Direct-current-direct-current converter control method and system for photovoltaic hydrogen production

Abstract

The application 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. The method comprises the following steps: determining a working mode according to input state information; when the working mode is a boost mode, determining a current dynamic boost duty ratio based on a maximum output voltage through a discrete PI control algorithm, and controlling the direct-current-direct-current converter to work according to the dynamic boost duty ratio and a fixed duty ratio; when the working mode is a buck mode, determining a current dynamic buck duty ratio based on the maximum output voltage through the discrete PI control algorithm, and controlling the direct-current-direct-current converter for photovoltaic hydrogen production to work according to the dynamic buck duty ratio and the fixed duty ratio; and when the working mode is an invalid mode, setting the current duty ratio as 0 and controlling the direct-current-direct-current converter for photovoltaic hydrogen production to work, which has the advantages that smooth switching control is adopted to realize the switching of the boost and buck modes, and the performance of photovoltaic hydrogen production is improved.

Description

Technical Field

[0001] This invention relates to the field of DC-DC converter control, and particularly to a DC-DC converter control method and system for photovoltaic hydrogen production. Background Technology

[0002] In areas far from the power grid, photovoltaic (PV) hydrogen production systems can provide an independent source of electricity and hydrogen. Utilizing the electricity generated by solar photovoltaics for water electrolysis to produce hydrogen contributes to sustainable energy production and reduces carbon emissions, making PV hydrogen production a crucial pathway for addressing energy and environmental issues. However, PV systems are susceptible to power instability due to factors such as weather changes, day-night cycles, seasonal variations, geographical conditions, and obstructions. This instability in PV output power leads to fluctuations in the output DC voltage, causing the input voltage to be lower or higher than the set reference output voltage. A buck-boost converter is needed to convert the power to achieve the required output voltage. While buck-boost converter control methods are valuable for achieving constant output voltage, they suffer from low efficiency, complex control, high component stress, noise sensitivity, and difficult mechanical design. Improved control methods or alternative topologies are needed to compensate for these shortcomings. Smooth switching, as an advanced control strategy, is commonly used in power system and power electronics management to reduce fluctuations and shocks during transitions between different power sources. Smooth switching between solar photovoltaic systems and the power grid can reduce conversion losses and significantly improve the overall system efficiency. Smooth control of buck-boost converters can optimize the stability of hydrogen production systems, extend equipment lifespan, and improve power quality.

[0003] In buck-boost converter control, methods are generally divided into voltage control and current control. With the continuous improvement of various control methods, analog control has gradually shifted to hybrid analog-digital control, with conventional linear control being the most widely used. One example is the widely used industrial controller PID (Proportional-Integral-Derivative Control). PID has advantages such as high accuracy and strong anti-interference capability. However, when applied to switching converters, because the controlled object is a strongly nonlinear system, conventional PID control is quite sensitive to control parameters and 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 interferences such as converter voltage and load changes, conventional PID control will experience problems such as reduced adjustment speed and reduced output voltage accuracy. In the PID control parameter selection criteria, the integral parameter is used to improve output accuracy and quickly reduce errors. However, as a crucial component in power electronic equipment, the converter requires frequent start-stop operations, sudden load increases / decreases, and the input voltage is constantly changing. In PID control, the integral term adjusts by accumulating the error. This can cause the output control to exceed the adjustment range within a very short time, leading to system saturation, increased overshoot, and compromised dynamic performance. If the error accumulates too quickly, it can even cause output oscillation. This situation is unacceptable in applications where high converter output requirements are necessary.

[0004] Therefore, there is a need to provide a DC-DC converter control system for photovoltaic hydrogen production, which can use smooth switching control to achieve the switching between boost and buck modes, thereby improving the performance of photovoltaic hydrogen production. Summary of the Invention

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

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

[0007] Further, based on the input status information, the operating mode is determined, including: S1, determining 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 yes, proceed to S2; if no, determine that the operating mode is an invalid mode; S2, calculating the buck-boost determination voltage based on the reference output voltage and hysteresis voltage; S3, determining whether the input voltage is greater than the buck-boost determination voltage; if yes, determine that the operating mode is a buck mode; if no, proceed to S4; S4, determining whether the input voltage is greater than the buck-boost determination voltage; if yes, determine that the operating mode is a boost mode; if no, determine that the operating mode is an invalid mode.

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

[0009] Furthermore, the hysteresis voltage is calculated based on the following formula: ,in, It is a hysteresis voltage. These are preset parameters. Greater than 0, For maximum output voltage, This is the minimum output voltage.

[0010] Furthermore, when the operating mode is boost mode, the current dynamic buck duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, including: obtaining an initial PI value based on the maximum output voltage; obtaining a buck PI value based on the initial PI value using the discrete PI control algorithm; obtaining an initial 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 operating mode is buck mode, the current dynamic boost duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, including: obtaining an initial PI value based on the maximum output voltage, input voltage, reference output voltage, and hysteresis voltage; obtaining a boost PI value based on the initial PI value using the discrete PI control algorithm; obtaining an initial 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, a second switch, a third switch, and a fourth switch, wherein the first switch and the second switch form a first bridge arm, and the third switch and the fourth switch form a second bridge arm; when the operating mode is boost mode, the duty cycle of the first switch is fixed at K1; when the operating mode is buck mode, the duty cycle of the fourth switch is fixed at K2, wherein K1+K2=1.

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

[0014] This invention provides a DC-DC converter control system for photovoltaic hydrogen production, applying the aforementioned DC-DC converter control method for photovoltaic hydrogen production, comprising: an information acquisition module for acquiring input state information; a mode determination module for determining an operating mode based on the input state information, wherein the operating mode is one of boost mode, buck mode, and inactive mode; a converter control module for determining the current dynamic boost duty cycle and obtaining a fixed duty cycle based on the maximum output voltage using a discrete PI control algorithm when the operating mode is boost mode, and controlling the DC-DC converter for photovoltaic hydrogen production to operate based on the dynamic boost duty cycle and the fixed duty cycle; the converter control module is further configured to determine the current dynamic buck duty cycle and obtaining a fixed duty cycle based on the maximum output voltage using a discrete PI control algorithm when the operating mode is buck mode, and controlling the DC-DC converter for photovoltaic hydrogen production to operate based on the dynamic buck duty cycle and the fixed duty cycle; the converter control module is further configured to set the current duty cycle to 0 and control the DC-DC converter for photovoltaic hydrogen production to operate when the operating mode is inactive mode.

[0015] Compared with existing technologies, the DC-DC converter control method and system for photovoltaic hydrogen production provided by this invention have at least the following advantages:

[0016] Applying DC-DC converters to photovoltaic hydrogen production systems aims to address the instability caused by variations in solar irradiance. This conversion module maintains stable output under different input voltage conditions, ensuring the continuity and efficiency of the hydrogen production process. Furthermore, replacing traditional PI control with a smooth switching control method not only enables seamless switching between boost and buck modes but also significantly improves the response speed and stability of the DC-DC converter under different operating conditions, thereby enhancing its performance and reliability. Attached Figure Description

[0017] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0018] Figure 1 This is a schematic flowchart illustrating a DC-DC converter control method for photovoltaic hydrogen production according to some embodiments of this specification;

[0019] Figure 2 This is a flowchart illustrating the determination of a working mode according to some embodiments of this specification;

[0020] Figure 3 This is a circuit diagram of a DC-DC converter for photovoltaic hydrogen production, shown according to some embodiments of this specification.

[0021] Figure 4 This is a schematic diagram of the DC-DC converter for photovoltaic hydrogen production in boost mode, according to some embodiments of this specification.

[0022] Figure 5 This is a schematic diagram of the DC-DC converter for photovoltaic hydrogen production in buck mode, according to some embodiments of this specification.

[0023] Figure 6 This is a driving waveform modulation diagram of a DC-DC converter for photovoltaic hydrogen production, shown in some embodiments of this specification.

[0024] Figure 7 This is a schematic diagram of a reference voltage variation waveform shown according to some embodiments of this specification;

[0025] Figure 8 This is a schematic diagram of a simulated waveform with an input of 1200V and a reference voltage of 1000V, as shown in some embodiments of this specification.

[0026] Figure 9 This is a schematic diagram of a simulated waveform with an input of 1200V and a reference voltage of 1500V, as shown in some embodiments of this specification.

[0027] Figure 10 This is a schematic diagram of a simulated waveform with an input of 1200V and a reference voltage of 1200V, as shown in some embodiments of this specification.

[0028] Figure 11 This is a schematic diagram of a DC-DC converter control system for photovoltaic hydrogen production, as shown in some embodiments of this specification. Detailed Implementation

[0029] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0030] Figure 1 This is a schematic flowchart illustrating a DC-DC converter control method for photovoltaic hydrogen production, as shown in some embodiments of this specification. Figure 1 As shown, the DC-DC converter control method for photovoltaic hydrogen production may include the following steps.

[0031] Step 110: Obtain input status information.

[0032] Specifically, the input status information may include the input voltage and the program check time.

[0033] Step 120: Determine the operating mode based on the input status information. The operating mode is one of the following: boost mode, buck mode, and invalid mode.

[0034] Figure 2 This is a flowchart illustrating the determination of the working mode according to some embodiments of this specification, such as... Figure 2 As shown, in some embodiments, step 120 specifically includes:

[0035] 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 yes, execute S2. If no, determine that the working mode is invalid. This is just an example. The program check time threshold can be 0.001 seconds and the input voltage threshold can be 10V.

[0036] S2. Calculate the buck-boost decision voltage based on the reference output voltage and the hysteresis voltage. The buck-boost decision voltage can be the sum of the reference output voltage and the hysteresis voltage.

[0037] S3. Determine if the input voltage is greater than the buck-boost determination voltage. If yes, determine that the working mode is buck mode. If no, execute S4.

[0038] S4. Determine if the input voltage is greater than the step-up / step-down determination voltage. If yes, determine the working mode as step-up mode; otherwise, determine the working mode as invalid mode.

[0039] In some embodiments, the hysteresis voltage is determined based on the output voltage range.

[0040] Specifically, The settings need to ensure that the DC-DC converter used for photovoltaic hydrogen production does not frequently jitter or become unstable when switching between buck and boost modes. The hysteresis voltage should be determined based on the actual input voltage fluctuation range to ensure correct mode switching and stability when the input voltage varies within a certain range. The hysteresis voltage value can be set as a certain percentage of the output voltage range.

[0041] In some embodiments, the hysteresis voltage is calculated based on the following formula:

[0042] ,

[0043] in, It is a hysteresis voltage. These are preset parameters. Greater than 0, For maximum output voltage, Minimum output voltage, The value range is (1%, 5%).

[0044] As an example only, the output voltage range can be set to 1000V to 1500V. If it is 3%, then .

[0045] Figure 3 This is a circuit diagram of a DC-DC converter for photovoltaic hydrogen production, as shown in some embodiments of this specification. Figure 3 As shown, taking a four-transistor DC-DC converter as an example, the control method of a DC-DC converter for photovoltaic hydrogen production is further explained. The DC-DC converter for photovoltaic hydrogen production includes a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. The first switch S1 and the second switch S2 form the first bridge arm H1, and the third switch S3 and the fourth switch S4 form the second bridge arm H2. The duty cycle of the first bridge arm H1 is the duty cycle K1 of the first switch S1, and the duty cycle of the second bridge arm H2 is the duty cycle K2 of the fourth switch S4.

[0046] Figure 4 This is a mode diagram of a DC-DC converter for photovoltaic hydrogen production in boost mode, as shown in some embodiments of this specification. Figure 4 As shown, when the input voltage is less than the output voltage, a boost operation is required. The DC-DC converter used for photovoltaic hydrogen production operates in boost mode, and one operating cycle includes the following three stages:

[0047] First stage: First switch S1 and third switch S3 are closed, second switch S2 and fourth switch S4 are open;

[0048] State: At this time, the input power supply is connected to the inductor L1 through the first switch S1, and the output load forms a loop through the third switch S3, the inductor L2 (or another inductor, depending on the circuit design) and the output capacitor C.

[0049] Function: The input voltage charges inductor L1, while the output load is powered by inductor L2 (or the previously stored energy) and output capacitor C. At this time, inductor L1 stores energy, preparing for the subsequent boost process.

[0050] The second stage: the first switch S1 and the fourth switch S4 are closed, and the second switch S2 and the third switch S3 are open;

[0051] State: The input power supply is still connected to the inductor L1 through S1, but at this time the output load forms a new circuit with the other end of the input power supply (usually ground or negative) and the output capacitor C through the fourth switch S4.

[0052] Function: This process is a transitional state. Inductor L1 continues to store energy, while the output load begins to draw energy from inductor L1 and output capacitor C. Simultaneously, the closing of the fourth switch S4 provides another energy transfer path for the subsequent boost process.

[0053] The third stage: the second switch S2 and the fourth switch S4 are closed, and the first switch S1 and the third switch S3 are open;

[0054] State: At this time, the input power supply is disconnected from inductor L1, but inductor L1 forms a loop with the output load through the second switch 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 S4.

[0055] Function: Inductor L1 releases the energy stored previously to power 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 voltage boost.

[0056] Figure 5 This is a schematic diagram of the DC-DC converter for photovoltaic hydrogen production in buck mode, as shown in some embodiments of this specification. Figure 5 As shown, when the input voltage is greater than the output voltage, a buck operation is required. One working cycle consists of three stages. In the first stage, the first switch S1 and the third switch S3 are closed, and the second switch S2 and the fourth switch S4 are open. In the second stage, the second switch S2 and the third switch S3 are closed, and the first switch S1 and the fourth switch S4 are open. In the third stage, the second switch S2 and the fourth switch S4 are closed, and the first switch S1 and the third switch S3 are open.

[0057] When the operating mode is boost mode, the duty cycle of the first switching transistor S1 is fixed at K1.

[0058] When the operating mode is buck mode, the duty cycle of the fourth switch S4 is fixed at K2, where K1+K2=1.

[0059] In some embodiments, the duty cycle K1 of the first switching transistor is determined based on the efficiency, power consumption, and / or stability of the DC-DC converter used for photovoltaic hydrogen production.

[0060] As an example only, a multiple regression model can be established, where the independent variables are efficiency, power consumption, and / or stability, and the dependent variable is the duty cycle of the first switching transistor. Experimental data can be collected, and the regression parameters of the multiple regression model can be determined using this data. The duty cycle K1 of the first switching transistor can be determined using a multiple regression model based on the efficiency, power consumption, and / or stability of a DC-DC converter used for photovoltaic hydrogen production.

[0061] When the input voltage is less than the output voltage, i.e., when a boost operation is required, fixing the duty cycle of the first switch S1 to K1 ensures a sufficiently long conduction time, improving the stability and efficiency of the output voltage. Simultaneously, dynamically adjusting the duty cycle of the fourth switch S4 allows for flexible adjustment based on actual needs, achieving precise control of the output voltage. When the input voltage is greater than the output voltage, i.e., when a buck operation is required, fixing the duty cycle of the fourth switch S4 to 0.1 ensures a sufficiently short conduction time, reducing voltage fluctuations and power consumption. Similarly, dynamically adjusting the duty cycle of the first switch S1 allows for flexible adjustment based on actual needs, achieving precise control of the output voltage. By setting fixed and dynamically adjustable duty cycles, effective energy conversion and stable output voltage can be achieved in different operating modes, improving the performance and efficiency of the DC-DC converter. In a DC-DC converter, the choice of the fixed duty cycle directly affects the stability, efficiency, and control accuracy of the output voltage. Therefore, when modifying the fixed duty cycle, factors such as circuit efficiency, power consumption, and stability must be comprehensively considered to ensure the converter's optimal performance. When adjusting the fixed duty cycle, it is also necessary to recalculate and adjust the dynamically adjusted duty cycle accordingly in order to maintain the stability and effectiveness of the entire control system.

[0062] Through simulation and debugging tests, the optimal fixed duty cycle of the first switch S1 was determined to be 0.9, and the optimal fixed duty cycle of the fourth switch S4 was determined to be 0.1.

[0063] Figure 6 This is a driving waveform modulation diagram of a DC-DC converter for photovoltaic hydrogen production, as shown in some embodiments of this specification, such as... Figure 6 As shown, the drive signal is centrally symmetrical, and the PWM modulation method is triangular modulation, in which the triangular carrier phase difference between the Buck half-bridge and the Boost half-bridge is 180°.

[0064] To achieve a natural switching between boost and buck modes, a smooth switching control method is adopted. Specifically, when a voltage difference is detected between the input and output voltages and a mode switching is required, the mode is switched, while the integral element in the integrator remains unchanged.

[0065] Step 130: When the operating mode is boost mode, the current dynamic boost duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, and a fixed duty cycle is obtained. Based on the dynamic boost duty cycle and the fixed duty cycle, the DC-DC converter used for photovoltaic hydrogen production is controlled to operate.

[0066] Specifically, it includes:

[0067] Based on the maximum output voltage, obtain the initial PI value, for example... ;

[0068] The step-down PI value is obtained by using a discrete PI control algorithm based on the initial PI value. );

[0069] Based on the maximum output voltage, obtain the initial boost PI value, for example... ;

[0070] Based on the buck PI value and the maximum output voltage, the current dynamic buck duty cycle is obtained, for example, .

[0071] Specifically, when the operating mode is boost mode, the first stage is as follows: the first switch S1 and the third switch S3 are closed, the second switch S2 and the fourth switch S4 are open, the duty cycle of the first switch S1 is a fixed duty cycle K1, and the duty cycle of the fourth switch S4 is the current dynamic buck duty cycle. The second stage is as follows: the first switch S1 and the fourth switch S4 are closed, the second switch S2 and the third switch S3 are open, and the duty cycle of the first switch S1 and the fourth switch S4 is the current dynamic boost duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. The third stage is as follows: the second switch S2 and the fourth switch S4 are closed, the first switch S1 and the third switch S3 are open, and the duty cycle of the second switch S2 and the fourth switch S4 is the current dynamic boost duty cycle determined by the discrete PI control algorithm based on the maximum output voltage.

[0072] Step 140: When the working mode is buck mode, the current dynamic buck duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, and the fixed duty cycle is obtained. Based on the dynamic buck duty cycle and the fixed duty cycle, the DC-DC converter used for photovoltaic hydrogen production is controlled to work.

[0073] Specifically, when the operating mode is buck mode, the first stage involves the first switch S1 and the third switch S3 being closed, and the second switch S2 and the fourth switch S4 being open. The duty cycle of the first switch S1 and the third switch S3 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. The second stage involves the second switch S2 and the third switch S3 being closed, and the duty cycle of the second switch S2 and the third switch S3 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. The first switch S1 and the fourth switch S4 are open. The third stage involves the second switch S2 and the fourth switch S4 being closed, and the first switch S1 and the third switch S3 being open. In this stage, the duty cycle of the fourth switch S4 is a fixed duty cycle K2, and the duty cycle of the second switch S2 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage.

[0074] Specifically, it includes:

[0075] The initial PI value is obtained based on the maximum output voltage, input voltage, reference output voltage, and hysteresis voltage. For example, ;

[0076] The boost PI value is obtained by using a discrete PI control algorithm based on the initial PI value. );

[0077] Based on the maximum output voltage, obtain the initial buck PI value, for example... ;

[0078] Based on the boost PI value and the maximum output voltage, the current dynamic boost duty cycle is obtained, for example, .

[0079] Step 150: When the working mode is invalid, set the current duty cycle to 0 and control the DC-DC converter used for photovoltaic hydrogen production to work.

[0080] The following section, based on experiments, explains the beneficial effects of the DC-DC converter control method used in photovoltaic hydrogen production.

[0081] A simulation was built using a two-transistor DC-DC converter as an example. The input voltage was set to 1200V, the output voltage varied within the range of 1000~1500V, the output current was 200A, and the switching frequency was 10kHz. Figure 7The 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 image shows the simulated waveform when the input is 1200V and the reference voltage is 1000V. Figure 9 The image shows the simulated waveform when the input is 1200V and the reference voltage is 1500V. Figure 10 The image shows the simulated waveform when the input voltage is 1200V and the reference voltage is 1200V. Figures 7-10 It can be seen that when the input voltage is 1200V and the reference voltage varies between 1000V and 1500V, the dual-tube DC-DC converter can achieve automatic switching between buck and boost modes.

[0082] Figure 11 This is a schematic diagram of a DC-DC converter control system for photovoltaic hydrogen production, as shown in some embodiments of this specification. Figure 11 As shown, the DC-DC converter control system for photovoltaic hydrogen production may include an information acquisition module, a mode determination module, and a converter control module.

[0083] The information acquisition module is used to acquire input status information;

[0084] The mode determination module is used to determine the operating mode based on the input status information, wherein the operating mode is one of boost mode, buck mode and invalid mode;

[0085] The converter control module is 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 boost mode, obtain the fixed duty cycle, and control the operation of the DC-DC converter for photovoltaic hydrogen production according to the dynamic boost duty cycle and the fixed duty cycle.

[0086] The converter control module is also used to determine the current dynamic buck duty cycle based on the maximum output voltage using a discrete PI control algorithm when the operating mode is buck mode, obtain the fixed duty cycle, and control the DC-DC converter for photovoltaic hydrogen production to operate according to the dynamic buck duty cycle and the fixed duty cycle.

[0087] The converter control module is also used to set the current duty cycle to 0 when the operating mode is invalid, and to control the operation of the DC-DC converter used for photovoltaic hydrogen production.

[0088] 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 details on the DC-DC converter control system for photovoltaic hydrogen production, please refer to the relevant description of the DC-DC converter control method for photovoltaic hydrogen production, which will not be repeated here.

[0089] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A control method for a DC-DC converter used in photovoltaic hydrogen production, characterized in that, include: Obtain input status information; Based on the input status information, the operating mode is determined, wherein the operating mode is one of boost mode, buck mode, and invalid mode; When the operating mode is boost mode, the current dynamic boost duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, and a fixed duty cycle is obtained. Based on the dynamic boost duty cycle and the fixed duty cycle, the DC-DC converter used for photovoltaic hydrogen production is controlled to operate. When the operating mode is buck mode, the current dynamic buck duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, and a fixed duty cycle is obtained. Based on the dynamic buck duty cycle and the fixed duty cycle, the DC-DC converter used for photovoltaic hydrogen production is controlled to operate. When the operating mode is invalid, the current duty cycle is set to 0, and the DC-DC converter used for photovoltaic hydrogen production is controlled to operate. The DC-DC converter for photovoltaic hydrogen production includes a first switch, a second switch, a third switch, and a fourth switch, wherein the first switch and the second switch form a first bridge arm, and the third switch and the fourth switch form a second bridge arm. When the operating mode is boost mode, the duty cycle of the first switch is fixed at K1. In the first stage: the first switch S1 and the third switch S3 are closed, the second switch S2 and the fourth switch S4 are open, and the duty cycle of the first switch S1 is a fixed duty cycle K1. In the second stage: the first switch S1 and the fourth switch S4 are closed, the second switch S2 and the third switch S3 are open, and the duty cycle of the first switch S1 and the fourth switch 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 S2 and the fourth switch S4 are closed, the first switch S1 and the third switch S3 are open, and the duty cycle of the second switch S2 and the fourth switch S4 is the current dynamic boost duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. When the operating mode is buck mode, the duty cycle of the fourth switch is fixed at K2, where K1+K2=1. In the first stage, the first switch S1 and the third switch S3 are closed, and the second switch S2 and the fourth switch S4 are open. The duty cycle of the first switch S1 and the third switch S3 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. In the second stage, the second switch S2 and the third switch S3 are closed, and the duty cycle of the second switch S2 and the third switch S3 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage. The first switch S1 and the fourth switch S4 are open. In the third stage, the second switch S2 and the fourth switch S4 are closed, and the first switch S1 and the third switch S3 are open. The duty cycle of the fourth switch S4 is a fixed duty cycle K2, and the duty cycle of the second switch S2 is the current dynamic buck duty cycle determined by the discrete PI control algorithm based on the maximum output voltage.

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

3. The DC-DC converter control method for photovoltaic hydrogen production according to claim 2, characterized in that, Based on the input status information, the working mode is determined, including: 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 yes, execute S2. If no, determine that the working mode is an invalid mode. S2. Calculate the buck-boost determination voltage based on the reference output voltage and hysteresis voltage; S3. Determine whether the input voltage is greater than the buck-boost determination voltage. If yes, determine that the working mode is buck mode. If no, execute S4. S4. Determine whether the input voltage is greater than the step-up / step-down determination voltage. If yes, determine that the working mode is step-up mode. If no, determine that the working mode is 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 the output voltage range.

5. The DC-DC converter control method for photovoltaic hydrogen production according to claim 4, characterized in that, The hysteresis voltage is calculated based on the following formula: ， in, It is a hysteresis voltage. These are preset parameters. Greater than 0, For maximum output voltage, This 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 operating mode is buck mode, the current dynamic buck duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, including: The initial PI value is obtained based on the maximum output voltage; The step-down PI value is obtained based on the initial PI value using a discrete PI control algorithm; Based on the aforementioned buck PI value and maximum output voltage, the current dynamic buck duty cycle is obtained.

7. The DC-DC converter control method for photovoltaic hydrogen production according to claim 3, characterized in that, When the operating mode is boost mode, the current dynamic boost duty cycle is determined based on the maximum output voltage using a discrete PI control algorithm, including: The initial PI value is obtained based on the maximum output voltage, input voltage, reference output voltage, and hysteresis voltage. The boost PI value is obtained based on the initial PI value using a discrete PI control algorithm; The current dynamic boost duty cycle is obtained based on 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 1-6, 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 switching transistor is determined to be K1.

9. A DC-DC converter control system for photovoltaic hydrogen production, characterized in that, The method for controlling a DC-DC converter for photovoltaic hydrogen production according to any one of claims 1-8 includes: The information acquisition module is used to acquire input status information; The mode determination module is used to determine the working mode based on the input status information, wherein the working mode is one of boost mode, buck mode and invalid mode; The converter control module is 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 boost mode, obtain the 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, when the working mode is buck mode, determine the current dynamic buck duty cycle based on the maximum output voltage using a discrete PI control algorithm, obtain the fixed duty cycle, and control the DC-DC converter used 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 and control the DC-DC converter used for photovoltaic hydrogen production to work when the working mode is invalid.

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