A large-capacity hydrogen production power supply suitable for medium-voltage AC power grid and a control method thereof

Abstract

The present invention discloses a large-capacity hydrogen production power supply suitable for a medium-voltage AC power grid and a control method thereof, and belongs to the field of high-power power electronics technology. The power supply includes a multi-pulse rectifier circuit, a DC transformer module, a hydrogen production electrolyzer, and a control module. The multi-pulse rectifier circuit rectifies the medium-voltage AC power into a medium-voltage DC voltage, and suppresses the DC voltage pulsation and the harmonic current injected into the power grid. The DC transformer module adopts an input series output parallel scheme to convert the medium-voltage DC voltage into a low-voltage DC voltage, which meets the low-voltage and high-current power supply requirements of the hydrogen production electrolyzer. The control method is implemented by a control module, which includes a three-closed-loop decoupling control algorithm and a protection algorithm, and its current inner loop improves the dynamic response. The present invention has the advantages of small input current ripple, small output voltage ripple, low cost, high reliability, and high control accuracy. The hydrogen production power supply of the present invention is suitable for a medium-voltage AC power grid and has a strong practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of high-power power electronics, and in particular to a large-capacity hydrogen production power supply suitable for a medium-voltage alternating current power grid and a control method thereof. Background Art

[0002] Hydrogen energy is a clean energy with high calorific value and no pollution. Vigorously developing the hydrogen production and energy storage industry is in line with the needs of improving the flexibility of the power system, enhancing the ability to absorb new energy, and reducing the abandonment of wind and solar power.

[0003] At present, it is often difficult to achieve a balance between cost and performance in the field of high-power hydrogen production power supply. Traditional hydrogen production power supplies often use rectifiers composed of transformers and thyristors. They have large capacity but have the disadvantages of serious harmonic pollution, low power factor, slow response, and low efficiency. They are easy to affect the power quality and stability of the power grid. If the thyristor rectifier fails, it may even make the system unable to work. If a PWM rectification scheme is adopted, although it can improve the power factor, reduce harmonic pollution, and increase the response speed, its capacity is small and it is not suitable for large-capacity hydrogen production power supply. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a large-capacity hydrogen production power supply suitable for a medium-voltage AC power grid and a control method thereof, so as to solve the problems of high input voltage, large electrolysis capacity and high power quality requirements in the prior art when producing hydrogen from renewable energy.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The present invention provides a large-capacity hydrogen production power supply suitable for a medium-voltage AC power grid, comprising: a multi-pulse rectifier circuit, a DC transformer module, a hydrogen production electrolyzer and a control module.

[0007] The multi-pulse rectifier current is located at the starting end of the hydrogen production equipment and connected to the medium-voltage power grid. It is composed of a multi-pulse phase-shifting rectifier transformer and an uncontrolled rectifier circuit cascaded. The multi-pulse phase-shifting rectifier transformer is connected to the medium-voltage AC power grid and outputs a phase-shifting voltage. The number of its low-voltage side windings is m, and m groups of phase-shifting voltages with the same phase angle and phase difference of π / (3m) are generated. The medium-voltage power grid can be a 10KV or 35KV power grid; of course, it is not limited to the above description, and it depends on the actual situation, all within the scope of protection of this application. The multi-pulse rectifier transformer can be a 12-pulse rectifier transformer, an 18-pulse rectifier transformer, a 24-pulse rectifier transformer or other multi-pulse rectifier transformer. The uncontrolled rectifier circuit is a three-phase diode rectifier bridge, whose input end is connected to a multi-pulse phase-shift rectifier transformer. The number of diode rectifier bridges is the same as the number of windings on the low-voltage side of the multi-pulse phase-shift rectifier, which is m. Its output ends are connected in parallel to achieve the purpose of harmonic cancellation, forming a (6m) pulse rectifier circuit, which is connected to the subsequent DC transformer module. The uncontrolled rectifier circuit reduces the harmonic content of the output voltage by increasing the number of pulses of the output DC voltage. The use of uncontrolled devices also reduces costs, improves reliability, and does not require additional control circuits. Optionally, an additional passive filter can be installed at the input end of the uncontrolled rectifier circuit to improve filtering capabilities.

[0008] The DC transformer module adopts an input series and output parallel structure. The DC transformer input side is connected in series by k submodules, thereby reducing the voltage division burden of the switch device, reducing the withstand voltage requirements and voltage stress of the switch device, and the DC transformer output side is connected in parallel by k submodules to meet the high current requirements of the hydrogen production electrolyzer. The DC transformer submodules adopt one or more of the isolated DC converters such as DAB converter, CLLLC converter, phase-shifted full-bridge converter, LLC converter, etc., which realizes electrical isolation while also realizing voltage conversion with a higher voltage ratio.

[0009] The hydrogen production electrolyzer has an input end connected to the DC transformer module, and is powered by an input series and output parallel DC transformer to produce hydrogen by electrolysis.

[0010] The control module is composed of a sampling circuit, a DSP controller, and a driving circuit. The sampling circuit converts electrical quantities such as the capacitor voltage of each submodule on the input side of the DC transformer, the capacitor voltage on the output side of the DC transformer, and the output current of each submodule on the output side of the DC transformer into an analog signal quantity of 0-3.3V, and the analog signal quantity is further output to the ADC port of the DSP controller. The DSP controller is responsible for the implementation of the control algorithm and the protection algorithm. After calculating the duty cycle, it outputs the PWM signal to the driving circuit through the EPWM port. If the number of DC transformer submodules is large, the DSP controller can be appropriately expanded. The driving circuit adopts optical isolation or magnetic isolation to achieve electrical isolation, and realizes level conversion to drive the IGBT module.

[0011] Furthermore, the present invention also provides a control method for a large-capacity hydrogen production power supply suitable for a medium-voltage AC power grid as described in any one of the above, including a three-closed-loop decoupling control algorithm and an overcurrent protection algorithm for a DC transformer. The three-closed-loop control algorithm includes an input voltage grading loop, an output voltage loop, and an inner current loop. In order to avoid interference of the input voltage grading loop with the output voltage loop, the input voltage grading loop and the output voltage loop need to be decoupled. In the input voltage grading loop, the input voltage grading control signal dsn corresponding to the nth basic circuit unit is not directly obtained, but is obtained by adding the output signals of the first n-1 input voltage grading loops to achieve decoupling control, avoid the influence of the input voltage grading loop on the output voltage loop, and facilitate the design of control parameters for each loop. The protection algorithm includes overvoltage protection, overcurrent protection, short-circuit protection and other algorithms for protecting the DC transformer.

[0012] Beneficial effects of the present invention:

[0013] The hydrogen production power supply described in the present invention has a small output voltage ripple, good working conditions for the hydrogen production electrolyzer, high hydrogen production efficiency, a wide adjustment range for the output current, an output power of up to megawatt level, and little harmonic pollution to the power grid, which can save investment in harmonic control. The front-stage multi-pulse rectifier circuit of the hydrogen production power supply described in the present invention adopts uncontrolled devices, which reduces costs and improves reliability, and adopts phase-shifting rectification technology to reduce the harmonic current injected into the power grid and improve the quality of electric energy. The rear-stage DC transformer of the hydrogen production power supply described in the present invention adopts an isolated power supply solution, which has better control accuracy and high safety. It is suitable for high voltage ratio occasions and can simultaneously meet the requirements of high input voltage and low output voltage and large current. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings.

[0015] Figure 1 It is a structural schematic diagram of the rectifier device of the present invention;

[0016] Figure 2 is a schematic diagram of system topology of an embodiment of the present invention;

[0017] Figure 3 is a schematic diagram of system control of an embodiment of the present invention;

[0018] Figure 4 is a simulation waveform diagram of the front-stage rectifier circuit of an embodiment of the present invention;

[0019] Figure 5 It is a simulation waveform diagram of the rear-stage DC transformer of the embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following is a description of the specific implementation of the present invention in conjunction with the accompanying drawings and an embodiment of a hydrogen production power supply with a voltage level of 35kVAC / 346V DC and a capacity of 1MVA. Obviously, the described embodiment is only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, ordinary technicians in this field will not be Figure 1 All other embodiments obtained under the premise of creative work belong to the protection scope of the present invention. The embodiment uses PLECS software to simulate and verify the system.

[0021] like Figure 1 As shown, the present invention is composed of a multi-pulse phase-shifting rectifier transformer, an uncontrolled rectifier circuit, a DC transformer module, and a hydrogen production electrolyzer.

[0022] like Figure 2 As shown in FIG. 1 , the embodiment of the present invention adopts a solution of cascading a 24-pulse rectifier circuit and an ISOP-DAB DC transformer. The front-stage 24-pulse rectifier circuit in the hydrogen production power source converts the 35kV AC power into g Rectified to 4kV DC in The front-stage 24-pulse rectifier circuit is composed of two three-winding phase-shifting rectifier transformers and four three-phase uncontrolled rectifier circuits. The low-voltage side windings of each three-winding transformer use y-type and d-type windings respectively, and their line voltages form a phase difference of 30°. The high-voltage side windings of the two three-winding phase-shifting rectifier transformers use the extended triangle connection method, which produces a phase shift of +7.5° and -7.5° respectively, so that the line voltages of the four low-voltage side windings of the two three-winding phase-shifting rectifier transformers are u abc,1 ,u abc,2 ,u abc,3 ,u abc,4 The phases are 15° apart. The input sides of the four uncontrolled rectifier circuits are connected to the low-voltage windings of two three-winding phase-shifting transformers, and their output sides are connected in parallel to obtain a medium-voltage DC voltage u in , thus forming a 24-pulse rectifier circuit. in In this embodiment, a passive filter Z is installed after the uncontrolled rectifier. filter The ISOP-DAB DC transformer of this embodiment includes 6 DAB modules, so that each DAB only needs to bear a voltage of less than 1kV, and the parallel connection on the output side also enables the IGBT of each DAB to disperse the output current required for hydrogen production by electrolysis, thereby improving system safety. For a single DAB module, its isolation transformer ratio is n:1, L r The leakage inductance of its isolation transformer, R p Its parasitic resistance, C ois the output capacitor. The ISOP-DAB DC transformer converts 4kV DC power into 346V DC power to meet the low voltage and high current requirements of the hydrogen production power supply. The control module of the hydrogen production power supply includes a DSP controller, a drive circuit and a sampling circuit. The sampling circuit converts the electrical quantity of the DC transformer into an analog quantity of 0-3.3V and passes it to the ADC module of the DSP controller. After the ADC module of the DSP controller inputs the analog signal, it performs the operation of the three-closed-loop decoupling control algorithm. In the protection algorithm of the DC transformer, the command current in the current inner loop increases the limit value to prevent the output current from being too large and avoid IGBT overcurrent. At the same time, the input voltage and output voltage are detected to achieve overvoltage protection. The DSP controller updates the PWM duty cycle value in real time during each switching cycle and outputs a PWM signal to the drive circuit. The drive circuit electrically isolates the DSP controller from the DC transformer switching device, performs level conversion, and outputs a drive signal to drive the switching device in the DC transformer. In this embodiment, the hydrogen production electrolyzer uses a resistive load R L replace.

[0023] like Figure 3 As shown, the control scheme of the embodiment of the present invention adopts a three-closed-loop decoupling control strategy, including an input voltage equalization controller G ui , output voltage controller G uo , output current controller G i The three-loop control adds a current inner loop based on the traditional double-loop control strategy to improve dynamic response and prevent overcurrent. The control signal d sn By the previous d s1 ,d s2 …d sn-1 The output voltage loop and the input voltage loop jointly determine the output current reference value i*oj. In the current loop, i*oj is subtracted from its actual output current i oj by G. i Get the shift ratio d j , and then get its switching signal s through the phase shift unit 1 ,s 2 ,s 3 ,s 4 ,s 5 ,s 6 ,s 7 ,s 8 , and then drive the DAB module. In this embodiment, N=6, that is, there are 6 DAB modules to form the ISOP-DAB converter.

[0024] like Figure 4 As shown, in the embodiment of the present invention, the 24-pulse rectifier circuit converts the medium voltage AC voltage ug The rectifier output is a medium voltage DC voltage u in , through the passive filter Z filter After filtering, u in Contains a small ripple component. a1 ,u a2 ,u a3 ,u a4 ,u b1 ,u b2 ,u b3 ,u b4 ,u c1 ,u c2 ,u c3 ,u c4 It is the line voltage output by each phase-shifting rectifier transformer.

[0025] like Figure 5 As shown, in the embodiment of the present invention, the ISOP-DAB DC transformer converts the DC voltage u output by the front-stage rectifier circuit in Converted to the DC voltage u required for the hydrogen production electrolyzer o ,i out is the output current of the DC transformer. The ISOP-DAB DC transformer has a good dynamic response. After the system starts, u o and i out Can reach steady state in a shorter time.

[0026] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A large-capacity hydrogen production power source suitable for medium-voltage AC power grid, characterized in that: The hydrogen production power supply comprises: a multi-pulse rectifier circuit, a DC transformer module, a hydrogen production electrolyzer and a control module; The input side of the multi-pulse rectifier circuit is connected to the medium voltage AC power grid; The DC transformer module is located between the multi-pulse rectifier circuit and the hydrogen production electrolyzer, and its input side is connected to the output side of the multi-pulse rectifier circuit; The input side of the hydrogen production electrolyzer is connected to the output side of the DC transformer module; The control module is composed of a sampling circuit, a DSP controller and a driving circuit; the control module is used to collect analog signals of voltage and current in the hydrogen production power supply and output corresponding PWM driving signals; The multi-pulse rectifier circuit is composed of a multi-pulse phase-shift rectifier transformer and an uncontrolled rectifier circuit in cascade; the low-voltage side of the multi-pulse phase-shift rectifier transformer outputs m groups of phase-shift voltages with equal line voltage amplitudes and phase angle differences of π / (3m) respectively; the uncontrolled rectifier circuit is a three-phase diode rectifier bridge, whose input end is connected to the multi-pulse phase-shift rectifier transformer, and whose output end is connected in parallel to form a pulse rectifier circuit connected to the DC transformer module; the number of the diode rectifier bridges is the same as the number of low-voltage side windings of the multi-pulse phase-shift rectifier transformer and is m.

2. The large-capacity hydrogen production power source suitable for medium-voltage AC power grid according to claim 1 is characterized in that: The multi-pulse phase-shifting rectifier transformer uses (m / 2) three-winding phase-shifting transformers to form m phase-shifting angles or uses m phase-shifting rectifier transformers with extended triangle windings on the secondary side.

3. The large-capacity hydrogen production power source suitable for medium-voltage AC power grid according to claim 1 is characterized in that: The DC transformer module adopts an input series and output parallel structure; the DC transformer input side is composed of k sub-modules connected in series, and the DC transformer output side is composed of k sub-modules connected in parallel.

4. The large-capacity hydrogen production power source suitable for medium-voltage AC power grid according to claim 1 is characterized in that: The sampling circuit converts the voltage and current signals into analog quantities of 0-3.3V, and transmits the analog quantities to the ADC module of the DSP controller; after the DSP controller collects the corresponding analog signals from the ADC module, it performs corresponding operations, calculates the duty cycle, and outputs the PWM signal to the drive circuit through the EPWM port; the drive circuit uses optical isolation or magnetic isolation to achieve electrical isolation, and realizes level conversion to drive the IGBT module.

5. A control method for a large-capacity hydrogen production power source suitable for a medium-voltage AC power grid as claimed in any one of claims 1 to 4, characterized in that: Contains three closed-loop decoupling control algorithms and protection algorithms for DC transformers.

6. The control method for a large-capacity hydrogen production power source suitable for a medium-voltage AC power grid according to claim 5 is characterized in that: The three-closed-loop decoupling control algorithm includes an input voltage balancing loop, an output voltage loop, and a current inner loop; in the input voltage balancing loop, the input voltage balancing control signal d corresponding to the nth basic circuit unit sn It is not obtained directly, but is obtained by adding the output signals of the first n-1 input balancing loops to achieve decoupling control.

7. The control method of a large-capacity hydrogen production power source suitable for a medium-voltage AC power grid according to claim 5 is characterized in that: The protection algorithm at least includes an overvoltage protection algorithm, an overcurrent protection algorithm and a short circuit protection algorithm.

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