Dual power battery system of vehicle and power distribution control method thereof

Abstract

The application discloses a dual-power battery system of a vehicle and a power distribution control method thereof, and belongs to the technical field of electric vehicles. The system comprises two groups of power batteries, two electric control units, two drive motors, a mechanical coupling device, a low-power isolation DCDC converter and a controller. The direct current output ends of the two groups of batteries are directly electrically connected with the direct current input ends of the corresponding electric control units, there is no direct current bus node shared by the two groups of batteries on the whole vehicle, and the two groups of batteries are only connected through the low-power isolation DCDC converter. The control method comprises the following steps: in a driving mode, power is distributed according to SOC deviation, and in a recovery mode, low-SOC batteries are preferentially charged; when any group of batteries fails, the low-power isolation DCDC provides emergency power supply from the healthy side to the fault side to maintain the auxiliary drive function; and when the SOC deviation is too large, the low-power isolation DCDC performs auxiliary equalization. The application completely eliminates circulating current, has low cost, is redundant and reliable, and is high in safety.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle technology, specifically to the field of electric vehicle power battery management technology, and particularly to a dual power battery system for a vehicle and its power distribution control method. Background Technology

[0002] The power battery system and its power supply architecture of electric vehicles are among the core technologies that determine the overall vehicle performance, safety, and economy. In large electric vehicles (such as electric mining dump trucks, electric heavy trucks, and electric construction machinery), due to the high power requirements (typically hundreds of kilowatts to megawatts) and long driving range requirements (usually requiring continuous operation for 4 to 8 hours or more), a single power battery pack often cannot simultaneously meet the demands in both power and energy dimensions. Therefore, using two or more power battery packs in combination for power supply has become a common technical approach for this type of vehicle.

[0003] Currently, the existing technologies for power battery architecture and power distribution schemes mainly take the following forms:

[0004] (a) Single large-capacity battery pack solution

[0005] This solution uses a single high-voltage battery pack to power all drive motors and auxiliary loads (including the steering pump, air pump, and air conditioning) of the vehicle. While simple in structure and easy to control, this solution has significant drawbacks: firstly, the capacity of a single battery pack is limited by chassis layout space and weight constraints, making it difficult to meet the long-range requirements of large electric vehicles; secondly, if this battery pack fails or its state of charge (SOC) is too low, the entire vehicle will completely lose power, causing it to break down. In harsh working environments such as mines and construction sites, the resulting economic losses and safety hazards are particularly prominent.

[0006] (ii) Direct parallel connection scheme of multiple battery DC buses

[0007] To compensate for the insufficient capacity of a single battery pack, some existing technologies connect two or more power battery packs directly in parallel on the high-voltage DC bus side to jointly power each electronic control unit. This solution can effectively expand the total battery capacity, but its fundamental flaw lies in the circulating current problem. Due to differences in manufacturing batches of each battery pack, there are deviations in initial internal resistance (the deviation of a single cell internal resistance can reach ±5%). Furthermore, in actual use, the different installation locations of each battery pack lead to differences in heat dissipation conditions, and different charge-discharge histories result in different aging rates, making it difficult to maintain consistency in the terminal voltage and state of charge (SOC) of each battery pack. When a battery pack with a higher terminal voltage discharges to a battery pack with a lower terminal voltage, a circulating current is formed. In the high-power application scenarios of large electric vehicles, the peak circulating current can reach hundreds of amperes, not only causing significant Joule heat loss and reducing overall vehicle energy efficiency, but also potentially triggering the over-temperature protection of the Battery Management System (BMS), leading to unexpected shutdowns. In addition, due to the different impedances of each battery branch, the discharge current is difficult to distribute in the expected proportion, further exacerbating the SOC imbalance problem and seriously affecting the overall lifespan of the battery pack.

[0008] (iii) Dual-motor independent drive but shared battery pack solution

[0009] Some existing technologies employ an architecture where dual motors are driven by two separate electronic controllers, with the two sets of motors mechanically coupled for output. However, the two sets of electronic controllers still share the same battery pack or the same high-voltage DC bus. While this solution achieves redundancy at the drive motor level, since the battery side remains a single power source, if the battery pack or high-voltage bus fails, both motors will simultaneously lose power, rendering the redundant drive function ineffective. This fails to truly solve the single-point-of-failure problem in the power supply chain.

[0010] (iv) Scheme of connecting dual battery packs in parallel to a common DC bus via a high-power isolated DC-DC converter

[0011] This solution represents a relatively advanced existing technology. Its basic architecture involves two sets of power batteries connected in parallel to the same high-voltage DC bus via their respective high-power isolated DC-DC converters. This common bus then supplies power to each electronic control unit. The electrical isolation function of the isolated DC-DC converters effectively cuts off the circulating current path between the battery packs, thus solving the circulating current problem in the aforementioned direct parallel connection scheme.

[0012] However, the plan still has the following prominent problems:

[0013] Firstly, the power rating of high-power isolated DC-DC converters needs to match the vehicle's drive power, typically ranging from tens to hundreds of kilowatts. The cost per unit is extremely high (tens of thousands to over one hundred thousand yuan), and two units are required for each vehicle, drastically increasing system costs. Secondly, high-power isolated DC-DC converters are bulky, occupying significant chassis space, which is particularly disadvantageous for electric vehicles where the overall layout is already tight. Furthermore, each stage of DC-DC conversion results in a 5% to 8% efficiency loss; when two DC-DC converters operate simultaneously, it not only increases the heat dissipation burden but also significantly reduces the vehicle's driving range.

[0014] Secondly, although the two battery sets achieve electrical isolation through an isolated DC-DC converter, electrical coupling still exists between them at the common DC bus node. In other words, this solution only addresses the circulating current problem between the two battery sets, but does not achieve physical independence between them at the power supply link level. When a short circuit or ground fault occurs on the common DC bus, energy from both batteries may be released to the fault point, and the impact of the fault cannot be limited to one side, thus the system's fault tolerance remains limited.

[0015] Third, if any battery pack or its connected DC-DC converter fails, although the other pack can still be powered through the common bus, the power supply to the electronic control unit and auxiliary drive load on the faulty side depends on the integrity of the common bus. If the common bus itself fails, the auxiliary drive functions on both sides will be lost simultaneously, and critical safety functions such as power steering and brake air supply cannot be guaranteed, posing a serious safety hazard.

[0016] In summary, existing multi-battery power supply solutions have varying degrees of shortcomings in areas such as circulating current suppression, system redundancy, fault isolation, cost control, and SOC balancing, making it difficult to simultaneously meet the comprehensive requirements of high reliability, high safety, and high economy for large electric vehicles. Therefore, there is an urgent need for a novel drive system and its control method that can fundamentally solve the above problems at the architectural level.

[0017] The technical problem to be solved by this invention is to overcome the defects of existing technologies, such as circulating current loss, high cost and large size of high-power isolated DC-DC converters, single-point failure risk in the power supply link, and inability to guarantee auxiliary drive function when multiple power batteries are connected in parallel. This invention provides a drive system with completely independent power supply for two power batteries and its power distribution control method, so that the two battery groups are completely independent electrically, completely eliminating the circulating current path from the physical level, and achieving dynamic SOC balancing and fault redundancy power supply at extremely low cost. Summary of the Invention

[0018] To address the problems existing in the parallel power supply of multiple power batteries, such as circulating current loss, high cost and large size of high-power isolated DC-DC converters, single-point failure risk in the power supply link, and inability to guarantee auxiliary drive function in case of failure, this invention provides a dual power battery system for vehicles and its power distribution control method. By constructing two electrically independent power links for the two battery groups, setting a low-power isolated DC-DC converter as an auxiliary energy bridge only between the two links, and combining it with a multi-objective power distribution algorithm based on SOC equalization and motor efficiency, this invention achieves complete elimination of circulating current, significant improvement in system redundancy reliability, and dynamic SOC equalization at low cost.

[0019] To achieve the above objectives, the present invention adopts the following technical solution:

[0020] A dual-battery system for a vehicle, characterized in that it comprises:

[0021] A first power battery pack and a second power battery pack; the DC output terminal of the first power battery pack is directly electrically connected to the DC input terminal of the first electronic control unit, and there are no other power conversion devices between them; the DC output terminal of the second power battery pack is directly electrically connected to the DC input terminal of the second electronic control unit, and there are no other power conversion devices between them; the first power battery pack and the second power battery pack do not share a DC bus node on the vehicle.

[0022] A first electronic control unit and a second electronic control unit; the AC output terminal of the first electronic control unit is electrically connected to the first drive motor assembly, and the AC output terminal of the second electronic control unit is electrically connected to the second drive motor assembly;

[0023] First drive motor group and second drive motor group;

[0024] A mechanical coupling device; the mechanical output ends of the first drive motor group and the second drive motor group are respectively connected to the mechanical coupling device, and the mechanical coupling device is used to superimpose the output torques of the first drive motor group and the second drive motor group and then transmit them out;

[0025] Low-power isolated DC-DC converter; the two ends of the low-power isolated DC-DC converter are respectively connected to the DC bus of the first and second power battery packs or the first and second electronic control units, and it has electrical isolation function and bidirectional power transmission capability;

[0026] The controller is communicatively connected to the first battery management system of the first power battery pack, the second battery management system of the second power battery pack, the first electronic control unit, the second electronic control unit, and the low-power isolated DC-DC converter.

[0027] Furthermore, the power rating of the low-power isolated DC-DC converter is from 1kW to 5kW.

[0028] Furthermore, the first and second electronic control units each independently integrate a main drive inverter, a high-voltage to low-voltage DC-DC converter, an oil pump controller, and an air pump controller; the main drive inverter is used to convert the battery DC power into AC power to drive the motor or perform regenerative braking rectification, the high-voltage to low-voltage DC-DC converter is used to convert high-voltage DC power into low-voltage power to supply power to the low-voltage load of the vehicle, the oil pump controller is used to control the hydraulic oil pump motor, and the air pump controller is used to control the air compressor motor.

[0029] Furthermore, the mechanical coupling device is any one of a dual-input single-output gearbox, a dual-motor reducer, or a drive axle coupling device; the mechanical coupling device is also equipped with a clutch for selectively disengaging a single-sided drive motor.

[0030] Furthermore, the controller is an independent vehicle controller, or a distributed controller formed by the first electronic control unit and the second electronic control unit through a communication bus.

[0031] Furthermore, a power distribution control method for a dual-battery system in a vehicle is characterized by comprising the following steps:

[0032] Step S1: The controller collects driver demand information, power battery pack information, drive motor pack information and vehicle status information in real time; and determines whether to enter drive mode or energy recovery mode based on the sign of the total demand power P_demand.

[0033] Step S2: When in driving mode, calculate the basic power allocation coefficient k_raw based on the deviation of the information of the first and second power battery packs, then calculate the original power allocation of the two power battery packs, and combine the battery power capacity constraint and motor efficiency optimization to determine the target driving power P1 of the first power battery pack and the target driving power P2 of the second power battery pack.

[0034] Step S3: When in energy recovery mode, the recovery power is allocated according to the reciprocal of the SOC of the two power battery packs, so that the power battery pack with the lower SOC can obtain a larger recovery charging power.

[0035] Step S4: The controller monitors the working status of the power battery pack and controls the low-power isolated DC-DC converter to perform auxiliary energy transfer between the two power battery packs based on the monitoring results; when the controller detects that the low-power isolated DC-DC converter has failed, the system degrades to the unassisted equalization mode and relies on drive power distribution to maintain the SOC within the preset controllable range.

[0036] Step S5: The controller monitors the system fault status in real time and performs fault-tolerant control.

[0037] Furthermore, step S2 specifically includes the following sub-steps:

[0038] (S2.1) Calculate the basic allocation coefficient k_raw: k_raw = 0.5 + λ_comprehensive / 2

[0039] Wherein, λ_comprehensive is a multi-factor comprehensive equilibrium correction factor that comprehensively considers SOC deviation, SOH difference and temperature difference;

[0040] Based on k_raw, the original allocated power is calculated as P1_raw = k_raw·P_demand, P2_raw = (1-k_raw)·P_demand;

[0041] (S2.2) Perform battery power capacity constraint check: If P1_raw is greater than P_bat1_max, then limit P1 to P_bat1_max, and the excess is borne by the second power battery pack; if P2_raw is greater than P_bat2_max, then limit P2 to P_bat2_max, and the excess is borne by the first power battery pack; adjust cyclically until the power distribution of both battery packs is within their respective allowable power ranges;

[0042] (S2.3) Optimize the high-efficiency zone of the motor: At the current speed, query the motor efficiency MAP. Under the constraint of P1+P2=P_demand, perform discretization search with the goal of maximizing the overall efficiency and reducing the SOC deviation trend to determine the final target drive power P1 of the first power battery pack and the target drive power P2 of the second power battery pack. If the SOC deviation exceeds the preset threshold, prioritize ensuring SOC balance.

[0043] (S2.4) The final determined P1 and P2 are converted into torque commands and sent to the first electronic control unit and the second electronic control unit, respectively.

[0044] Furthermore, the multi-factor comprehensive equilibrium correction factor λ_comprehensive = λ_SOC×W_soc + λ_SOH×W_soh + λ_T×W_T;

[0045] Wherein, λ_SOC is the SOC deviation factor, λ_SOH is the SOH difference factor, and λ_T is the temperature difference factor;

[0046] W_soc is the SOC deviation weight, W_soh is the SOH difference weight, and W_T is the temperature difference weight, and W_soc+W_soh+W_T=1.

[0047] Furthermore, in step S2.1:

[0048] SOC deviation factor λ_SOC=(SOC1-SOC2) / (SOC1+SOC2);

[0049] SOH difference factor λ_SOH=(SOH1-SOH2) / (SOH1+SOH2), wherein when SOH1<SOH2, the power distribution proportion of the first power battery pack is reduced;

[0050] Temperature difference factor λ_T=(T1-T2) / (T1+T2), wherein when any battery temperature T exceeds a preset temperature range, the maximum allowable power of the corresponding battery is reduced according to a temperature correction function.

[0051] Further, in the step S3, assuming that the braking demand recovery power is P_rec_demand, then:

[0052] P_rec1=P_rec_demand×SOC2 / (SOC1+SOC2)

[0053] P_rec2=P_rec_demand×SOC1 / (SOC1+SOC2)

[0054] If P_rec1 is greater than the maximum allowable recovery power P_rec1_max of the first power battery pack, P_rec1 is limited to P_rec1_max, and the excess part is borne by the second power battery pack; if the total recovery capacity is insufficient, the remaining braking force is supplemented by mechanical braking.

[0055] Further, in the step S4, the auxiliary energy transmission at least includes one of the following working conditions:

[0056] In the first working condition, when any set of power battery fails, the low-power isolated DCDC converter takes power from the power battery pack on the healthy side to provide emergency power supply to the electric control unit on the fault side;

[0057] In the second working condition, when both sets of power batteries are normal but the SOC deviation between the two sets exceeds a preset threshold, the low-power isolated DCDC converter transmits electric energy from the high SOC side to the low SOC side for auxiliary equalization charging.

[0058] Further, when any set of power battery fails, the controller immediately cuts off the main power output on the fault side, and the power battery pack on the healthy side drives the vehicle to operate at reduced power through the corresponding electric control unit and drive motor; at the same time, the controller starts the low-power isolated DCDC converter, takes power from the DC bus on the healthy side, and provides emergency power supply to the DC bus of the electric control unit on the fault side after isolation conversion, so as to maintain the auxiliary drive function inside the electric control unit on the fault side.

[0059] Furthermore, the emergency power supply has a power of 1kW to 5kW, and the auxiliary drive function includes steering oil pump control and air pump control.

[0060] Furthermore, when both sets of power batteries are normal but the SOC deviation exceeds a preset threshold and the current operating condition meets the auxiliary balancing conditions, the controller sends a balancing mode command to the low-power isolated DC-DC converter. The low-power isolated DC-DC converter controls the high-SOC power battery pack to trickle charge the low-SOC power battery pack. The controller monitors the SOC change in real time, and automatically shuts down the low-power isolated DC-DC converter and exits the balancing mode after the SOC deviation is reduced to the preset range.

[0061] Furthermore, the activation conditions for the auxiliary equalization are: the vehicle is in a parked state or under light load, and the SOC deviation is greater than 5%; the exit condition for the equalization mode is that the SOC deviation is reduced to within 3%; when the vehicle receives the driver's start command during the auxiliary equalization process, the controller immediately exits the equalization mode and returns to the drive mode power distribution process.

[0062] Furthermore, the low-power isolated DC-DC converter is trickle-charged with a power control of 1kW to 2kW.

[0063] Furthermore, step S2 also includes: when the vehicle is parked or under light load and the deviation between SOC1 and SOC2 is greater than a preset threshold, the controller starts the low-power isolated DC-DC converter to perform auxiliary equalization charging from the high SOC side to the low SOC side until the SOC deviation is reduced to the preset range.

[0064] Furthermore, the preset threshold for the SOC deviation is 5%, and the preset range is 3%.

[0065] Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

[0066] 1. Completely eliminate circulation problems and improve system security.

[0067] This invention employs an architecture where two sets of power batteries are completely independently powered. The two sets of batteries share no common DC bus nodes on the vehicle, thus physically eliminating the circulating current path and resulting in zero circulating current. Compared to existing direct parallel connection schemes, this completely avoids the hundreds of amperes of circulating current loss and the risk of BMS over-temperature protection caused by inconsistent battery parameters, significantly improving system safety.

[0068] 2. Significantly reduces system costs and saves deployment space.

[0069] This invention requires only one low-power isolated DC-DC converter with a power rating of 1kW to 5kW, while existing advanced solutions require two high-power isolated DC-DC converters ranging from tens to hundreds of kilowatts. The cost of the low-power isolated DC-DC converter is expected to be only 10% to 15% of that of the high-power isolated DC-DC converter, significantly reducing the overall drive system cost. Simultaneously, due to the substantial reduction in power device specifications, the converter's size and weight are reduced by approximately 60% to 75%, significantly saving chassis layout space and facilitating vehicle integration design.

[0070] 3. Improve system efficiency and extend driving range

[0071] In normal driving mode, this invention directly supplies power from the battery to the electronic control unit (ECU), eliminating the need for a DC-DC converter and avoiding the 5%–8% efficiency loss found in existing high-power isolated DC-DC converter solutions. A low-power isolated DC-DC converter is only activated for auxiliary balancing and emergency power supply, with negligible efficiency loss (less than 1%). Through comprehensive optimization control of the motor's high-efficiency range, the vehicle's driving range can be increased by 5%–8%.

[0072] 4. Achieve dual-link redundancy and eliminate the risk of single point of failure.

[0073] In this invention, two sets of batteries, two sets of electronic controls, and two motors form a completely independent dual-power link. A single component failure in any link will not affect the independent operation of the other link. Even if any set of batteries, electronic controls, or motors fails, the vehicle can still be driven by the healthy link, effectively avoiding vehicle breakdowns due to single-point failures. This is particularly suitable for operational scenarios with extremely high reliability requirements, such as mines and construction sites.

[0074] 5. Critical auxiliary drive functions are not lost in the event of a malfunction, ensuring driving safety.

[0075] When a battery pack fails, this invention draws power from the healthy battery via a low-power isolated DC-DC converter to provide emergency power to the faulty electronic control unit (ECU). This allows the integrated oil pump controller and air pump controller within the faulty ECU to continue operating, ensuring that critical safety functions such as power steering and brake air supply are not lost. This technical effect is not available in existing solutions, significantly improving driving safety in fault conditions.

[0076] 6. Significant SOC dynamic balancing effect, extending battery life.

[0077] This invention utilizes a three-pronged approach: power allocation based on SOC deviation in drive mode, priority charging of low SOC batteries in energy recovery mode, and low-power isolated DC-DC-assisted trickle equalization. This approach can control the SOC deviation between the two battery packs within ±3% during vehicle operation, effectively preventing overcharging or over-discharging of a single battery pack and extending the overall cycle life of the battery pack by approximately 20%.

[0078] 7. Balancing motor efficiency to improve overall vehicle economy

[0079] While ensuring SOC balance as the primary objective, this invention performs a discretized search by querying the motor efficiency MAP to make the power distribution point as close as possible to the high-efficiency zone of the motor, thereby optimizing the overall efficiency of the vehicle and improving energy economy without sacrificing SOC balance.

[0080] 8. The system is flexible in expansion and convenient in maintenance.

[0081] In this invention, the two battery sets and two electric drive systems are independent of each other. When an increase in overall vehicle power is required, the two battery sets or motors can be upgraded independently without redesigning complex current sharing control strategies. The two battery sets can be charged independently, supporting simultaneous fast charging with dual charging guns, and the charging time is no worse than that of a single-battery system. The two battery sets can be inspected and replaced independently without downtime of the entire vehicle, reducing maintenance costs and improving uptime.

[0082] 9. The control algorithm is simple and reliable, suitable for engineering implementation.

[0083] The power allocation algorithm of this invention uses SOC as the main control variable, supplemented by SOH and temperature correction. It has low computational complexity, fast convergence speed, and is suitable for implementation in embedded real-time control systems. It is easy to implement in engineering and has high reliability.

[0084] In summary, this invention, starting from the system architecture level, solves multiple technical problems such as circulation, cost, redundancy, balance, safety, and efficiency simultaneously with simple and economical technical means, resulting in outstanding comprehensive technical effects and significant social and economic benefits. It is suitable for widespread application in various types of large electric vehicles. Attached Figure Description

[0085] Figure 1 This is a schematic diagram of the overall architecture of the dual power battery system of the present invention;

[0086] Figure 2 This is a flowchart illustrating the control logic of the power distribution control method of the present invention.

[0087] Figure 3 This is a schematic diagram of the power and energy flow topology of the dual-power battery system of the present invention under normal driving conditions;

[0088] Figure 4This is a schematic diagram of the power and energy flow topology of the dual-power battery system of the present invention under energy recovery conditions;

[0089] Figure 5 This is a schematic diagram of the power and energy flow topology of the dual-power battery system of the present invention under emergency conditions of single-cell battery failure;

[0090] Figure 6 This is a schematic diagram of the power and energy flow topology of the dual-power battery system of the present invention under equalization charging conditions. Detailed Implementation

[0091] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations thereof. In the absence of conflict, the embodiments and technical features in the embodiments can be combined with each other.

[0092] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. The term "connection" should be interpreted broadly; for example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a signal connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0093] like Figure 1 As shown, the present invention provides a dual power battery system for a vehicle, which consists of a first power battery pack BAT1, a low-power isolated DC-DC converter, a second power battery pack BAT2, a first electronic control unit MCU1, a second electronic control unit MCU2, a first drive motor group M1, a second drive motor group M2, a mechanical coupling device, and a vehicle controller VCU.

[0094] Both the first power battery pack BAT1 and the second power battery pack BAT2 use high-voltage power battery packs, with rated voltages selectable from 540V, 640V, or 800V depending on the vehicle model. In a preferred embodiment of the present invention, BAT1 and BAT2 use the same rated voltage (e.g., 640V) and the same rated capacity (e.g., 280Ah), and the two battery packs are independently arranged on both sides or at the front and rear ends of the vehicle chassis to optimize the overall vehicle weight distribution.

[0095] BAT1 is equipped with a first battery management system (BMS1), and BAT2 is equipped with a second battery management system (BMS2). Each BMS has standard functions such as voltage detection, current detection, temperature detection, SOC estimation, SOH estimation, insulation monitoring, and overcurrent and overtemperature protection. BMS1 and BMS2 are connected to the VCU via a CAN communication bus, and report information such as SOC (accuracy controlled within ±3%), SOH (accuracy controlled within ±5%), highest single-cell voltage, lowest single-cell voltage, highest temperature, lowest temperature, maximum allowable discharge power P_bat_max, and maximum allowable recycle power P_rec_max for their respective battery packs in real time.

[0096] In this invention, BAT1 and BAT2 are not electrically connected in any direct parallel manner—that is, there are no shared wires or busbars between the positive output terminals of BAT1 and BAT2, and similarly, there are no shared wires or busbars between the negative output terminals of BAT1 and BAT2. In other words, there is no shared high-voltage DC bus node between the two battery banks in the entire vehicle. This feature is achieved at the physical wiring level: two independent positive wires are led out from the positive terminals of BAT1 and BAT2, respectively, and two independent negative wires are led out from the negative terminals of BAT1 and BAT2, respectively, each independently routed to its corresponding electronic control unit, without any electrical junction points in between.

[0097] It should be noted that the aforementioned feature of "no common DC bus node" is one of the core structural features of this invention. In this invention, BAT1 forms an independent power link only with MCU1, and BAT2 forms another independent power link only with MCU2. The two links achieve controlled indirect energy exchange only through a low-power isolated DC-DC converter. There is no common node that allows the two battery groups to be directly electrically coupled.

[0098] The low-power isolated DC-DC converter is one of the key components of this invention. One end of the converter is connected to the DC bus of BAT1 or MCU1, and the other end is connected to the DC bus of BAT2 or MCU2. In a preferred embodiment of this invention, the high-voltage input terminal of the low-power isolated DC-DC converter is connected to the positive and negative terminals of the DC bus of MCU1 (i.e., in parallel with the bus of BAT1), and the high-voltage output terminal is connected to the positive and negative terminals of the DC bus of MCU2 (i.e., in parallel with the bus of BAT2).

[0099] Low-power isolated DC-DC converters have a power rating of 1kW to 5kW, which is much smaller than the high-power isolated DC-DC converters in existing technologies (typically in the tens to hundreds of kW range). Their internal topology employs a dual active bridge (DAB) or LLC resonant converter topology, achieving electrical isolation between the input and output sides through a high-frequency transformer. The isolation voltage level is no lower than the insulation withstand voltage requirements of the power battery system (typically 3750VAC or higher).

[0100] This converter has bidirectional power transfer capability—it can transfer power from BAT1 to BAT2, and vice versa, with the specific direction determined by the VCU based on the SOC comparison results of the two battery banks. Bidirectional transfer is achieved by adjusting the phase difference between the drive signals of the primary and secondary side switches. This is an inherent characteristic of dual active bridge topologies and is well-known in the field, so it will not be elaborated further here.

[0101] The low-power isolated DC-DC converter also features controllable output voltage / current, allowing the VCU to send target voltage or current commands via CAN communication. In auxiliary balancing mode, the converter outputs 1kW to 2kW trickle charging power from the high SOC side to the low SOC side in a constant current manner. In emergency power supply mode, the converter provides stable high-voltage DC power to the fault-side bus in a constant voltage manner, with the voltage setting consistent with the battery's rated voltage (e.g., 640V), and the power output capability is increased to 3kW to 5kW to ensure the power supply needs of the auxiliary drive load.

[0102] Because of their lower power ratings, low-power isolated DC-DC converters can be designed with higher switching frequencies (e.g., above 100kHz), resulting in significantly smaller transformer and filter sizes compared to high-power DC-DC converters. In terms of cost, the material cost of a single 1kW~5kW isolated DC-DC converter is expected to be only 10%~15% of that of a tens-of-kWs-level high-power DC-DC converter. Regarding reliability, due to the lower current stress on power devices and lower heat dissipation requirements, their mean time between failures (MTBF) is expected to be significantly better than that of high-power DC-DC converters.

[0103] The DC input terminal of the first electronic control unit MCU1 is directly electrically connected to the output terminal of BAT1 via a high-voltage cable, without any power conversion devices (such as DC-DC converters, contactors, or other power devices) between them, in order to achieve the highest efficiency in power transmission. Similarly, the DC input terminal of the second electronic control unit MCU2 is directly electrically connected to the output terminal of BAT2.

[0104] MCU1 and MCU2 are all-in-one integrated electronic control units, each of which integrates the following functional modules:

[0105] (1) Main drive inverter: It is composed of three-phase full-bridge IGBT or SiC MOSFET power modules, which convert the DC power from the battery into AC power with adjustable frequency and voltage to drive the motor, or rectify the AC power generated by the motor into DC power to charge the battery during regenerative braking. The selection of power modules is determined according to the motor power. For example, for a 200kW motor, Infineon FF600R12ME4 or IGBT modules of equivalent specifications can be selected. The drive circuit adopts vector control or direct torque control strategies to improve the efficiency of the motor in the full speed range.

[0106] (2) High-voltage to low-voltage DC-DC converter: Converts high-voltage DC power (such as 640V) to 24V or 12V low-voltage DC power to power the low-voltage loads of the vehicle (such as lamps, instruments, controllers, fans, etc.). The power rating of this DC-DC converter is usually 1kW to 3kW, and it adopts LLC resonant converter topology to achieve high conversion efficiency (typically 92%~95%).

[0107] (3) Oil pump controller: provides drive control for the hydraulic oil pump motor, which provides hydraulic power for the power steering system, lifting system and lubrication system. The oil pump controller adopts a three-phase inverter bridge, and the power level is determined according to the power of the oil pump motor, usually from 5kW to 15kW.

[0108] (4) Air pump controller: provides drive control for the air compressor motor, which provides compressed air to the braking system. The air pump controller also uses a three-phase inverter bridge, and the power rating is usually 3kW to 10kW.

[0109] Both the oil pump controller and the air pump controller mentioned above can be started and stopped independently, and the VCU sends control commands according to the vehicle status (such as steering operation, brake air pressure, etc.).

[0110] All the aforementioned functional modules of MCU1 draw their DC power from its DC input bus—BAT1. Similarly, all functional modules of MCU2 draw their DC power from BAT2. There are no shared DC bus nodes between MCU1 and MCU2; their DC inputs are completely independent.

[0111] The first drive motor group M1 and the second drive motor group M2 can be permanent magnet synchronous motors or asynchronous induction motors. In a preferred embodiment of the present invention, M1 and M2 are selected from permanent magnet synchronous motors of the same model, which have the characteristics of high efficiency, high power density and wide speed range. The rated power of the motors can be determined according to the requirements of the vehicle. For example, for a 90-ton electric mining truck, two permanent magnet synchronous motors with a rated power of 200kW can be selected, and the peak power can reach 2×300kW.

[0112] The three-phase AC output of MCU1 is connected to the stator winding lead of M1 via a high-voltage shielded cable, and the three-phase AC output of MCU2 is connected to the stator winding lead of M2. Each motor has a built-in resolver or Hall position sensor to detect the rotor position and speed, which are fed back to the corresponding MCU via a dedicated signal line to achieve closed-loop control.

[0113] The mechanical coupling device is used to mechanically superimpose the output torques of M1 and M2 and then transmit them to the wheels. In a preferred embodiment of the invention, the mechanical coupling device employs a dual-input single-output gearbox, having two input shafts and one output shaft. The output shaft of M1 is connected to the first input shaft of the gearbox via a coupling, and the output shaft of M2 is connected to the second input shaft of the gearbox via a coupling. Inside the gearbox, the torques of the two input shafts are superimposed through a gear pair and then output through the output shaft, which is connected to the drive axle via a transmission shaft.

[0114] In another preferred embodiment of the invention, the mechanical coupling device adopts a dual-motor reducer structure, that is, the output shafts of M1 and M2 are respectively connected to their respective reduction gear sets, and the two reduction gear sets jointly drive the same output gear ring or output shaft. This structure is suitable for wheel-side drive or central drive schemes.

[0115] In another preferred embodiment of the present invention, the mechanical coupling device adopts a drive bridge coupling method, with M1 and M2 respectively connected to the two input ends of the drive bridge, and torque superposition is achieved inside the drive bridge through differential or rigid coupling.

[0116] To enhance system flexibility, the mechanical coupling device also includes a clutch (such as a dry clutch or a wet multi-plate clutch) that can selectively disengage M1 or M2 completely. When a single motor or electronic control unit fails, the clutch can disconnect the mechanical connection of the faulty motor, preventing additional wear and tear due to dragging. When further system efficiency needs to be improved under light load conditions, one motor can be actively disengaged, allowing the other motor to drive the system independently.

[0117] The controller in this invention can be an independent vehicle controller (VCU) or a distributed controller composed of MCU1 and MCU2 working together via a high-speed CAN bus or vehicle Ethernet.

[0118] In a preferred embodiment of the present invention, an independent VCU is used as the main controller. The VCU is a 32-bit microcontroller conforming to automotive standards (such as Infineon TC277 or NXP MPC5744P), which has rich peripherals such as multiple CAN interfaces, analog input interfaces (for accelerator pedal and brake pedal signal acquisition), digital input interfaces (for gear position signals, ignition signals, etc.), PWM output, and low-side drive output.

[0119] The VCU communicates with BMS1 and BMS2 via the CAN1 bus to obtain detailed status information of the two battery banks; it communicates with MCU1 and MCU2 via the CAN2 bus to send torque / power commands and receive motor operating status; and it communicates with the low-power isolated DC-DC converter via the CAN3 bus to send power / voltage commands and receive its operating status.

[0120] The VCU internally stores calibration data such as the motor efficiency MAP table, various temperature correction curves, and SOC equalization control parameters.

[0121] The VCU executes a power allocation algorithm during runtime to control the power distribution of the dual-battery system, such as... Figure 2 As shown, the present invention provides a power distribution control method for a dual-power battery system, the specific steps of which are as follows:

[0122] Step S1: Signal Acquisition and Mode Determination

[0123] After the system is powered on, the VCU first completes the communication handshake and self-test of each module. After confirming that BMS1, BMS2, MCU1, MCU2 and the low-power isolated DC-DC converter are all online and fault-free, the system enters normal operation.

[0124] The VCU executes the following acquisition tasks in a fixed cycle (e.g., 10ms):

[0125] (1) Acquire the accelerator pedal opening signal α (0%~100%) and the brake pedal opening signal β (0%~100%) through the analog input channel;

[0126] (2) Acquire gear position signals (D, R, N, P) through digital input channels;

[0127] (3) Read SOC1, SOH1, temperature T1, maximum allowable discharge power P_bat1_max, and maximum allowable recovery power P_rec1_max from BMS1 via CAN1 bus;

[0128] (4) Read SOC2, SOH2, temperature T2, maximum allowable discharge power P_bat2_max, and maximum allowable recovery power P_rec2_max from BMS2 via CAN1 bus;

[0129] (5) Read the current speed n1 and operating status from MCU1 via CAN2 bus;

[0130] (6) Read the current speed n2 and operating status from MCU2 via CAN2 bus;

[0131] (7) Read the vehicle speed signal via the CAN bus.

[0132] The VCU calculates the total power demand P_demand based on the accelerator pedal opening α, the brake pedal opening β, and the current vehicle speed v. The calculation method is as follows:

[0133] In D or R gear, if α > 0 (i.e., the accelerator pedal is depressed), the total drive power demand is:

[0134] P_demand=α×P_rated_total

[0135] Where P_rated_total is the rated total drive power of the vehicle. In this mode, if P_demand>0, then it is in drive mode.

[0136] If β > 0 (i.e., the brake pedal is depressed) and the vehicle speed v > the set minimum recovery speed (e.g., 5 km / h), the total recovery power required is:

[0137] P_rec_demand=β×P_rec_rated

[0138] Where P_rec_rated is the power recovered from braking demand. In this mode, P_demand = -P_rec_demand < 0, indicating that it is in energy recovery mode.

[0139] If α=0 and β=0, the vehicle is in a coasting state. The VCU can decide whether to enter a mild recovery mode based on the vehicle speed and SOC.

[0140] Step S2: Power Allocation in Drive Mode

[0141] like Figure 2 and Figure 3 The diagram shows the detailed execution process of power allocation in drive mode.

[0142] In this embodiment, the vehicle parameters are set as follows: rated total power 400kW (M1 and M2 each 200kW), BAT1 and BAT2 are both 640V / 280Ah lithium iron phosphate battery packs, current state is: SOC1=80%, SOC2=65%, SOH1=95%, SOH2=92%, T1=35℃, T2=45℃, current speed of M1 and M2 is 3000rpm, P_bat1_max=250kW, P_bat2_max=230kW, driver accelerator pedal opening α=80%, then P_demand=320kW.

[0143] (S2.1) Calculate the basic allocation coefficient

[0144] Calculate the SOC deviation factor λ_SOC:

[0145] λ_SOC=(SOC1-SOC2) / (SOC1+SOC2)=(80%-65%) / (80%+65%)=15% / 145%≈0.103

[0146] Since SOC1 > SOC2, λ_SOC is a positive value, indicating that more power should be allocated to BAT2 with a lower SOC.

[0147] Calculate the SOH (State of Health) difference factor λ_SOH:

[0148] λ_SOH=(SOH1-SOH2) / (SOH1+SOH2)=(95%-92%) / (95%+92%)=3% / 187%≈0.016

[0149] Since BAT1 has a higher SOH, its power proportion can be appropriately increased, and the power allocation proportion of BAT2 can be reduced to protect the aged battery.

[0150] Temperature correction factor:

[0151] When the temperature T of any battery is higher than T_max (usually 50~55°C) or lower than T_min (usually -10°C), the maximum allowable power of this battery will be automatically reduced to avoid high and low temperature damage. Usually, 20~40°C is set as the ideal operating range of the battery, allowing it to operate at maximum power. When T < T_min or T > T_max, f_temp(T)=0; when 20°C < T < 40°C, f_temp(T)=1, and P_bat_max_actual=P_bat_max×f_temp(T).

[0152] The temperature of BAT1 is 35°C, which is within the ideal operating range of 20~40°C, f_temp(T)=1, then the actual allowable power of BAT1: P_bat1_max_actual=P_bat1_max×f_temp(T)=250kW×1=250kW.

[0153] The temperature of BAT2 is 45°C, which is slightly higher than the ideal range but does not exceed T_max (55°C). Calculated according to the linear reduction function: f_temp(T)=1-(45-40) / (55-40)×0.3=1-5 / 15×0.3=0.90, then the actual allowable power of BAT2: P_bat2_max_actual=P_bat2_max×f_temp(T)=230kW×0.90=207kW.

[0154] Calculate the temperature correction factor λ_T=(T1-T2) / (T1+T2)=(35-45) / (35+45)≈-0.12.

[0155] After considering SOC deviation, SOH difference, and temperature correction, a multi-factor comprehensive equilibrium correction factor is obtained:

[0156] λ_synthetic=λ_SOC×W_soc+λ_SOH×W_soh+λ_T×W_T

[0157] Assuming the weights are configured as W_soc=0.6, W_soh=0.3, W_T=0.1, and W_soc+W_soh+W_T=1, and the weights can be adjusted according to the calibration conditions, then:

[0158] λ_comprehensive=λ_SOC×W_soc+λ_SOH×W_soh+λ_T×W_T=0.103×0.6+0.016×0.3+(-0.012)×0.1=0.0618+0.0048-0.012≈0.0546

[0159] The basic allocation coefficient is:

[0160] k_raw = 0.5 + λ_comprehensive / 2 = 0.5 + 0.0546 / 2 = 0.5273

[0161] That is, BAT1 accounts for 52.7% and BAT2 accounts for 47.3%. The original power allocation is:

[0162] P1_raw=k_raw·P_demand=0.527×320kW≈168.6kW

[0163] P2_raw=(1-k_raw)·P_demand=0.473×320kW≈151.4kW

[0164] (S2.2) Battery power capacity constraint check

[0165] If P1_raw > maximum allowable power P_bat_max, then limit P1 to P_bat_max, and the remaining power is borne by P2; similarly handle the case where P2 exceeds its limit; cyclically adjust until the power distribution is within the capacity range of the two battery groups.

[0166] In this embodiment, BAT1's P_bat1_max = 250kW and P1_raw = 170.6kW are within limits. BAT2's actual usable power P_bat2_max_actual = 207kW and P2_raw = 149.4kW are also within limits. No adjustment is needed.

[0167] (S2.3) Optimization of the high-efficiency zone of the motor

[0168] At the current rotational speed n, the motor efficiency MAP is consulted to obtain the efficiencies η1(P1) and η2(P2) corresponding to different power points. Under the constraint P1+P2=P_demand, a discretization search is used to determine the P1 value that maximizes the overall efficiency η_total and minimizes the SOC deviation trend. If the SOC deviation exceeds a set threshold (e.g., 5%), SOC balance is prioritized, followed by efficiency. While ensuring that the SOC deviation trend of the two battery groups decreases, P1 and P2 are fine-tuned within the constraints to optimize the overall system efficiency.

[0169] In this embodiment, when the current speed n=3000rpm is set, both MCU1 and MCU2 have reported the current speed. Since M1 and M2 are connected by a mechanical coupling device, it can be assumed that n1≈n2=n.

[0170] The VCU internally stores efficiency maps of M1 and M2, stored in tabular form in non-volatile memory. Within the power range P (P1∈[0,250kW], P2∈[0,207kW] and P1+P2=320kW), a discrete search is performed with a step size of 1kW to obtain the efficiencies η1(P1) and η2(P2) corresponding to different power points. The overall efficiency under each power combination is then calculated.

[0171] η_total=[P1·η1(P1)+P2·η2(P2)] / P_demand.

[0172] Assuming that η1≈95.2% and η2≈94.8% are found near P1=170kW and P2=150kW, the overall efficiency η_total=[P1·η1(P1)+P2·η2(P2)] / P_demand=(170*0.952+150*0.948) / 320≈95.0%. If the search finds that η1≈95.5% and η2≈95.0% when P1=160kW and P2=160kW, the overall efficiency is ≈95.25% and the SOC deviation still shows a decreasing trend (because the power undertaken by BAT1 decreases and the power undertaken by BAT2 increases), then the VCU can be fine-tuned to select P1=160kW and P2=160kW to improve the overall system efficiency while ensuring that the SOC balancing effect does not deteriorate.

[0173] (S2.4) Low-power isolated DC-DC converter assisted equalization (optional step)

[0174] When the vehicle is parked, lightly loaded, or when the SOC deviation continues to widen, the VCU activates a low-power isolated DC-DC converter to trickle charge from the high SOC side to the low SOC side at a relatively low power (e.g., 1-2 kW) to help level the SOC and prevent the deviation from widening further. Figure 6 As shown.

[0175] In this embodiment, the current SOC deviation is 15%, which is greater than the preset threshold of 5%. However, the vehicle is currently in driving operation, and the drive power distribution has already achieved a balancing effect (BAT2 bears slightly more power than BAT1). Therefore, the low-power isolated DC-DC auxiliary equalization is not activated to prioritize drive performance. If the SOC deviation is still greater than 5% when the vehicle is stopped, then auxiliary equalization is activated.

[0176] (S2.5) Command Issuance

[0177] P1 and P2 are converted into torque commands T1=P1 / ω and T2=P2 / ω, and then sent to MCU1 and MCU2 via CAN.

[0178] In this embodiment, the VCU sends P1=160kW and P2=160kW to MCU1 and MCU2. The torque command is calculated using the formula T=P / ω, where ω=2πn / 60≈314rad / s. Therefore, T1=160000 / 314≈509.6Nm and T2≈509.6Nm. The VCU sends T1 and T2 as target torque commands to MCU1 and MCU2.

[0179] Step S3: Power Allocation in Energy Recovery Mode

[0180] like Figure 2 and Figure 4 The diagram illustrates the detailed execution process of power allocation in energy recovery mode.

[0181] In this embodiment, it is assumed that when the vehicle brakes, the braking demand for regenerative power P_rec_demand = 120kW, the current SOC state of the two battery groups is SOC1 = 80% and SOC2 = 65% (consistent with the aforementioned driving state), P_rec1_max = 80kW and P_rec2_max = 90kW.

[0182] (S3.1) Prioritize allocating recovered power to batteries with low SOC.

[0183] The VCU performs the initial allocation of recovered power according to the following formula:

[0184] P_rec1=P_rec_demand×SOC2 / (SOC1+SOC2);

[0185] P_rec2=P_rec_demand×SOC1 / (SOC1+SOC2).

[0186] In this embodiment,

[0187] P_rec1=P_rec_demand×SOC2 / (SOC1+SOC2)=120×65% / (80%+65%)=120×65 / 145≈53.8kW,

[0188] P_rec2=P_rec_demand×SOC1 / (SOC1+SOC2)=120×80% / (80%+65%)=120×80 / 145≈66.2kW,

[0189] As can be seen, since SOC2 (65%) is lower than SOC1 (80%), BAT2 achieved a recovery power of 66.2kW, which is higher than BAT1's 53.8kW, thus achieving the balanced goal of prioritizing charging low SOC batteries.

[0190] (S3.2) Recycling capacity constraints

[0191] If P_rec1 > P_rec1_max, then P_rec1 is limited to P_rec1_max, and the excess is borne by P_rec2 (P_rec2_max needs to be checked); if the total recovery capacity is insufficient, the remaining braking force is supplemented by mechanical braking.

[0192] In this embodiment, it was checked that P_rec1=53.8kW≤P_rec1_max=80kW, which is within the limit; P_rec2=66.2kW≤P_rec2_max=90kW, which is also within the limit. Therefore, no adjustment is required.

[0193] If we assume P_rec_demand = 200kW, and according to the above formula, the allocation result is P_rec1 = 89.7kW > 80kW, P_rec2 = 110.3kW > 90kW, then both battery banks exceed their recovery capacity. In this case, the VCU limits P_rec1 to 80kW and P_rec2 to 90kW, for a total recovery power of 170kW. The remaining 30kW of braking force is supplemented by the mechanical braking system (air brake or hydraulic retarder). Simultaneously, the VCU sends a mechanical braking compensation request signal to the braking controller via the CAN bus.

[0194] (S3.3) Command Issuance

[0195] The recovered power is converted into a negative torque command and sent to MCU1 and MCU2.

[0196] In this embodiment, the VCU converts P_rec1 and P_rec2 into negative torque commands (regenerative braking torque) and sends them to MCU1 and MCU2 for execution.

[0197] Step S4: Emergency power supply in fault mode

[0198] The fault types are divided into three categories: single battery failure, excessive SOC deviation of dual batteries, and low-power isolated DC-DC failure.

[0199] like Figure 2 and Figure 5 As shown, the detailed execution process of power distribution under fault emergency conditions is as follows, specifically the detailed execution process of emergency power supply when a single battery fails.

[0200] Fault Scenario 1: BAT1 completely fails. The VCU detects abnormal voltage in BAT1, BMS failure, or low SOC and cannot continue to supply power.

[0201] In this embodiment, assuming that when the vehicle is driving on a mining road, the BMS1 detects that the voltage of a certain cell inside the BAT1 is continuously lower than 2.5V (the lower limit of lithium iron phosphate battery), determines that the battery is seriously faulty, and reports it to the VCU.

[0202] Once the VCU confirms the fault, it should immediately perform the following operations:

[0203] (1) A "main power cut-off" command is sent to MCU1 via CAN. The main drive inverter inside MCU1 is protected by sealing tubes, and the main positive relay is disconnected, completely cutting off the power connection between BAT1 and MCU1. The residual energy of the DC bus capacitor of MCU1 is automatically discharged to below the safe voltage.

[0204] (2) The vehicle power is independently handled by the BAT2→MCU2→M2 link. The VCU sends torque commands to the MCU2 according to the driver's throttle requirements, but is limited by the power of a single motor (200kW), which limits the maximum speed and maximum acceleration, thus achieving reduced power operation.

[0205] (3) At the same time, the VCU sends an “emergency power supply mode” command to the low-power isolated DC-DC converter, setting the target output voltage to 640V (consistent with the rated voltage of BAT1) and the power limit to 5kW. The low-power isolated DC-DC converter draws power from the BAT2 side (DC bus of MCU2), and outputs a stable 640V voltage to the DC bus of MCU1 after high-frequency isolation conversion.

[0206] (4) After MCU1 receives emergency power, its internal high-voltage to low-voltage DC-DC module resumes operation, providing power to the power steering pump controller and the air pump controller. Assuming the rated power of the power steering pump motor is 3kW and the rated power of the air pump motor is 2kW, the total power when the two work simultaneously is 5kW, which is exactly within the rated output range of the low-power isolated DC-DC.

[0207] (5) Under this condition, MCU1 does not drive M1, but only maintains the auxiliary drive function. The driver can still get steering assistance (the steering wheel operation force is normal), the braking system can still maintain sufficient air pressure, and the vehicle can be safely driven to the repair shop or safe parking area.

[0208] It should be noted that if the faulty side is BAT2 while BAT1 is healthy, the processing logic is completely symmetrical: BAT1 → MCU1 → M1 drives the vehicle, and the low-power isolated DC-DC converter draws power from the BAT1 side to provide emergency power to MCU2, ensuring the auxiliary drive function inside MCU2.

[0209] like Figure 2 and Figure 6 As shown, the detailed execution process of power distribution under fault emergency conditions is specifically the detailed execution process of emergency power supply when the single SOC deviation is too large.

[0210] Fault Scenario 2: Both battery banks are normal, but the SOC deviation is too large. The VCU judges that the SOC deviation exceeds the safety threshold of 5%, and the current operating conditions are not suitable for quick equalization through drive power distribution (such as light load or parking).

[0211] In this embodiment, it is assumed that after the vehicle completes a transportation task, it stops to wait for loading. At this time, the VCU detects SOC1=82% and SOC2=71%, with a deviation of 11%, which is greater than the preset threshold of 5%. The vehicle is in a parked state and the gear is in neutral (N), so there is no drive power requirement, which meets the conditions for auxiliary equalization start-up.

[0212] The VCU determines that SOC1 > SOC2 and decides to transfer energy from BAT1 to BAT2 for equalization charging. The specific execution process is as follows:

[0213] (1) The VCU sends the “equalization mode” command to the low-power isolated DC-DC converter via CAN. The transmission direction is “forward” (BAT1→BAT2). The target output current is determined by combining the allowable charging current and charging power requirements of BAT2.

[0214] (2) Set the equalization power to 1.5kW (within the range of 1kW~2kW), and the target charging current I_chg=1500W / 640V≈2.34A. This current value is much lower than the standard charging current of the power battery (usually 0.3C~0.5C), which is within the safe trickle charging range and will not have an adverse effect on the battery life.

[0215] (3) The low-power isolated DC-DC converter starts working, taking power (about 640V) from the DC bus of MCU1 on the BAT1 side. After high-frequency inversion by the DAB converter, isolation by the transformer, rectification and filtering, it outputs 640V / 2.34A to the DC bus of MCU2 to charge BAT2.

[0216] (4) The VCU continuously monitors the changes in SOC1 and SOC2. As equalization charging proceeds, SOC1 gradually decreases and SOC2 gradually increases, and the deviation gradually narrows. After about 2 hours (charging amount of about 3kWh), SOC1 drops to 80.5% and SOC2 rises to 72.5%, and the deviation narrows to 8%, but still has not reached the exit threshold.

[0217] (5) After balancing for about 1 hour, SOC1≈79.7% and SOC2≈73.3%, the deviation decreased to about 6.4%, further approaching the target threshold of 3%. The actual balancing time is affected by the battery capacity and balancing power. For a 280Ah battery pack, it may take longer to reduce the deviation from 11% to less than 3%. The VCU continuously monitors until the deviation drops to less than 3%, then automatically exits the balancing mode and sends a "stop" command to shut down the low-power isolated DC-DC converter.

[0218] It should be noted that in practical applications, considering energy transfer efficiency (typical efficiency of low-power isolated DC-DC converters is 90%~94%), approximately 6%~10% of electrical energy is lost as heat during the balancing process. However, given the small balancing power (1kW~2kW), the absolute value of this heat loss is very small, and its impact on the overall vehicle energy consumption can be ignored.

[0219] If the vehicle receives a driver start command (such as shifting into D gear) during the equalization process, the VCU will immediately determine the priority of drive demand, exit the equalization mode, and return to the drive mode power distribution process in step S2 to ensure that the vehicle's power response is not affected.

[0220] like Figure 2 As shown, in the fault scenario 3: low-power isolated DC-DC fault scenario, the system is degraded to the unassisted equalization mode, but the SOC can still be maintained within a controllable range by relying on the drive power distribution.

[0221] In this embodiment, if the low-power isolated DC-DC converter itself malfunctions (such as a power transistor short circuit or a control chip malfunction), the VCU, upon detecting the fault status reported by the converter, immediately stops sending any commands to the DC-DC converter and displays a message to the instrument stating "Equalization system fault, please repair promptly." The system's response strategy at this time is as follows:

[0222] (1) In drive mode, the power distribution algorithm can still be executed normally (unaffected by DC-DC). The SOC deviation is controlled within a controllable range by drive power distribution. Only the auxiliary trickle equalization cannot be performed when the car is stopped.

[0223] (2) In energy recovery mode, the recovered power allocation algorithm remains unaffected;

[0224] (3) In the case of a single battery failure, if the DCDC fails at the same time, it will be impossible to provide emergency power to the faulty side electronic control through the DCDC. At this time, the vehicle will only be driven by the healthy side. The driver should pay attention to the changes in power steering and brake air supply (loss of auxiliary drive function) and drive to a safe area at a low speed.

[0225] Step S5: Fault Diagnosis and Fault Tolerance Control

[0226] The VCU monitors the fault status of the BMS, MCU, and low-power isolated DC-DC converter in real time, executes a hierarchical fault-tolerance strategy, and records fault logs.

[0227] In this embodiment, the VCU has an internal fault diagnosis module that polls the fault status of each subsystem every 10ms. Fault levels are divided into three levels:

[0228] Level 1 fault (minor): such as intermittent loss of CAN communication, deviation of a temperature sensor reading, etc. The VCU records the fault code and illuminates the warning light, and the vehicle continues to operate normally;

[0229] Level 2 fault (medium): such as SOC deviation continuing to increase and unable to converge, low-power isolated DC-DC converter over-temperature protection, etc. The VCU records the fault code, illuminates the warning light and takes corresponding degraded measures (such as turning off the DC-DC equalization function).

[0230] Level 3 fault (serious): such as abnormal battery voltage, insulation fault, motor overcurrent, etc., the VCU will immediately perform fault isolation and emergency handling.

[0231] The above detailed embodiments illustrate preferred implementations of the present invention, but the scope of protection of the present invention is not limited to the specific structures and control parameters described. It should be understood that those skilled in the art can make various changes, modifications, substitutions, and variations to the above embodiments without departing from the basic principles of the present invention. These changes are all equivalent substitutions or simplified modifications of the present invention.

[0232] It should be noted that the various variant implementation schemes listed in this section are merely illustrative examples, intended to demonstrate the adaptability and scalability of the core inventive concept of this invention under different application scenarios and implementation conditions, and are not intended to limit the scope of protection of this invention. Any technical solution that incorporates the core inventive concept of this invention—namely, "two sets of power batteries are electrically completely independent and have no common DC bus node"—and achieves power distribution control and / or auxiliary drive function assurance under this architecture, regardless of any differences in specific implementation details such as controller architecture, energy storage device type, mechanical coupling method, and specific DC-DC topology from the preferred embodiments of this invention, falls within the scope of protection of this invention.

[0233] In other words, the core protection of this invention lies in the architectural concept and overall technical solution of "physical isolation + low-power bridging + intelligent allocation," rather than being limited to a specific hardware selection, a specific control parameter value, or a specific mechanical connection form. Any adaptive adjustments and equivalent substitutions made by those skilled in the art based on the basic principles and inventive concept of this invention after reading this specification should be considered part of this invention.

[0234] The following describes specific implementations of the present invention in the above-mentioned optional aspects with reference to specific variant embodiments, but these variants should not be construed as an exhaustive limitation of the present invention.

[0235] 1. Controller architecture variant solutions

[0236] In a variant embodiment of the present invention, no independent VCU is used. The power distribution control algorithm is executed collaboratively by MCU1 and MCU2 via high-speed communication (such as automotive Ethernet or FlexRay). Specifically, MCU1 acts as the master node and MCU2 acts as the slave node. After collecting driver signals and battery information, MCU1 calculates the power distribution scheme and sends the distribution result to MCU2 for execution via the communication bus. This scheme saves the hardware cost of an independent VCU, but the master-slave synchronization and fault arbitration mechanisms require more complex design, making it suitable for cost-sensitive applications.

[0237] 2. Variations of different battery chemistry systems

[0238] In a variant embodiment of the present invention, BAT1 and BAT2 can use batteries with different chemical systems, such as BAT1 being a lithium iron phosphate battery (high safety, long cycle life) and BAT2 being a ternary lithium battery (high energy density). In this case, the rated voltages of the two battery groups may differ, requiring the low-power isolated DC-DC converter to have a wider input / output voltage range (e.g., input 400V~750V, output 400V~750V) to adapt to different voltage platforms. Regarding the control strategy, since the SOC estimation methods and optimal operating ranges differ for different chemical systems, the VCU needs to store independent SOC-SOH temperature and power limit models for each battery group. The allocation algorithm no longer simply compares the absolute value of SOC, but rather compares the normalized offset of SOC relative to its ideal operating range. This variant requires more complex calibration and control strategies, but it has certain value in specific application scenarios (such as simultaneously pursuing range and safety).

[0239] 3. Variant scheme without mechanical coupling device

[0240] In a variant embodiment of the invention, M1 and M2 are not connected by a mechanical coupling device, but instead drive the front and rear axles of the vehicle respectively (i.e., an independent front and rear axle drive scheme), achieving natural coupling of the two motor drives through the road surface. In this case, the rotational speeds of M1 and M2 are no longer forced to be equal, and the VCU needs to add wheel speed coordination control and anti-slip control functions to prevent excessive wheel speed differences between the front and rear axles from causing vehicle instability. This scheme eliminates the mechanical coupling device, allowing for more flexible chassis layout, but it places higher demands on the VCU's control algorithm.

[0241] 4. Simplified variant of low-power isolated DC-DC converter

[0242] In a simplified variant of this invention, the low-power isolated DC-DC converter is completely eliminated, and there is no electrical connection between the two battery banks. State of Charge (SOC) balancing is achieved solely through drive power distribution and reclaimed power distribution. This solution further reduces system cost and complexity, but its drawbacks are: SOC cannot be balanced when the system is parked, and it cannot supply power to the auxiliary drive load on the faulty side when a single battery bank fails, reducing safety redundancy. This variant is suitable for applications that are extremely cost-sensitive and have low reliability requirements, but the scope of protection of its corresponding technical solution may be narrowed due to the omission of core differentiating components.

[0243] 5. Alternative solutions for the equilibrium method

[0244] In a variant embodiment of the present invention, the balancing function is handled independently by a power allocation algorithm, without the use of a low-power isolated DC-DC converter. That is, SOC balancing is achieved solely through SOC-sensitive power allocation in the drive mode in step S2 and SOC reciprocal allocation in the recycling mode in step S3. This scheme has a slow balancing rate, and the SOC cannot be balanced during long periods of vehicle parking. This variant is suitable for applications that frequently switch between charging and discharging during the work cycle (such as forklifts and loaders).

[0245] 6. Emergency Power Supply Alternatives

[0246] In a variant embodiment of the present invention, the emergency power supply function is achieved by a small-capacity auxiliary battery built into the fault-side electronic control unit. When the main battery fails, it automatically switches to the auxiliary battery to maintain the auxiliary drive function. However, this solution increases the additional battery cost and size, and the auxiliary battery has a limited capacity, which cannot support long-term operation. Therefore, it is more reasonable to use a low-power isolated DC-DC converter to draw power from the healthy side in the main solution.

[0247] The dual-power battery system and its power distribution control method described in this invention are particularly suitable for, but not limited to, the following application scenarios:

[0248] (1) Electric mining dump truck (mining truck): The mining working environment is harsh and the road surface is rugged, which places extremely high demands on the reliability and safety of vehicles. The design of two sets of batteries with completely independent power supply in this invention ensures that if either set of batteries fails due to vibration, high temperature or other reasons, the vehicle can still drive out of the mining area by itself, avoiding production interruption and safety risks caused by breakdown. At the same time, the emergency guarantee of power steering and brake air supply is crucial for the safety of mining trucks in heavy-load downhill conditions.

[0249] (2) Electric heavy-duty trucks (tractor units): Long-distance trunk line transportation has high requirements for driving range and charging efficiency. The dual-gun independent fast charging function of this invention can quickly replenish power when the vehicle is parked and resting. The power distribution algorithm maintains SOC balance during operation, which helps to extend battery pack life and reduce operating costs.

[0250] (3) Electric construction machinery (loaders, excavators, etc.): Construction machinery operates under complex and variable conditions, and frequent start-stop and heavy-load operations cause drastic fluctuations in battery SOC. The dynamic power allocation based on SOC in this invention can adapt to drastic fluctuations in power demand, maintain SOC within a reasonable operating range, and avoid a decrease in available power due to SOC imbalance.

[0251] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-power battery system for a vehicle, characterized in that, include: A first power battery pack and a second power battery pack; the DC output terminal of the first power battery pack is directly electrically connected to the DC input terminal of the first electronic control unit, and there are no other power conversion devices between them; the DC output terminal of the second power battery pack is directly electrically connected to the DC input terminal of the second electronic control unit, and there are no other power conversion devices between them; the first power battery pack and the second power battery pack do not share a DC bus node on the vehicle. A first electronic control unit and a second electronic control unit; the AC output terminal of the first electronic control unit is electrically connected to the first drive motor assembly, and the AC output terminal of the second electronic control unit is electrically connected to the second drive motor assembly; First drive motor group and second drive motor group; Mechanical coupling device; The mechanical output ends of the first drive motor group and the second drive motor group are respectively connected to the mechanical coupling device, which is used to superimpose the output torques of the first drive motor group and the second drive motor group and then transmit them out. Low-power isolated DC-DC converter; the two ends of the low-power isolated DC-DC converter are respectively connected to the DC bus of the first and second power battery packs or the first and second electronic control units, and it has electrical isolation function and bidirectional power transmission capability; The controller is communicatively connected to the first battery management system of the first power battery pack, the second battery management system of the second power battery pack, the first electronic control unit, the second electronic control unit, and the low-power isolated DC-DC converter.

2. The dual-power battery system according to claim 1, characterized in that, The power rating of the low-power isolated DC-DC converter is 1kW to 5kW.

3. The dual-power battery system according to claim 1, characterized in that, The first and second electronic control units each independently integrate a main drive inverter, a high-voltage to low-voltage DC-DC converter, an oil pump controller, and an air pump controller. The main drive inverter is used to convert the battery DC power into AC power to drive the motor or perform regenerative braking rectification. The high-voltage to low-voltage DC-DC converter is used to convert high-voltage DC power into low-voltage power to supply power to the low-voltage load of the vehicle. The oil pump controller is used to control the hydraulic oil pump motor, and the air pump controller is used to control the air compressor motor.

4. The dual-power battery system according to claim 1, characterized in that, The mechanical coupling device is any one of a dual-input single-output gearbox, a dual-motor reducer, or a drive axle coupling device; the mechanical coupling device is also provided with a clutch for selectively disengaging a single-sided drive motor.

5. The dual-power battery system according to claim 1, characterized in that, The controller is an independent vehicle controller, or a distributed controller formed by the first electronic control unit and the second electronic control unit through a communication bus.

6. A power distribution control method for a dual-power battery system, characterized in that, Includes the following steps: Step S1: The controller collects driver demand information, power battery pack information, drive motor pack information and vehicle status information in real time. It will determine whether to enter drive mode or energy recovery mode based on the sign of the total power demand P_demand; Step S2: When in driving mode, calculate the basic power allocation coefficient k_raw based on the deviation of the information of the first and second power battery packs, then calculate the original power allocation of the two power battery packs, and combine the battery power capacity constraint and motor efficiency optimization to determine the target driving power P1 of the first power battery pack and the target driving power P2 of the second power battery pack. Step S3: When in energy recovery mode, the recovery power is allocated according to the reciprocal of the SOC of the two power battery packs, so that the power battery pack with the lower SOC can obtain a larger recovery charging power. Step S4: The controller monitors the working status of the power battery pack and controls the low-power isolated DC-DC converter to perform auxiliary energy transfer between the two power battery packs based on the monitoring results; when the controller detects that the low-power isolated DC-DC converter has failed, the system degrades to the unassisted equalization mode and relies on drive power distribution to maintain the SOC within the preset controllable range. Step S5: The controller monitors the system fault status in real time and performs fault-tolerant control.

7. The power distribution control method according to claim 6, characterized in that, Step S2 specifically includes the following sub-steps: (S2.1) Calculate the basic allocation coefficient k_raw: k_raw = 0.5 + λ_comprehensive / 2 Wherein, λ_comprehensive is a multi-factor comprehensive equilibrium correction factor that comprehensively considers SOC deviation, SOH difference and temperature difference; Based on k_raw, the original allocated power is calculated as P1_raw = k_raw·P_demand, P2_raw = (1-k_raw)·P_demand; (S2.2) Perform battery power capacity constraint check: If P1_raw is greater than P_bat1_max, then limit P1 to P_bat1_max, and the excess is borne by the second power battery pack; if P2_raw is greater than P_bat2_max, then limit P2 to P_bat2_max, and the excess is borne by the first power battery pack; adjust cyclically until the power distribution of both battery packs is within their respective allowable power ranges; (S2.3) Optimize the high-efficiency zone of the motor: At the current speed, query the motor efficiency MAP. Under the constraint of P1+P2=P_demand, perform discretization search with the goal of maximizing the overall efficiency and reducing the SOC deviation trend to determine the final target drive power P1 of the first power battery pack and the target drive power P2 of the second power battery pack. If the SOC deviation exceeds the preset threshold, prioritize ensuring SOC balance. (S2.4) The final determined P1 and P2 are converted into torque commands and sent to the first electronic control unit and the second electronic control unit, respectively.

8. The power distribution control method according to claim 7, characterized in that, The multi-factor comprehensive equilibrium correction factor λ_comprehensive = λ_SOC×W_soc + λ_SOH×W_soh + λ_T×W_T; Wherein, λ_SOC is the SOC deviation factor, λ_SOH is the SOH difference factor, and λ_T is the temperature difference factor; W_soc is the SOC deviation weight, W_soh is the SOH difference weight, and W_T is the temperature difference weight, and W_soc+W_soh+W_T=1.

9. The power distribution control method according to claim 8, characterized in that, In step S2.1: The SOC deviation factor λ_SOC=(SOC1-SOC2) / (SOC1+SOC2); The SOH difference factor λ_SOH=(SOH1-SOH2) / (SOH1+SOH2), and when SOH1<SOH2, the power distribution proportion of the first power battery pack is reduced; The temperature difference factor λ_T=(T1-T2) / (T1+T2), and when any battery temperature T exceeds the preset temperature range, the maximum allowable power of the corresponding battery is reduced according to the temperature correction function.

10. The power distribution control method according to claim 6, characterized in that, In the step S3, assuming the required braking recovery power is P_rec_demand, then: P_rec1=P_rec_demand×SOC2 / (SOC1+SOC2) P_rec2=P_rec_demand×SOC1 / (SOC1+SOC2) If P_rec1 is greater than the maximum allowable recovery power P_rec1_max of the first power battery pack, P_rec1 is limited to P_rec1_max, and the excess part is undertaken by the second power battery pack; if the total recovery capacity is insufficient, the remaining braking force is supplemented by mechanical braking.

11. The power distribution control method according to claim 6, characterized in that, In the step S4, the auxiliary energy transmission at least includes one of the following working conditions: In the first working condition, when any power battery pack fails, the low-power isolated DCDC converter takes power from the power battery pack on the healthy side to provide emergency power supply to the electric control unit on the faulty side; In the second working condition, when both power battery packs are normal but the SOC deviation between the two packs exceeds the preset threshold, the low-power isolated DCDC converter transmits electric energy from the high SOC side to the low SOC side for auxiliary equalization charging.

12. The power distribution control method according to claim 11, characterized in that, When any power battery pack fails, the controller immediately cuts off the main power output on the faulty side, and the power battery pack on the healthy side drives the vehicle to operate at reduced power through the corresponding electric control unit and drive motor; at the same time, the controller starts the low-power isolated DCDC converter, takes power from the DC bus on the healthy side, and provides emergency power supply to the DC bus of the electric control unit on the faulty side after isolation conversion, so as to maintain the auxiliary drive function inside the electric control unit on the faulty side.

13. The power distribution control method according to claim 12, characterized in that, The power of the emergency power supply is 1kW to 5kW, and the auxiliary drive function includes steering oil pump control and air pump control.

14. The power distribution control method according to claim 11, characterized in that, When both power battery packs are normal but the SOC deviation exceeds the preset threshold and the current working condition meets the auxiliary equalization condition, the controller sends an equalization mode instruction to the low-power isolated DCDC converter, and the low-power isolated DCDC converter controls the high SOC power battery pack to perform trickle charging to the low SOC power battery pack; the controller monitors the SOC change in real time, and automatically turns off the low-power isolated DCDC converter and exits the equalization mode after the SOC deviation is reduced to the preset range.

15. The power distribution control method according to claim 14, characterized in that, The starting condition of the auxiliary equalization is that the vehicle is in a stopped state or a light-load working condition, and the SOC deviation is greater than 5%; the exit condition of the equalization mode is that the SOC deviation is reduced to within 3%; when the vehicle receives a driver start instruction during the auxiliary equalization process, the controller immediately exits the equalization mode and returns to the power distribution process of the driving mode.

16. The power distribution control method according to claim 14, characterized in that, The low-power isolated DC-DC converter is trickle-charged with a power control of 1kW to 2kW.

17. The power distribution control method according to claim 6, characterized in that, Step S2 further includes: when the vehicle is parked or under light load and the deviation between SOC1 and SOC2 is greater than a preset threshold, the controller starts the low-power isolated DC-DC converter to perform auxiliary equalization charging from the high SOC side to the low SOC side until the SOC deviation is reduced to the preset range.

18. The power distribution control method according to claim 17, characterized in that, The preset threshold for the SOC deviation is 5%, and the preset range is 3%.

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