Hybrid electric locomotive and power battery pack capacity balancing control method and system

Abstract

The present invention discloses a hybrid locomotive and power battery pack capacity balancing control method and system. The control method comprises obtaining the capacity difference between a first power battery pack and a second power battery pack and the required traction force during a dynamic traction phase; allocating the required traction force based on the capacity difference, causing the first traction converter and the second traction converter to respectively provide the allocated traction force, thereby achieving capacity balancing control between the first and second power battery packs. While maintaining the same hardware circuitry, the present invention controls the two traction converters to enable the power battery pack with a higher state of charge to provide greater traction energy to the entire vehicle, achieving dynamic capacity balancing between the two power battery packs and preventing the significant impact of power loss on locomotive operation.

Description

Technical Field

[0001] The present invention belongs to the field of rail transportation technology, and in particular relates to a hybrid locomotive and a power battery pack capacity balancing control method and system. Background Art

[0002] As hybrid locomotives become increasingly common in the rail transit industry, demands for the battery's endurance are also increasing. Improving battery endurance inevitably requires increasing battery capacity. For safety reasons, large-capacity batteries are now grouped and energy is divided across multiple battery cabinets to ensure safety.

[0003] When multiple power battery cabinets are supplying power to the traction inverter, the positive and negative terminals of all the power batteries can be connected in parallel into a single group before being connected to the traction inverter. This approach can minimize capacity differences between the individual power battery cabinets. However, this approach has the disadvantage that if a short circuit or other fault occurs in one of the traction inverters, the locomotive will lose all power until the fault is corrected, potentially causing serious problems such as machine failure (i.e., inability to operate due to a machine failure).

[0004] Therefore, in the current design method, multiple power battery cabinets are divided into two groups (such as Figure 1 The first power battery pack and the first power battery pack shown in the figure respectively supply power to the first traction inverter and the second traction inverter. At this time, even if there is a problem with one of the traction inverters, the redundant operation of the locomotive can be guaranteed by cutting off, isolating and other measures, and the fault can be checked after returning to the depot.

[0005] This design also has a problem: hybrid locomotives are mostly used for shunting operations, which have a long wheel stop time (i.e., the railway hump shunting yard stops shunting operations so that maintenance units can start repairing equipment). This causes the first power battery pack that supplies power to the first auxiliary inverter to decrease in power slowly, while the second power battery pack 2 that supplies power to the second auxiliary inverter decreases in power quickly. Figure 2 When the wheels are stopped for more than a certain period of time, the capacity of the two power battery packs will be very different. The first power battery pack may even drop to the level of feed protection while the second power battery pack is still at a higher level. In this case, the locomotive will lose power, which will have a great impact on the use of the locomotive. Summary of the Invention

[0006] The purpose of the present invention is to provide a hybrid electric locomotive and a power battery pack capacity balancing control method and system to solve the capacity imbalance problem of two power battery packs in traditional power battery design methods.

[0007] The present invention solves the above technical problems through the following technical solutions: A power battery pack capacity balancing control method is applied to a vehicle, wherein the power battery pack includes a first power battery pack and a second power battery pack, the first power battery pack is connected to a first traction converter, and the second power battery pack is connected to a second traction converter; the control method includes:

[0008] In the dynamic traction phase, the capacity difference between the first power battery pack and the second power battery pack and the required traction force are obtained;

[0009] The required traction force is distributed according to the capacity difference, so that the first traction converter and the second traction converter respectively provide the distributed traction force, thereby achieving capacity balancing control of the first power battery pack and the second power battery pack.

[0010] Furthermore, allocating the required traction force according to the capacity difference so that the first traction converter and the second traction converter respectively provide the allocated traction force specifically includes:

[0011] When the capacity difference is less than a first capacity difference threshold, the required traction force is equally distributed so that the first traction converter and the second traction converter respectively provide the same traction force;

[0012] When the capacity difference is greater than or equal to a first capacity difference threshold, the required traction force is unequally distributed, the required traction power is calculated based on the required traction force, and the unequal distribution ratio is determined based on the required traction power.

[0013] Furthermore, determining the unequal distribution ratio according to the required traction power includes:

[0014] When the required traction power is greater than the power threshold, the unequal distribution ratio is m:n; where m>n and n≠0, the traction converter corresponding to the power battery pack with a higher state of charge provides a greater traction force, and the traction converter corresponding to the power battery pack with a lower state of charge provides a smaller traction force;

[0015] When the required traction power is less than or equal to the power threshold, the unequal distribution ratio is m:n; where m>n and n=0, the traction converter corresponding to the power battery pack with a higher state of charge provides all the required traction power.

[0016] Furthermore, when the required traction power is greater than the power threshold, the unequal distribution ratio is 0.55:0.45.

[0017] Preferably, whether the required traction power is greater than a power threshold is determined according to the level of the driver controller handle; wherein, the power threshold is 50% of the rated power of the vehicle.

[0018] Furthermore, the first auxiliary inverter in the first traction converter is connected to the first auxiliary transformer via a first contactor, the second auxiliary inverter in the second traction converter is connected to the second auxiliary transformer via a second contactor, and the second end of the first contactor is connected to the second end of the second contactor via a third contactor; wherein the second ends of the first contactor and the second contactor are ends close to the corresponding auxiliary transformers;

[0019] The control method also includes power battery pack capacity balancing control in the static standby stage, specifically including:

[0020] Obtaining a capacity difference between the first power battery pack and the second power battery pack;

[0021] When the capacity difference is less than a second capacity difference threshold, controlling the first contactor and the second contactor to close, and controlling the third contactor to open, so that the auxiliary system operates in a normal power supply mode;

[0022] When the capacity difference is greater than or equal to the second capacity difference threshold, the contactor corresponding to the power battery pack with a higher state of charge and the third contactor are controlled to close, and the contactor corresponding to the power battery pack with a lower state of charge is controlled to open, so that all auxiliary loads are powered by the power battery pack with a higher state of charge.

[0023] Furthermore, the second capacity difference threshold is greater than the first capacity difference threshold; wherein, the first capacity difference threshold is the capacity difference threshold during capacity balancing control in the dynamic traction stage.

[0024] Based on the same concept, the present invention provides a power battery pack capacity balancing control system, wherein the power battery pack includes a first power battery pack and a second power battery pack, wherein the first power battery pack is connected to a first traction converter, and the second power battery pack is connected to a second traction converter; the system includes:

[0025] The central control unit is configured to obtain, during a dynamic traction phase, a capacity difference between the first power battery pack and the second power battery pack and a required traction force; allocate the required traction force according to the capacity difference, and send the allocated two traction forces to the first traction control unit and the second traction control unit, respectively;

[0026] a first traction force control unit, configured to control the first traction converter according to the traction force allocated by the central control unit, so that the first traction converter provides corresponding traction force;

[0027] The second traction force control unit is configured to control the second traction converter according to the traction force allocated by the central control unit, so that the second traction converter provides corresponding traction force.

[0028] Furthermore, the central control unit distributes the required traction force according to the capacity difference, specifically including:

[0029] When the capacity difference is less than a first capacity difference threshold, the required traction force is equally distributed so that the first traction converter and the second traction converter provide the same traction force;

[0030] When the capacity difference is greater than or equal to a first capacity difference threshold, the required traction force is unequally distributed, the required traction power is calculated based on the required traction force, and the unequal distribution ratio is determined based on the required traction power.

[0031] Furthermore, the first auxiliary inverter in the first traction converter is connected to the first auxiliary transformer via a first contactor, the second auxiliary inverter in the second traction converter is connected to the second auxiliary transformer via a second contactor, and the second end of the first contactor is connected to the second end of the second contactor via a third contactor; wherein the second ends of the first contactor and the second contactor are ends close to the corresponding auxiliary transformers;

[0032] The central control unit is further configured to obtain a capacity difference between the first power battery pack and the second power battery pack during a static standby phase; when the capacity difference is less than a second capacity difference threshold, control the first contactor and the second contactor to close, and control the third contactor to disconnect, so that the auxiliary system operates in a normal power supply mode; when the capacity difference is greater than or equal to the second capacity difference threshold, control the contactor and the third contactor corresponding to the power battery pack with a higher state of charge to close, and control the contactor corresponding to the power battery pack with a lower state of charge to disconnect, so that the power battery pack with a higher state of charge supplies power to all auxiliary loads.

[0033] Based on the same concept, the present invention provides a hybrid locomotive, comprising the power battery pack capacity balancing control system as described above.

[0034] Beneficial effects

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] On the basis of keeping the hardware circuit unchanged, the present invention controls two traction converters to enable the power battery pack with a higher state of charge to provide greater traction energy to the entire vehicle, thereby achieving dynamic capacity balance of the two power battery packs and avoiding the significant impact of power loss on locomotive use.

[0037] The present invention does not require modification of the original hardware circuit, has good economical efficiency, and improves the reliability of the control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is a schematic diagram of the power supply principle of power batteries in grouping in the background technology of the present invention;

[0040] Figure 2 This is a schematic diagram of the power supply principle of the existing locomotive auxiliary circuit in the background technology of the present invention;

[0041] Figure 3 It is a flow chart of the power battery pack capacity balancing control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0043] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0044] Example 1

[0045] like Figure 1 As shown, when the power batteries are grouped for power supply, the power batteries are divided into two groups, namely a first power battery group and a second power battery group. The first power battery group is connected to the first traction inverter, and the second power battery group is connected to the second traction inverter. The first power battery group supplies power to the first traction inverter, and the second power battery group supplies power to the second traction inverter.

[0046] like Figure 3 As shown, a power battery pack capacity balancing control method provided by an embodiment of the present invention includes capacity balancing control in the dynamic traction stage and capacity balancing control in the static standby stage. The central control unit CCU determines whether the locomotive is in the dynamic traction stage or the static standby stage based on whether the locomotive speed V is greater than 0. The capacity balancing control in the dynamic traction stage includes:

[0047] Step A1: The central control unit CCU identifies the operating state of the locomotive (speed V is greater than 0) and obtains the capacity difference ΔSOC between the first power battery pack and the second power battery pack and the required traction force F;

[0048] Step A2: The central control unit CCU allocates the required traction force F according to the capacity difference ΔSOC obtained in step A1, and sends the two allocated traction forces F1 / F2 to the first traction control unit TCU1 and the second traction control unit TCU2, respectively, so that the first traction control unit TCU1 controls the first traction inverter to provide the allocated traction force F1, and the second traction control unit TCU2 controls the second traction inverter to provide the allocated traction force F2, thereby achieving capacity balancing control between the first power battery pack and the second power battery pack; wherein F=F1+F2.

[0049] In a specific embodiment of the present invention, the central control unit CCU allocates the required traction force F according to the capacity difference ΔSOC obtained in step A1, specifically including:

[0050] When the capacity difference ΔSOC is less than the first capacity difference threshold, it indicates that the charge states of the first power battery pack and the second power battery pack are similar. The locomotive operates in normal traction mode, with the first traction converter and the second traction converter jointly pulling the vehicle. The first traction converter and the second traction converter have the same traction power. Therefore, the central control unit CCU equally distributes the required traction force F so that the first traction converter and the second traction converter provide the same traction force, that is, the traction force F1 / F2 provided by the first traction converter and the second traction converter are both 0.5F.

[0051] When the capacity difference ΔSOC is greater than or equal to the first capacity difference threshold, the locomotive enters the SOC dynamic balancing mode, and the central control unit CCU distributes the required traction force F unequally, calculates the required traction power S based on the required traction force F, and determines the unequal distribution ratio based on the required traction power S;

[0052] When the capacity difference △SOC is equal to 0, exit the SOC dynamic balancing mode.

[0053] In a specific embodiment of the present invention, determining the unequal distribution ratio according to the required traction power includes:

[0054] When the required traction power S is greater than the power threshold, the unequal distribution ratio is m:n; where m>n and n≠0, the traction converter corresponding to the power battery pack with a higher state of charge provides greater traction force, and the traction converter corresponding to the power battery pack with a lower state of charge provides less traction force;

[0055] When the required traction power S is less than or equal to the power threshold, the unequal distribution ratio is m:n; where m>n and n=0, the traction converter corresponding to the power battery pack with a higher state of charge provides all the required traction power.

[0056] For example, if the state of charge of the first power battery pack is higher and the state of charge of the second power battery pack is lower, then when the required traction power S is greater than the power threshold, the traction force F1 provided by the first traction converter corresponding to the first power battery pack is mF / (m+n), and the traction force F2 provided by the second traction converter corresponding to the second power battery pack is nF / (m+n). That is, the first traction converter and the second traction converter jointly pull the current, but the traction power of the first traction converter is greater than the traction power of the second traction converter. The first power battery pack provides more traction energy than the second power battery pack, thereby achieving dynamic capacity balancing control of the power battery packs.

[0057] When the required traction power S is less than or equal to the power threshold, the first traction inverter corresponding to the first power battery pack provides the entire traction force F (i.e., F=F1), that is, the first traction inverter is used for traction alone, the first power battery pack provides all traction energy, and the second power battery pack does not provide traction energy, so that the capacity of the first power battery pack and the second power battery pack are gradually balanced.

[0058] In this embodiment, when the required traction power S is greater than the power threshold, the unequal distribution ratio is 0.55:0.45, that is, the traction force F1 provided by the first traction converter is 0.55F, and the traction force F2 provided by the second traction converter is 0.45F.

[0059] In this embodiment, whether the required traction power S is greater than the power threshold is determined based on the level of the driver controller handle; wherein the power threshold is 50% of the rated power Smax of the vehicle (i.e., the maximum level of the driver controller handle).

[0060] like Figure 2 As shown, the first auxiliary inverter in the first traction converter is connected to the first auxiliary transformer through the first contactor K01, the second auxiliary inverter in the second traction converter is connected to the second auxiliary transformer through the second contactor K02, and the second end of the first contactor K01 is connected to the second end of the second contactor K02 through the third contactor K03; wherein, the second end of the first contactor K01 and the second contactor K02 refers to the end close to the corresponding auxiliary transformer.

[0061] The output side of the first auxiliary transformer is connected to multiple variable-frequency and variable-voltage load branches, while the output side of the second auxiliary transformer is connected to multiple fixed-frequency and constant-voltage load branches. Each variable-frequency and variable-voltage load branch or each fixed-frequency and constant-voltage load branch is connected to the corresponding auxiliary transformer via multiple relay contacts. The output of the first auxiliary transformer is also connected to the output of the second auxiliary transformer via a fourth relay K04.

[0062] Capacity balancing control during the static standby phase includes:

[0063] Step B1: The central control unit CCU identifies the running state of the locomotive (speed V is equal to 0) and obtains the capacity difference ΔSOC between the first power battery pack and the second power battery pack;

[0064] Step B2: The central control unit CCU controls the switching states of the first contactor K01, the second contactor K02 and the third contactor K03 according to the capacity difference ΔSOC obtained in step B1, so as to achieve capacity balancing control between the first power battery pack and the second power battery pack.

[0065] Specifically, when the capacity difference ΔSOC is less than the second capacity difference threshold, indicating that the state of charge of the first power battery pack and the second power battery pack are similar, the central control unit CCU controls the first contactor K01 and the second contactor K02 to close, and controls the third contactor K03 to open, so that the auxiliary system operates in a normal power supply mode, that is, the first power battery pack supplies power to the VVVF auxiliary load, and the second power battery pack supplies power to the CVCF auxiliary load;

[0066] When the capacity difference △SOC is greater than or equal to the second capacity difference threshold, the locomotive enters the SOC static balancing mode, controls the contactor corresponding to the power battery pack with a higher state of charge and the third contactor K03 to close, and controls the contactor corresponding to the power battery pack with a lower state of charge to open, and the power battery pack with a higher state of charge supplies power to all auxiliary loads;

[0067] When the capacity difference ΔSOC is greater than or equal to the first capacity difference threshold or the locomotive is in the dynamic traction stage (speed V is greater than 0), the SOC static balancing mode is exited.

[0068] In this embodiment, the second capacity difference threshold is greater than the first capacity difference threshold. The second capacity difference threshold is set to 10%, and the first capacity difference threshold is set to 5%.

[0069] For example, if the state of charge of the first power battery pack is higher and the state of charge of the second power battery pack is lower, the first contactor K01 and the third contactor K03 corresponding to the first power battery pack are controlled to be closed, and the second contactor K02 corresponding to the second power battery pack is controlled to be disconnected. The first power battery pack supplies power to all auxiliary loads, gradually reducing the capacity difference between the first power battery pack and the second power battery pack, thereby achieving capacity balancing control of the power battery packs.

[0070] Example 2

[0071] An embodiment of the present invention provides a power battery pack capacity balancing control system comprising:

[0072] The central control unit CCU is configured to obtain the capacity difference ΔSOC between the first power battery pack and the second power battery pack and the required traction force F during the dynamic traction phase; allocate the required traction force F based on the capacity difference ΔSOC, and send the allocated two traction forces F1 / F2 to the first traction control unit TCU1 and the second traction control unit TCU2, respectively; where F=F1+F2;

[0073] a first traction control unit TCU1, configured to control the first traction converter according to the traction force allocated by the central control unit CCU, so that the first traction converter provides a corresponding traction force F1;

[0074] The second traction control unit TCU2 is configured to control the second traction converter according to the traction force allocated by the central control unit CCU, so that the second traction converter provides a corresponding traction force F2.

[0075] In a specific embodiment of the present invention, the central control unit CCU allocates the required traction force F according to the capacity difference ΔSOC, specifically including:

[0076] When the capacity difference ΔSOC is less than a first capacity difference threshold, the required traction force F is equally distributed so that the first traction converter and the second traction converter provide the same traction force;

[0077] When the capacity difference ΔSOC is greater than or equal to the first capacity difference threshold, the required traction force F is unequally distributed, and the required traction power S is calculated based on the required traction force F, and the unequal distribution ratio is determined based on the required traction power S.

[0078] In a specific embodiment of the present invention, the central control unit CCU determines the unequal distribution ratio according to the required traction power, including:

[0079] When the required traction power S is greater than the power threshold, the unequal distribution ratio is m:n; where m>n and n≠0, the traction converter corresponding to the power battery pack with a higher state of charge provides greater traction force, and the traction converter corresponding to the power battery pack with a lower state of charge provides less traction force;

[0080] When the required traction power S is less than or equal to the power threshold, the unequal distribution ratio is m:n; where m>n and n=0, the traction converter corresponding to the power battery pack with a higher state of charge provides all the required traction power.

[0081] In a specific embodiment of the present invention, the central control unit is further used to obtain the capacity difference △SOC between the first power battery pack and the second power battery pack during the static standby stage; when the capacity difference △SOC is less than the second capacity difference threshold, the first contactor K01 and the second contactor K02 are controlled to be closed, and the third contactor K03 is controlled to be disconnected, so that the auxiliary system operates in a normal power supply mode; when the capacity difference △SOC is greater than or equal to the second capacity difference threshold, the contactor corresponding to the power battery pack with a higher state of charge and the third contactor K03 are controlled to be closed, and the contactor corresponding to the power battery pack with a lower state of charge is controlled to be disconnected, so that the power battery pack with a higher state of charge supplies power to all auxiliary loads.

[0082] In some embodiments of the present invention, the power battery pack capacity balancing control system may be combined with the features of any power battery pack capacity balancing control method described in Example 1 of the present application; and vice versa.

[0083] Example 3

[0084] An embodiment of the present invention provides a hybrid locomotive, comprising any power battery pack capacity balancing control system described in any one of the second embodiments of the present application.

[0085] The above disclosure is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, and they should all be covered by the scope of protection of the present invention.

Claims

1. A power battery pack capacity balancing control method, applied to a vehicle, wherein the power battery pack includes a first power battery pack and a second power battery pack, wherein the first power battery pack is connected to a first traction converter, and the second power battery pack is connected to a second traction converter; characterized in that: The control method includes: In the dynamic traction phase, the capacity difference between the first power battery pack and the second power battery pack and the required traction force are obtained; Distributing the required traction force according to the capacity difference, so that the first traction converter and the second traction converter respectively provide the distributed traction force, thereby achieving capacity balancing control between the first power battery pack and the second power battery pack; Allocating the required traction force according to the capacity difference so that the first traction converter and the second traction converter respectively provide the allocated traction force specifically includes: When the capacity difference is less than a first capacity difference threshold, the required traction force is equally distributed so that the first traction converter and the second traction converter respectively provide the same traction force; When the capacity difference is greater than or equal to a first capacity difference threshold, the required traction force is unequally distributed, the required traction power is calculated based on the required traction force, and the unequal distribution ratio is determined based on the required traction power; Determining the unequal distribution ratio according to the required traction power includes: When the required traction power is greater than the power threshold, the unequal distribution ratio is m:n; where m>n and n≠0, the traction converter corresponding to the power battery pack with a higher state of charge provides a greater traction force, and the traction converter corresponding to the power battery pack with a lower state of charge provides a smaller traction force; When the required traction power is less than or equal to the power threshold, the unequal distribution ratio is m:n; where m>n and n=0, the traction converter corresponding to the power battery pack with a higher state of charge provides all the required traction power.

2. The power battery pack capacity balancing control method according to claim 1, characterized in that: When the required traction power is greater than the power threshold, the unequal distribution ratio is 0.55:0.

45.

3. The power battery pack capacity balancing control method according to claim 1, characterized in that: Determine whether the required traction power is greater than a power threshold based on the driver controller handle level; wherein, the power threshold is 50% of the rated power of the vehicle.

4. The power battery pack capacity balancing control method according to any one of claims 1 to 3, characterized in that: The first auxiliary inverter in the first traction converter is connected to the first auxiliary transformer via a first contactor, the second auxiliary inverter in the second traction converter is connected to the second auxiliary transformer via a second contactor, and the second end of the first contactor is connected to the second end of the second contactor via a third contactor; wherein the second ends of the first contactor and the second contactor are ends close to the corresponding auxiliary transformers; The control method also includes power battery pack capacity balancing control in the static standby stage, specifically including: Obtaining a capacity difference between the first power battery pack and the second power battery pack; When the capacity difference is less than a second capacity difference threshold, controlling the first contactor and the second contactor to close, and controlling the third contactor to open, so that the auxiliary system operates in a normal power supply mode; When the capacity difference is greater than or equal to the second capacity difference threshold, the contactor corresponding to the power battery pack with a higher state of charge and the third contactor are controlled to close, and the contactor corresponding to the power battery pack with a lower state of charge is controlled to open, so that all auxiliary loads are powered by the power battery pack with a higher state of charge.

5. The power battery pack capacity balancing control method according to claim 4, characterized in that: The second capacity difference threshold is greater than the first capacity difference threshold; wherein, the first capacity difference threshold is the capacity difference threshold during capacity balancing control in the dynamic traction stage.

6. A power battery pack capacity balancing control system, wherein the power battery pack comprises a first power battery pack and a second power battery pack, wherein the first power battery pack is connected to a first traction converter, and the second power battery pack is connected to a second traction converter; characterized in that: The system comprises: The central control unit is configured to obtain, during a dynamic traction phase, a capacity difference between the first power battery pack and the second power battery pack and a required traction force; allocate the required traction force according to the capacity difference, and send the allocated two traction forces to the first traction control unit and the second traction control unit, respectively; a first traction force control unit, configured to control the first traction converter according to the traction force allocated by the central control unit, so that the first traction converter provides corresponding traction force; a second traction force control unit, configured to control the second traction converter according to the traction force allocated by the central control unit, so that the second traction converter provides corresponding traction force; The central control unit distributes the required traction force according to the capacity difference, specifically including: When the capacity difference is less than a first capacity difference threshold, the required traction force is equally distributed so that the first traction converter and the second traction converter provide the same traction force; When the capacity difference is greater than or equal to a first capacity difference threshold, the required traction force is unequally distributed, the required traction power is calculated based on the required traction force, and the unequal distribution ratio is determined based on the required traction power; Determining the unequal distribution ratio according to the required traction power includes: When the required traction power is greater than the power threshold, the unequal distribution ratio is m:n; where m>n and n≠0, the traction converter corresponding to the power battery pack with a higher state of charge provides a greater traction force, and the traction converter corresponding to the power battery pack with a lower state of charge provides a smaller traction force; When the required traction power is less than or equal to the power threshold, the unequal distribution ratio is m:n; where m>n and n=0, the traction converter corresponding to the power battery pack with a higher state of charge provides all the required traction power.

7. The power battery pack capacity balancing control system according to claim 6, characterized in that: The first auxiliary inverter in the first traction converter is connected to the first auxiliary transformer via a first contactor, the second auxiliary inverter in the second traction converter is connected to the second auxiliary transformer via a second contactor, and the second end of the first contactor is connected to the second end of the second contactor via a third contactor; wherein the second ends of the first contactor and the second contactor are ends close to the corresponding auxiliary transformers; The central control unit is further configured to obtain a capacity difference between the first power battery pack and the second power battery pack during a static standby phase; when the capacity difference is less than a second capacity difference threshold, control the first contactor and the second contactor to close, and control the third contactor to disconnect, so that the auxiliary system operates in a normal power supply mode; when the capacity difference is greater than or equal to the second capacity difference threshold, control the contactor and the third contactor corresponding to the power battery pack with a higher state of charge to close, and control the contactor corresponding to the power battery pack with a lower state of charge to disconnect, so that the power battery pack with a higher state of charge supplies power to all auxiliary loads.

8. A hybrid locomotive, characterized in that: The locomotive includes the power battery pack capacity balancing control system according to claim 6 or 7.

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