A DC microgrid system using fuel cells and a control method thereof

Abstract

The present invention relates to the field of microgrid technology, and specifically to a DC microgrid system and control method using fuel cells. The DC microgrid system using fuel cells includes a power grid, a first DC bus and a second DC bus, an energy storage module connected between the first DC bus and the second DC bus, a distributed energy generation module connected to the second DC bus, the first DC bus connected to a load module, and the first DC bus connected to the power grid. During operation, the microgrid system of the present invention supplies power to the load module through the energy storage module. Regardless of the operating state of the distributed energy generation module, the electric energy generated by the module is pre-stored in the energy storage module. The energy demand of the load on the microgrid system is directly supplied by the energy storage module, without the need to pay close attention to the intermittent nature of the distributed energy. This reduces the difficulty of energy scheduling and control, improves the responsiveness of the microgrid system to the load, and enhances the reliability, stability, and scalability of the microgrid system.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrids, and in particular to a direct current microgrid system using a fuel cell and a control method thereof. Background Art

[0002] In recent years, with growing awareness of environmental protection and the gradual depletion of fossil fuels, distributed energy generation technology has seen widespread development. The electricity output from distributed energy power stations is generally DC and cannot be directly used by the AC grid. Instead, it undergoes a complex series of energy conversion processes. This led to the concept of a DC microgrid system. A microgrid (also known as a microgrid) refers to a small power generation and distribution system consisting of distributed power sources, energy storage devices, energy conversion devices, loads, and monitoring and protection devices. The system's core component is a DC bus, which simplifies the integration of distributed energy resources and reduces the cost of power electronics. The research and development of DC microgrid-related technologies has long attracted widespread attention. Telecommunications companies in countries such as Sweden, Japan, France, and the United States began researching and introducing 300-400V DC power distribution for data centers in the 1990s. Furthermore, DC regional power distribution for naval vessels, aviation, and automation systems, particularly DC power supply for electric traction, has matured, providing a promising opportunity for the promotion and application of DC microgrids. In existing DC microgrid technology, distributed energy sources such as wind power, photovoltaic power, fuel cell power, and hydrogen production typically transmit power to a common DC bus through their respective DC / DC converters, which then output the power to the AC grid through DC / AC converters. This approach fails to address the intermittent nature of distributed energy generation, as power generation is constrained by environmental factors. For example, photovoltaic power generation is dependent on solar radiation intensity, while wind power generation is dependent on natural wind volume. Consequently, energy scheduling and control are difficult, hindering timely and rapid response. This issue is even more pronounced in islanded operation, making the entire system dependent on the AC grid. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a DC microgrid system using a fuel cell, and a control method using the DC microgrid system using a fuel cell.

[0004] The present invention is implemented by the following scheme:

[0005] A DC microgrid system using fuel cells includes a power grid. The DC microgrid system using fuel cells also includes a first DC bus and a second DC bus, an energy storage module connected between the first DC bus and the second DC bus, a distributed energy generation module connected to the second DC bus, the first DC bus connected to a load module, and the first DC bus connected to the power grid; the energy storage module includes an energy storage battery group and a fuel cell power generation group connected in parallel with the energy storage battery group.

[0006] Furthermore, the fuel cell power generation group includes a fuel cell and a water electrolysis hydrogen production device connected to the fuel cell; the energy storage battery group includes a plurality of storage batteries.

[0007] Furthermore, the load module includes at least one DC load connected to the first DC bus, and at least one AC load connected to the first DC bus.

[0008] Furthermore, the DC load is connected to the first DC bus through a first DC / DC converter, and the AC load is connected to the first DC bus through a first DC / AC converter.

[0009] Furthermore, the energy storage module and the first DC bus, and the energy storage module and the second DC bus are connected via a second DC / DC converter, and the first DC bus and the power grid are connected via an AC / DC converter.

[0010] Furthermore, the distributed energy generation module includes a photovoltaic power generation unit and a wind power generation unit.

[0011] Furthermore, the photovoltaic power generation unit is connected to the second DC bus via a third DC / DC converter, and the wind power generation unit is connected to the second DC bus via a second DC / AC converter.

[0012] A control method employs the aforementioned DC microgrid system employing a fuel cell, wherein the energy storage module discharges electricity to a first DC bus for use by a load module, and the operating mode of the energy storage device is adjusted according to the power demand of the load. The distributed energy generation module generates electricity and charges the energy storage module via a second DC bus. When the energy storage battery pack of the energy storage module is fully charged, the excess electricity is input into the water electrolysis hydrogen production device of the fuel cell power generation group to produce hydrogen and store it.

[0013] Furthermore, the operation modes of the energy storage device include a charging mode, a discharging mode, and a charge-discharge mode.

[0014] Furthermore, the adjusting the operating mode of the energy storage device includes the following steps:

[0015] Step 1: When the load power of the load module is less than 10%, the energy storage module is adjusted to operate in charging mode. The power generated by the distributed energy generation module is first used to charge the energy storage battery pack. When the energy storage battery pack is fully charged, the excess power is input into the water electrolysis hydrogen production device of the fuel cell power generation group to produce hydrogen and store it;

[0016] Step 2: When the input power of the distributed energy generation module is less than 10% of the rated power, the energy storage module is adjusted to operate in the discharge mode, and the load module is powered by the energy storage battery pack. When the energy storage battery pack is insufficient, the load module is powered by the fuel cell generation pack.

[0017] Step 3: When the power of the load module is greater than 10% of the rated value and the input power of the distributed energy generation module is greater than 10% of the rated power, the energy storage module is adjusted to operate in the charge and discharge mode, and a certain number of batteries are turned on to supply power according to the power demand of the load module. When the power demand of the load module exceeds the limit of the energy storage battery group, the fuel cell power generation group is used for power supply, or the fuel cell power generation group and the power grid are used to coordinate power supply.

[0018] Furthermore, in step 2, if the energy storage battery group and the fuel cell power generation group are insufficient in power, the power grid will be used for power supply.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The two DC busbars provided in the present invention are connected through an energy storage module. When the microgrid system is running, the energy storage battery group and fuel cell power generation group of the energy storage module are used to supply power to the load module. Regardless of the operating state of the distributed energy generation module, the electric energy generated by it is pre-stored in the energy storage module. The energy demand of the load on the microgrid system is directly supplied by the energy storage module. Combined with the control of energy scheduling in the DC microgrid system, there is no need to pay close attention to the intermittent situation of distributed energy, thereby reducing the difficulty of energy scheduling control, improving the responsiveness of the microgrid system to the load, and enhancing the reliability, stability and scalability of the microgrid system, so that distributed energy can be plug-and-play. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural diagram of a DC microgrid system using fuel cells provided by the present invention.

[0022] Included in the figure are:

[0023] Grid 1, first DC bus 2, DC load 3, AC load 4, energy storage battery pack 5, fuel cell 6, water electrolysis hydrogen production device 7, second DC bus 8, photovoltaic power generation unit 9, wind power generation unit 10, first DC / DC converter 11, first DC / AC converter 12, second DC / DC converter 13, AC / DC converter 14, third DC / DC converter 15, second DC / AC converter 16. DETAILED DESCRIPTION

[0024] To facilitate those skilled in the art to understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and drawings.

[0025] Reference Figure 1 The present invention provides a DC microgrid system using a fuel cell 6, including a power grid 1. The DC microgrid system using the fuel cell 6 also includes a first DC bus 2 and a second DC bus 8, an energy storage module connected between the first DC bus 2 and the second DC bus 8, a distributed energy generation module connected to the second DC bus 8, the first DC bus 2 is connected to a load module, and the first DC bus 2 is connected to the power grid 1; the energy storage module includes an energy storage battery group 5 and a fuel cell power generation group connected in parallel with the energy storage battery group 5.

[0026] The fuel cell power generation unit includes a fuel cell 6 and a water electrolysis hydrogen production device 7 connected to the fuel cell 6. The energy storage battery pack 5 includes multiple batteries. The number of batteries and fuel cells 6 can be adjusted based on the scale and load of the microgrid 1. Batteries serve as the primary power source due to their strong load response capabilities. However, the fuel cell 6 is relatively slow to start up and has a lag in load response, so it is generally used as a backup power source.

[0027] The load module includes at least one DC load 3 connected to the first DC bus 2 , and at least one AC load 4 connected to the first DC bus 2 .

[0028] The DC load 3 is connected to the first DC bus 2 via a first DC / DC converter 11 , and the AC load 4 is connected to the first DC bus 2 via a first DC / AC converter 12 .

[0029] The energy storage module and the first DC bus 2 and the energy storage module and the second DC bus 8 are connected via a second DC / DC converter 13 , and the first DC bus 2 and the grid 1 are connected via an AC / DC converter 14 .

[0030] The distributed energy generation module includes a photovoltaic power generation unit 9 and a wind power generation unit 10. In specific implementation, tidal power generation, geothermal power generation, etc. can also be used.

[0031] The photovoltaic power generation unit 9 is connected to the second DC bus 8 via a third DC / DC converter 15, and the wind power generation unit 10 is connected to the second DC bus 8 via a second DC / AC converter 16. The third DC / DC converter 15 of the photovoltaic power generation unit 9 operates in MPPT mode, allowing the photovoltaic power generation to be input into the second DC bus 8 at maximum power. The second DC / AC converter 16 of the wind power generation unit 10 controls the amount of wind power input to the second DC bus 8 based on the wind speed (reducing energy loss by changing the wind turbine's operating frequency through the DC / AC converter).

[0032] In this embodiment, the specifications of the DC / DC converter, AC / DC converter, and DC / AC converter are set according to the scale of the microgrid 1 and the load size.

[0033] The present invention also provides a control method, which uses the aforementioned DC microgrid system using fuel cells, wherein the energy storage module discharges to the first DC bus for use by the load module, and the operating mode of the energy storage device is adjusted according to the power demand of the load. The distributed energy generation module generates electricity and charges the energy storage module via the second DC bus. When the energy storage battery pack of the energy storage module is fully charged, the excess electricity is input into the water electrolysis hydrogen production device of the fuel cell power generation group to produce hydrogen and store it.

[0034] The operation modes of the energy storage device include charging mode, discharging mode, and charge-discharge mode.

[0035] Adjusting the operating mode of the energy storage device comprises the following steps:

[0036] Step 1: When the load power of the load module is less than 10%, the energy storage module is adjusted to operate in charging mode. The power generated by the distributed energy generation module is first used to charge the energy storage battery pack. When the energy storage battery pack is fully charged, the excess power is input into the water electrolysis hydrogen production device of the fuel cell power generation group to produce hydrogen and store it;

[0037] Step 2: When the input power of the distributed energy generation module is less than 10% of the rated power, the energy storage module is adjusted to operate in the discharge mode, and the load module is powered by the energy storage battery pack. When the energy storage battery pack is insufficient, the load module is powered by the fuel cell generation pack.

[0038] In step 3, when the power of the load module is greater than 10% of the rated value and the input power of the distributed energy generation module is greater than 10% of the rated power, the energy storage module is adjusted to operate in the charge and discharge mode, and a certain number of batteries are turned on to supply power according to the power demand of the load module. When the power demand of the load module exceeds the limit of the energy storage battery group, the fuel cell generation group is used for power supply, or the fuel cell generation group and the grid are used to provide power in a coordinated manner (the total power of the load module is greater than the total power of the energy storage battery group + fuel cell).

[0039] In step 2, if the energy storage battery group and the fuel cell power generation group are insufficient in power, the power grid will be used for power supply.

[0040] The two DC busbars provided in the present invention are connected through an energy storage module. When the microgrid system is running, the energy storage battery group and fuel cell power generation group of the energy storage module are used to supply power to the load module. Regardless of the operating state of the distributed energy generation module, the electric energy generated by it is pre-stored in the energy storage module. The energy demand of the load on the microgrid system is directly supplied by the energy storage module. Combined with the control of energy scheduling in the DC microgrid system, there is no need to pay close attention to the intermittent situation of distributed energy, thereby reducing the difficulty of energy scheduling control, improving the responsiveness of the microgrid system to the load, and enhancing the reliability, stability and scalability of the microgrid system, so that distributed energy can be plug-and-play.

[0041] In the description of the present invention, it should be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0042] Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0043] In the present invention, unless otherwise expressly specified or limited, the terms "connection" and "fixed" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0044] Although the present invention has been described with reference to the above specific embodiments, it will be apparent to those skilled in the art that many substitutions, modifications, and variations can be made based on the above. Therefore, all such substitutions, modifications, and variations are intended to fall within the scope of the appended claims.

Claims

1. A control method for a DC microgrid system using a fuel cell, characterized in that: The DC microgrid system using fuel cells includes a power grid, a first DC bus and a second DC bus, an energy storage module connected between the first DC bus and the second DC bus, a distributed energy generation module connected to the second DC bus, the first DC bus connected to the load module, and the first DC bus connected to the power grid; the energy storage module includes an energy storage battery group and a fuel cell power generation group connected in parallel with the energy storage battery group. The energy storage module discharges to the first DC bus for use by the load module, and adjusts the operating mode of the energy storage device according to the power demand of the load. The distributed energy generation module generates electricity and charges the energy storage module via the second DC bus. When the energy storage battery pack of the energy storage module is fully charged, the excess electricity is input into the water electrolysis hydrogen production device of the fuel cell power generation group to produce hydrogen and store it; The operation modes of the energy storage device include charging mode, discharging mode, and charge-discharge mode. Adjusting the operating mode of the energy storage device comprises the following steps: Step 1: When the load power of the load module is less than 10%, the energy storage module is adjusted to operate in charging mode. The power generated by the distributed energy generation module is first used to charge the energy storage battery pack. When the energy storage battery pack is fully charged, the excess power is input into the water electrolysis hydrogen production device of the fuel cell power generation group to produce hydrogen and store it; Step 2: When the input power of the distributed energy generation module is less than 10% of the rated power, the energy storage module is adjusted to operate in the discharge mode, and the load module is powered by the energy storage battery pack. When the energy storage battery pack is insufficient, the load module is powered by the fuel cell generation pack. Step 3: When the power of the load module is greater than 10% of the rated value and the input power of the distributed energy generation module is greater than 10% of the rated power, the energy storage module is adjusted to operate in the charge and discharge mode, and a certain number of batteries are turned on to supply power according to the power demand of the load module. When the power demand of the load module exceeds the limit of the energy storage battery group, the fuel cell power generation group is used for power supply, or the fuel cell power generation group and the power grid are used to coordinate power supply.

2. The control method according to claim 1, characterized in that: The fuel cell power generation group includes a fuel cell and a water electrolysis hydrogen production device connected to the fuel cell; the energy storage battery group includes a plurality of storage batteries.

3. The control method according to claim 1, wherein: The load module includes at least one DC load connected to the first DC bus and at least one AC load connected to the first DC bus.

4. The control method according to claim 3, characterized in that: The DC load is connected to the first DC bus through a first DC / DC converter, and the AC load is connected to the first DC bus through a first DC / AC converter.

5. The control method according to claim 1, characterized in that: The energy storage module and the first DC bus are connected, as well as the energy storage module and the second DC bus are connected via a second DC / DC converter, and the first DC bus and the power grid are connected via an AC / DC converter.

6. The control method according to claim 1, characterized in that: The distributed energy generation module includes a photovoltaic power generation unit and a wind power generation unit.

7. The control method according to claim 6, characterized in that: The photovoltaic power generation unit is connected to the second DC bus via a third DC / DC converter, and the wind power generation unit is connected to the second DC bus via a second DC / AC converter.

8. The control method according to claim 1, characterized in that: In step 2, if the energy storage battery group and the fuel cell power generation group are insufficient in power, the power grid will be used for power supply.

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