A Design Method of Converter for Alkaline Water Electrolysis Hydrogen Production System

Abstract

The present invention discloses a converter design method suitable for an alkaline electrolysis hydrogen production system, specifically: first, the electrolysis power and source voltage of the alkaline electrolyzer are determined, secondly, the inductor and capacitor values are set according to the input and output parameters, and then the DC / DC buck converter topology is reasonably designed based on the calculation, so that it satisfies the alkaline electrolyzer to operate at the rated power and has high economy, ensuring that the alkaline electrolysis hydrogen production system performs stable power electrolysis, avoiding the impact of frequent start and stop on the equipment, and increasing the system life. At the same time, the economy of the electrolysis system and the range of topology selection are increased, and more cost-saving converter topologies can be selected while ensuring power. The present invention is suitable for alkaline electrolysis hydrogen production occasions and meets the rated electrolysis power of the electrolyzer while ensuring certain economic benefits. It is suitable for alkaline electrolysis hydrogen production systems that need to operate at a stable output power and meet economy at the same time.

Description

Technical Field

[0001] The invention belongs to the field of power electronics and relates to a converter design method suitable for an alkaline electrolysis hydrogen production system. Background Art

[0002] Renewable energy hydrogen production (green hydrogen) is an important direction for the future development of hydrogen energy. One of the links in the new energy electrolysis hydrogen production process is water electrolysis hydrogen production. Currently, there are three mainstream directions of water electrolysis hydrogen production, namely alkaline water electrolysis hydrogen production, proton exchange membrane water electrolysis hydrogen production and high-temperature solid oxide water electrolysis hydrogen production.

[0003] Common alkaline water electrolysis hydrogen production systems generally generate electricity from renewable energy to the DC bus, and then connect to the electrolyzer device through a DC / DC step-down converter to perform water electrolysis reaction (such as Figure 1 Since alkaline electrolysis hydrogen production systems are usually used in MW-level high-power applications, the DC / DC converter design suitable for alkaline electrolysis hydrogen production systems is complex and costly due to the voltage and current resistance characteristics of individual switching devices. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a converter design method suitable for an alkaline electrolysis hydrogen production system.

[0005] The present invention provides a converter design method suitable for an alkaline electrolysis hydrogen production system. First, the electrolysis power and source voltage of the alkaline electrolyzer are determined. Second, the inductor and capacitor values are set according to the input and output parameters. Finally, a DC / DC buck converter topology is rationally designed based on the calculations to ensure that the alkaline electrolyzer operates at the rated power and has high economic efficiency. This ensures that the alkaline electrolysis hydrogen production system performs stable power electrolysis, avoids the impact of frequent starts and stops on the equipment, and increases the system life. At the same time, it increases the economy of the electrolysis system and the range of topology options. While ensuring power, more cost-effective converter topologies can be selected. The specific steps are:

[0006] Step 1: The electrolytic cell source measurement adopts the constant voltage input mode, and determines the electrolysis power and source measurement voltage of the alkaline electrolytic cell.

[0007] Step 2: Based on the electrolysis voltage and current of the electrolytic cell and the fixed input voltage, logical inductance and capacitance values are given through calculation to calculate the required withstand voltage and current values of each switching device.

[0008] Step 3: Select a switching device of a certain specification and build a DC / DC topology based on the calculated voltage and current withstand values of the switching device.

[0009] Step 4: Change the switching devices of different types and specifications, and build more DC / DC topologies by changing the number of parallel circuits or the number of levels to meet the rated output while also meeting the device specifications.

[0010] Step 5: Count the different devices between the topology before and after the device change, and compare their economic performance before and after.

[0011] Step 6: Repeat steps 4-5, change the topology, and explore the economic indicators of different types and specifications of switching devices when used in alkaline electrolysis hydrogen production scenarios.

[0012] Furthermore, step 2 is specifically as follows:

[0013] Step 2.1: Based on the alkaline electrolyzer electrolysis power and fixed input voltage determined in step 1, give logical inductance and capacitance values.

[0014] Step 2.2: To unify the parameters of the switching devices, set the duty cycle of each switching device to 0.5. According to the law of conservation of magnetic flux, the peak current that each switching device bears when it is turned on is ,in, V S Measure voltage for electrolytic cell source; V O is the electrolysis voltage of the electrolytic cell; I O is the electrolysis current of the electrolytic cell; N 1 、 N 2 are the number of turns on the primary and secondary sides of the transformer respectively; T is the switching converter period; L is the inductance value.

[0015] Step 2.3: According to the multi-level topology requirements, the voltage value that each switch device withstands when it is turned off is ,in, n is the number of converter levels.

[0016] Furthermore, step 3 is specifically as follows:

[0017] Step 3.1: Adapt the topology of the step-down transformer connected to the alkaline electrolyzer according to the selected switch device parameters.

[0018] Step 3.2: If the voltage withstand value of the switching device is not enough, increase the voltage level; if the current withstand value of the switching device is not enough, add a parallel circuit.

[0019] Furthermore, step 4 is specifically as follows:

[0020] Step 4.1: Change the same device to a different type with different specifications or change the device to a different type.

[0021] Step 4.2: Adjust the topology to meet the rated power output of the alkaline electrolyzer according to the specifications of the switching devices.

[0022] Furthermore, step 5 is specifically as follows:

[0023] Step 5.1: Calculate the total price of all components in the buck converter suitable for the alkaline electrolyzer before changing the topology.

[0024] Step 5.2: Calculate the second total price of all components in the buck converter suitable for alkaline electrolyzer after the topology is changed.

[0025] Step 5.3: Compare the economic benefits before and after changing the topology.

[0026] Furthermore, step 6 is specifically as follows:

[0027] Step 6.1: Select a variety of switching devices of different types and specifications, and change the topology to adapt it to the electrolysis power of the electrolyzer.

[0028] Step 6.2: Compare the economic benefits before and after changing the topology. Under the premise of not changing the electrolysis power of the alkaline electrolyzer, select the switching device and topology with relatively higher economic benefits.

[0029] The beneficial technical effects of the present invention are:

[0030] (1) The present invention enables the alkaline electrolytic cell to perform electrolysis at a stable power, thereby avoiding the impact of frequent start-stop on the equipment and increasing the life of the system.

[0031] (2) While ensuring stable output power, the present invention increases the economy of the electrolysis system by comparing a variety of switching devices of different types and specifications and making a choice.

[0032] (3) Compared with the traditional isolated buck converter used in alkaline electrolysis hydrogen production, the present invention increases the range of topology options, and can select more cost-saving converter topologies while ensuring power. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flowchart of the new energy hydrogen production process.

[0034] Figure 2 The flowchart of the converter design method of the present invention is applicable to the alkaline electrolysis hydrogen production system.

[0035] Figure 3 This is a schematic diagram of a three-level half-bridge converter built with IGBT switching tubes.

[0036] Figure 4 This is a schematic diagram of a five-level half-bridge converter built with IGBT switching tubes, which can reduce the voltage stress of the switching tubes to half of the original.

[0037] Figure 5 This is a schematic diagram of a three-level two-phase parallel half-bridge converter built with IGBT switching tubes, which can reduce the current stress of the switching tube to half of the original.

[0038] Figure 6 This is a schematic diagram of a three-level half-bridge converter built with MOSFET switching tubes. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0040] Because alkaline electrolysis hydrogen production systems require energy to be transmitted from renewable energy sources such as photovoltaic and wind power to the DC bus and then output to the electrolyzer via a DC / DC step-down converter, and considering that alkaline water electrolysis hydrogen production systems often operate in high-power applications ranging from tens of kW to tens of MW, the switching devices in traditional DC / DC converters are not able to withstand such high power. Therefore, it is necessary to improve the traditional DC / DC converter topology to ensure that the devices can operate in a stable state while ensuring the economic efficiency of the alkaline hydrogen production system.

[0041] For alkaline electrolysis hydrogen production, safety considerations necessitate the use of high-frequency transformers for electrical isolation in DC / DC converters. This requires increasing the number of levels to reduce the voltage experienced by individual switching devices, and adding parallel circuits to reduce the current experienced by individual switching devices. The topology selection can be made based on the voltage and current withstand ratings of various switching devices, taking into account economic considerations.

[0042] The flow chart of the converter design method for alkaline electrolysis hydrogen production system of the present invention is as follows: Figure 2 As shown, first, the electrolysis power and source voltage of the alkaline electrolyzer are determined. Secondly, the inductor and capacitor values are set according to the input and output parameters. Then, the DC / DC buck converter topology is reasonably designed based on the calculation to ensure that the alkaline electrolyzer operates at the rated power and has high economic efficiency. This ensures that the alkaline electrolysis hydrogen production system performs stable power electrolysis, avoids the impact of frequent start-stop on the equipment, and increases the system life. At the same time, it increases the economy of the electrolysis system and the range of topology selection. While ensuring power, more cost-saving converter topologies can be selected. The specific steps are:

[0043] Step 1: The electrolytic cell source measurement adopts the constant voltage input mode, and determines the electrolysis power and source measurement voltage of the alkaline electrolytic cell.

[0044] Step 2: Based on the electrolysis voltage and current of the electrolytic cell and the fixed input voltage, logical inductance and capacitance values are given through calculation to calculate the required withstand voltage and current values of each switching device.

[0045] Step 2.1: Based on the alkaline electrolyzer electrolysis power and fixed input voltage determined in step 1, give logical inductance and capacitance values.

[0046] Step 2.2: To unify the parameters of the switching devices, set the duty cycle of each switching device to 0.5. According to the law of conservation of magnetic flux, the peak current that each switching device bears when it is turned on is ,in, V S Measure voltage for electrolytic cell source; V O is the electrolysis voltage of the electrolytic cell; I O is the electrolysis current of the electrolytic cell; N 1 、 N 2 are the number of turns on the primary and secondary sides of the transformer respectively; T is the switching converter period; L is the inductance value.

[0047] Step 2.3: According to the multi-level topology requirements, the voltage value that each switch device withstands when it is turned off is ,in, n is the number of converter levels.

[0048] Step 3: Select a switching device of a certain specification and build a DC / DC topology based on the calculated voltage and current withstand values of the switching device.

[0049] Step 3.1: According to the parameters of the selected switching devices, adjust the topology of the step-down transformer connected to the alkaline electrolyzer. Take IGBT as an example, Figure 3 .

[0050] Step 3.2: If the voltage withstand value of the switch device is not enough, increase the voltage level, such as Figure 4 If the current carrying capacity of the switch device is not enough, add a parallel circuit, such as Figure 5 .

[0051] Step 4: Change the switching devices of different types and specifications, and build more DC / DC topologies by changing the number of parallel circuits or the number of levels to meet the rated output while also meeting the device specifications.

[0052] Step 4.1: Change the same device of different types and specifications, such as IGBT devices of different specifications; or change different types of devices, such as IGBT, MOSFET, GTO and other fully controlled switching devices. Take MOSFET as an example, Figure 6 .

[0053] Step 4.2: Adjust the topology to meet the rated power output of the alkaline electrolyzer according to the specifications of the switching devices.

[0054] Step 5: Count the different devices between the topology before and after the device change, and compare their economic performance before and after.

[0055] Step 5.1: Calculate the total price of all components in the buck converter suitable for the alkaline electrolyzer before changing the topology.

[0056] Step 5.2: Calculate the second total price of all components in the buck converter suitable for alkaline electrolyzer after the topology is changed.

[0057] Step 5.3: Compare the economic benefits before and after changing the topology.

[0058] Step 6: Repeat steps 4-5, change the topology, and explore the economic indicators of different types and specifications of switching devices when used in alkaline electrolysis hydrogen production scenarios.

[0059] Step 6.1: Select a variety of switching devices of different types and specifications, and change the topology to adapt it to the electrolysis power of the electrolyzer.

[0060] Step 6.2: Compare the economic benefits before and after changing the topology. Under the premise of not changing the electrolysis power of the alkaline electrolyzer, select the switching device and topology with relatively higher economic benefits.

[0061] The present invention is directed to a DC / DC step-down converter that inputs electricity generated by photovoltaic and wind power to the DC bus and then to the electrolyzer. When the alkaline electrolyzer operates at a constant voltage input, the topology of fully controlled switching devices of different types and specifications is modified to meet the rated power output of the same alkaline electrolyzer. By comparing their economic costs, the most suitable topology that meets the electrolysis power is ultimately selected. This makes it suitable for alkaline electrolysis hydrogen production applications and meets the rated electrolysis power of the electrolyzer while ensuring a certain level of economic benefit. It is suitable for alkaline electrolysis hydrogen production systems that require stable output power and are economical.

Claims

1. A converter design method suitable for an alkaline electrolysis hydrogen production system, characterized in that: The following steps are involved: Step 1: The electrolytic cell source measurement adopts the constant voltage input mode, and determines the electrolysis power and source measurement voltage of the alkaline electrolytic cell; Step 2: Based on the electrolytic cell electrolysis voltage and electrolysis current and the fixed input voltage, the required withstand voltage and current values of each switching device are calculated by calculating the logical inductance and capacitance values. Step 2.1: Based on the alkaline electrolytic cell electrolysis power and fixed input voltage determined in step 1, set logical inductance and capacitance values; Step 2.2: To unify the parameters of the switching devices, set the duty cycle of each switching device to 0.

5. According to the law of conservation of magnetic flux, the peak current that each switching device bears when it is turned on is Among them, V S The source voltage of the electrolytic cell is measured; V O is the electrolysis voltage of the electrolytic cell; I O is the electrolytic current of the electrolytic cell; N1 is the number of turns on the primary side of the transformer; N2 is the number of turns on the secondary side of the transformer; T is the switching converter period, and L is the inductance value; Step 2.3: According to the multi-level topology requirements, the voltage value that each switch device withstands when it is turned off is Where n is the number of converter levels; Step 3: Select a switching device of a certain specification and build a DC / DC topology based on the calculated withstand voltage and current values of the switching device. Step 3.1: Adapt the topology of the step-down transformer connected to the alkaline electrolyzer according to the selected switch device parameters; Step 3.2: If the voltage withstand value of the switching device is not enough, increase the voltage level; if the current withstand value of the switching device is not enough, add a parallel circuit; Step 4: Change the switching devices of different types and specifications, and build more DC / DC topologies by changing the number of parallel circuits or the number of levels to meet the rated output while also meeting the device specifications. Step 4.1: Change the same device to a different type with different specifications or change the device to a different type; Step 4.2: Adjust the topology to meet the rated power output of the alkaline electrolyzer according to the specifications of the switching devices; Step 5: Count the different devices between the topology before and after the device change, and compare their economic performance before and after; Step 5.1: Calculate the total price of all components in the buck converter suitable for the alkaline electrolyzer before changing the topology; Step 5.2: Calculate the second total price of all components in the buck converter suitable for the alkaline electrolyzer after the topology is changed; Step 5.3: Compare the economic benefits before and after changing the topology Step 6: Repeat steps 4-5, changing the topology, and exploring the economic indicators of different types and specifications of switching devices when applied to alkaline electrolysis hydrogen production scenarios; Step 6.1: Select a variety of switching devices of different types and specifications, and change the topology to adapt to the electrolytic power of the electrolyzer; Step 6.2: Compare the economic benefits before and after changing the topology. Under the premise of not changing the electrolysis power of the alkaline electrolyzer, select the switching device and topology with relatively higher economic benefits.

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