Low-voltage power supply system and method for lithium battery of shield electric locomotive

Abstract

The present invention provides a low-voltage power supply system and method for a lithium battery of a shield electric traction locomotive, belonging to the technical field of lithium battery systems. The low-voltage power supply system for lithium battery includes a BMS, a switch module, a start switch, a low-voltage power supply battery, a DC / DC converter, and a blocking unit. The start switch is respectively connected to the keyon pin of the BMS and the positive electrode of the low-voltage power supply battery. The blocking unit is arranged between the positive electrode of the low-voltage power supply battery and the positive power supply port of the BMS. The negative power supply port of the BMS is connected to the control pin of the DC / DC converter through the switch module. When the start switch is closed, the low-voltage power supply battery supplies power to the switch module, causing the switch module to conduct, so as to control the control pin of the DC / DC converter to conduct with a low level, thereby controlling the operation of the DC / DC converter to supply power to the BMS.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery systems, and particularly to a low-voltage power supply system and method for a shield electric locomotive using lithium batteries. Background Art

[0002] In modern tunnel construction, as a key device, the stable and reliable operation of a shield electric locomotive is crucial for the project progress and safety. There are many problems in the power supply system of traditional shield electric locomotives, especially in the aspect of low-voltage power supply, which has become an important factor restricting the performance improvement of the locomotive.

[0003] Currently, most of the lithium batteries for shield electric locomotives refer to the low-voltage power supply scheme of conventional high-voltage lithium batteries. Lead-acid batteries are used to supply power to the BMS and internal components, and then DC-DC is used to convert high voltage to low voltage to charge the lead-acid batteries. In this scheme, the lead-acid batteries are directly connected to the BMS for constant power supply. When the lithium batteries are working, the lead-acid batteries are in a continuous charging and discharging process. However, the service life of lead-acid batteries is much lower than that of lithium batteries. Therefore, during the entire use process of the lithium battery system, it is inevitable to replace the lead-acid batteries. The process of replacing lead-acid batteries will inevitably damage the protection level of the lithium battery system; moreover, lead-acid batteries are more likely to leak liquid and release hydrogen during use, and have a greater self-discharge rate and are more likely to be over-discharged during long-term storage, posing a greater safety risk when installed in the lithium battery system. Summary of the Invention

[0004] The present invention provides a low-voltage power supply system and method for a shield electric locomotive using lithium batteries to solve the problems of short battery life and high danger existing in the prior art.

[0005] To achieve the above object, on the one hand, an embodiment of the present invention provides a low-voltage power supply system for a shield electric locomotive using lithium batteries. The low-voltage power supply system for lithium batteries includes a battery management system BMS, a switch module, a start switch, a low-voltage power supply battery, a DC / DC converter, and a blocking unit. The start switch is respectively connected to the keyon pin of the BMS and the positive electrode of the low-voltage power supply battery. The blocking unit is arranged between the positive electrode of the low-voltage power supply battery and the positive power supply port of the BMS. The negative power supply port of the BMS is connected to the control pin of the DC / DC converter through the switch module. When the start switch is closed, the low-voltage power supply battery supplies power to the switch module, causing the switch module to conduct, so as to control the control pin of the DC / DC converter to conduct with a low level, thereby controlling the DC / DC converter to work and supply power to the BMS.

[0006] Optionally, the start switch is a double-knife self-resetting switch.

[0007] Optionally, the blocking unit is a reverse diode for isolating the low-voltage power supply battery from the power supply port of the BMS.

[0008] Optionally, the switch module includes a relay K1 and its configured normally open switch, and a relay K2 and its configured normally open switch connected in parallel with the relay K1. When the start switch is closed, the coil of the relay K1 obtains power supply from the low-voltage power supply battery and is attracted, the control pin of the DC / DC converter accesses a low-level signal and starts to work, outputs voltage to supply power to the BMS, the keyon pin of the BMS obtains a high-level signal through the start switch, the BMS determines that the lithium battery is activated, attracts the relay K2, enables the control pin of the DC / DC converter to remain enabled, and the lithium battery enters the power-on process.

[0009] Optionally, the low-voltage power supply system of the lithium battery is further configured with a national standard charging port for charging and a supporting charging relay. The BMS is used to detect the CC2 hardware connection signal of each charging port to determine whether each charging port is safely connected to a charging gun, and when it is safely connected, determine whether the state of the lithium battery meets the requirement for entering charging.

[0010] Optionally, the low-voltage power supply system of the lithium battery is further configured with an external high-voltage power supply system. The positive and negative poles of the external high-voltage power supply system are connected to the DC / DC converter.

[0011] On the other hand, the present invention also provides a method for supplying low-voltage power to a lithium battery, which is applied to the above-mentioned low-voltage power supply system of the lithium battery. The method for supplying low-voltage power to the lithium battery includes: when a keyon signal is received and the duration of the keyon signal is within a preset time, detecting the CC2 hardware connection signal and the charging communication signal of the charging port. The keyon signal is a high-level signal obtained by the keyon pin of the BMS through the start switch when the start switch is pressed; when the connection signal and the charging communication signal are detected and the state of the lithium battery meets the charging requirement, attracting the corresponding charging relay to charge the lithium battery; when the keyon signal disappears, the connection signal disappears or the lithium battery is fully charged, ending the charging.

[0012] Optionally, the method for supplying low-voltage power to the lithium battery further includes: when the connection signal and the charging communication signal are not detected and the state of the lithium battery meets the discharging requirement, attracting the discharging relay to discharge the lithium battery; judging whether to end the discharging according to the duration of the keyon signal.

[0013] Optionally, the ending of the discharging or the ending of the charging includes: disconnecting all relays, reporting information on the end of charging or discharging, and delaying power-off and entering the sleep state.

[0014] On the other hand, the present invention also provides a shield electric traction locomotive, and the shield electric traction locomotive includes the above-mentioned lithium battery low-voltage power supply system.

[0015] The present invention provides a lithium battery low-voltage power supply system and method for a shield electric traction locomotive. The present invention uses a blocking unit for isolation, and cooperates with a start switch, a switch module, and a low-voltage small-capacity lithium battery to supply power to the low-voltage control system of the entire lithium battery through DC / DC and an external low-voltage power supply interface, with lower cost, longer lifespan, and higher safety. Moreover, the present invention adds a total negative relay at the negative electrode to avoid the risk of thermal runaway caused by the adhesion of the heating relay. Through the above method, the present invention establishes an effective lithium battery low-voltage power supply system and method, achieving safer high-voltage and low-voltage separation, lower failure rate of components, simplifying the start-up and power-down operation processes, and being able to intelligently judge the battery state, improving operation convenience and system safety, and comprehensively enhancing the overall performance and reliability of the low-voltage power supply system of the shield electric traction locomotive. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. In the drawings:

[0017] Figure 1 is the electrical principle structure schematic diagram of the lithium battery low-voltage power supply system of the present invention;

[0018] Figure 2 is the flowchart of the lithium battery low-voltage power supply method of the present invention;

[0019] Figure 3 is another flowchart of the lithium battery low-voltage power supply method of the present invention;

[0020] Figure 4 is the logic flowchart of the lithium battery low-voltage power supply method of the present invention;

[0021] Figure 5 is another electrical principle structure schematic diagram of the lithium battery low-voltage power supply system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following will detail the specific embodiments of the embodiments of the present invention with reference to the drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the embodiments of the present invention, and are not used to limit the embodiments of the present invention.

[0023] It should be noted that in the technical solution of this application, the acquisition, transmission, storage, use, processing, etc. of data all comply with the relevant provisions of national laws and regulations. In the embodiments of this application, some existing industry solutions such as certain software, components, models, etc. may be mentioned. They should be regarded as exemplary, and their purpose is only to illustrate the feasibility in the implementation of the technical solution of this application, but it does not mean that the applicant has already or necessarily used this solution.

[0024] In modern tunnel construction, as a key equipment, the stability and reliability of the shield electric traction locomotive are crucial for the project progress and safety. However, there are a series of problems in the low-voltage power supply system of the existing shield electric traction locomotive in terms of battery performance, charging management, starting and power-off operations, etc. There is an urgent need for an innovative technical solution to solve these problems, so as to improve the overall performance and reliability of the shield electric traction locomotive and meet the growing tunnel construction requirements.

[0025] In view of this problem, the present invention provides a lithium battery low-voltage power supply system and method for a shield electric traction locomotive. By using lithium batteries to replace traditional lead-acid batteries, problems such as low energy density, slow charging, and short life are solved, and the endurance and operation efficiency are improved; at the same time, a total negative relay is added to the negative electrode to avoid the risk of thermal runaway caused by the adhesion of the heating relay; the starting and power-off operation processes are also simplified, the battery state is intelligently judged, the operation convenience and system safety are improved, the overall performance and reliability of the low-voltage power supply system of the shield electric traction locomotive are comprehensively improved, and the cost is lower and the life is longer.

[0026] The following will be combined with Figures 1 - 4 Specifically describe the present invention.

[0027] Figure 1 is a schematic diagram of the electrical principle structure of the lithium battery low-voltage power supply system provided by the embodiment of the present invention.

[0028] As Figure 1 shown, the embodiment of the present invention provides a lithium battery low-voltage power supply system for a shield electric traction locomotive. The lithium battery low-voltage power supply system includes a battery management system BMS, a switch module, a start switch, a low-voltage power supply battery, a DC / DC converter, and a blocking unit. The start switch is respectively connected to the keyon pin of the BMS and the positive electrode of the low-voltage power supply battery. The blocking unit is arranged between the positive electrode of the low-voltage power supply battery and the positive power supply port of the BMS. The negative power supply port of the BMS is connected to the control pin of the DC / DC converter through the switch module. When the start switch is closed, the low-voltage power supply battery supplies power to the switch module, making the switch module conduct, so as to control the control pin of the DC / DC converter to conduct with the low level, thereby controlling the DC / DC converter to work and supply power to the BMS.

[0029] Preferably, the DC / DC converter in the embodiment of the present invention is a DC / DC converter with a control pin. The operation of the DC / DC converter is controlled by controlling the high and low levels of the control pin of the DC / DC converter. The control pin of the DC / DC converter is a high-impedance pin, and the current during conduction is in the microampere level. Therefore, the relay for connecting the high and low levels by the controller will not generate a large current impact during operation, and there is no risk of adhesion for this relay. When the DC / DC converter is working, it can not only supply power to the BMS but also to the low-voltage power supply battery to ensure that the low-voltage power supply battery is always in a state close to full charge.

[0030] Preferably, the start switch K in the embodiment of the present invention is a double-pole self-resetting switch.

[0031] The double-pole self-resetting switch has two independent circuit paths, that is, two sets of contacts. These two sets of contacts can control two different circuits simultaneously or control different parts of the same circuit. In this low-voltage power supply system for lithium batteries, one set of contacts can be used to send a start signal to the BMS, and the other set of contacts can be used to control the on / off of other auxiliary circuits. The double-pole self-resetting switch can control the power-on and power-off of the lithium battery without other complex operations, with lower cost and better customer experience.

[0032] Preferably, the blocking unit is a reverse diode D1, which is used to isolate the low-voltage power supply battery from the power supply port of the BMS.

[0033] When the double-pole button switch pops up, the low-voltage power supply battery does not supply power to the BMS. Only when the double-pole button is pressed, the low-voltage power supply battery supplies power to the BMS. Therefore, the low-voltage power supply battery does not need a large capacity, so a lithium battery with a smaller volume, smaller capacity, and longer life is selected.

[0034] Preferably, the switch module includes a relay K1 and its configured normally open switch, and a relay K2 and its configured normally open switch connected in parallel with the relay K1.

[0035] When the start switch is closed, the coil of the relay K1 obtains power supply from the low-voltage power supply battery and is attracted. The control pin of the DC / DC converter accesses a low-level signal and starts to work, and the output voltage supplies power to the BMS. The keyon pin of the BMS obtains a high-level signal through the start switch, and the BMS determines that the lithium battery is activated, attracts the relay K2, enables the control pin of the DC / DC converter to be maintained, and the lithium battery enters the power-on process.

[0036] In a preferred embodiment of the present invention, when the start switch is pressed, the relay K1 coil is powered by the low-voltage power supply battery. The conduction of the K1 relay is used to control the control pin of the DC / DC converter to conduct with the low level, thereby controlling the operation of the DC / DC converter. After the DC / DC converter operates, it directly powers the BMS. Among them, the relay K1 only conducts the low-level signal, and its signal current is only a few microamperes. Therefore, a relay with a smaller power and over-current capacity can be selected for the relay K1 to ensure its long service life. At the same time, since the power of the relay K1 is very small, the current when the contacts of the start switch are in contact and disconnected is very small, ensuring that the start switch has a long service life. Therefore, the present invention achieves high-voltage and low-voltage separation, is safer, and has a lower failure rate of components.

[0037] Preferably, the lithium battery low-voltage power supply system is further configured with a national standard charging port for charging and a supporting charging relay. The BMS is used to detect the CC2 hardware connection signal of each charging port to determine whether each charging port is safely connected to the charging gun, and when it is safely connected, it determines whether the state of the lithium battery meets the condition for entering charging.

[0038] In a preferred embodiment of the present invention, since the shield tunneling electric locomotive belongs to a rail vehicle, in order to facilitate vehicle charging, national standard charging ports are installed on both sides of the vehicle. The present invention detects whether the charging gun is plugged into the national standard charging port through the hardware detection interface of the BMS. Only when the charging gun is plugged in, the charging relay K5 corresponding to the charging port of the lithium battery will be energized, ensuring that the charging port without the plugged gun is not charged with high voltage, which is safer. And the user can freely choose single-gun charging and double-gun charging according to the on-site conditions, making it more flexible to use.

[0039] Preferably, the lithium battery low-voltage power supply system is further configured with an external high-voltage power supply system. The positive and negative poles of the external high-voltage power supply system are connected to the DC / DC converter, and the DC / DC converter can convert the external high voltage into a suitable low voltage to supply power to the system.

[0040] As Figure 5 shown, the external high-voltage power supply system includes a total negative relay K3, a heating film HT, and a heating relay K8. The heating relay K8 is connected to the heating film HT to control the on and off of the heating film HT. The heating film HT is connected to the contact of the total negative relay K3 close to the load end. When the heating relay K8 fails due to adhesion, the total negative relay K3 disconnects the heating circuit.

[0041] The invention adds a total negative relay K3 at the negative pole to meet the dual protection requirements of CE / UL certification. And the heating film is connected to the contact of the total negative relay K3 close to the load end. When the heating relay K8 fails due to adhesion, the total negative relay K3 with a larger over-current can be used to disconnect the heating circuit. Avoid the risk of thermal runaway caused by the adhesion of the heating relay K8.

[0042] Preferably, the BMS is configured to: monitor the operating data of the lithium battery, including temperature, current, and power;

[0043] Change the charge and discharge state of the lithium battery according to the start switch signal and control the closing of all relays.

[0044] The BMS can monitor the operating data of the lithium battery in real time and receive the start switch K signal, and then switch the charge and discharge state of the lithium battery by changing the closing state of the relay.

[0045] Preferably, the BMS is further configured to: when the lithium battery is charging, when the monitored temperature of the lithium battery is greater than the allowable charging temperature and less than the optimal operating temperature, turn on the heating relay; when the monitored temperature of the lithium battery is less than the allowable charging temperature, disconnect the total negative relay; when the lithium battery is discharging, when the temperature of the lithium battery is less than the optimal operating temperature, turn on the heating relay; when the temperature of the lithium battery reaches the optimal operating temperature, turn off the heating relay.

[0046] For example, when the lithium battery is charging, the optimal operating temperature is, for example, 25 degrees, the allowable charging temperature is, for example, 0 degrees, and when the monitored temperature of the lithium battery is, for example, 10 degrees, the BMS turns on the heating relay K8 to energize the heating film HT to heat the lithium battery and enter the charging and heating mode; when the monitored temperature of the lithium battery is, for example, -5 degrees, the BMS disconnects the total negative relay K3 to enter the pure heating mode. When the lithium battery is discharging, the optimal operating temperature is, for example, 20 degrees, and when the monitored temperature of the lithium battery is, for example, 10 degrees, the BMS turns on the heating relay K8 to heat the lithium battery. When the lithium battery is heated to 20 degrees, the BMS disconnects the heating relay K8 to stop heating.

[0047] The heating strategy for charging and heat preservation and the heating strategy for discharging and preheating ensure that the battery cells are in the optimal state during the use of the lithium battery and do not easily trigger the protection of the battery cells, thus causing a sudden power-off of the lithium battery system during use.

[0048] Preferably, the present invention also reserves an external start power supply interface, and the BMS can also be activated by an external power supply in the case of abnormalities of the built-in low-voltage power supply battery and the DC / DC converter.

[0049] Figure 2 It is a flowchart of the method for supplying low-voltage power to a lithium battery provided by an embodiment of the present invention.

[0050] As Figure 2 shown, a method for supplying low-voltage power to a lithium battery provided by the present invention is applied to the above-mentioned low-voltage power supply system for a lithium battery. The method for supplying low-voltage power to a lithium battery includes:

[0051] Step 101, when a keyon signal is received and the duration of the keyon signal is within a preset time, detect the CC2 hardware connection signal and the charging communication signal of the charging port. The keyon signal is a high-level signal obtained by the keyon pin of the BMS through the start switch when the start switch is pressed;

[0052] Step 102, when the connection signal and the charging communication signal are detected and the state of the lithium battery meets the charging requirements, engage the corresponding charging relay to charge the lithium battery;

[0053] Step 103, end the charging when the keyon signal disappears, the connection signal disappears, or the lithium battery is fully charged.

[0054] Preferably, in Step 101, when the start switch is pressed, the coil of relay K1 obtains power supply from the low-voltage power supply battery and engages. After relay K1 engages, the control pin of the DC / DC converter accesses a low-level signal and starts to work, outputting 24V to supply power to the BMS. At the same time, the keyon pin of the BMS obtains a high-level signal through the start switch. In this way, when the start switch is pressed, the BMS obtains 24V power supply and detects the keyon signal. At this time, the BMS determines that the low-voltage power supply battery is activated and immediately engages relay K2 to keep the DC control pin enabled, and the lithium battery enters the power-on process.

[0055] During the above process, due to the function of the reverse diode D1, the low-voltage power supply battery is only used to supply power to K1. When the DC / DC converter starts to work, the low-voltage power supply battery ends its discharge. At this time, the low-voltage power supply battery is in a floating charge state by the DC / DC converter, and the power is maintained above 90%.

[0056] Preferably, in Step 102, the BMS determines whether each charging port is safely connected to the charging gun by separately detecting the CC2 hardware connection signal of each charging port. After reliable connection, the charging relay of the corresponding charging port is opened to ensure that the charging interface without a connected charging gun is not powered.

[0057] Preferably, in Step 103, to determine whether the lithium battery is fully charged, since the lithium battery does not communicate with the entire vehicle, when there is a large feedback current under a high voltage state, the lithium battery is prone to trigger an overvoltage fault. Therefore, the lithium battery adopts a low-voltage pulse charging scheme. Each time the highest single cell is charged to 3.45V, the charging current is halved and charging continues, and so on, until the current is less than 0.1C. This charging scheme can ensure that the battery voltage will not be very high when the battery charging ends and the battery power can be guaranteed to be in a high state.

[0058] As Figure 3 shown, a method for low-voltage power supply of a lithium battery provided by the present invention further includes:

[0059] Step 201: When the connection signal and the charging communication signal are not detected and the state of the lithium battery meets the discharge requirement, the discharge relay K6 is closed to discharge the lithium battery.

[0060] Step 202: Determine whether to end the discharge according to the duration of the keyon signal.

[0061] Preferably, determining whether to end the discharge according to the duration of the keyon signal includes: if the duration of the keyon signal is greater than the preset time, continue discharging; if the duration of the keyon signal is less than the preset time, end the discharge.

[0062] In a preferred embodiment of the present invention, when the start switch is pressed, the BMS will detect the keyon high-level signal. When the start switch is continuously pressed for more than the preset time, the BMS considers that the user needs to power down the lithium battery, and at this time, the lithium battery enters the power-down process. Combining with the power-on step, a start switch can realize the functions of short-press power-on and long-press power-off.

[0063] For example, as Figure 4 shown, the preset time is, for example, 5 seconds. When the start switch is pressed for more than 5 seconds, that is, when the duration of the keyon signal exceeds 5 seconds, the lithium battery continues to be discharged. When the start switch is pressed within 5 seconds, that is, when the duration of the keyon signal does not exceed 5 seconds, the discharge of the lithium battery ends.

[0064] Preferably, ending the discharge or ending the charging includes: disconnecting all relays, reporting the end information of charging or discharging, and delaying power-down and entering the sleep state. When the system determines that the charging or discharging is over, it will automatically cut off all relays and stop the lithium battery from discharging.

[0065] A method for low-voltage power supply of a lithium battery provided by the present invention converts the charge and discharge states through the duration of the keyon signal, detects the CC2 hardware connection signal and the charging communication signal of the charging port, and closes the corresponding relays to perform the charge and discharge operations. A start switch can realize short-press power-on and long-press power-off, simplifying the power-on and power-off operation process.

[0066] A lithium battery low-voltage power supply system and method for a shield electric traction locomotive provided by the invention enable the low-voltage power supply battery to supply power to the BMS only for a short time through a blocking unit and a switching module, extending the service life of the low-voltage power supply battery, making the separation of high and low voltages safer, and having a lower failure rate of components. At the same time, the relay K1 selects a relay with a smaller power and over-current capacity, delaying its own service life. The power-on and power-off of the lithium battery can be controlled through a start switch, simplifying the power-on and power-off process and enhancing the user experience. In addition, whether a charging gun is plugged into the national standard charging port is detected through the hardware detection interface of the BMS. Only when the charging gun is plugged in will the charging relay corresponding to the charging port of the lithium battery be energized, ensuring that the charging port without the plugged-in gun does not carry high voltage and improving the safety of the power supply system.

[0067] On the other hand, the invention also protects a shield electric traction locomotive, and the shield electric traction locomotive includes the above lithium battery low-voltage power supply system.

[0068] It should be understood that in various embodiments of the invention, the magnitudes of the sequence numbers of the above processes do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the invention.

[0069] In addition, the terms "system" and "network" are often used interchangeably in this article. The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0070] It should be understood that in the embodiments of the invention, "B corresponding to A" means that B is associated with A, and B can be determined according to A. However, it should also be understood that determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0071] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the invention.

[0072] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0073] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed couplings or direct couplings or communication connections to each other can be indirect couplings or communication connections through some interfaces, devices, or units, and can also be in electrical, mechanical, or other forms of connection.

[0074] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiments of the present invention.

[0075] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0076] Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by hardware, or by firmware, or by a combination thereof. When implemented in software, the above functions can be stored in a computer-readable medium or transmitted as one or more instructions or codes on a computer-readable medium. The computer-readable medium includes computer storage media and communication media, where the communication media includes any medium that facilitates the transfer of a computer program from one place to another. The storage media can be any available medium that can be accessed by a computer. By way of example but not limitation: the computer-readable medium can include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection can suitably be a computer-readable medium. For example, if the software is transmitted using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technologies such as infrared, radio and microwave from a website, server or other remote source, then the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, wireless and microwave are included in the definition of the medium. As used in the present invention, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks generally reproduce data magnetically, while discs reproduce data optically with a laser. The above combinations should also be included within the scope of protection of the computer-readable medium.

[0077] In summary, the above are only the preferred embodiments of the technical solution of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-voltage power supply system for a lithium battery of a shield electric locomotive, characterized in that The low-voltage power supply system of the lithium battery includes a battery management system BMS, a switch module, a start switch, a low-voltage power supply battery, a DC / DC converter, and a blocking unit. The start switch is respectively connected to the keyon pin of the BMS and the positive electrode of the low-voltage power supply battery. The blocking unit is arranged between the positive electrode of the low-voltage power supply battery and the positive power supply port of the BMS. The negative power supply port of the BMS is connected to the control pin of the DC / DC converter through the switch module. When the start switch is closed, the low-voltage power supply battery supplies power to the switch module, making the switch module conduct, so as to control the control pin of the DC / DC converter to conduct with the low level, thereby controlling the DC / DC converter to work and supply power to the BMS. The switch module includes a relay K1 and its configured normally open switch, and a relay K2 and its configured normally open switch connected in parallel with the relay K1. When the start switch is closed, the coil of the relay K1 obtains power supply from the low-voltage power supply battery and is attracted, and the control pin of the DC / DC converter accesses a low-level signal and starts to work, and the output voltage supplies power to the BMS. The keyon pin of the BMS obtains a high-level signal through the start switch, and the BMS judges that the lithium battery is activated, attracts the relay K2, and keeps the control pin of the DC / DC converter enabled, and the lithium battery enters the power-on process.

2. The low-voltage power supply system for a lithium battery according to claim 1, wherein The start switch is a double-knife self-resetting switch.

3. The low-voltage power supply system for a lithium battery according to claim 1, characterized in that, The blocking unit is a reverse diode, which is used to isolate the low-voltage power supply battery from the power supply port of the BMS.

4. The low-voltage power supply system for a lithium battery according to claim 1, wherein The low-voltage power supply system of the lithium battery is also configured with a national standard charging port for charging and a supporting charging relay. The BMS is used to detect the CC2 hardware connection signal of each charging port to judge whether each charging port is safely connected to the charging gun. And when it is safely connected, judge whether the state of the lithium battery meets the requirement for charging.

5. The low-voltage power supply system for a lithium battery according to claim 1, characterized in that, The low-voltage power supply system of the lithium battery is also configured with an external high-voltage power supply system, and the positive and negative poles of the external high-voltage power supply system are connected to the DC / DC converter.

6. A method for supplying power to a lithium battery at low voltage, characterized in that, Applied to the low-voltage power supply system of the lithium battery according to claims 1-5, the method for supplying power to the lithium battery includes: When a keyon signal is received and the duration of the keyon signal is within a preset time, detect the CC2 hardware connection signal and the charging communication signal of the charging port. The keyon signal is a high-level signal obtained by the keyon pin of the BMS through the start switch when the start switch is pressed. When the connection signal and the charging communication signal are detected and the state of the lithium battery meets the charging requirements, attract the corresponding charging relay to charge the lithium battery. When the keyon signal disappears, the connection signal disappears or the lithium battery is fully charged, end the charging. When the connection signal and the charging communication signal are not detected and the state of the lithium battery meets the discharge requirements, attract the discharge relay to discharge the lithium battery. Judge whether to end the discharge according to the duration of the keyon signal. After the end of the discharge or the end of the charging, it also includes: Disconnect all relays, report the information of the end of charging or discharging, and delay powering off and going to sleep.

7. A shield electric tractor locomotive, characterized in that, The shield electric locomotive includes the lithium battery low-voltage power supply system described in any one of claims 1-5.

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