Direct-current micro-grid system applying fuel cell and control method
Technical Field
The invention relates to the technical field of micro-grids, in particular to a direct-current micro-grid system applying a fuel cell and a control method.
Background
In recent years, distributed energy power generation technology has been widely developed with the increasing awareness of human beings on environmental protection and the gradual scarcity of fossil fuels. The electricity output by the distributed energy power station is generally direct current, can not be directly used by an alternating current large power grid, and needs to go through a series of complex electric energy conversion processes. Therefore, a concept of a dc Micro-Grid system is proposed, and a Micro-Grid (Micro-Grid) is also translated into a Micro-Grid, which refers to a small power generation and distribution system composed of a distributed power supply, an energy storage device, an energy conversion device, a load, a monitoring and protection device, and the like. The system main body is composed of a direct current bus, so that the access difficulty of distributed energy is reduced, and the cost of power electronic devices is reduced. For a long time, research and development of related technologies of direct current micro-grids have been receiving wide attention from all circles. Communication companies in countries such as Sweden, Japan, France and the United states have started research and introduction of 300-400V data center direct current power distribution in the 90 s of the 20 th century. In addition, direct-current regional power distribution of warships, aviation and automatic systems, especially the electric traction direct-current power supply technology is mature, and a good opportunity is provided for popularization and application of the direct-current micro-grid. In the existing direct current micro-grid technology, distributed energy sources such as wind power generation, photovoltaic power generation, fuel cell power generation and hydrogen production energy power generation mostly transmit electric energy to the same direct current bus through respective DC/DC conversion units, and then the electric energy is output to an alternating current power grid through a DC/AC conversion unit. Therefore, the control of energy scheduling is difficult, timeliness and quick response cannot be achieved, the influence of the problem in an island operation mode is more obvious, and the whole system has dependence on an alternating current large power grid.
Disclosure of Invention
In order to solve the above problems, the present invention provides a dc microgrid system using a fuel cell, and a control method of the dc microgrid system using the fuel cell.
The invention is realized by adopting the following scheme:
a direct-current microgrid system using fuel cells comprises a power grid, a first direct-current bus, a second direct-current bus, an energy storage module and a distributed energy generation module, wherein the first direct-current bus is connected between the first direct-current bus and the second direct-current bus; the energy storage module comprises an energy storage battery pack and a fuel cell power generation pack connected with the energy storage battery pack in parallel.
Further, the fuel cell power generation set comprises a fuel cell and a water electrolysis hydrogen production device connected with the fuel cell; the energy storage battery pack comprises a plurality of storage batteries.
Further, the load module comprises at least one direct current load connected with the first direct current bus and at least one alternating current load connected with the first direct current bus.
Further, the direct current load is connected with the first direct current bus through the first DC/DC converter, and the alternating current load is connected with the first direct current bus through the first DC/AC converter.
Furthermore, the energy storage module and the first direct current bus, and the energy storage module and the second direct current bus are connected through a second DC/DC converter, and the first direct current bus and the power grid are connected through an AC/DC converter.
Furthermore, the distributed energy power generation module comprises a photovoltaic power generation unit and a wind power generation unit.
Further, the photovoltaic power generation unit is connected with the second direct current bus through a third DC/DC converter, and the wind power generation unit is connected with the second direct current bus through a second DC/AC converter.
The control method is characterized in that the direct current micro-grid system using the fuel cell is applied, the energy storage module discharges to the first direct current bus for the load module to use, the operation mode of the energy storage device is adjusted according to the power requirement of the load, the distributed energy power generation module generates power and charges the energy storage module through the second direct current bus, and when the charging of the energy storage battery pack of the energy storage module is completed, redundant electric quantity is input into the water electrolysis hydrogen production device of the fuel cell power generation pack to produce hydrogen and store the hydrogen.
Further, the operation modes of the energy storage device include a charging mode, a discharging mode and a charging and discharging mode.
Further, the adjusting the operation mode of the energy storage device comprises the following steps:
step 1, when the load power of a load module is less than 10%, the energy storage module is adjusted to operate in a charging mode, the electric quantity generated by a distributed energy power generation module preferentially charges an energy storage battery pack, and when the energy storage battery pack is charged, redundant electric quantity is input into a water electrolysis hydrogen production device of a fuel cell power generation pack to produce and store hydrogen;
step 2, when the input power of the distributed energy power generation module is less than 10% of the rated power, the energy storage module is adjusted to operate in a discharging mode, the load module is powered by the energy storage battery pack, and when the electric quantity of the energy storage battery pack is insufficient, the fuel cell power generation pack supplies power;
and 3, when the power of the load module is more than 10% of the rated power and the input power of the distributed energy power generation module is more than 10% of the rated power, adjusting the energy storage module to operate in a charge-discharge mode, starting a certain number of storage batteries for supplying power according to the power requirement of the load module, and when the power requirement of the load module exceeds the limit of the energy storage battery pack, supplying power by using the fuel cell power generation pack, or cooperatively supplying power by using the fuel cell power generation pack and a power grid.
Further, in step 2, if the electric quantities of the energy storage battery pack and the fuel cell power generation pack are insufficient, power is supplied by a power grid.
Compared with the prior art, the invention has the following beneficial effects:
the two direct current buses are connected through the energy storage module, when the micro-grid system runs, the energy storage battery pack of the energy storage module and the fuel cell power generation pack supply power to the load module, no matter the distributed energy power generation module runs in any state, the electric energy generated by the distributed energy power generation module is pre-stored in the energy storage module, the energy demand of the load on the micro-grid system is directly supplied by the energy storage module, and the intermittent condition of the distributed energy is not required to be closely concerned by combining the control of energy scheduling in the direct current micro-grid system, so that the difficulty of energy scheduling control is reduced, the response capability of the micro-grid system to the load is improved, the reliability, the stability and the expansibility of the micro-grid system are enhanced, and the distributed.
Drawings
Fig. 1 is a structural diagram of a dc microgrid system using fuel cells according to the present invention.
The figure includes:
the system comprises a power grid 1, a first direct current bus 2, a direct current load 3, an alternating current load 4, an energy storage battery pack 5, a fuel cell 6, a water electrolysis hydrogen production device 7, a second direct current bus 8, a photovoltaic power generation unit 9, a wind power generation unit 10, a first DC/DC converter 11, a first DC/AC converter 12, a second DC/DC converter 13, an AC/DC converter 14, a third DC/DC converter 15 and a second DC/AC converter 16.
Detailed Description
To facilitate an understanding of the present invention for those skilled in the art, the present invention will be described in further detail below with reference to specific embodiments and accompanying drawings.
Referring to fig. 1, the direct current microgrid system using a fuel cell 6 provided by the invention comprises a power grid 1, and further comprises a first direct current bus 2, a second direct current bus 8, an energy storage module connected between the first direct current bus 2 and the second direct current bus 8, and a distributed energy generation module connected with the second direct current bus 8, wherein the first direct current bus 2 is connected with a load module, and the first direct current bus 2 is connected with the power grid 1; the energy storage module comprises an energy storage battery pack 5 and a fuel cell power generation pack connected with the energy storage battery pack 5 in parallel.
The fuel cell power generation set comprises a fuel cell 6 and a water electrolysis hydrogen production device 7 connected with the fuel cell 6; the energy storage battery pack 5 includes a plurality of storage batteries, and the number of the storage batteries and the number of the fuel cells 6 can be set according to the scale of the microgrid 1 and the load size. The storage battery has strong load response capability, so the storage battery is used as a main power supply energy source. The fuel cell 6 is relatively slow to start up and there is a hysteresis in the load response, typically as a backup power source.
The load module comprises 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.
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.
The energy storage module and the first direct current bus 2 and the energy storage module and the second direct current bus 8 are connected through a second DC/DC converter 13, and the first direct current bus 2 and the power grid 1 are connected through an AC/DC converter 14.
The distributed energy power generation module comprises a photovoltaic power generation unit 9 and a wind power generation unit 10, and tidal power generation, geothermal power generation and the like can be adopted during specific implementation.
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 the MPPT mode, and allows photovoltaic power generation to be input to the second DC bus 8 with the maximum power. The second DC/AC converter 16 of the wind power generation unit 10 controls the energy input amount of the wind power generation to the second DC bus 8 according to the magnitude of the wind force (the energy loss is reduced by changing the operating frequency of the fan by DC/AC).
The specifications of the DC/DC converter, the AC/DC converter, and the DC/AC converter in the present embodiment are set according to the scale of the microgrid 1 and the size of the load.
The invention also provides a control method, wherein the direct current micro-grid system using the fuel cell is applied, the energy storage module discharges to the first direct current bus for the load module to use, the operation mode of the energy storage device is adjusted according to the power requirement of the load, the distributed energy power generation module generates power and charges the energy storage module through the second direct current bus, and when the charging of the energy storage battery pack of the energy storage module is completed, redundant electric quantity is input into the hydrogen production device for electrolyzing water of the fuel cell power generation pack to produce hydrogen and store the hydrogen.
The operation modes of the energy storage device comprise a charging mode, a discharging mode and a charging and discharging mode.
The adjusting of the operating mode of the energy storage device comprises the steps of:
step 1, when the load power of a load module is less than 10%, the energy storage module is adjusted to operate in a charging mode, the electric quantity generated by a distributed energy power generation module preferentially charges an energy storage battery pack, and when the energy storage battery pack is charged, redundant electric quantity is input into a water electrolysis hydrogen production device of a fuel cell power generation pack to produce and store hydrogen;
step 2, when the input power of the distributed energy power generation module is less than 10% of the rated power, the energy storage module is adjusted to operate in a discharging mode, the load module is powered by the energy storage battery pack, and when the electric quantity of the energy storage battery pack is insufficient, the fuel cell power generation pack supplies power;
and 3, when the power of the load module is more than 10% of the rated power and the input power of the distributed energy power generation module is more than 10% of the rated power, adjusting the energy storage module to operate in a charge-discharge mode, starting a certain number of storage batteries for supplying power according to the power requirement of the load module, and when the power requirement of the load module exceeds the limit of the energy storage battery pack, supplying power by using the fuel cell power generation pack or cooperatively supplying power by using the fuel cell power generation pack and a power grid (the total power of the load module is more than the total power of the energy storage battery pack and the fuel cell).
In the step 2, if the electric quantity of the energy storage battery pack and the electric quantity of the fuel cell power generation pack are insufficient, power is supplied by a power grid.
The two direct current buses are connected through the energy storage module, when the micro-grid system runs, the energy storage battery pack of the energy storage module and the fuel cell power generation pack supply power to the load module, no matter the distributed energy power generation module runs in any state, the electric energy generated by the distributed energy power generation module is pre-stored in the energy storage module, the energy demand of the load on the micro-grid system is directly supplied by the energy storage module, and the intermittent condition of the distributed energy is not required to be closely concerned by combining the control of energy scheduling in the direct current micro-grid system, so that the difficulty of energy scheduling control is reduced, the response capability of the micro-grid system to the load is improved, the reliability, the stability and the expansibility of the micro-grid system are enhanced, and the distributed.
In the description of the present invention, it is to be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings and are only for convenience in describing the present invention and simplifying the description, but are not intended to indicate or imply that the indicated devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, e.g., as meaning permanently attached, removably attached, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
While the invention has been described in conjunction with the specific embodiments set forth above, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the included claims.