DC-DC converter control method and system for photovoltaic hydrogen production

Abstract

The invention provides a direct current-direct current converter control method and system for photovoltaic hydrogen production, and relates to the field of direct current-direct current converter control, and the method comprises the steps: determining a working mode according to the input state information; when the working mode is a boost mode, determining a current dynamic boost duty ratio based on the maximum output voltage through a discrete PI control algorithm, and controlling the DC-DC converter to work according to the dynamic boost duty ratio and a fixed duty ratio; when the working mode is a step-down mode, determining a current dynamic step-down duty ratio based on the maximum output voltage through a discrete PI control algorithm, and controlling a direct current-direct current converter for photovoltaic hydrogen production to work according to the dynamic step-down duty ratio and a fixed duty ratio; when the working mode is the invalid mode, the current duty ratio is set to be 0, the direct current-direct current converter used for photovoltaic hydrogen production is controlled to work, and the method has the advantages that smooth switching control is adopted to achieve switching of the step-up mode and the step-down mode, and the photovoltaic hydrogen production performance is improved.

Description

Technical Field

[0001] The present invention relates to the field of direct current (DC)-to-DC converter control, and in particular to a control method and system for a DC-to-DC converter used for photovoltaic hydrogen production. Background Art

[0002] In areas far from the power grid, photovoltaic hydrogen production systems can provide an independent way to supply electricity and hydrogen, and use the electricity generated by solar photovoltaics to produce hydrogen by electrolysis of water, which helps to achieve sustainable energy production and reduce carbon emissions. Therefore, photovoltaic hydrogen production systems have become one of the important paths to solve energy and environmental problems. However, due to factors such as weather changes, day and night changes, seasonal changes, geographical conditions, and obstructions, photovoltaic systems have the characteristic of unstable power generation. The instability of photovoltaic output power will cause fluctuations in the output DC voltage, making the input voltage lower or higher than the set reference output voltage. A buck-boost converter is required to convert power so that the voltage meets the output requirements. The buck-boost converter control method has its unique value in achieving a constant output voltage, but it has many disadvantages such as low efficiency, complex control, high component stress, noise sensitivity, and difficult mechanical design. Improved control methods or other topological structures are needed to make up for its shortcomings. Smooth switching, as an advanced control strategy, is usually used in power system and power electronic equipment management to reduce fluctuations and shocks when the system switches between different power sources. In the switching process between the solar photovoltaic system and the power grid, smooth switching can reduce conversion losses and significantly improve the efficiency of the overall system. Smooth control of the buck-boost converter can optimize the stability of the hydrogen production system, extend the life of the equipment, and improve the quality of power.

[0003] In terms of the control methods of buck-boost converters, they are generally divided into voltage control and current control. With the continuous improvement of various control methods, analog control has gradually turned into analog-digital hybrid control, and the most widely used is conventional linear control. For example, the widely used industrial controller PID (Proportional-Integral-Derivative Control) control. PID has the advantages of high precision and strong anti-interference ability, but when it is applied to switching converters, because the controlled object is a strong nonlinear system, conventional PID control is sensitive to control parameters and is significantly affected by parameter changes. The selection of PID parameters is generally based on the small signal mathematical model of the circuit. For large signal interference such as converter voltage and load changes, conventional PID control will produce problems such as reduced adjustment speed and reduced output voltage accuracy. In the PID control parameter selection criteria, the integral parameter is to improve output accuracy and quickly reduce errors. However, as an important link in power electronic equipment, the converter needs to start and stop frequently, increase / drop load suddenly, and the input voltage also changes at any time. In the process of PID regulation, the integral term is regulated by accumulating the error, which results in the output control exceeding the regulation range in a very short time, causing the system to enter a saturated state, increasing the overshoot, and affecting the dynamic performance. If the error accumulates too quickly, the output may also oscillate. This situation is not allowed in places where the converter output requirements are high.

[0004] Therefore, it is necessary to provide a DC-DC converter control system for photovoltaic hydrogen production, which is used to realize the switching of boost and buck modes by adopting smooth switching control, so as to improve the performance of photovoltaic hydrogen production. Summary of the invention

[0005] The present invention provides a control method for a DC-DC converter for photovoltaic hydrogen production, comprising: obtaining input state information; determining an operating mode according to the input state information, wherein the operating mode is one of a boost mode, a buck mode and an invalid mode; when the operating mode is the boost mode, determining a current dynamic boost duty cycle based on a maximum output voltage through a discrete PI control algorithm, obtaining a fixed duty cycle, and controlling the operation of the DC-DC converter for photovoltaic hydrogen production according to the dynamic boost duty cycle and the fixed duty cycle; when the operating mode is the buck mode, determining a current dynamic buck duty cycle based on a maximum output voltage through a discrete PI control algorithm, obtaining a fixed duty cycle, and controlling the operation of the DC-DC converter for photovoltaic hydrogen production according to the dynamic buck duty cycle and the fixed duty cycle; when the operating mode is the invalid mode, setting the current duty cycle to 0, and controlling the operation of the DC-DC converter for photovoltaic hydrogen production.

[0006] Furthermore, the obtaining of input status information includes: obtaining input voltage and program check time.

[0007] Further, the working mode is determined according to the input status information, including: S1, judging whether the input voltage is greater than the input voltage threshold, and whether the program check time is greater than the program check time threshold, if so, executing S2, if not, judging that the working mode is an invalid mode; S2, calculating the buck-boost judgment voltage according to the reference output voltage and the hysteresis voltage; S3, judging whether the input voltage is greater than the buck-boost judgment voltage, if so, judging that the working mode is the buck mode, if not, executing S4; S4, judging whether the input voltage is greater than the buck-boost judgment voltage, if so, judging that the working mode is the boost mode, if not, judging that the working mode is an invalid mode.

[0008] Further, the hysteresis voltage is determined based on an output voltage range.

[0009] Furthermore, the hysteresis voltage is calculated based on the following formula: ,in, is the hysteresis voltage, is the preset parameter, greater than 0, is the maximum output voltage, is the minimum output voltage.

[0010] Furthermore, when the working mode is the boost mode, the current dynamic buck duty cycle is determined based on the maximum output voltage through a discrete PI control algorithm, including: obtaining an initialization PI value based on the maximum output voltage; obtaining a buck PI value based on the initialization PI value through a discrete PI control algorithm; obtaining an initialization boost PI value based on the maximum output voltage; and obtaining the current dynamic buck duty cycle based on the buck PI value and the maximum output voltage.

[0011] Furthermore, when the working mode is the buck mode, the current dynamic boost duty cycle is determined based on the maximum output voltage through a discrete PI control algorithm, including: obtaining an initialization PI value based on the maximum output voltage, the input voltage, the reference output voltage and the hysteresis voltage; obtaining a boost PI value based on the initialization PI value through a discrete PI control algorithm; obtaining an initialization buck PI value based on the maximum output voltage; and obtaining the current dynamic boost duty cycle based on the boost PI value and the maximum output voltage.

[0012] Furthermore, the DC-DC converter for photovoltaic hydrogen production includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, wherein the first switch tube and the second switch tube constitute a first bridge arm, and the third switch tube and the fourth switch tube constitute a second bridge arm; when the working mode is a boost mode, the duty cycle of the first switch tube is fixed to K1; when the working mode is a buck mode, the duty cycle of the fourth switch tube is fixed to K2, wherein K1+K2=1.

[0013] Further, based on the efficiency, power consumption and / or stability of the DC-DC converter for photovoltaic hydrogen production, the duty cycle of the first switch tube is determined to be K1.

[0014] The present invention provides a DC-DC converter control system for photovoltaic hydrogen production, which uses the above-mentioned DC-DC converter control method for photovoltaic hydrogen production, including: an information acquisition module, used to acquire input state information; a mode determination module, used to determine the working mode according to the input state information, wherein the working mode is one of a boost mode, a buck mode and an invalid mode; a converter control module, used to determine the current dynamic boost duty cycle based on the maximum output voltage through a discrete PI control algorithm when the working mode is the boost mode, obtain a fixed duty cycle, and control the DC-DC converter for photovoltaic hydrogen production to work according to the dynamic boost duty cycle and the fixed duty cycle; the converter control module is also used to determine the current dynamic buck duty cycle based on the maximum output voltage through a discrete PI control algorithm when the working mode is the buck mode, obtain a fixed duty cycle, and control the DC-DC converter for photovoltaic hydrogen production to work according to the dynamic buck duty cycle and the fixed duty cycle. The converter control module is also used to set the current duty cycle to 0 when the working mode is the invalid mode, and control the DC-DC converter for photovoltaic hydrogen production to work.

[0015] Compared with the prior art, the DC-DC converter control method and system for photovoltaic hydrogen production provided by the present invention have at least the following beneficial effects: The application of DC-DC converters in photovoltaic hydrogen production systems is intended to cope with the instability of photovoltaic power generation systems caused by changes in sunlight. Through this conversion module, stable output can be maintained under different input voltage conditions to ensure the continuity and efficiency of the hydrogen production process. In addition, the use of smooth switching control methods instead of traditional PI control can not only achieve seamless switching between boost and buck modes, but also significantly improve the response speed and stability of the DC-DC converter under different working conditions, thereby improving the working performance and reliability of the DC-DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein: Figure 1 is a flow chart of a DC-DC converter control method for photovoltaic hydrogen production according to some embodiments of this specification; Figure 2 is a schematic diagram of a process for determining a working mode according to some embodiments of this specification; Figure 3 is a circuit diagram of a DC-DC converter for photovoltaic hydrogen production according to some embodiments of this specification; Figure 4 is a modal schematic diagram of a DC-DC converter for photovoltaic hydrogen production in a boost mode according to some embodiments of this specification; Figure 5 is a modal schematic diagram of a DC-DC converter for photovoltaic hydrogen production in a buck mode according to some embodiments of this specification; Figure 6 It is a driving waveform modulation diagram of a DC-DC converter for photovoltaic hydrogen production according to some embodiments of this specification; Figure 7 is a schematic diagram of a reference voltage variation waveform according to some embodiments of this specification; Figure 8 It is a schematic diagram of a simulation waveform with an input of 1200V and a reference voltage of 1000V according to some embodiments of this specification; Fig. 9 It is a schematic diagram of a simulation waveform with an input of 1200V and a reference voltage of 1500V according to some embodiments of this specification; Fig.10 It is a schematic diagram of a simulation waveform with an input of 1200V and a reference voltage of 1200V according to some embodiments of this specification; Fig.11 It is a module schematic diagram of a DC-DC converter control system for photovoltaic hydrogen production according to some embodiments of this specification. DETAILED DESCRIPTION

[0017] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0018] Figure 1 is a flow chart of a DC-DC converter control method for photovoltaic hydrogen production according to some embodiments of this specification, such as Figure 1 As shown, the DC-DC converter control method for photovoltaic hydrogen production may include the following steps.

[0019] Step 110, obtaining input status information.

[0020] Specifically, the input status information may include input voltage and program check time.

[0021] Step 120, determining a working mode according to the input state information, wherein the working mode is one of a boost mode, a buck mode and an invalid mode.

[0022] Figure 2 is a flowchart of determining the working mode according to some embodiments of this specification, such as Figure 2 As shown, in some embodiments, step 120 specifically includes: S1, determine whether the input voltage is greater than the input voltage threshold, and whether the program check time is greater than the program check time threshold. If so, execute S2, if not, determine that the working mode is an invalid mode. For example only, the program check time threshold can be 0.001 seconds, and the input voltage threshold can be 10V; S2. Calculate the buck-boost determination voltage according to the reference output voltage and the hysteresis voltage, wherein the buck-boost determination voltage may be the sum of the reference output voltage and the hysteresis voltage; S3, determine whether the input voltage is greater than the buck-boost determination voltage, if so, determine that the working mode is buck mode, if not, execute S4; S4. Determine whether the input voltage is greater than the step-up / step-down determination voltage. If so, determine that the working mode is the step-up mode. If not, determine that the working mode is the invalid mode.

[0023] In some embodiments, the hysteresis voltage is determined based on the output voltage range.

[0024] Specifically, The setting needs to ensure that the DC-DC converter used for photovoltaic hydrogen production will not frequently jitter or become unstable when switching between buck mode and boost mode. The hysteresis voltage is determined according to the actual input voltage fluctuation range to ensure that the mode can be switched correctly and remain stable when the input voltage changes within a certain range. The value of the hysteresis voltage can be set to a certain proportion of the output voltage range.

[0025] In some embodiments, the hysteresis voltage is calculated based on the following formula: , in, is the hysteresis voltage, is the preset parameter, greater than 0, is the maximum output voltage, is the minimum output voltage, The value range is (1%, 5%).

[0026] As an example only, the output voltage range may be set to 1000V to 1500V. If .

[0027] Figure 3 is a circuit diagram of a DC-DC converter for photovoltaic hydrogen production according to some embodiments of this specification, such as Figure 3 As shown, taking a four-tube DC-DC converter as an example, the control method of the DC-DC converter for photovoltaic hydrogen production is further described. The DC-DC converter for photovoltaic hydrogen production includes a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4, wherein the first switch tube S1 and the second switch tube S2 form a first bridge arm H1, and the third switch tube S3 and the fourth switch tube S4 form a second bridge arm H2. The duty cycle of the first bridge arm H1 is the duty cycle K1 of the first switch tube S1, and the duty cycle of the second bridge arm H2 is the duty cycle K2 of the fourth switch tube S4.

[0028] Figure 4 is a modal schematic diagram of a DC-DC converter for photovoltaic hydrogen production in a boost mode according to some embodiments of this specification, such as Figure 4 As shown in the figure, when the input voltage is less than the output voltage, a boost operation is required. The DC-DC converter used for photovoltaic hydrogen production works in the boost mode. One working cycle includes the following three stages: The first stage: the first switch tube S1 and the third switch tube S3 are closed, and the second switch tube S2 and the fourth switch tube S4 are opened; State: At this time, the input power supply is connected to the inductor L1 through the first switch tube S1, and the output load forms a loop with the inductor L2 (or another inductor, depending on the circuit design) and the output capacitor C through the third switch tube S3.

[0029] Function: The input voltage charges the inductor L1, while the output load is powered by the inductor L2 (or the previous energy storage) and the output capacitor C. At this time, the inductor L1 stores energy to prepare for the subsequent boost process.

[0030] The second stage: the first switch tube S1 and the fourth switch tube S4 are closed, and the second switch tube S2 and the third switch tube S3 are opened; State: The input power supply is still connected to the inductor L1 through S1, but at this time the output load forms a new loop with the other end of the input power supply (usually the ground or the negative pole) and the output capacitor C through the fourth switch tube S4.

[0031] Function: This process is a transition state, the inductor L1 continues to store energy, and the output load begins to obtain energy from the inductor L1 and the output capacitor C. At the same time, due to the closing of the fourth switch tube S4, another energy transmission path is provided for the subsequent boost process.

[0032] The third stage: the second switch tube S2 and the fourth switch tube S4 are closed, and the first switch tube S1 and the third switch tube S3 are opened; State: At this time, the input power supply is disconnected from the inductor L1, but the inductor L1 forms a loop with the output load through the second switch tube S2. At the same time, the output load is still connected to the other end of the input power supply and the output capacitor C through the fourth switch tube S4.

[0033] Function: Inductor L1 releases the previously stored energy to supply power to the output load. This process is one of the key steps in the boost process, because the energy released by inductor L1 is added to the output voltage, thereby achieving boost.

[0034] Figure 5 is a schematic diagram of a DC-DC converter for photovoltaic hydrogen production in a buck mode according to some embodiments of this specification, such as Figure 5 As shown, when the input voltage is greater than the output voltage, a step-down operation (buck) is required. A working cycle includes three stages. In the first stage, the first switch tube S1 and the third switch tube S3 are closed, and the second switch tube S2 and the fourth switch tube S4 are opened. In the second stage, the second switch tube S2 and the third switch tube S3 are closed, and the first switch tube S1 and the fourth switch tube S4 are opened. In the third stage, the second switch tube S2 and the fourth switch tube S4 are closed, and the first switch tube S1 and the third switch tube S3 are opened.

[0035] When the working mode is the boost mode, the duty cycle of the first switch tube S1 is fixed to K1.

[0036] When the working mode is the buck mode, the duty cycle of the fourth switch tube S4 is fixed to K2, where K1+K2=1.

[0037] In some embodiments, the duty cycle K1 of the first switch tube is determined based on the efficiency, power consumption and / or stability of the DC-DC converter for photovoltaic hydrogen production.

[0038] As an example only, a multiple regression model can be established, wherein the independent variables of the multiple regression model are efficiency, power consumption and / or stability, and the dependent variable of the multiple regression model is the duty cycle of the first switch tube. Test data can be collected, and the regression parameters of the multiple regression model can be determined through the test data. The duty cycle K1 of the first switch tube can be determined based on the efficiency, power consumption and / or stability of the DC-DC converter for photovoltaic hydrogen production through the multiple regression model.

[0039] When the input voltage is less than the output voltage, that is, when a boost operation is required, the duty cycle of the first switch tube S1 is fixed to K1, which can ensure a sufficiently long conduction time and improve the stability and efficiency of the output voltage. At the same time, the duty cycle of the fourth switch tube S4 can be flexibly adjusted according to actual needs to achieve precise control of the output voltage. When the input voltage is greater than the output voltage, that is, when a buck operation is required, the duty cycle of the fourth switch tube S4 is fixed to 0.1 to ensure a sufficiently short conduction time and reduce voltage fluctuations and power consumption. Similarly, the duty cycle of the first switch tube S1 can be flexibly adjusted according to actual needs to achieve precise control of the output voltage. By setting a fixed and dynamically adjusted duty cycle, effective energy conversion and stable output voltage can be achieved in different working modes, improving the performance and efficiency of the DC-DC converter. In a DC-DC converter, the choice of a fixed duty cycle will directly affect the stability, efficiency and control accuracy of the output voltage. Therefore, when modifying the fixed duty cycle, it is necessary to comprehensively consider factors such as circuit efficiency, power consumption, stability, etc. to ensure that the working performance of the converter reaches the best state. When adjusting the fixed duty cycle, the dynamically adjusted duty cycle also needs to be recalculated and adjusted accordingly to maintain the stability and effectiveness of the entire control system.

[0040] Through simulation debugging tests, it is determined that the optimal fixed duty cycle of the first switch tube S1 is 0.9, and the optimal fixed duty cycle of the fourth switch tube S4 is 0.1.

[0041] Figure 6 is a driving waveform modulation diagram of a DC-DC converter for photovoltaic hydrogen production according to some embodiments of this specification, such as Figure 6 As shown, the driving signal is centrally symmetrical, and the PWM modulation mode is triangular modulation, wherein the phase difference between the triangular carriers of the Buck half-bridge and the Boost half-bridge is 180°.

[0042] In order to achieve natural switching between boost and buck modes, a smooth switching control method is adopted. The specific control logic is that when a voltage difference between the input and output is detected and it is determined that a mode switch is required, the mode switch is performed, and the integral link in the integrator remains unchanged.

[0043] Step 130, when the working mode is the boost mode, the current dynamic boost duty cycle is determined based on the maximum output voltage through a discrete PI control algorithm, a fixed duty cycle is obtained, and the DC-DC converter used for photovoltaic hydrogen production is controlled according to the dynamic boost duty cycle and the fixed duty cycle.

[0044] Specifically include: According to the maximum output voltage, the initialization PI value is obtained, for example, ; The step-down PI value is obtained according to the initialization PI value through the discrete PI control algorithm ( ); According to the maximum output voltage, the initial boost PI value is obtained, for example, ; According to the buck PI value and the maximum output voltage, the current dynamic buck duty cycle is obtained, for example, .

[0045] Specifically, when the working mode is the boost mode, in the first stage: the first switch tube S1 and the third switch tube S3 are closed, the second switch tube S2 and the fourth switch tube S4 are disconnected, the duty cycle of the first switch tube S1 is a fixed duty cycle K1, and the duty cycle of the fourth switch tube S4 is the current dynamic step-down duty cycle; in the second stage: the first switch tube S1 and the fourth switch tube S4 are closed, the second switch tube S2 and the third switch tube S3 are disconnected, and the duty cycle of the first switch tube S1 and the fourth switch tube S4 is the current dynamic boost duty cycle determined by the discrete PI control algorithm based on the maximum output voltage; in the third stage: the second switch tube S2 and the fourth switch tube S4 are closed, the first switch tube S1 and the third switch tube S3 are disconnected, and the second switch tube S2 and the fourth switch tube S4 are the current dynamic boost duty cycle determined by the discrete PI control algorithm based on the maximum output voltage.

[0046] Step 140, when the working mode is the buck mode, the current dynamic buck duty cycle is determined based on the maximum output voltage through a discrete PI control algorithm, a fixed duty cycle is obtained, and the DC-DC converter used for photovoltaic hydrogen production is controlled according to the dynamic buck duty cycle and the fixed duty cycle.

[0047] Specifically, when the working mode is the buck mode, the first stage is that the first switch tube S1 and the third switch tube S3 are closed, the second switch tube S2 and the fourth switch tube S4 are disconnected, and the duty cycle of the first switch tube S1 and the third switch tube S3 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. The second stage is that the second switch tube S2 and the third switch tube S3 are closed, the duty cycle of the second switch tube S2 and the third switch tube S3 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage, and the first switch tube S1 and the fourth switch tube S4 are disconnected. The third stage is that the second switch tube S2 and the fourth switch tube S4 are closed, and the first switch tube S1 and the third switch tube S3 are disconnected, wherein the duty cycle of the fourth switch tube S4 is a fixed duty cycle K2, and the duty cycle of the second switch tube S2 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage.

[0048] Specifically include: According to the maximum output voltage, input voltage, reference output voltage and hysteresis voltage, the initialization PI value is obtained, for example, ; The boost PI value is obtained by the discrete PI control algorithm according to the initial PI value ( ); According to the maximum output voltage, the initial step-down PI value is obtained, for example, ; According to the boost PI value and the maximum output voltage, the current dynamic boost duty cycle is obtained, for example, .

[0049] Step 150: When the working mode is the invalid mode, the current duty cycle is set to 0, and the DC-DC converter for photovoltaic hydrogen production is controlled to work.

[0050] The beneficial effects of the DC-DC converter control method for photovoltaic hydrogen production are described below in conjunction with experiments.

[0051] Take the dual-tube DC-DC converter as an example for simulation construction, set the input voltage to 1200V, the output voltage to vary in the range of 1000~1500V, the output current to 200A, and the switching frequency to 10kHz. Figure 7 The figure shows the simulated waveform of the output voltage changing with the reference voltage when the input voltage is maintained at 1200V. Figure 8 The following is a simulation waveform when the input voltage is 1200V and the reference voltage is 1000V. Fig. 9 The following is the simulation waveform when the input voltage is 1200V and the reference voltage is 1500V. Fig.10 The figure shows the simulation waveform when the input voltage is 1200V and the reference voltage is 1200V. Figure 7-Figure 10It can be seen that when the input voltage is 1200V and the reference voltage changes between 1000V and 1500V, the dual-tube DC-DC converter can realize automatic switching between the buck-boost mode.

[0052] Fig.11 is a module schematic diagram of a DC-DC converter control system for photovoltaic hydrogen production according to some embodiments of this specification, such as Fig.11 As shown, a DC-DC converter control system for photovoltaic hydrogen production may include an information acquisition module, a mode determination module and a converter control module.

[0053] An information acquisition module, used to obtain input status information; A mode determination module, used to determine the working mode according to the input state information, wherein the working mode is one of a boost mode, a buck mode and an invalid mode; A converter control module, for determining a current dynamic boost duty cycle based on a maximum output voltage through a discrete PI control algorithm when the working mode is a boost mode, obtaining a fixed duty cycle, and controlling the operation of a DC-DC converter for photovoltaic hydrogen production according to the dynamic boost duty cycle and the fixed duty cycle; The converter control module is also used to determine the current dynamic buck duty cycle based on the maximum output voltage through a discrete PI control algorithm when the working mode is the buck mode, obtain a fixed duty cycle, and control the operation of the DC-DC converter for photovoltaic hydrogen production according to the dynamic buck duty cycle and the fixed duty cycle. The converter control module is also used to set the current duty cycle to 0 when the working mode is the invalid mode, so as to control the operation of the DC-DC converter used for photovoltaic hydrogen production.

[0054] The DC-DC converter control system for photovoltaic hydrogen production can be used to execute the DC-DC converter control method for photovoltaic hydrogen production. For more descriptions of the DC-DC converter control system for photovoltaic hydrogen production, please refer to the relevant descriptions of the DC-DC converter control method for photovoltaic hydrogen production, which will not be repeated here.

[0055] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A DC-DC converter control method for photovoltaic hydrogen production, characterized in that: include: Get input status information; Determine a working mode according to the input state information, wherein the working mode is one of a boost mode, a buck mode and an invalid mode; When the working mode is the boost mode, the current dynamic boost duty cycle is determined based on the maximum output voltage through a discrete PI control algorithm, a fixed duty cycle is obtained, and the DC-DC converter for photovoltaic hydrogen production is controlled to work according to the dynamic boost duty cycle and the fixed duty cycle; When the working mode is the buck mode, the current dynamic buck duty cycle is determined based on the maximum output voltage through a discrete PI control algorithm, a fixed duty cycle is obtained, and the DC-DC converter for photovoltaic hydrogen production is controlled to work according to the dynamic buck duty cycle and the fixed duty cycle; When the working mode is the invalid mode, the current duty cycle is set to 0, and the DC-DC converter for photovoltaic hydrogen production is controlled to work.

2. The DC-DC converter control method for photovoltaic hydrogen production according to claim 1, characterized in that: The obtaining of input status information includes: Get input voltage and program check time.

3. The DC-DC converter control method for photovoltaic hydrogen production according to claim 2, characterized in that: Determining a working mode according to the input state information includes: S1, determine whether the input voltage is greater than the input voltage threshold, and whether the program check time is greater than the program check time threshold, if so, execute S2, if not, determine that the working mode is an invalid mode; S2. Calculate the boost / buck determination voltage based on the reference output voltage and the hysteresis voltage; S3, determining whether the input voltage is greater than the buck-boost determination voltage, if so, determining that the working mode is the buck mode, if not, executing S4; S4. Determine whether the input voltage is greater than the step-up / step-down determination voltage. If so, determine that the working mode is the step-up mode. If not, determine that the working mode is the invalid mode.

4. The DC-DC converter control method for photovoltaic hydrogen production according to claim 3, characterized in that: The hysteresis voltage is determined based on an output voltage range.

5. The DC-DC converter control method for photovoltaic hydrogen production according to claim 4, characterized in that: Calculate the hysteresis voltage based on the following formula: ， in, is the hysteresis voltage, is the preset parameter, greater than 0, is the maximum output voltage, is the minimum output voltage.

6. The DC-DC converter control method for photovoltaic hydrogen production according to claim 3, characterized in that: When the working mode is the boost mode, the current dynamic buck duty cycle is determined based on the maximum output voltage by a discrete PI control algorithm, including: According to the maximum output voltage, an initialization PI value is obtained; The voltage reduction PI value is obtained according to the initialization PI value through the discrete PI control algorithm; According to the maximum output voltage, an initialization boost PI value is obtained; The current dynamic buck duty cycle is obtained according to the buck PI value and the maximum output voltage.

7. The DC-DC converter control method for photovoltaic hydrogen production according to claim 3, characterized in that: When the working mode is the buck mode, the current dynamic boost duty cycle is determined based on the maximum output voltage by a discrete PI control algorithm, including: Obtaining an initialized PI value according to the maximum output voltage, the input voltage, the reference output voltage and the hysteresis voltage; The boost PI value is obtained according to the initialization PI value through the discrete PI control algorithm; According to the maximum output voltage, an initialization step-down PI value is obtained; The current dynamic boost duty cycle is obtained according to the boost PI value and the maximum output voltage.

8. The DC-DC converter control method for photovoltaic hydrogen production according to any one of claims 1 to 7, characterized in that: The DC-DC converter for photovoltaic hydrogen production comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, wherein the first switch tube and the second switch tube form a first bridge arm, and the third switch tube and the fourth switch tube form a second bridge arm; When the working mode is the boost mode, the duty cycle of the first switch tube is fixed to K1; When the working mode is the buck mode, the duty cycle of the fourth switch tube is fixed to K2, wherein K1+K2=1.

9. The DC-DC converter control method for photovoltaic hydrogen production according to any one of claims 1 to 6, characterized in that: Based on the efficiency, power consumption and / or stability of the DC-DC converter for photovoltaic hydrogen production, the duty cycle of the first switch tube is determined to be K1.

10. A DC-DC converter control system for photovoltaic hydrogen production, characterized in that: The DC-DC converter control method for photovoltaic hydrogen production according to any one of claims 1 to 9 comprises: An information acquisition module, used to obtain input status information; A mode determination module, used to determine an operating mode according to the input state information, wherein the operating mode is one of a boost mode, a buck mode and an invalid mode; A converter control module, for determining a current dynamic boost duty cycle based on a maximum output voltage through a discrete PI control algorithm when the working mode is a boost mode, obtaining a fixed duty cycle, and controlling the operation of a DC-DC converter for photovoltaic hydrogen production according to the dynamic boost duty cycle and the fixed duty cycle; The converter control module is also used to, when the working mode is the buck mode, determine the current dynamic buck duty cycle based on the maximum output voltage through a discrete PI control algorithm, obtain a fixed duty cycle, and control the operation of the DC-DC converter for photovoltaic hydrogen production according to the dynamic buck duty cycle and the fixed duty cycle; The converter control module is further used to, when the working mode is the invalid mode, set the current duty cycle to 0, and control the operation of the DC-DC converter used for photovoltaic hydrogen production.

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