Two-stage hydrogen production converter and control method and device thereof

Abstract

The invention relates to the technical field of hydrogen production power supplies, and discloses a two-stage hydrogen production converter and a control method and device thereof.The two-stage hydrogen production converter is characterized in that the alternating current end of a three-level voltage source converter is connected with an alternating current power supply, and the direct current end of the three-level voltage source converter is connected with the input end of a DC-DC circuit; the three-level voltage source converter is used for converting alternating current into direct current; the output end of the DC-DC circuit is connected with a load, and the DC-DC circuit is used for reducing the voltage of the direct current. According to the three-level voltage source converter, the rectification function from alternating current electric energy to direct current electric energy is achieved, and the functions of reducing direct current output voltage and increasing the direct current output voltage are achieved after the three-level voltage source converter is connected with the DC-DC circuit in series. The three-level voltage source converter controls the direct-current output voltage and alternating-current reactive power of the rectifier through phase control over trigger pulses, the DC-DC circuit can eliminate output current ripples and effectively reduce the switching frequency and the filtering inductance at the same time, and then the size and the weight of the whole hydrogen production converter are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production power supply, and in particular to a two-stage hydrogen production converter and a control method and device thereof. Background Art

[0002] With the rapid development of China's economy, the traditional energy system dominated by fossil energy is facing the development dilemma of resource depletion and environmental pollution. Energy transformation aimed at developing renewable energy, reducing the use of traditional fossil energy and reducing carbon emissions is an effective way to break the deadlock. Clean fuel hydrogen has the advantages of high efficiency and pollution-free. As a high-quality secondary energy source, it has great application potential in energy storage and utilization. The development of clean energy hydrogen production technology such as wind and light can not only alleviate the impact of intermittent new energy power generation, but also greatly reduce the cost of hydrogen production, providing power for my country to achieve the goals of carbon peak and carbon neutrality. As a key device for connecting the electrolyzer to the power grid, the selection and design of high-power hydrogen production converters are particularly important. At present, the traditional single-stage hydrogen production power supply is used.

[0003] The traditional single-stage hydrogen production power supply has the problems of large DC output ripple, inability to simultaneously control the harmonic content of the AC and DC sides, and large requirements for AC reactive compensation devices, which makes it difficult to meet the use requirements of low ripple and high power hydrogen production scenarios. Therefore, it is particularly important to study the two-stage hydrogen production converter topology with low voltage and high current, high efficiency, low current ripple, and the ability to simultaneously control the DC and AC harmonic content. Summary of the invention

[0004] In view of this, the present invention provides a two-stage hydrogen production converter and a control method and device thereof to overcome the problems of high ripple output of hydrogen production power supply, inability to simultaneously control harmonics on both DC and AC sides, and low voltage transformation ratio in the prior art.

[0005] In a first aspect, the present invention provides a two-stage hydrogen production converter, comprising: a three-level voltage source converter and a DC-DC circuit, wherein the AC end of the three-level voltage source converter is connected to an AC power source, the DC end of the three-level voltage source converter is connected to an input end of the DC-DC circuit, and the three-level voltage source converter is used to convert AC power into DC power; the output end of the DC-DC circuit is connected to a load, and the DC-DC circuit is used to step down the DC power.

[0006] The three-level voltage source converter of the present invention realizes the rectification function of AC power to DC power, and realizes the function of reducing the DC output voltage and increasing the DC output voltage after being connected in series with the DC-DC circuit. The three-level voltage source converter controls the DC output voltage and AC reactive power of the rectifier by controlling the phase of the trigger pulse. The DC-DC circuit can effectively reduce the switching frequency and filter inductance while eliminating the output current ripple, thereby reducing the volume and weight of the entire hydrogen production converter.

[0007] In an optional embodiment, a three-level voltage source converter includes: three load impedances, three AC inductors, a first DC capacitor, a second DC capacitor, three bridge arm circuits and three clamping circuits, wherein the first end of each bridge arm circuit is connected to the first end of the first DC capacitor and the positive input end of the DC-DC circuit, the second end of each bridge arm circuit is connected to the second end of the second DC capacitor and the negative input end of the DC-DC circuit, and the midpoint of each bridge arm circuit is connected to one phase of the AC power supply through an AC inductor and a load impedance in sequence; the first end of each clamping circuit is connected to the midpoint of the upper half bridge arm of a bridge arm circuit, and the second end of each clamping circuit is connected to the midpoint of the lower half bridge arm of the corresponding bridge arm circuit; the second end of the first DC capacitor is respectively connected to the first end of the second DC capacitor and the midpoint of each clamping circuit and then grounded.

[0008] In an optional embodiment, each bridge arm circuit includes: a first main switch device, a second main switch device, a third main switch device, a fourth main switch device, and four freewheeling diodes, wherein the first end of the first main switch device is connected to the first end of the first DC capacitor and the positive input end of the DC-DC circuit, and the second end of the first main switch device is connected to the first end of the second main switch device and the first end of a clamping circuit; the second end of the second main switch device is connected to one phase of the AC power supply through an AC inductor and a load impedance in sequence; the first end of the third main switch device is connected to the second end of the second main switch device, and the second end of the third main switch device is connected to the first end of the fourth main switch device; the second end of the fourth main switch device is connected to the second end of the second DC capacitor and the negative input end of the DC-DC circuit; the first main switch device, the second main switch device, the third main switch device, and the fourth main switch device are all connected in reverse parallel with a freewheeling diode.

[0009] In an optional embodiment, each clamping circuit includes: a first clamping diode and a second clamping diode, wherein the cathode of the first clamping diode is connected to the second end of the first main switching device, the anode of the first clamping diode is connected to the cathode of the second clamping diode and the second end of the first DC capacitor; and the anode of the second clamping diode is connected to the second end of the third main switching device.

[0010] In an optional embodiment, the DC-DC circuit is a three-phase stacked interleaved parallel Buck circuit, which includes: three step-down branches and a support capacitor, wherein the first end of each step-down branch is connected to the positive DC end of the three-level voltage source converter, the second end of each step-down branch is connected to the first end of the support capacitor, and the third end of each step-down branch is connected to the negative DC end of the three-level voltage source converter and the second end of the support capacitor; the two ends of the support capacitor are connected to the load.

[0011] In an optional embodiment, each step-down branch includes: a controllable switch, a diode, and an energy storage inductor, wherein the first end of the controllable switch is connected to the positive DC end of the three-level voltage source converter, the second end of the controllable switch is connected to the cathode of the diode and the first end of the energy storage inductor; the second end of the energy storage inductor is connected to the first end of the support capacitor; the anode of the diode is connected to the negative DC end of the three-level voltage source converter and the second end of the support capacitor.

[0012] In a second aspect, the present invention provides a control method for a two-stage hydrogen production converter. The two-stage hydrogen production converter is based on the first aspect and its optional implementation mode, and the control method includes: based on a constant DC voltage control method, current decoupling the three-level voltage source converter to obtain a d-axis component and a q-axis component of a sinusoidal reference fundamental voltage, and obtaining a trigger pulse of the three-level voltage source converter according to a phase signal of an AC power supply, the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage; based on the output reference voltage and the output voltage of a three-phase stacked interleaved parallel Buck circuit, double closed-loop controlling the three-phase stacked interleaved parallel Buck circuit to obtain a three-phase DC voltage reference value, and based on the three-phase DC voltage reference value, using phase shift control to obtain a trigger pulse of the three-phase stacked interleaved parallel Buck circuit.

[0013] In an optional embodiment, based on the constant DC voltage control method, the process of current decoupling the three-level voltage source converter includes: performing PI control and current limiting on the difference between the DC voltage command and the DC voltage of the three-level voltage source converter to obtain a d-axis reference current; decoupling the three-level voltage source converter current according to the d-axis reference current, the q-axis reference current, the d-axis AC power supply current, the q-axis AC power supply current, the d-axis AC power supply voltage, and the q-axis AC power supply voltage to obtain the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage.

[0014] In an optional embodiment, the process of obtaining a three-phase DC voltage reference value includes: performing PI control on the difference between the output reference voltage and the output voltage of the three-phase stacked interlaced parallel Buck circuit to obtain a DC current reference value; using the ratio of the DC current reference value to the number of phases as the DC current reference value of each phase; performing PI control on the difference between the DC current reference value of each phase and the energy storage inductor current of each phase step-down branch to obtain a three-phase DC voltage reference value.

[0015] In an optional embodiment, the process of obtaining a trigger pulse of a three-phase stacked interleaved parallel Buck circuit using phase shift control includes: using a one-phase triangular wave as a reference triangular wave, and using 120° and 240° of the reference triangular wave as the triangular waves of the other two phases respectively; based on the three-phase DC voltage reference value and the triangular wave of each phase, a preset modulation method is used to obtain the trigger pulse of the three-phase stacked interleaved parallel Buck circuit.

[0016] In a third aspect, the present invention provides a control device for a two-stage hydrogen production converter. The two-stage hydrogen production converter is based on the first aspect and its optional implementation mode, and the device includes: a first control module, which is used to perform current decoupling on a three-level voltage source converter based on a constant DC voltage control method to obtain a d-axis component and a q-axis component of a sinusoidal reference fundamental voltage, and obtain a trigger pulse of the three-level voltage source converter according to a phase signal of an AC power supply, the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage; and a second control module, which is used to perform double closed-loop control on a three-phase stacked interleaved parallel Buck circuit based on an output reference voltage and an output voltage of the three-phase stacked interleaved parallel Buck circuit to obtain a three-phase DC voltage reference value, and based on the three-phase DC voltage reference value, obtain a trigger pulse of the three-phase stacked interleaved parallel Buck circuit by using phase shift control.

[0017] In a fourth aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the control method of the two-stage hydrogen production converter according to the second aspect or any corresponding embodiment thereof by executing the computer instructions.

[0018] In a fifth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the control method for a two-stage hydrogen production converter according to the second aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a composition diagram of a two-stage hydrogen production converter according to an embodiment of the present invention;

[0021] Figure 2 is a specific circuit structure diagram of a two-stage hydrogen production converter according to an embodiment of the present invention;

[0022] Figure 3 is a flow chart of a control method for a two-stage hydrogen production converter according to an embodiment of the present invention;

[0023] Figure 4 is a control block diagram of a constant DC voltage control according to an embodiment of the present invention;

[0024] Figure 5 is a control block diagram of a three-level voltage source converter according to an embodiment of the present invention;

[0025] Figure 6 is a control block diagram of a three-phase stacked interleaved parallel Buck circuit according to an embodiment of the present invention;

[0026] Figure 7 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0028] In this embodiment, a two-stage hydrogen production converter is provided. Figure 1 As shown, it includes: a three-level voltage source converter and a DC-DC circuit.

[0029] like Figure 1As shown, the AC end of the three-level voltage source converter is connected to the AC power supply, the DC end of the three-level voltage source converter is connected to the input end of the DC-DC circuit, and the three-level voltage source converter is used to convert AC power into DC power. The output end of the DC-DC circuit is connected to the load, and the DC-DC circuit is used to step down the DC power.

[0030] Specifically, the three-level voltage source converter realizes the rectification function of AC power to DC power, and after being connected in series with the DC-DC circuit, it realizes the function of reducing the DC output voltage and increasing the DC output voltage. The three-level voltage source converter controls the DC output voltage V of the rectifier by controlling the phase of the trigger pulse. dc and AC reactive power Q ac The DC-DC circuit can effectively reduce the switching frequency and filter inductance while eliminating the output current ripple, thereby reducing the volume and weight of the entire hydrogen production converter.

[0031] In an optional implementation, the three-level voltage source converter includes: three load impedances, three AC inductors, a first DC capacitor, a second DC capacitor, three bridge arm circuits and three clamping circuits.

[0032] Specifically, the first end of each bridge arm circuit is connected to the first end of the first DC capacitor and the positive input end of the DC-DC circuit, the second end of each bridge arm circuit is connected to the second end of the second DC capacitor and the negative input end of the DC-DC circuit, and the midpoint of each bridge arm circuit is connected to one phase of the AC power supply through an AC inductor and a load impedance in sequence; the first end of each clamp circuit is connected to the midpoint of the upper half of a bridge arm circuit, and the second end of each clamp circuit is connected to the midpoint of the lower half of the corresponding bridge arm circuit; the second end of the first DC capacitor is respectively connected to the first end of the second DC capacitor and the midpoint of each clamp circuit and then grounded.

[0033] Specifically, the first ends of the three bridge arm circuits are connected to one point, the second ends of the three bridge arm circuits are connected to one point to form a three-phase full-bridge structure, and each bridge arm circuit is connected to a clamping circuit. Optionally, each bridge arm circuit includes: a first main switch device, a second main switch device, a third main switch device, a fourth main switch device, and four freewheeling diodes, wherein the first end of the first main switch device is connected to the first end of the first DC capacitor and the positive input end of the DC-DC circuit, the second end of the first main switch device is connected to the first end of the second main switch device and the first end of a clamping circuit; the second end of the second main switch device is connected to one phase of the AC power supply through an AC inductor and a load impedance in sequence; the first end of the third main switch device is connected to the second end of the second main switch device, and the second end of the third main switch device is connected to the first end of the fourth main switch device; the second end of the fourth main switch device is connected to the second end of the second DC capacitor and the negative input end of the DC-DC circuit; the first main switch device, the second main switch device, the third main switch device, and the fourth main switch device are all connected to a freewheeling diode in reverse parallel.

[0034] Optionally, each clamping circuit includes: a first clamping diode and a second clamping diode, wherein the cathode of the first clamping diode is connected to the second end of the first main switching device, the anode of the first clamping diode is connected to the cathode of the second clamping diode and the second end of the first DC capacitor; and the anode of the second clamping diode is connected to the second end of the third main switching device.

[0035] Exemplarily, the three-level voltage source converter topology is as follows: Figure 2 As shown, the impedance R a ~R c are load impedance, inductance L a ~L c are AC inductors, capacitor C1 is the first DC capacitor, capacitor C2 is the second DC capacitor, each bridge arm circuit includes main switch devices VT1~VT4, and each main switch device is connected in reverse parallel with a freewheeling diode, each clamping circuit includes clamping diodes VD1 and VD2, and the DC side voltage is U dc , the voltage of the two DC capacitors is U dc / 2.

[0036] Figure 2 In the figure, the AC side of the three-level voltage source converter is connected to the AC power supply through the load impedance. The AC inductance includes the inductance of the phase reactor, the leakage inductance of the transformer and the internal inductance of the AC power supply. The AC side resistance includes the resistance in the phase reactor and the internal resistance of the AC source. The load neutral point is recorded as O.

[0037] Figure 2In the three-level voltage source converter, the output of each phase depends only on the DC side voltage and the switching state of the power switch device, and has nothing to do with the direction of the load current. When VT1 and VT2 of each phase are turned on at the same time, the level of the output terminal a to the neutral point O is +U dc / 2; when VT2 and VT3 are turned on at the same time, the output terminal is connected to point O, so its level is 0; when VT3 and VT4 are turned on at the same time, the level of the output point is -U dc / 2, so each phase bridge arm can output 3 level states. The conversion circuit composed of three-phase bridge arms is called a diode clamped three-level rectifier.

[0038] In an optional embodiment, the DC-DC circuit is a three-phase stacked interleaved parallel Buck circuit, which includes: three step-down branches and a support capacitor, wherein the first end of each step-down branch is connected to the positive DC end of the three-level voltage source converter, the second end of each step-down branch is connected to the first end of the support capacitor, and the third end of each step-down branch is connected to the negative DC end of the three-level voltage source converter and the second end of the support capacitor; the two ends of the support capacitor are connected to the load.

[0039] Optionally, each step-down branch includes: a controllable switch, a diode, and an energy storage inductor, wherein the first end of the controllable switch is connected to the positive DC end of the three-level voltage source converter, the second end of the controllable switch is connected to the cathode of the diode and the first end of the energy storage inductor; the second end of the energy storage inductor is connected to the first end of the support capacitor. The anode of the diode is connected to the negative DC end of the three-level voltage source converter and the second end of the support capacitor.

[0040] For example, a three-phase stacked interleaved parallel Buck circuit is as follows: Figure 2 As shown, switches T1-T3 are controllable switches of each step-down branch, diodes D1-D3 are diodes of each step-down branch, inductors L1-L3 are energy storage inductors of each step-down branch, and C r For the support capacitor.

[0041] Figure 3 In the circuit, the switch tubes of each branch are complementary, and T1, T2 and T3 are turned on successively with an interval of 120°. dc and V o are the input and output voltages of the converter respectively; I dcmain is the main branch output current. Let’s assume that the compensation branch filter inductor L AX And the main branch N phase inductance L1, L2...L N The inductance values ​​are the same, that is, L1=L2=......=L N =L ax= L. In this embodiment, the three-phase staggered parallel Buck converter with branch phase number N=3 and duty cycle of 0.5 is subjected to working modal analysis, and the analysis of other duty cycles is similar.

[0042] In this embodiment, a control method for a two-stage hydrogen production converter is provided. The two-stage hydrogen production converter based on the above embodiment and its optional implementation methods is as follows: Figure 3 As shown, the control method includes:

[0043] Step S1: Based on the constant DC voltage control method, current decoupling is performed on the three-level voltage source converter to obtain the d-axis component and q-axis component of the sinusoidal reference fundamental voltage, and a trigger pulse of the three-level voltage source converter is obtained according to the phase signal of the AC power supply, the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage.

[0044] Optionally, based on the constant DC voltage control method, the process of current decoupling the three-level voltage source converter includes: Figure 4 As shown, for the DC voltage command (u dref ) and the DC voltage (u dc ) to perform PI control and current limiting to obtain the d-axis reference current (i dref );like Figure 5 As shown, according to the d-axis reference current (i dref ), q-axis reference current (i qref ), d-axis AC power supply current (i d ), q-axis AC power supply current (i q ), d-axis AC power supply voltage (u sd ), q-axis AC power supply voltage (u sq ), decouple the current of the three-level voltage source converter and obtain the d-axis component of the sinusoidal reference fundamental voltage (u dref ) and q-axis component (u qref ).

[0045] refer to Figure 4 , Figure 5 According to Kirchhoff's voltage-current law, the differential equations of the AC system, DC side current and power of the front-stage three-level VSC rectifier are as follows (1).

[0046]

[0047] Among them, i a 、i b 、i c are the AC inductor currents of phase A, phase B, and phase C respectively; u s is the AC power supply voltage; K is; u d is the DC output voltage; R is the load resistance; δ is the AC phase angle; uc1 is the first DC capacitor voltage; u c2 is the second DC capacitor voltage; S ap , S bp , S cp are the upper bridge arm switching functions of the three phases a, b, and c respectively; i o is the VSC output current; P d Power delivered to the VSC.

[0048] The active power injected into the rectifier is defined as:

[0049]

[0050] By performing Park transformation and rearrangement on the above equations (1) and (2), the mathematical model of the synchronous rotating dq axis coordinate system of the three-level voltage source converter can be obtained as follows: equation (3).

[0051]

[0052] Among them, i sd is the d-axis AC power supply current; i sq is the q-axis AC power supply current; u q is the d-axis AC power supply voltage.

[0053] Therefore, according to the above analysis, the structure diagram of the rectifier system containing the current decoupling controller based on the synchronous rotating coordinate system can be obtained, as shown in Figure 5 As shown in the figure, the current controller outputs u dref and u qref They correspond to the d-axis and q-axis components of the sinusoidal reference fundamental voltage expected to be output by the converter. According to the voltage reference component and the AC power phase signal, the trigger pulse of each bridge arm can be obtained through pulse width modulation. Figure 5 The current reference value i in sdref 、i sqref The inner loop current control adopts current feedback and grid voltage feedforward to improve the tracking response characteristics of the current controller.

[0054] When the active power on both sides of the rectifier is unbalanced, it will cause fluctuations in the DC voltage. At this time, the active current will charge (or discharge) the DC side capacitor until the DC voltage stabilizes at the set value. Therefore, for a rectifier controlled by a fixed DC voltage, it is equivalent to an active balance node. Figure 4 The figure shows a constant DC voltage controller. The DC voltage and DC voltage command deviation are adjusted by PI as the reference value of active current i sdref .

[0055] Step S2: Based on the output reference voltage and the output voltage of the three-phase stacked interleaved parallel Buck circuit, the three-phase stacked interleaved parallel Buck circuit is double-closed-loop controlled to obtain a three-phase DC voltage reference value, and based on the three-phase DC voltage reference value, a phase shift control is used to obtain a trigger pulse of the three-phase stacked interleaved parallel Buck circuit.

[0056] Optionally, the process of obtaining a three-phase DC voltage reference value includes: performing PI control on the difference between the output reference voltage and the output voltage of the three-phase stacked interlaced parallel Buck circuit to obtain a DC current reference value; using the ratio of the DC current reference value to the number of phases as the DC current reference value of each phase, performing PI control on the difference between the DC current reference value of each phase and the energy storage inductor current of each phase step-down branch to obtain a three-phase DC voltage reference value.

[0057] According to Kirchhoff's voltage-current law, the inductor current ripple of each phase of the subsequent three-phase stacked interleaved parallel Buck circuit can be obtained as shown in formula (4).

[0058]

[0059] Among them, Δi1 is the DC ripple output by the first-phase Buck converter; Δi2 is the DC ripple output by the second-phase Buck converter; Δi3 is the DC ripple output by the third-phase Buck converter; ΔI AX is the total DC ripple output by the three-phase Buck converter; t on is the conduction time of the Buck converter; D is the duty cycle of the Buck converter; V dco is the Buck converter output voltage; V CAX is the Buck converter input voltage; L AX is the inductance of the Buck converter; f s is the Buck converter switching frequency.

[0060] The total output current ripple ΔI of the three-phase stacked interleaved parallel Buck circuit is obtained by linear superposition dcmain As shown in formula (5).

[0061]

[0062] In an optional embodiment, the process of obtaining a trigger pulse of a three-phase stacked interleaved parallel Buck circuit using phase shift control includes: using a one-phase triangular wave as a reference triangular wave, and using 120° and 240° of the reference triangular wave as the triangular waves of the other two phases respectively; based on the three-phase DC voltage reference value and the triangular wave of each phase, a preset modulation method is used to obtain the trigger pulse of the three-phase stacked interleaved parallel Buck circuit.

[0063] Specifically, the stable output voltage of the three-phase stacked interleaved parallel Buck circuit is the prerequisite for current sharing control. Only when the output voltage can be stabilized at the target voltage, it is meaningful to control the current sharing of the three-phase branches. Figure 6 As shown, the voltage loop is used as the outer control loop to stabilize the converter output voltage, and the DC bus voltage V o With a given reference voltage V ref Compare and get a voltage error signal V e ; After PI adjustment, the reference current I is obtained ref , the reference current is divided by the number of phases and compared with the inductive currents I1, I2, and I3 of the inductive elements at the input end of each phase. In this way, three independent current loops with the same structure are connected in parallel to form an inner control loop. After PI regulation, it is input into the carrier phase shift pulse width modulation. With the first phase triangle wave as a reference, the second phase is shifted by 120° and the third phase is shifted by 240° to achieve accurate phase shift of each phase drive signal and generate trigger signals for each switch device T1, T2, and T3 of the main branch.

[0064] A mathematical model is established for the average rate of change of the inductor current and capacitor voltage during the switching period. After Laplace transform and linearization processing, the transfer functions of the ideal continuous conduction mode are obtained through small signal modeling as shown in Formula (6).

[0065]

[0066] In this embodiment, the above simulation model is built in PSCAD / EMTDC. The new hydrogen production power supply has an average output DC voltage of 5.35kV, an output voltage peak-to-peak value of 0.25kV, and a voltage ripple ratio of 4.6%; the average output DC current is 42.1kA, the output current peak-to-peak value is 2.1kA, and the current ripple ratio is 5.0%. By analyzing and comparing the voltage and current ripple content of the traditional hydrogen production power supply and the new two-stage hydrogen production power supply, it can be obtained that the new two-stage hydrogen production power supply has a larger output current and lower DC ripple, which is suitable for electrolytic hydrogen production scenarios. The new two-stage hydrogen production power supply can not only improve the efficiency and purity of the hydrogen production power supply, and ensure the safe and stable operation of the hydrogen production system, but also the larger output current can increase the amount of hydrogen produced per unit time and increase economic benefits.

[0067] In this embodiment, a control device for a two-stage hydrogen production converter is also provided, which is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0068] In this embodiment, a control device for a two-stage hydrogen production converter is provided. The two-stage hydrogen production converter based on the above embodiment and any optional implementation manner thereof includes:

[0069] The first control module is used to perform current decoupling on the three-level voltage source converter based on a constant DC voltage control method to obtain a d-axis component and a q-axis component of a sinusoidal reference fundamental voltage, and obtain a trigger pulse of the three-level voltage source converter according to a phase signal of an AC power source and the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage;

[0070] The second control module is used to obtain a three-phase DC voltage reference value by performing double closed-loop control on the three-phase stacked interleaved parallel Buck circuit based on the output reference voltage and the output voltage of the three-phase stacked interleaved parallel Buck circuit, and based on the three-phase DC voltage reference value, obtain a trigger pulse of the three-phase stacked interleaved parallel Buck circuit by using phase shift control.

[0071] The control device of the two-stage hydrogen production converter in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0072] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0073] An embodiment of the present invention further provides a computer device having the control device of the above-mentioned two-stage hydrogen production converter.

[0074] See also Figure 7 , Figure 7 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Figure 7 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 7 A processor 10 is taken as an example.

[0075] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0076] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0077] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created by the use of a computer device based on the presentation of a small program landing page, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0078] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0079] The computer device further comprises a communication interface 30 for the computer device to communicate with other devices or a communication network.

[0080] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0081] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A two-stage hydrogen production converter, characterized in that: include: A three-level voltage source converter and a DC-DC circuit, wherein: The AC end of the three-level voltage source converter is connected to an AC power source, the DC end of the three-level voltage source converter is connected to an input end of the DC-DC circuit, and the three-level voltage source converter is used to convert AC power into DC power; The output end of the DC-DC circuit is connected to a load, and the DC-DC circuit is used to reduce the voltage of the direct current.

2. The two-stage hydrogen production converter according to claim 1, characterized in that: The three-level voltage source converter comprises: three load impedances, three AC inductors, a first DC capacitor, a second DC capacitor, three bridge arm circuits and three clamping circuits, wherein: The first end of each of the bridge arm circuits is connected to the first end of the first DC capacitor and the positive input end of the DC-DC circuit, the second end of each of the bridge arm circuits is connected to the second end of the second DC capacitor and the negative input end of the DC-DC circuit, and the midpoint of each of the bridge arm circuits is connected to one phase of the AC power supply via an AC inductor and a load impedance in sequence; The first end of each clamp circuit is connected to the midpoint of the upper half bridge arm of a bridge arm circuit, and the second end of each clamp circuit is connected to the midpoint of the lower half bridge arm of the corresponding bridge arm circuit; The second end of the first DC capacitor is respectively connected to the first end of the second DC capacitor and the midpoint of each clamping circuit and then grounded.

3. The two-stage hydrogen production converter according to claim 2, characterized in that: Each of the bridge arm circuits comprises: a first main switch device, a second main switch device, a third main switch device, a fourth main switch device, and four freewheeling diodes, wherein: The first end of the first main switch device is connected to the first end of the first DC capacitor and the positive input end of the DC-DC circuit, and the second end of the first main switch device is connected to the first end of the second main switch device and the first end of a clamping circuit; The second end of the second main switch device is connected to a phase of the AC power source through an AC inductor and a load impedance in sequence; The first end of the third main switch device is connected to the second end of the second main switch device, and the second end of the third main switch device is connected to the first end of the fourth main switch device; The second end of the fourth main switch device is connected to the second end of the second DC capacitor and the negative input end of the DC-DC circuit; The first main switch device, the second main switch device, the third main switch device, and the fourth main switch device are all connected in reverse parallel with a freewheeling diode.

4. The two-stage hydrogen production converter according to claim 3, characterized in that: Each of the clamping circuits comprises: a first clamping diode and a second clamping diode, wherein: The cathode of the first clamping diode is connected to the second end of the first main switch device, and the anode of the first clamping diode is connected to the cathode of the second clamping diode and the second end of the first DC capacitor; An anode of the second clamping diode is connected to the second end of the third main switching device.

5. The two-stage hydrogen production converter according to claim 3, characterized in that: The DC-DC circuit is a three-phase stacked interleaved parallel Buck circuit, which includes: three step-down branches and a support capacitor, wherein: The first end of each of the step-down branches is connected to the positive DC end of the three-level voltage source converter, the second end of each of the step-down branches is connected to the first end of the support capacitor, and the third end of each of the step-down branches is connected to the negative DC end of the three-level voltage source converter and the second end of the support capacitor; Two ends of the support capacitor are connected to the load.

6. The two-stage hydrogen production converter according to claim 5, characterized in that: Each of the voltage-reducing branches includes: a controllable switch, a diode, and an energy storage inductor, wherein: The first end of the controllable switch is connected to the positive DC end of the three-level voltage source converter, and the second end of the controllable switch is connected to the cathode of the diode and the first end of the energy storage inductor; The second end of the energy storage inductor is connected to the first end of the support capacitor; The anode of the diode is connected to the negative DC terminal of the three-level voltage source converter and the second end of the support capacitor.

7. A control method for a two-stage hydrogen production converter, characterized in that: Based on the two-stage hydrogen production converter according to any one of claims 3 to 6, the control method comprises: Based on the constant DC voltage control method, current decoupling is performed on the three-level voltage source converter to obtain the d-axis component and q-axis component of the sinusoidal reference fundamental voltage, and a trigger pulse of the three-level voltage source converter is obtained according to the phase signal of the AC power supply and the d-axis component and q-axis component of the sinusoidal reference fundamental voltage; Based on the output reference voltage and the output voltage of the three-phase stacked interleaved parallel Buck circuit, the three-phase stacked interleaved parallel Buck circuit is double-closed-loop controlled to obtain a three-phase DC voltage reference value, and based on the three-phase DC voltage reference value, phase shift control is used to obtain a trigger pulse of the three-phase stacked interleaved parallel Buck circuit.

8. The control method of the two-stage hydrogen production converter according to claim 7, characterized in that: The process of current decoupling of a three-level voltage source converter based on a constant DC voltage control method includes: Performing PI control and current limiting on the difference between the DC voltage command and the DC voltage of the three-level voltage source converter to obtain a d-axis reference current; According to the d-axis reference current, the q-axis reference current, the d-axis AC power supply current, the q-axis AC power supply current, the d-axis AC power supply voltage, and the q-axis AC power supply voltage, the three-level voltage source converter current is decoupled to obtain the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage.

9. The control method of the two-stage hydrogen production converter according to claim 7, characterized in that: The process of obtaining the three-phase DC voltage reference value includes: The difference between the output reference voltage and the output voltage of the three-phase stacked interlaced parallel Buck circuit is subjected to PI control to obtain a DC current reference value; Using the ratio of the DC current reference value to the number of phases as a DC current reference value for each phase; The difference between the DC current reference value of each phase and the energy storage inductor current of each phase step-down branch is controlled by PI to obtain a three-phase DC voltage reference value.

10. The control method of the two-stage hydrogen production converter according to claim 7, characterized in that: The process of obtaining the trigger pulse of the three-phase stacked interleaved parallel Buck circuit by phase shift control includes: A single-phase triangle wave is used as a reference triangle wave, and 120° and 240° of the reference triangle wave are used as triangle waves of the other two phases respectively; Based on the three-phase DC voltage reference value and the triangular wave of each phase, a trigger pulse of the three-phase stacked interleaved parallel Buck circuit is obtained by using a preset modulation method.

11. A control device for a two-stage hydrogen production converter, characterized in that: Based on the two-stage hydrogen production converter according to any one of claims 3 to 6, the device comprises: A first control module is used to perform current decoupling on the three-level voltage source converter based on a constant DC voltage control method to obtain a d-axis component and a q-axis component of a sinusoidal reference fundamental voltage, and obtain a trigger pulse of the three-level voltage source converter according to a phase signal of an AC power source and the d-axis component and the q-axis component of the sinusoidal reference fundamental voltage; The second control module is used to obtain a three-phase DC voltage reference value by performing double closed-loop control on the three-phase stacked interleaved parallel Buck circuit based on the output reference voltage and the output voltage of the three-phase stacked interleaved parallel Buck circuit, and based on the three-phase DC voltage reference value, obtain a trigger pulse of the three-phase stacked interleaved parallel Buck circuit by using phase shift control.

12. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the control method of the two-stage hydrogen production converter according to any one of claims 7 to 10 by executing the computer instructions.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the control method of the two-stage hydrogen production converter according to any one of claims 7 to 10.

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