Hydrogen production power supply and low voltage ride through control method and device thereof

Abstract

The invention relates to a hydrogen production power supply and a low voltage ride through control method and device thereof, and belongs to the technical field of hydrogen production equipment. The method comprises the following steps: if the power grid voltage drops below a power grid voltage drop threshold value but the drop degree does not enable the direct current bus voltage to be less than the direct current bus voltage drop threshold value; a step-down circuit driving pulse signal of the hydrogen production power supply is generated by adopting a first duty ratio calculated according to the principle that the output power of the step-down circuit is not changed before and after the power grid voltage drops; and if the drop degree of the power grid voltage reaches that the direct-current bus voltage is smaller than the direct-current bus voltage drop threshold value, generating a driving pulse signal of the step-down circuit by adopting a second duty ratio calculated according to the allowable minimum power percentage of the electrolytic cell. The control device and the hydrogen production power supply both comprise a control unit for implementing the method. While safe and stable operation of the hydrogen production power supply is ensured, the power supply power of the electrolytic bath can be maintained to the maximum extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production equipment, and in particular relates to a hydrogen production power supply and a low voltage ride-through control method and device thereof. Background Art

[0002] In the field of hydrogen production by water electrolysis, the power supply for hydrogen production by water electrolysis usually includes a rectifier circuit and a step-down circuit. The input end of the rectifier circuit is connected to the power grid, and the output end of the rectifier circuit is connected to the input end of the step-down circuit through a DC bus. The output end of the step-down circuit is connected to the electrolyzer of the hydrogen production equipment. The power supply circuit rectifies the grid voltage and converts it into an appropriate DC voltage to power the electrolyzer. When the grid voltage drops, it will pose a threat to the safe and stable operation of the hydrogen production power supply and the electrolyzer. The current industry regulations on the low voltage ride-through capability of the hydrogen production power supply are: when the voltage amplitude of the hydrogen production power supply is less than the rated voltage and greater than or equal to 20% of the rated voltage value, the rectifier power supply should be reliably powered to ensure the safe operation of the power supply object. Therefore, it is necessary to formulate a low voltage ride-through control strategy for the hydrogen production power supply to maintain the power supply of the electrolyzer as much as possible while ensuring the safe operation of the hydrogen production power supply.

[0003] In order to make the water electrolysis hydrogen production device have the function of low voltage ride-through, the Chinese invention patent application with publication number CN116937636A discloses a voltage control system and method for a hydrogen production device. The hydrogen production power supply unit in the system includes a control unit, an uncontrolled rectifier power supply unit whose input end is connected to the power grid, and a fully controlled rectifier power supply unit. When the power grid voltage is normal, the uncontrolled rectifier power supply unit is controlled to supply power to the electrolyzer to ensure that the stack can operate at full capacity; when the power grid voltage drops, the fully controlled rectifier power supply unit is controlled to supply power to the electrolyzer to achieve derating operation after the power grid voltage drops, ensuring that the stack completes low voltage ride-through and improves work efficiency. Although this method mentions that the use of a fully controlled rectifier power supply can achieve low voltage ride-through of the system, when the power grid voltage drops, the fully controlled rectifier power supply unit is directly controlled to achieve derating operation of the electrolyzer. This control method cannot maximize the power supply power of the electrolyzer, which has a significant impact on the stable operation of the hydrogen production device. Summary of the invention

[0004] The purpose of the present invention is to provide a hydrogen production power supply and a low voltage ride-through control method and device thereof, so as to solve the problem that the existing hydrogen production power supply voltage control method cannot maximize the power supply of the electrolyzer while ensuring the safe and stable operation of the hydrogen production power supply when the grid voltage drops.

[0005] The present invention provides a low voltage ride-through control method for a hydrogen production power supply to solve the above technical problems: when the grid voltage drops, if the grid voltage drops below the grid voltage drop threshold value but the drop degree does not reach the point where the DC bus voltage is less than the DC bus voltage drop threshold value, a first duty cycle is used to generate a step-down circuit drive pulse signal for the hydrogen production power supply, and the first duty cycle is calculated based on the principle that the output power of the step-down circuit remains unchanged before and after the grid voltage drops; if the grid voltage drops to the point where the DC bus voltage is less than the DC bus voltage drop threshold value, a second duty cycle is used to generate a step-down circuit drive pulse signal for the hydrogen production power supply, and the second duty cycle is calculated based on the minimum power percentage allowed by the electrolyzer.

[0006] Furthermore, when calculating the first duty cycle based on the principle that the output power of the step-down circuit remains unchanged before and after the grid voltage drops, it is determined whether the rectifier circuit of the hydrogen production power supply is overloaded. If the rectifier circuit is not overloaded, the first duty cycle is equal to the ratio of the step-down circuit output voltage setting value to the DC bus voltage setting value; if the rectifier circuit is overloaded, the first duty cycle is equal to the ratio of the step-down circuit output voltage setting value to the DC bus voltage setting value multiplied by a first coefficient; the first coefficient is calculated based on the real-time value of the grid voltage after the grid voltage drops, the active power output when the grid voltage is normal, and the maximum current allowed to be output by the grid connection point.

[0007] Furthermore, the method for judging whether the rectifier circuit of the hydrogen production power supply is overloaded is: The rectifier circuit is not overloaded. The rectifier circuit is overloaded; wherein, U d_LVRT is the voltage positive sequence active component when the grid voltage drops, Ud_N is the voltage positive sequence active component when the grid is normal, i d_N is the active component of the output current when the grid voltage is normal, i d_max The maximum value of the active component of the current allowed to be output by the grid-connected point.

[0008] Furthermore, the calculation formula of the first coefficient K is: in, U d_LVRT is the voltage positive sequence active component when the grid voltage drops, Ud_N is the voltage positive sequence active component when the grid is normal, i d_N is the active component of the output current when the grid voltage is normal, i d_max The maximum value of the active component of the current allowed to be output by the grid-connected point.

[0009] Furthermore, the calculation formula of the second duty cycle DR2 is: in, U o_set is the output voltage setting value of the step-down circuit, U dc_setis the DC bus voltage setting value, r elzer is the minimum power percentage allowed for the electrolyzer.

[0010] Furthermore, when the grid voltage recovers to make the DC bus voltage greater than the second set voltage value and the grid voltage is not greater than the first set voltage value, the first duty cycle is used to generate a drive pulse signal for the step-down circuit of the hydrogen production power supply; the second set voltage value is equal to the DC bus voltage drop threshold value plus the DC bus voltage drop callback bias value, and the first set voltage value is equal to the grid voltage drop threshold value plus the grid voltage drop callback bias value.

[0011] Furthermore, when the grid voltage recovers to above the first set voltage value, a third duty cycle is used to generate a drive pulse signal for the step-down circuit of the hydrogen production power supply; the third duty cycle is calculated based on the deviation between the given value of the output current of the step-down circuit and the real-time value of the output current, and the first set voltage value is equal to the grid voltage drop threshold value plus the grid voltage drop callback bias value.

[0012] Furthermore, a dual closed-loop control strategy of a voltage outer loop and a current inner loop with DC power feedforward control is adopted to control the rectifier circuit of the hydrogen production power supply, wherein the DC power feedforward control refers to calculating the DC power feedforward value based on the electrolyzer power value and the positive-sequence active component of the grid voltage, and using the DC power feedforward value to calculate the active current setting value of the current inner loop.

[0013] The beneficial effects of the present invention are as follows: the present invention is an improved invention. When the grid voltage drops, the present invention drives and controls the step-down part of the hydrogen production power supply. When the grid voltage drops slightly, the duty cycle used to generate the step-down part driving pulse signal adopts the duty cycle derived from the unchanged output power of the step-down circuit before and after the grid drops. Because the duty cycle is still calculated according to the output power of the step-down circuit before the drop when the grid voltage drops, the power supply of the electrolyzer can be maintained constant. When the grid voltage drops to a large extent, the duty cycle adopts the duty cycle calculated according to the minimum power percentage allowed by the electrolyzer, so as to maintain the minimum power operation of the electrolyzer. Therefore, this means can prevent the grid voltage from dropping too much to maintain the stability of the DC bus and cause the hydrogen production power supply to shut down, so that the electrolyzer cannot operate normally. In summary, the present invention can maintain the power supply of the electrolyzer as constant as possible while ensuring the safe and stable operation of the hydrogen production power supply, and reduce the impact of the grid voltage drop on the stable operation of the hydrogen production device.

[0014] The present invention provides a low voltage ride-through control device for a hydrogen production power source to solve the above technical problems, and includes a processor, a memory, and a computer program stored in the memory. The processor is used to execute the computer program to implement the low voltage ride-through control method for a hydrogen production power source described above.

[0015] The beneficial effects of the present invention are as follows: the present invention is an improved invention. When the grid voltage drops, the present invention drives and controls the step-down part of the hydrogen production power supply. When the grid voltage drops slightly, the duty cycle used to generate the step-down part driving pulse signal adopts the duty cycle derived from the unchanged output power of the step-down circuit before and after the grid drops. Because the duty cycle is still calculated according to the output power of the step-down circuit before the drop when the grid voltage drops, the power supply of the electrolyzer can be maintained constant. When the grid voltage drops to a large extent, the duty cycle adopts the duty cycle calculated according to the minimum power percentage allowed by the electrolyzer, so as to maintain the minimum power operation of the electrolyzer. Therefore, this means can prevent the grid voltage from dropping too much to maintain the stability of the DC bus and cause the hydrogen production power supply to shut down, so that the electrolyzer cannot operate normally. In summary, the present invention can maintain the power supply of the electrolyzer as constant as possible while ensuring the safe and stable operation of the hydrogen production power supply, and reduce the impact of the grid voltage drop on the stable operation of the hydrogen production device.

[0016] The hydrogen production power supply provided by the present invention to solve the above-mentioned technical problems includes a rectifier circuit, a step-down circuit and a control unit. The input end of the rectifier circuit is used to connect to the power grid, the output end of the rectifier circuit is connected to the input end of the step-down circuit through a DC bus, the output end of the step-down circuit is used to connect to the electrolyzer of the hydrogen production device, and the control unit controls the connection between the rectifier circuit and the step-down circuit. The control unit is used to implement the low voltage ride-through control method of the hydrogen production power supply described above.

[0017] The beneficial effects of the present invention are as follows: the present invention is an improved invention. When the grid voltage drops, the present invention drives and controls the step-down part of the hydrogen production power supply. When the grid voltage drops slightly, the duty cycle used to generate the step-down part driving pulse signal adopts the duty cycle derived from the unchanged output power of the step-down circuit before and after the grid drops. Because the duty cycle is still calculated according to the output power of the step-down circuit before the drop when the grid voltage drops, the power supply of the electrolyzer can be maintained constant. When the grid voltage drops to a large extent, the duty cycle adopts the duty cycle calculated according to the minimum power percentage allowed by the electrolyzer, so as to maintain the minimum power operation of the electrolyzer. Therefore, this means can prevent the grid voltage from dropping too much to maintain the stability of the DC bus and cause the hydrogen production power supply to shut down, so that the electrolyzer cannot operate normally. In summary, the present invention can maintain the power supply of the electrolyzer as constant as possible while ensuring the safe and stable operation of the hydrogen production power supply, and reduce the impact of the grid voltage drop on the stable operation of the hydrogen production device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a hydrogen production device according to an embodiment of the present invention;

[0019] Figure 2is a control block diagram of the voltage reduction part of the hydrogen production power supply according to an embodiment of the present invention;

[0020] Figure 3 is a flow chart of grid voltage drop depth detection according to an embodiment of the present invention;

[0021] Figure 4 is a flow chart of DC bus voltage drop detection according to an embodiment of the present invention;

[0022] Figure 5 is a control block diagram of the rectifier part of the hydrogen production power supply according to an embodiment of the present invention;

[0023] Figure 6 This is a RTDS semi-physical simulation waveform diagram when the grid voltage of the embodiment of the present invention drops to 0.9pu;

[0024] Figure 7 This is a RTDS semi-physical simulation waveform diagram when the grid voltage drops to 0.2pu according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, the hydrogen production power supply usually includes a rectifier circuit and a step-down circuit. The input end of the rectifier circuit is used to connect to the power grid, the output end of the rectifier circuit is connected to the input end of the step-down circuit through a DC bus, and the output end of the step-down circuit is used to connect to the electrolyzer.

[0027] Based on the circuit structure of the above hydrogen production power supply, the basic idea of ​​the present invention is: when the grid voltage drops, the electrolyzer is no longer directly ordered to reduce power, but when the grid voltage drops slightly, the output power of the step-down circuit is maintained as unchanged as possible, and when the grid voltage drops significantly, the electrolyzer is controlled to reduce power. In this way, the power supply of the electrolyzer can be maintained constant to the maximum extent, and the impact of the grid voltage drop on the stable operation of the hydrogen production device can be reduced as much as possible.

[0028] A method for controlling low voltage ride-through of a hydrogen production power supply

[0029] Based on the above basic idea, the low voltage ride-through control method of the hydrogen production power supply of the present invention is: when the grid voltage drops, if the grid voltage drops below the grid voltage drop threshold value but the drop degree does not reach the DC bus voltage less than the DC bus voltage drop threshold value, a first duty cycle is used to generate a step-down circuit drive pulse signal for the hydrogen production power supply, and the first duty cycle is calculated based on the principle that the output power of the step-down circuit remains unchanged before and after the grid voltage drops; if the grid voltage drops to the extent that the DC bus voltage is less than the DC bus voltage drop threshold value, a second duty cycle is used to generate a drive pulse signal for the step-down circuit of the hydrogen production power supply, and the second duty cycle is calculated based on the minimum power percentage allowed by the electrolyzer.

[0030] like Figure 3 As shown in the figure, when the grid voltage is normal, the driving control of the buck circuit is realized through the current control loop, specifically: the buck circuit output current given value i o_ref The feedback value of the step-down circuit i o The duty cycle is obtained by the PI controller through the PWM modulation link. The duty cycle generates a PWM drive signal for the step-down part of the hydrogen production power supply through the PWM modulation link. When the grid voltage drops, the degree of its drop usually goes through a process from small to large. When the drop degree of the grid voltage is not large, the duty cycle can be switched to the first duty cycle DR1 to control the operation of the step-down circuit. However, when the drop degree of the grid voltage is too large, it will be difficult to maintain the stability of the DC bus if the step-down circuit is controlled by the first duty cycle DR1, which will cause the hydrogen production power supply equipment to shut down and the electrolyzer to fail to work normally. To this end, the present invention sets a grid voltage drop threshold value and a DC bus voltage drop threshold value, and judges the drop degree of the grid voltage according to the above two threshold values, and adopts different duty cycles according to the drop degree of the grid voltage to obtain the driving pulse signal of the step-down part of the hydrogen production power supply. Therefore, when the grid voltage drops, the present invention can maximize the power supply of the electrolyzer while ensuring the safe and stable operation of the hydrogen production power supply.

[0031] Furthermore, when driving and controlling the buck circuit, in order to prevent the rectifier circuit from being overloaded and causing damage to the internal components of the rectifier circuit, the present invention also determines the overload condition of the rectifier circuit when calculating the first duty cycle DR1, and adopts different methods to obtain the first duty cycle DR1 according to the overload condition of the rectifier circuit. Specifically, if the rectifier circuit is not overloaded, the first duty cycle DR1 is equal to the output voltage setting value U of the buck circuit. o_set and DC bus voltage setting value U dc_set If the rectifier circuit is overloaded, the first duty cycle DR1 is equal to the output voltage setting value U of the step-down circuit. o_set and DC bus voltage setting value U dc_setThe first coefficient K is calculated based on the real-time value of the grid voltage after the grid voltage drops, the active power output when the grid voltage is normal, and the maximum current allowed to be output by the grid connection point.

[0032] Preferably, when the present invention determines the overload condition of the rectifier circuit, the judgment method adopted is: if The rectifier circuit is not overloaded. The rectifier circuit is overloaded; U d_LVRT is the voltage positive sequence active component when the grid voltage drops, Ud_N is the voltage positive sequence active component when the grid is normal, i d_N is the active component of the output current when the grid voltage is normal, i d_max The maximum value of the active component of the current allowed to be output by the grid-connected point.

[0033] Preferably, the first duty cycle DR1 is calculated as:

[0034]

[0035] in, U o_set is the output voltage setting value of the step-down circuit, U dc_set is the DC bus voltage setting value, U d_LVRT is the voltage positive sequence active component when the grid voltage drops, U d_N is the voltage positive sequence active component when the power grid is normal, i d_N is the active component of the output current when the grid voltage is normal, i d_max To allow the maximum value of the active current component output by the grid-connected point, is the calculation formula of the first coefficient K, that is U d_N ·i d_N It is the active power output when the grid voltage is normal.

[0036] Preferably, the second duty cycle DR2 is calculated as follows: in, U o_set is the output voltage setting value of the step-down circuit, U dc_set is the DC bus voltage setting value, r elzer is the minimum power percentage allowed for the electrolyzer.

[0037] In order to avoid frequent switching of the duty cycle of the driving pulse signal of the step-down circuit generating the hydrogen production power supply when the grid voltage fluctuates, the present invention sets a first set voltage value and a second set voltage value, and the first set voltage value is equal to the grid voltage drop threshold value U LVRT Plus the grid voltage drop callback bias value U BiasThe second set voltage value is equal to the DC bus voltage drop threshold value U Trans Plus the DC bus voltage drop callback bias value U TBias . If the grid voltage drops to a level that makes the DC bus voltage less than the DC bus voltage drop threshold value, the second duty cycle is used to generate the driving pulse signal of the step-down part. However, the duty cycle is not switched when the grid voltage recovers to a level that makes the DC bus voltage greater than or equal to the DC bus voltage drop threshold value. Instead, the duty cycle is switched when the grid voltage recovers to a level that makes the DC bus voltage greater than the second set voltage value. Similarly, when the grid voltage drops below the grid voltage drop threshold value, the first duty cycle is used to generate the driving pulse signal of the step-down part. However, the duty cycle is not switched when the grid voltage recovers to a level that makes the DC bus voltage greater than or equal to the grid voltage drop threshold value. Instead, the duty cycle is switched when the grid voltage recovers to above the first set voltage value. In this way, frequent switching of the duty cycle caused by the grid voltage fluctuating above and below the grid voltage drop threshold value or the DC bus voltage fluctuating above and below the DC bus voltage drop threshold value is prevented.

[0038] Specifically, when the grid voltage is restored to a level that makes the DC bus voltage greater than the second set voltage value, and the grid voltage is not greater than the first set voltage value, the first duty cycle is used to generate a driving pulse signal for the step-down circuit of the hydrogen production power supply; when the grid voltage is restored to above the first set voltage value, the third duty cycle is used to generate a driving pulse signal for the step-down circuit of the hydrogen production power supply; the third duty cycle is based on the step-down circuit output current given value i o_ref The real-time value of the output current of the step-down circuit i o The deviation between them is calculated by the PI controller.

[0039] like Figure 4 As shown, when the grid voltage U dP Less than the grid voltage drop threshold value U LVRT When the grid voltage U dP Greater than the grid voltage drop threshold value U LVRT The grid voltage drop callback bias value U Trans When the sum of LVRT_Flag and LVRT_Flag is reached, set the flag LVRT_Flag to 0.

[0040] like Figure 5 As shown, when the DC bus voltage U dc Less than the DC bus voltage drop threshold value U Trans When the DC bus voltage U dc Greater than the DC bus voltage drop threshold value U Trans The DC bus voltage drops and the callback bias value U TBias When the sum of , sets the flag Volt_Trans_Flag = 0.

[0041] like Figure 3 As shown, when LVRT_Flag=0, the third duty cycle calculated according to the deviation between the given output current value of the step-down circuit and the real-time output current value is used to generate the driving pulse signal of the step-down circuit of the hydrogen production power supply; when the flag LVRT_Flag=1, it switches to the first duty cycle DR1; when the flag Volt_Trans_Flag=1, it switches to the second duty cycle DR2.

[0042] For the rectifier circuit part of the hydrogen production power supply, in order to stabilize the DC bus voltage, the prior art usually adopts a dual closed loop of a voltage outer loop and a current inner loop to drive and control the rectifier circuit. However, when calculating the given value of the active current of the current inner loop, it depends on the output result of the voltage outer loop, and when the grid voltage drops, it is necessary to wait until the DC bus voltage responds before it can be reflected in the output result of the voltage outer loop. Therefore, when the grid voltage drops, the voltage outer loop responds slowly, thereby affecting the response speed of the DC bus voltage stable regulation. To this end, the present application improves the conventional dual closed-loop control strategy of a voltage outer loop and a current inner loop, and adds a DC power feedforward control to the dual closed-loop control, thereby obtaining a dual closed-loop control strategy of a voltage outer loop and a current inner loop with a DC power feedforward control, wherein the DC power feedforward control refers to the control of the DC bus voltage according to the electrolyzer power value P. dc and the grid voltage positive sequence active component U dP Calculate the DC power feedforward value, and use the DC power feedforward value to calculate the active current setting value i of the current inner loop d_ref In this way, when the grid voltage drops, it no longer depends on the DC bus voltage in the voltage outer loop to respond. The drop can be directly reflected in the calculation of the active current setting value of the current inner loop by the DC power feedforward value. That is, when the grid voltage drops, if the voltage outer loop does not respond in time, the DC power feedforward value can be used as the active current setting value of the current inner loop, thereby improving the response speed of the DC bus voltage loop, maintaining the stability of the DC bus voltage at the moment of grid voltage drop and recovery, and realizing rapid regulation of the DC bus voltage.

[0043] Preferably, if Figure 2 As shown in the figure, the process of controlling the rectifier circuit of the hydrogen production power supply by adopting the double closed-loop control strategy of voltage outer loop and current inner loop with DC power feedforward control includes: setting the DC bus voltage feedback value u dc and DC bus voltage setting value u dc_ref The current deviation value is obtained after the PI controller, and the current deviation value is compared with the DC power feedforward value P dc / U dP Add together to get the active current given value i d_ref , set the active current given value id_ref The active current feedback value i of the grid-connected point d_fdb The voltage deviation value is obtained after the PI controller, and the voltage deviation value is combined with the grid voltage active component feedforward value u d Add them together to get the active control quantity.

[0044] Furthermore, the given value of reactive current i q_ref With reactive current feedback i q_fdb The reactive voltage deviation value is obtained by the PI controller, and the reactive voltage deviation value is compared with the reactive component feedforward value U q The reactive control quantity is obtained by adding them together; the active control quantity and the reactive control quantity are modulated by SVPWM to generate a PWM drive signal for the rectifier part of the hydrogen production power supply.

[0045] The following RTDS semi-physical simulation is used to further illustrate that the control method of the present invention has a good control effect when the grid voltage drops.

[0046] Figure 6 The RTDS semi-physical simulation waveform when the grid voltage drops to 0.9pu. From top to bottom, they are the grid voltage, DC bus voltage, AC output current and DC output voltage of the step-down circuit. During the grid voltage drop, the bus voltage remains unchanged at 800V, the duty cycle of the hydrogen production power supply step-down part is switched to DR1, the DC output voltage of the step-down circuit remains unchanged at 500V, and the electrolyzer power is constant.

[0047] Figure 7 The RTDS semi-physical simulation waveform when the grid voltage drops to 0.2pu. From top to bottom, they are the grid voltage, DC bus voltage, AC output current, and DC output voltage of the buck circuit. During the grid voltage drop, the DC bus voltage has transient fluctuations and then stabilizes at 800V. The duty cycle of the hydrogen power supply step-down part is switched to DR2, the DC output voltage of the buck circuit is reduced, and the electrolyzer operates at the lowest power.

[0048] Embodiment of a low voltage ride through control device for hydrogen production power supply

[0049] The control device includes a processor, a memory and a computer program stored in the memory. The processor is used to execute the computer program to implement a low-voltage ride-through control method for a hydrogen production power source. The method is the method in the above-mentioned embodiment of the low-voltage ride-through control method for a hydrogen production power source and will not be described in detail here.

[0050] A hydrogen production power supply embodiment

[0051] The hydrogen production power supply includes a rectifier circuit, a step-down circuit and a control unit. The input end of the rectifier circuit is used to connect to the power grid, the output end of the rectifier circuit is connected to the input end of the step-down circuit through a DC bus, and the output end of the step-down circuit is used to connect to the electrolyzer of the hydrogen production device. The control unit controls the connection between the rectifier circuit and the step-down circuit. The control unit is used to implement a low-voltage ride-through control method for the hydrogen production power supply. The method is the method in the above-mentioned embodiment of the low-voltage ride-through control method for the hydrogen production power supply, which will not be described in detail here.

[0052] The rectifier circuit may be an NPC circuit (neutral point clamped three-level circuit), an ANPC circuit (active neutral point clamped three-level circuit), a two-level rectifier circuit, etc. The step-down circuit may be a Buck circuit, etc. Preferably, as Figure 1 As shown, the rectifier circuit of the hydrogen production power supply of the present invention is preferably an ANPC circuit, and the step-down circuit is preferably a Buck circuit.

[0053] The hydrogen production system of the present invention includes a hydrogen production power supply and an electrolyzer. The hydrogen production power supply includes a rectifier circuit, a step-down circuit and a control unit. The input end of the rectifier circuit is used to connect to the power grid, the output end of the rectifier circuit is connected to the input end of the step-down circuit through a DC bus, the output end of the step-down circuit is connected to the electrolyzer, the control unit controls the connection between the rectifier circuit and the step-down circuit, and the control unit is used to implement a low-voltage ride-through control method for the hydrogen production power supply. The method is the method in the above-mentioned embodiment of the low-voltage ride-through control method for the hydrogen production power supply, and will not be described in detail here.

[0054] The rectifier circuit may be an NPC circuit (neutral point clamped three-level circuit), an ANPC circuit (active neutral point clamped three-level circuit), a two-level rectifier circuit, etc. The step-down circuit may be a Buck circuit, etc. Preferably, as Figure 1 As shown, the rectifier circuit of the hydrogen production power supply of the present invention is preferably an ANPC circuit, and the step-down circuit is preferably a Buck circuit.

Claims

1. A method for controlling low voltage ride-through of a hydrogen production power supply, characterized in that: The method is as follows: when the grid voltage drops, if the grid voltage drops below the grid voltage drop threshold value but the drop degree does not reach the point where the DC bus voltage is less than the DC bus voltage drop threshold value, a first duty cycle is used to generate a step-down circuit drive pulse signal for a hydrogen production power supply, and the first duty cycle is calculated based on the principle that the output power of the step-down circuit remains unchanged before and after the grid voltage drops; if the grid voltage drops to the point where the DC bus voltage is less than the DC bus voltage drop threshold value, a second duty cycle is used to generate a step-down circuit drive pulse signal for a hydrogen production power supply, and the second duty cycle is calculated based on the minimum power percentage allowed by the electrolyzer.

2. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 1, characterized in that: When calculating the first duty cycle based on the principle that the output power of the step-down circuit remains unchanged before and after the grid voltage drops, it is determined whether the rectifier circuit of the hydrogen production power supply is overloaded. If the rectifier circuit is not overloaded, the first duty cycle is equal to the ratio of the step-down circuit output voltage setting value to the DC bus voltage setting value; if the rectifier circuit is overloaded, the first duty cycle is equal to the ratio of the step-down circuit output voltage setting value to the DC bus voltage setting value multiplied by a first coefficient; the first coefficient is calculated based on the real-time value of the grid voltage after the grid voltage drops, the active power output when the grid voltage is normal, and the maximum current allowed to be output by the grid connection point.

3. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 2, characterized in that: The method for judging whether the rectifier circuit of the hydrogen power supply is overloaded is: The rectifier circuit is not overloaded. The rectifier circuit is overloaded; wherein, U d_LVRT is the voltage positive sequence active component when the grid voltage drops, U d_N is the voltage positive sequence active component when the power grid is normal, i d_N is the active component of the output current when the grid voltage is normal, i d_max The maximum value of the active component of the current allowed to be output by the grid-connected point.

4. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 2, characterized in that: The calculation formula of the first coefficient K is: in, U d_LVRT is the voltage positive sequence active component when the grid voltage drops, U d_N is the voltage positive sequence active component when the power grid is normal, i d_N is the active component of the output current when the grid voltage is normal, i d_max The maximum value of the active component of the current allowed to be output by the grid-connected point.

5. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 1, characterized in that: The calculation formula of the second duty cycle DR2 is: in, U o_set is the output voltage setting value of the step-down circuit, U dc_set is the DC bus voltage setting value, r elzer is the minimum power percentage allowed for the electrolyzer.

6. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 1, characterized in that: When the grid voltage is restored to a level that makes the DC bus voltage greater than the second set voltage value, and the grid voltage is not greater than the first set voltage value, the first duty cycle is used to generate a driving pulse signal for the step-down circuit of the hydrogen production power supply; The second set voltage value is equal to the DC bus voltage drop threshold value plus the DC bus voltage drop callback bias value, and the first set voltage value is equal to the grid voltage drop threshold value plus the grid voltage drop callback bias value.

7. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 1, characterized in that: When the grid voltage recovers to above the first set voltage value, a third duty cycle is used to generate a driving pulse signal for the step-down circuit of the hydrogen production power supply; The third duty cycle is calculated based on the deviation between the given value of the output current of the step-down circuit and the real-time value of the output current, and the first set voltage value is equal to the grid voltage drop threshold value plus the grid voltage drop callback bias value.

8. The method for controlling low voltage ride-through of a hydrogen production power supply according to claim 1, characterized in that: A dual closed-loop control strategy of a voltage outer loop and a current inner loop with DC power feedforward control is adopted to control the rectifier circuit of the hydrogen production power supply, wherein the DC power feedforward control refers to calculating the DC power feedforward value according to the electrolyzer power value and the positive sequence active component of the grid voltage, and using the DC power feedforward value to calculate the active current setting value of the current inner loop.

9. A low voltage ride-through control device for a hydrogen production power source, the control device comprising a processor, a memory and a computer program stored in the memory, characterized in that: The processor is used to execute the computer program to implement the low voltage ride-through control method for a hydrogen production power source as described in any one of claims 1 to 8.

10. A hydrogen production power supply, comprising a rectifier circuit, a step-down circuit and a control unit, wherein the input end of the rectifier circuit is used to connect to a power grid, the output end of the rectifier circuit is connected to the input end of the step-down circuit through a DC bus, the output end of the step-down circuit is used to connect to an electrolyzer of a hydrogen production device, and the control unit controls the connection between the rectifier circuit and the step-down circuit, characterized in that: The control unit is used to implement the low voltage ride-through control method for a hydrogen production power source as described in any one of claims 1 to 8.

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