A 10MW high-power hydrogen fuel cell locomotive direct current comprehensive power system

Abstract

The application provides a 10MW high-power hydrogen fuel cell locomotive direct-current comprehensive power system, which comprises a hybrid energy storage module and a traction motor driving module, an alternating current side of the hybrid energy storage half-bridge MMC module is connected with a transformer, a secondary side of the transformer is connected with a rectifier, alternating current is converted into direct current and is transmitted to a low-voltage direct-current bus, the low-voltage direct-current bus supplies power for connected auxiliary loads, a sub-module side of the hybrid energy storage half-bridge MMC module is connected with a battery system, a direct-current side of the hybrid energy storage half-bridge MMC module is connected with a high-voltage direct-current bus, an alternating current side of the traction motor driving half-bridge MMC module is connected with an asynchronous motor load, a sub-module side of the traction motor driving half-bridge MMC module is connected with a hydrogen fuel cell system, and a direct-current side of the traction motor driving half-bridge MMC module is connected with the high-voltage direct-current bus. The application can effectively improve the locomotive traction power, greatly improve the robustness and stability of the system, and improve the energy utilization efficiency of the whole vehicle.

Description

Technical Field

[0001] This invention relates to the field of traction power supply technology for new energy locomotives, and in particular to a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system. Background Technology

[0002] Currently, non-electrified railways primarily rely on diesel locomotives for power supply, generating electricity from diesel engines to supply traction loads with AC 27.5kV power at low efficiency (most energy is lost as heat) and causing severe environmental pollution. Using hydrogen fuel cells and batteries as locomotive power sources, and regulating and distributing the DC power generated by these components through an onboard DC integrated power system, converting it into AC power for traction and auxiliary loads via converters, is a popular research direction with economic, green, and low-carbon advantages. However, hydrogen fuel cells have lower energy density, requiring greater mass and volume to produce the same power compared to a diesel engine. Locomotive size and mass are limited, necessitating a more streamlined power system topology. Furthermore, increasing locomotive power necessitates raising the voltage level of the DC integrated power system. Current traditional solutions suffer from significant energy waste due to high losses in converter switching transistors under high voltage conditions, limiting the potential for increasing locomotive voltage levels.

[0003] To improve the output power of hydrogen fuel cell vehicles while minimizing the overall vehicle weight and volume, a new power system topology needs to be found.

[0004] Currently, existing locomotive DC integrated power systems mainly adopt centralized access. Hydrogen fuel cells and batteries are connected in series or parallel to form battery packs, and electrical energy is transferred to the load through converters. There are two specific structural forms: 1) Multiple hydrogen fuel cells or batteries are first connected in series or parallel to form battery packs, which are then connected to the DC bus through Boost and bidirectional DC-DC converters, respectively. The electrical energy on the DC bus is transferred to the traction motor and auxiliary loads through DC-AC converters; 2) Hydrogen fuel cell packs are connected to the DC bus through unidirectional DC-DC converters, and battery packs are directly connected to the DC bus. The electrical energy on the DC bus is transferred to the traction motor and auxiliary loads through DC-AC converters.

[0005] Traditional topologies connect batteries in series or parallel to form a group, using a single converter to transmit power. This approach suffers from poor stability and a high failure rate. If the converter fails, the entire vehicle will lose power and become inoperable. Furthermore, in a series configuration, a failure in any one battery cell can also render the entire vehicle inoperable and even pose a safety hazard.

[0006] In traditional topologies, components such as switching thyristors withstand large voltages and currents, severely limiting the increase in locomotive power, with the current maximum power only reaching 2.4MW. Furthermore, this can easily lead to switching transistor failures and shutdowns, and the excessive voltage and current results in significant conduction losses.

[0007] It is evident that the above two methods suffer from poor stability and difficulty in significantly increasing the overall vehicle power, which are detrimental to the development, promotion, and stable operation of hydrogen fuel cell locomotives.

[0008] Therefore, it is essential to design a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system. Summary of the Invention

[0009] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system.

[0010] To achieve the above objectives, the present invention provides the following solution:

[0011] This invention provides a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system, comprising: a low-voltage DC bus, a transformer, a hybrid energy storage module, a high-voltage DC bus, and a traction motor drive module. The hybrid energy storage module consists of a hybrid energy storage half-bridge MMC module and a battery system. The traction motor drive module consists of a traction motor-driven half-bridge MMC module and a hydrogen fuel cell system. The AC side of the hybrid energy storage half-bridge MMC module is connected to the transformer, and the secondary side of the transformer is connected to a rectifier to convert AC to DC and transmit it to the low-voltage DC bus. The low-voltage DC bus supplies power to the connected auxiliary loads. The sub-module side of the hybrid energy storage half-bridge MMC module is connected to the battery system. The DC side of the hybrid energy storage half-bridge MMC module is connected to the high-voltage DC bus. The AC side of the traction motor-driven half-bridge MMC module is connected to an asynchronous motor load. The sub-module side of the traction motor-driven half-bridge MMC module is connected to the hydrogen fuel cell system. The DC side of the traction motor-driven half-bridge MMC module is connected to the high-voltage DC bus.

[0012] Preferably, the positive terminal of the battery system is connected to the inductor L. m The inductor L m The emitter of transistor S4 and the collector of transistor S5 are connected. A diode is connected between the emitter and collector of transistors S4 and S5. The emitter of transistor S5 is connected to the negative terminal of the battery system. The positive and negative terminals of the sub-module side of the hybrid energy storage half-bridge MMC module are respectively connected to the collector of transistor S4 and the emitter of transistor S5.

[0013] Preferably, the positive electrode of the hydrogen fuel cell system is connected to the inductor L.m The inductor L m A diode's positive terminal is connected to the collector of transistor S4. Another diode is connected between the emitter and collector of transistor S4. The emitter of transistor S4 is connected to the negative terminal of the hydrogen fuel cell system. The positive and negative terminals of the sub-module side of the hybrid energy storage half-bridge MMC module are respectively connected to the inductor L. m The negative terminal of the connected diode and the emitter of transistor S4.

[0014] Preferably, multiple traction motor drive modules are provided.

[0015] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0016] This invention provides a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system, including a low-voltage DC bus, a transformer, a hybrid energy storage module, a high-voltage DC bus, and a traction motor drive module. The hybrid energy storage module consists of a hybrid energy storage half-bridge MMC module and a battery system. The traction motor drive module consists of a traction motor-driven half-bridge MMC module and a hydrogen fuel cell system. The AC side of the hybrid energy storage half-bridge MMC module is connected to the transformer, and the secondary side of the transformer is connected to a rectifier to convert AC to DC and transmit it to the low-voltage DC bus. The low-voltage DC bus supplies power to the connected auxiliary loads. The sub-module side of the hybrid energy storage half-bridge MMC module is connected to the battery system. The DC side of the hybrid energy storage half-bridge MMC module is connected to the high-voltage DC bus. The AC side of the traction motor-driven half-bridge MMC module is connected to an asynchronous motor load. The sub-module side of the traction motor-driven half-bridge MMC module is connected to the hydrogen fuel cell system. The DC side of the traction motor-driven half-bridge MMC module is connected to the high-voltage DC bus. The proposed hydrogen fuel cell locomotive DC integrated power system can effectively improve the locomotive's traction power, increasing the overall vehicle power to 10MW. When a battery in the power system fails, the impact of the failure can be minimized, significantly improving the system's robustness and stability. This topology facilitates real-time energy management and allocation, thereby improving the overall vehicle's energy utilization efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1This is a schematic diagram of the DC integrated power system structure of a 10MW-class high-power hydrogen fuel cell locomotive according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the traditional MMC and its sub-module SM topology;

[0020] Figure 3 This is a schematic diagram showing the connection between the MMC submodule SM and the battery energy storage system;

[0021] Figure 4 This is a schematic diagram showing the connection between the MMC submodule SM and the hydrogen fuel cell system;

[0022] Figure 5 This is a schematic diagram of the electrical system topology of a traditional hydrogen fuel cell hybrid vehicle. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system, which can realize the efficient and stable power supply of hydrogen fuel cells and batteries to the traction and auxiliary systems, increase the power of the hydrogen fuel cell locomotive to 10MW, realize energy recovery and utilization, and reduce the degree of harm of battery failure to the operation of the whole vehicle, with good robustness and economy.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1As shown, this invention provides a 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system, including: a low-voltage DC bus, a transformer, a hybrid energy storage module, a high-voltage DC bus, and a traction motor drive module. The hybrid energy storage module consists of a hybrid energy storage half-bridge modular multilevel converter (MMC) module and a battery system. The traction motor drive module consists of a traction motor drive half-bridge MMC module and a hydrogen fuel cell system. The AC side of the hybrid energy storage half-bridge MMC module is connected to the transformer, and the secondary side of the transformer is connected to a rectifier to convert AC to DC and transmit it to the low-voltage DC bus. The low-voltage DC bus supplies power to the connected auxiliary loads. The sub-module side of the hybrid energy storage half-bridge MMC module is connected to the battery system. The DC side of the hybrid energy storage half-bridge MMC module is connected to the high-voltage DC bus. The AC side of the traction motor drive half-bridge MMC module is connected to an asynchronous motor load. The sub-module side of the traction motor drive half-bridge MMC module is connected to the hydrogen fuel cell system. The DC side of the traction motor drive half-bridge MMC module is connected to the high-voltage DC bus.

[0027] The difference between half-bridge MMC and full-bridge MMC lies in the number of switching devices in the sub-modules (SM). Both can be used in this scenario. Each sub-module of the half-bridge consists of two sets of switching devices, which is more cost-effective than the four sets required by the full-bridge, and has certain advantages.

[0028] The positive terminal of the battery system is connected to the inductor L. m The inductor L m The emitter of transistor S4 and the collector of transistor S5 are connected. A diode is connected between the emitter and collector of transistors S4 and S5. The emitter of transistor S5 is connected to the negative terminal of the battery system. The positive and negative terminals of the sub-module side of the hybrid energy storage half-bridge MMC module are respectively connected to the collector of transistor S4 and the emitter of transistor S5.

[0029] The positive electrode of the hydrogen fuel cell system is connected to the inductor L. m The inductor L m A diode's positive terminal is connected to the collector of transistor S4. Another diode is connected between the emitter and collector of transistor S4. The emitter of transistor S4 is connected to the negative terminal of the hydrogen fuel cell system. The positive and negative terminals of the sub-module side of the hybrid energy storage half-bridge MMC module are respectively connected to the inductor L. m The negative terminal of the connected diode and the emitter of transistor S4.

[0030] The traction motor drive module is provided in multiple ways.

[0031] MMC has 6 bridge arms, each containing N sub-modules. Each sub-module in a traditional MMC consists of two switches (each switch consisting of an IGBT and an anti-parallel diode) and a capacitor, such as... Figure 2 As shown, this invention improves upon the traditional MMC submodule by incorporating the battery system into the submodule via a DC-DC converter. Figure 1 In the left-side hybrid energy storage module, the MMC submodule is connected to the lithium titanate battery (other types of batteries, such as lithium iron phosphate, can also be used, but their performance is inferior to lithium titanate batteries) via a bidirectional DC-DC connection, forming a configuration such as... Figure 3 The hybrid energy storage module shown in the diagram has an MMC submodule in the right-side traction motor drive module connected to the hydrogen fuel cell via a Boost converter. The difference from a bidirectional DC-DC converter is that the upper arm of the converter is replaced by a diode instead of an IGBT. Figure 4 As shown, the bidirectional DC-DC converter between the battery and the submodule and the Boost converter between the hydrogen fuel cell and the submodule both adopt voltage outer loop and current inner loop control to provide a stable submodule voltage. The function of the submodule capacitor is to temporarily store the energy generated by the battery pack and release the energy when the submodule switch receives a signal to turn on.

[0032] By switching multiple sub-modules on the upper and lower bridge arms according to a certain pattern, DC voltage support and the conversion between DC and AC voltages are achieved. Let the output voltage of the sub-module be u. SM At any given time, the number of upper and lower bridge arm submodules activated is complementary and their sum equals N. For example, when the number of upper bridge arm SM activated is m, the number of lower bridge arm activated is Nm. The voltages of the upper and lower bridge arms at this time are:

[0033]

[0034] DC port voltage U dc AC port voltage u o and the voltages u of the upper and lower bridge arms p u n The relationship is shown in the following formula:

[0035]

[0036] This topology also includes two sets of DC buses, one high and one low. The high-voltage bus serves as the energy exchange hub between the hydrogen fuel cell, hybrid energy storage, and traction motor, while the low-voltage bus serves as the energy exchange hub between the hybrid energy storage and auxiliary power supply. Both play a crucial role in the energy allocation and management of the entire vehicle. The direction of energy flow depends on the specific operating conditions. For the energy storage module, it can both charge and discharge the battery. When the locomotive is running normally, i.e., the power output of the hydrogen fuel cell is exactly equal to the power required by the traction motor, the two modules supply power to the traction load and the auxiliary load, respectively. There is no energy exchange between the two MMCs on the high-voltage bus. There is energy exchange between the battery energy storage and the auxiliary power supply module on the low-voltage DC bus. When the power output of the hydrogen fuel cell is greater than the traction load, resulting in excess energy, or when the energy generated by the locomotive's regenerative braking motor flows back, this energy is transferred to the hybrid energy storage module through the high-voltage DC bus to charge the battery. When the locomotive is accelerating or climbing, and the power output of the hydrogen fuel cell is insufficient to drive the traction load alone, the energy stored in the energy storage module is transferred to the traction motor drive module through the high-voltage DC bus, together with the hydrogen fuel cell, to supply power to the traction load.

[0037] The working model of this invention is described below:

[0038] When the locomotive is running, the hydrogen fuel cell prioritizes powering the locomotive's traction load and auxiliary load. Generally speaking, the auxiliary power supply load is a constant value, while the traction load changes with the locomotive's acceleration, deceleration, and uphill / downhill conditions. It mainly consists of three operating conditions:

[0039] (1) When the power required by the traction and auxiliary load is less than the power output by the hydrogen fuel cell, the hydrogen fuel cell in the motor drive module works to supply power to the traction motor and auxiliary load separately. The battery in the hybrid energy storage module does not work. The working mode of the hybrid energy storage module is the same as that of the traditional MMC, with only the inverter function.

[0040] (2) When the power required for traction and auxiliary loads is greater than the power output of the hydrogen fuel cell, the hydrogen fuel cell in the motor drive module works and all the power it outputs is used to drive the traction motor. At this time, the battery in the hybrid energy storage module also starts to work, and part of the output power is used to power all auxiliary loads, and the other part makes up for the power difference of the hydrogen fuel cell traction motor.

[0041] (3) When the hydrogen fuel is exhausted and the fuel cell cannot work properly, the battery in the auxiliary power supply module works to supply power to the traction motor and auxiliary load separately. The hydrogen fuel cell in the traction motor drive module does not work. The MMC working mode of the hybrid energy storage module is the same as that of the traditional MMC, with only the inverter function.

[0042] This invention provides an embodiment that, for the designed power system topology, gives the selection of system parameters such as battery power and bus voltage for a 10MW locomotive. These parameters have been proven to be reasonable and feasible in the Simulink simulation of Matlab, and can also provide a reference for the design of parameters for locomotives of other power levels. The specific parameters are shown in Table 1.

[0043] Table 1 Detailed Parameters of Power System Components

[0044]

[0045] This invention has the following advantages:

[0046] 1. Modular design, easy to expand and with low failure rate; the electrical system topology of traditional hydrogen fuel cell hybrid vehicles is as follows: Figure 5 As shown, this topology uses centralized battery access, where multiple battery packs are first connected in series and parallel to form a battery pack, and then all battery power is transferred to the DC bus via a DC-DC converter. Although this topology is simple to control, it cannot provide high power due to the limitations of transistor voltage and current, and it cannot be expanded according to power demand. Furthermore, if one battery in a battery pack fails to work properly, it will affect the entire branch connected in series, causing a relatively large impact. However, with MMC, any submodule can be controlled independently without affecting each other, as long as the total number of submodules in operation in the bridge arm at any given time is N. When the power demand is high, the number of submodules in each bridge arm can be increased as needed, making it easy to expand. Moreover, when a battery connected to a certain submodule fails to work, that submodule can be taken out of operation, and other submodules can provide power, resulting in better operational stability.

[0047] 2. Significantly increase the power rating of the locomotive. Due to the limited number of transistors in the converter, the voltage bearing capacity of the converter in the traditional topology is relatively low. Therefore, the DC bus voltage level should not be designed too high, generally around several hundred volts. However, MMC uses more transistors, which can significantly increase the DC bus voltage and increase the power to 5-6 times the original.

[0048] 3. The multi-source system operates more flexibly. As mentioned above, the MMC can have different functions for different operating conditions. Its main advantage is that it can utilize the three-port characteristics of the MMC, namely, DC, AC and sub-module ports can all be used as power interfaces for energy transmission, conversion and distribution, which greatly improves the flexibility of the topology and its adaptability to complex operating conditions.

[0049] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0050] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A 10MW-class high-power hydrogen fuel cell locomotive DC integrated power system, characterized in that, include: The system comprises a low-voltage DC bus, a transformer, a hybrid energy storage module, a high-voltage DC bus, and a traction motor drive module. The hybrid energy storage module consists of a hybrid energy storage half-bridge MMC module and a battery system. The traction motor drive module consists of a traction motor drive half-bridge MMC module and a hydrogen fuel cell system. The AC side of the hybrid energy storage half-bridge MMC module is connected to the transformer, and the secondary side of the transformer is connected to a rectifier to convert AC to DC and transmit it to the low-voltage DC bus. The low-voltage DC bus supplies power to the connected auxiliary loads. The sub-module side of the hybrid energy storage half-bridge MMC module is connected to the battery system. The DC side of the hybrid energy storage half-bridge MMC module is connected to the high-voltage DC bus. The AC side of the traction motor drive half-bridge MMC module is connected to an asynchronous motor load. The sub-module side of the traction motor drive half-bridge MMC module is connected to the hydrogen fuel cell system. The DC side of the traction motor drive half-bridge MMC module is connected to the high-voltage DC bus. The positive terminal of the battery system is connected to the first inductor L. m The first inductor L m The emitter of the first transistor S4 and the collector of the second transistor S5 are connected. A diode is connected between the emitter and collector of the first transistor S4 and between the emitter and collector of the second transistor S5. The emitter of the second transistor S5 is connected to the negative terminal of the battery system. The positive and negative terminals of the sub-module side of the hybrid energy storage half-bridge MMC module are respectively connected to the collector of the first transistor S4 and the emitter of the second transistor S5. The positive electrode of the hydrogen fuel cell system is connected to a second inductor L. m The second inductor L m The anode of the first diode is connected to the collector of the third transistor S4. Another diode is connected between the emitter and collector of the third transistor S4. The emitter of the third transistor S4 is connected to the cathode of the hydrogen fuel cell system. The positive and negative terminals of the submodule side of the hybrid energy storage half-bridge MMC module are respectively connected to the second inductor L. m The cathode of the first diode and the emitter of the third transistor S4 are connected together.

2. The system according to claim 1, characterized in that, The traction motor drive module is provided in multiple ways.

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