Braking energy flywheel-hydrogen production-fuel cell power generation system for traction substation

Abstract

The utility model belongs to the field of electrified railways, and particularly discloses a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system which comprises a flywheel energy storage module, an electrolytic hydrogen production module and a hydrogen fuel cell module. The flywheel energy storage module and the electrolytic hydrogen production module are both connected to a traction bus, the output end of the electrolytic hydrogen production module is connected with the input end of the hydrogen fuel cell module, and the output end of the hydrogen fuel cell module is connected with a local load and / or a power distribution network of a railway system; the traction bus is connected with a power coordination controller capable of acquiring the real-time power of the traction bus; and the flywheel energy storage module and the electrolytic hydrogen production module access respective power signals to the power coordination controller. The system is suitable for recovery, hydrogen production and power generation of braking energy of a traction substation, the recovery rate of regenerative braking energy is improved, and the electric charge expenditure of a railway system is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of electrified railways, specifically a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system. Background Technology

[0002] With the world facing increasing energy shortages, energy conservation and emission reduction have become a global research topic, and energy recovery and reuse are effective means of achieving this. In recent years, with the development of electrified railways towards higher speeds and heavier loads, railways, as a key energy-consuming industry, have enormous potential in energy recovery and reuse.

[0003] Currently, all traction motors installed on trains are capable of regenerative braking. This means that the traction motors operate in two modes: motor and generator. When the train is traction-driven, the traction motor functions as a motor; when the train is undergoing electric braking, the motor switches to generator mode, and the mechanical energy generated during electric braking is regenerated into electrical energy. Typically, after the regenerative braking energy is consumed by the traction trainset and traction power supply equipment, about 50% of the regenerative braking energy is still fed back to the external power grid via the traction transformer. When a large amount of regenerative braking energy is fed back to the grid, it is charged either in reverse (not counted) or in reverse (counted in the forward direction), causing significant economic losses to the railway sector. Furthermore, due to the three-phase asymmetry of the returned regenerative braking energy, it causes voltage fluctuations, harmonics, and negative sequence problems to the power grid.

[0004] There are three main ways to utilize regenerative braking energy in trains: (1) direct utilization, which means optimizing train operation so that regenerative braking energy is used preferentially by trains with the same power supply arm in traction mode; (2) feedback utilization, which means sending regenerative braking energy back to the power supply network of other voltage levels in the railway system (such as 10kV power system) through feedback devices; (3) energy storage utilization, which means storing or releasing regenerative braking energy through energy storage equipment to realize the recycling and utilization of regenerative braking energy and suppress voltage fluctuations in the traction network. However, all three methods have inherent technical barriers when applying regenerative braking energy in traction substations: (1) Direct utilization will lead to a decrease in the flexibility of train operation. When the length of a single traction power supply arm in AC electrified railway is short, the utilization rate of regenerative braking energy will be reduced; (2) Feedback utilization will result in a single inverter being unable to realize the feedback utilization of regenerative braking energy in electrified railways due to differences in power supply systems. Even if a three-phase inverter is connected in parallel at the DC port of the RPC (Railway Power Regulator) to realize feedback utilization, the utilization rate is heavily dependent on the load of the 10kV power system. At the same time, the regenerative braking energy with strong impact and high randomness may affect the power supply safety of the 10kV power system; (3) The energy storage utilization method has outstanding flexibility compared to the other two methods. However, the single braking process in electrified railways has the characteristics of large braking power, long duration, and large cumulative regenerative braking energy. The rated power and rated capacity requirements of the power type energy storage system are high, which will significantly increase the safety hazards of closed energy systems. Utility Model Content

[0005] The purpose of this invention is to provide a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system. Utilizing the advantages of flywheel power and response performance, hydrogen is produced online in real time, and the electrical energy recovered by the flywheel is promptly converted into hydrogen with high stability and large storage capacity potential, thereby improving the recovery rate of renewable braking energy. At the same time, the hydrogen produced online is delivered directly to the railway system's internal power system for use, reducing the railway system's electricity costs.

[0006] To achieve the above objectives, the technical method adopted by this utility model is as follows:

[0007] A traction substation braking energy flywheel-hydrogen production-fuel cell power generation system includes a flywheel energy storage module, an electrolysis hydrogen production module, and a hydrogen fuel cell module installed in the traction substation. The external power grid is connected to the rails and traction bus via traction transformers. Both the flywheel energy storage module and the electrolysis hydrogen production module are connected to the traction bus. The output terminal of the electrolysis hydrogen production module is connected to the input terminal of the hydrogen fuel cell module, and the output terminal of the hydrogen fuel cell module is connected to the local load and / or the railway system's distribution network. A power coordination controller capable of acquiring the real-time power of the traction bus is connected to the traction bus. The flywheel energy storage module and the electrolysis hydrogen production module input their respective power signals to the power coordination controller.

[0008] As a limitation: the flywheel energy storage module is connected to the traction bus via a DC-AC bidirectional converter, the electrolysis hydrogen production module is connected to the traction bus via an AC-DC converter, the traction bus is connected to the traction transformer via a feeder, the rail is connected to the traction transformer via a return line, and the output of the hydrogen fuel cell module is connected to the local load and / or the railway system's power distribution network via a DC-DC converter, a grid-connected inverter, and a filter.

[0009] As further specified: a voltage transformer is connected to the traction bus, a current transformer is connected to the feeder, the first input terminal of the power coordination controller is connected to the secondary side of the voltage transformer, the second input terminal of the power coordination controller is connected to the secondary side of the current transformer, the third input terminal of the power coordination controller is connected to the state-of-charge output terminal of the flywheel energy storage module, the fourth input terminal of the power coordination controller is connected to the state-of-charge output terminal of the electrolysis hydrogen production module, the first output terminal of the power coordination controller is connected to the control terminal of the DC-AC bidirectional converter, and the second output terminal of the power coordination controller is connected to the control terminal of the AC-DC converter.

[0010] As further specified: the DC-DC converter is a Boost converter, the grid-connected inverter is an H-bridge inverter, the filter is an LCL filter, the Boost converter is controlled by an MPPT controller, and the H-bridge inverter is controlled by a dual-loop PI controller.

[0011] The beneficial effects achieved by this utility model, due to the adoption of the above-mentioned solution, compared with the prior art, are as follows:

[0012] (1) The present invention provides a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system, which connects a flywheel energy storage module and an electrolysis hydrogen production module to the traction bus, and regulates the power output of the system through a power coordination controller. Taking advantage of the flywheel energy storage module's ability to charge and discharge frequently with high power and short time, it can quickly absorb and release renewable braking energy in a timely manner, recover the regenerative braking energy of the train, produce hydrogen online, and convert the electrical energy recovered by the flywheel into hydrogen with high stability and large storage capacity potential in a timely manner. This is equivalent to expanding the capacity of the flywheel energy storage module, solving the problem of limited energy storage capacity of the flywheel energy storage module, and improving the recovery rate of renewable braking energy. The produced hydrogen is applied to hydrogen fuel cells to provide power compensation for the railway system and reduce the railway system's electricity expenditure.

[0013] (2) The present invention provides a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system. The output end of the hydrogen fuel cell module is connected to the local load and / or railway system distribution network through a DC-DC converter, a grid-connected inverter and a filter. The DC-DC converter is controlled by an MPPT controller and the grid-connected inverter is controlled by a dual-loop PI controller. This can effectively suppress grid pressure fluctuations and improve the output power of the hydrogen fuel cell.

[0014] In summary, this utility model is applicable to the recovery, hydrogen production, and power generation of braking energy in traction substations, improving the recovery rate of renewable braking energy and reducing electricity costs for railway systems. Attached Figure Description

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 This is a schematic diagram of the structure of a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system according to an embodiment of the present invention;

[0017] Figure 2 This is a circuit diagram of the hydrogen fuel cell module connected to the grid according to an embodiment of this utility model;

[0018] In the diagram: 1. Boost converter; 2. H-bridge inverter; 3. LCL filter. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments. However, those skilled in the art should understand that the present invention is not limited to the following embodiments. Any improvements and equivalent changes made based on the specific embodiments of the present invention are within the scope of protection of the claims of the present invention.

[0020] An embodiment of a traction substation braking energy flywheel-hydrogen production-fuel cell power generation system

[0021] A traction substation braking energy flywheel-hydrogen production-fuel cell power generation system, such as Figure 1As shown, the system includes a flywheel energy storage module, an electrolysis hydrogen production module, and a hydrogen fuel cell module installed in the traction substation. The external power grid is connected to the rails and traction busbar via a traction transformer. The rails are connected to the traction transformer via a return line, and the traction busbar is connected to the traction transformer via a feeder. The pantograph on the train draws current from the traction busbar to provide power to the train, and the current flows to the rails after passing through the train. The flywheel energy storage module is connected to the traction busbar via a DC-AC bidirectional converter, and the electrolysis hydrogen production module is connected to the traction busbar via an AC-DC converter. The output of the electrolysis hydrogen production module is connected to the input of the hydrogen fuel cell module. The hydrogen produced by the electrolysis hydrogen production module is input into the hydrogen fuel cell module to provide fuel. The output of the hydrogen fuel cell module is connected to the local load and / or the railway system's distribution network via a DC-DC converter, a grid-connected inverter, and a filter. Figure 2 As shown, the DC-DC converter is a Boost converter 1, the grid-connected inverter is an H-bridge inverter 2, and the filter is an LCL filter 3. The Boost converter 1 is controlled by an MPPT controller, which monitors the output current and voltage of the hydrogen fuel cell module in real time and outputs a PWM drive signal to control the switching of the power switching transistors in the Boost converter 1. The H-bridge inverter 2 is controlled by a dual-loop PI controller, which controls the voltage loop and current loop of the H-bridge inverter 2 to output an AC current that is in phase and frequency with the voltage of the railway system's distribution network, thereby achieving the purpose of supplying power to the local load and transmitting electrical energy to the railway system's distribution network. A voltage transformer is connected to the traction bus, and a current transformer is connected to the feeder. The first input terminal of the power coordination controller is connected to the secondary side of the voltage transformer, and the second input terminal of the power coordination controller is connected to the secondary side of the current transformer. The power coordination controller obtains the real-time power of the traction bus through the voltage transformer and the current transformer. The third input terminal of the power coordination controller is connected to the state-of-charge output terminal of the flywheel energy storage module, and the fourth input terminal of the power coordination controller is connected to the state-of-charge output terminal of the electrolysis hydrogen production module. The first output terminal of the power coordination controller is connected to the control terminal of the DC-AC bidirectional converter, and the second output terminal of the power coordination controller is connected to the control terminal of the AC-DC converter.

[0022] In this embodiment, the flywheel energy storage module adopts an existing flywheel energy storage system. The flywheel stores regenerative braking energy and releases energy. The DC-AC bidirectional converter enables bidirectional power flow. When energy flows from the traction bus into the flywheel, the DC-AC bidirectional converter is responsible for charging the flywheel; when energy flows from the flywheel into the traction bus, the DC-AC bidirectional converter is responsible for discharging the flywheel. The electrolysis hydrogen production module adopts an existing electrolysis hydrogen production system. The energy released by the flywheel is converted from alternating current to direct current by an AC-DC converter, providing power to the electrolyzer. The electrolyzer decomposes water into hydrogen and oxygen, which are then stored in hydrogen and oxygen storage tanks. The hydrogen fuel cell module adopts an existing PEMFC hydrogen fuel cell stack. The hydrogen produced by the electrolysis hydrogen production system serves as the fuel for the PEMFC hydrogen fuel cell stack. During train braking, based on deceleration requirements, the train transmits mechanical energy to the drive motor via wheels, deceleration mechanisms, and transmission mechanisms to enter a power generation state. Regenerative braking energy is stored in the flywheel. When the flywheel energy storage system is full, the power coordination controller controls the flywheel energy storage system to release energy. The electrolysis hydrogen production system receives the energy released by the flywheel energy storage system, realizing energy transfer within the flywheel. After the flywheel energy release is complete, the system switches back to flywheel charging mode. This coordinated control of regenerative braking energy between the flywheel energy storage system and the electrolysis hydrogen production system solves the problem of limited energy storage capacity in the flywheel energy storage system and improves the recovery rate of regenerative braking energy. The produced hydrogen is then used in hydrogen fuel cell stacks to provide power compensation for the railway system, reducing the railway system's electricity costs.

Claims

1. A traction substation braking energy flywheel-hydrogen production-fuel cell power generation system, characterized in that, The system includes a flywheel energy storage module, an electrolysis hydrogen production module, and a hydrogen fuel cell module installed in the traction substation. The external power grid is connected to the rails and traction bus via traction transformers. Both the flywheel energy storage module and the electrolysis hydrogen production module are connected to the traction bus. The output of the electrolysis hydrogen production module is connected to the input of the hydrogen fuel cell module, and the output of the hydrogen fuel cell module is connected to the local load and / or the railway system's distribution network. A power coordination controller capable of acquiring the real-time power of the traction bus is connected to the traction bus. The flywheel energy storage module and the electrolysis hydrogen production module connect their respective power signals to the power coordination controller.

2. The traction substation braking energy flywheel-hydrogen production-fuel cell power generation system according to claim 1, characterized in that, The flywheel energy storage module is connected to the traction bus via a DC-AC bidirectional converter, the electrolysis hydrogen production module is connected to the traction bus via an AC-DC converter, the traction bus is connected to the traction transformer via a feeder, the rail is connected to the traction transformer via a return line, and the output of the hydrogen fuel cell module is connected to the local load and / or the railway system's power distribution network via a DC-DC converter, a grid-connected inverter, and a filter.

3. The traction substation braking energy flywheel-hydrogen production-fuel cell power generation system according to claim 2, characterized in that, A voltage transformer is connected to the traction bus, and a current transformer is connected to the feeder. The first input terminal of the power coordination controller is connected to the secondary side of the voltage transformer, the second input terminal of the power coordination controller is connected to the secondary side of the current transformer, the third input terminal of the power coordination controller is connected to the state-of-charge output terminal of the flywheel energy storage module, the fourth input terminal of the power coordination controller is connected to the state-of-charge output terminal of the electrolysis hydrogen production module, the first output terminal of the power coordination controller is connected to the control terminal of the DC-AC bidirectional converter, and the second output terminal of the power coordination controller is connected to the control terminal of the AC-DC converter.

4. A traction substation braking energy flywheel-hydrogen production-fuel cell power generation system according to claim 2 or 3, characterized in that, The DC-DC converter is a Boost converter, the grid-connected inverter is an H-bridge inverter, and the filter is an LCL filter. The Boost converter is controlled by an MPPT controller, and the H-bridge inverter is controlled by a dual-loop PI controller.

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