0146] S603, the hydrogen production DC power supply enters MPPT mode.

[0147] In practical applications, based on the pre-set correspondence between the input voltage of the hydrogen production DC power supply and the maximum limiting value, there are multiple ways to obtain the specific implementation of the corresponding maximum limiting value. The following explains two methods:

[0148] 1) Based on the input voltage, the maximum output electrical parameters are obtained according to the pre-set relationship between the input voltage and the maximum output electrical parameters.

[0149] The maximum output electrical parameter is used as the target output value; that is, the output electrical parameter is given directly.

[0150] 2) Based on the input voltage, the corresponding relationship between the preset input voltage and the duty cycle or conduction angle of the power electronic switching device is used to obtain the duty cycle limit value or conduction angle limit value.

[0151] Among them, the output electrical parameters corresponding to the duty cycle limit value or the conduction angle limit value are used as the target output value; that is, given the duty cycle limit value or the conduction angle limit value.

[0152] In practical applications, each electrical parameter is at least one of voltage, current, and power.

[0153] Specifically, the working process of a photovoltaic DC off-grid hydrogen production system will be explained using two schemes:

[0154] 1. When the photovoltaic array is illuminated by light, it outputs DC voltage.

[0155] 2. The hydrogen production DC power supply starts up after receiving the start command from the hydrogen production system controller.

[0156] 3. The hydrogen production DC power supply receives output electrical parameter commands from the hydrogen production system controller, such as one of the following: output voltage command Uref1, current command Iref1, and power command Pref1.

[0157] 4. Calculate / detect the input voltage Vpv of the hydrogen production DC power supply, and obtain the corresponding maximum output electrical parameters based on the pre-set correspondence between the input voltage Vpv and the maximum output electrical parameters.

[0158] 5. Take the smaller value between the output electrical parameter command and the maximum output electrical parameter as the target output value, such as one of the target output voltage Uref2, target output current Iref2, and target output power Pref2.

[0159] 6. Calculate / detect the current output electrical parameters.

[0160] 7. Determine the relationship between the current output electrical parameters and the target output value.

[0161] That is, the current output voltage Ufdb is compared with the target output voltage Uref_2; the current output current Ifdb is compared with the target output current Iref_2; and the current output power Ifdb is compared with the target output power Pref_2.

[0162] 7.1 When the current output electrical parameters are greater than or equal to the target output value, execute and control the actual output electrical parameters of the hydrogen production DC power supply according to the target output value; then execute steps 3 to 7.

[0163] 7.2 Conversely, the hydrogen production DC power supply performs MPPT and then returns to steps 3 to 7.

[0164] Note: The relationship between the input voltage Vpv and the maximum output voltage Umax of the hydrogen production DC power supply can be represented by a function:

[0165] Umax = function(Vpv);

[0166] Here, the function is a monotonically non-decreasing function, meaning that a unique Vpv value corresponds to a unique Umax value. For example:

[0167] Umax = (Vpv - 800) / 1300 * Umax_N, with an upper limit of Umax_N and a lower limit of 0.

[0168] Umax_N is the rated value of Umax.

[0169] Similarly, the input voltage Vpv and the maximum current Imax of the hydrogen production DC power supply can also be characterized as a monotonically non-decreasing function; the input voltage Vpv and the maximum power Pmax of the hydrogen production DC power supply can also be characterized as a monotonically non-decreasing function.

[0170] Note: The definition of a monotonically non-decreasing function is: for any two independent variables x1 and x2, if f(x1)≥f(x2) when x1>x2, then f(x) is a monotonically non-decreasing function.

[0171] It should be noted that in the existing technology, when a sudden drop in photovoltaic power occurs (the photovoltaic power change is usually <10ms), the hydrogen production DC power supply cannot detect and respond to the photovoltaic power change in time (the MPPT period is usually >100ms). This will cause the input voltage (i.e., PV voltage) of the hydrogen production DC power supply to oscillate, or even cause the voltage to drop sharply below the operating voltage of the hydrogen production DC power supply, ultimately causing power failure shutdown or power outage shutdown, triggering abnormalities in the hydrogen production system, and posing safety risks.

[0172] In this embodiment, when a sudden drop in photovoltaic power occurs (the photovoltaic power fluctuation is typically <10ms), the hydrogen production DC power supply can adjust its output power instantaneously (obtained through sampling, with a response time typically <1ms) based on the sudden change in input voltage (i.e., PV voltage). This balances the input and output power, preventing power outages due to input voltage oscillations or excessively low input voltage, thus ensuring the safe and stable operation of the hydrogen production system. Furthermore, the power supply can continue performing MPPT after the photovoltaic power recovers.

[0173] Another embodiment of this application provides a photovoltaic DC off-grid hydrogen production system.

[0174] like Figure 7 As shown, the photovoltaic DC off-grid hydrogen production system includes: a photovoltaic array, a hydrogen production DC power supply, an electrolyzer, and a hydrogen production system controller.

[0175] The output of the photovoltaic array is connected to the input of the hydrogen production DC power supply.

[0176] The output of the hydrogen production DC power supply is connected to the electrolyzer.

[0177] The hydrogen production DC power supply is connected to the hydrogen production system controller via communication.

[0178] The hydrogen production DC power supply is used to implement the control method of the photovoltaic DC off-grid hydrogen production system.

[0179] For details on the working process and principle of the hydrogen production DC power supply, please refer to the control method of the photovoltaic DC off-grid hydrogen production system provided in any of the above embodiments. They will not be repeated here, and are all within the protection scope of this application.

[0180] In practical applications, such as Figure 8 As shown, it also includes a photovoltaic DC power supply positioned between the photovoltaic array and the hydrogen production DC power supply.

[0181] The photovoltaic array's DC output terminal is connected to a photovoltaic DC power supply, the photovoltaic DC power supply's DC output terminal is connected to a hydrogen production DC power supply, and the hydrogen production DC power supply's DC output terminal is connected to an electrolyzer.

[0182] The voltage between the output terminal of the photovoltaic DC power supply and the input terminal of the hydrogen production DC power supply is defined as the DC bus voltage. This DC bus voltage is typically greater than 1000V.

[0183] Similarly, the input voltage Vpv of the hydrogen production DC power supply is the DC bus voltage.

[0184] In this embodiment, the stable operation of the photovoltaic DC off-grid hydrogen production system can be ensured without adding any additional hardware or equipment, avoiding situations such as sudden reduction in photovoltaic power, PV voltage fluctuations, or even falling below the input voltage limit of the hydrogen production DC power supply.

[0185] The features described in the various embodiments of this specification can be substituted for or combined with each other. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0186] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0187] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a photovoltaic DC off-grid hydrogen production system, characterized in that, Hydrogen production DC power supplies used in photovoltaic DC off-grid hydrogen production systems include: Receive output electrical parameter commands; Determine the input voltage of the hydrogen production DC power supply, and determine the maximum amplitude limit based on the correspondence between the input voltage and the maximum amplitude limit; Based on the output electrical parameter command, the maximum amplitude limit value, and the current output electrical parameters of the hydrogen production DC power supply, the operating state of the hydrogen production DC power supply and the actual output electrical parameters controlling the hydrogen production DC power supply to be in the operating state are determined; wherein, the operating state includes: MPPT mode and non-MPPT mode; Determine whether the input voltage of the hydrogen production DC power supply is less than a preset voltage threshold; If so, the maximum amplitude limit value is used as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode; The step of determining the operating state of the hydrogen-producing DC power supply based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen-producing DC power supply, and the actual output electrical parameters for controlling the hydrogen-producing DC power supply to be in the operating state, includes: When the current output electrical parameters of the hydrogen production DC power supply are greater than or equal to the value of the output electrical parameter instruction, the hydrogen production DC power supply enters the non-MPPT mode and executes the output electrical parameter instruction as a control instruction so that the actual output electrical parameters of the hydrogen production DC power supply in the non-MPPT mode are the value of the output electrical parameter instruction. When the current output electrical parameters of the hydrogen production DC power supply are less than the value of the output electrical parameter command, the hydrogen production DC power supply enters the MPPT mode.

2. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 1, characterized in that, Before determining the operating state of the hydrogen production DC power supply based on the output electrical parameter command, the maximum limiting value, and the current output electrical parameters of the hydrogen production DC power supply, the method further includes: Determine the current output electrical parameters of the hydrogen production DC power supply.

3. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 1, characterized in that, The maximum limiting value is the maximum output electrical parameter, and / or the duty cycle limiting value or the conduction angle limiting value.

4. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 1, characterized in that, The maximum amplitude limit value is the maximum output electrical parameter; Using the maximum limit value as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode includes: using the maximum output electrical parameters as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

5. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 1, characterized in that, The maximum amplitude limit value is either the duty cycle amplitude limit value or the conduction angle amplitude limit value; Using the maximum limiting value as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode includes: using the duty cycle limiting value or the conduction angle limiting value as a control command to control the on / off switching of the power electronic switching devices in the hydrogen production DC power supply, thereby controlling the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode.

6. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 1, characterized in that, The maximum amplitude limit value is either the duty cycle amplitude limit value or the conduction angle amplitude limit value; Based on the output electrical parameter command, the maximum limit value, and the current output electrical parameters of the hydrogen production DC power supply, after determining the operating state of the hydrogen production DC power supply and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding operating state, the method further includes: If the calculated duty cycle or conduction angle of the power electronic switching device exceeds the corresponding duty cycle limit or conduction angle limit, then the power electronic switching device of the hydrogen production DC power supply shall be controlled according to the duty cycle limit or conduction angle limit. If the calculated duty cycle or conduction angle of the power electronic switching device does not exceed the corresponding duty cycle limit or conduction angle limit, then the calculation result of the duty cycle or conduction angle shall be executed.

7. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 2, characterized in that, Based on the output electrical parameter command, the maximum amplitude limit, and the current output electrical parameters of the hydrogen production DC power supply, the operating state of the hydrogen production DC power supply and the actual output electrical parameters for controlling the hydrogen production DC power supply to be in the corresponding operating state are determined, including: The smaller value between the output electrical parameter command and the maximum limiting value is taken as the target output value; wherein, the maximum limiting value is the maximum output electrical parameter; Based on the current output electrical parameters of the hydrogen-generating DC power supply and the target output value, the operating state of the hydrogen-generating DC power supply is determined, as well as the actual output electrical parameters for controlling the hydrogen-generating DC power supply to be in the corresponding operating state.

8. The control method for the photovoltaic DC off-grid hydrogen production system according to claim 7, characterized in that, Based on the current output electrical parameters of the hydrogen-generating DC power supply and the target output value, the operating state of the hydrogen-generating DC power supply is determined, and the actual output electrical parameters for controlling the hydrogen-generating DC power supply to be in the corresponding operating state include: Determine whether the current output electrical parameter is greater than or equal to the target output value; If so, the hydrogen production DC power supply enters non-MPPT mode, and the target output value is used as a control command to control the actual output electrical parameters of the hydrogen production DC power supply in non-MPPT mode. If not, the hydrogen-generating DC power supply enters MPPT mode.

9. The control method for the photovoltaic DC off-grid hydrogen production system according to any one of claims 1-8, characterized in that, The maximum output electrical parameter, output electrical parameter command, current output electrical parameter, and actual output electrical parameter are all at least one of voltage, current, and power.

10. A photovoltaic DC off-grid hydrogen production system, characterized in that, include: Photovoltaic array, hydrogen production DC power supply, electrolyzer, and hydrogen production system controller; The output terminal of the photovoltaic array is connected to the input terminal of the hydrogen production DC power supply; The output terminal of the hydrogen production DC power supply is connected to the electrolytic cell; The hydrogen production DC power supply is communicatively connected to the hydrogen production system controller. The hydrogen-generating DC power supply is used to execute the control method of the photovoltaic DC off-grid hydrogen production system as described in any one of claims 1-9.

11. The photovoltaic DC off-grid hydrogen production system according to claim 10, characterized in that, It also includes a photovoltaic DC power supply disposed between the photovoltaic array and the hydrogen production DC power supply.

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