Voltage control device, method and vehicle for dual-motor hybrid power system

Abstract

The present invention discloses a voltage control device, method and vehicle for a dual-motor hybrid power system. The device performs voltage closed-loop control according to Tq_GM via a generator inverter, and performs voltage closed-loop control according to VCM_U_batt_Tg via a bidirectional voltage conversion unit. This device can stabilize the voltage on the power battery side, ensure that the power battery charge and discharge power is lower than a set value, ensure the stability of the DCDC converter input voltage, and ensure the stability of the power supply of the 12V power supply system. By "equivalently preloading" the drive motor torque to the generator and high-voltage platform voltage closed-loop control, the device can ensure the stability of the high-voltage platform voltage, ensure the normal operation of the drive motor, and improve the environmental adaptability of the entire vehicle.

Description

Technical Field

[0001] The present invention belongs to the field of hybrid vehicle control, and in particular relates to a voltage control device, method and vehicle of a dual-motor hybrid vehicle system. Background Art

[0002] In a dual-motor hybrid system, one motor is a generator (GM) and the other is a drive motor (TM). This system has two drive modes: at low speeds, the drive motor alone drives the vehicle, while at high speeds, the engine alone or both the engine and the drive motor drive the vehicle. When the power battery is at extremely low or high temperatures or in a faulty state, the charge and discharge currents must be below a certain level. In this case, the power battery's power is limited, the voltage cannot be stabilized, and the vehicle will not operate normally.

[0003] CN113619559A discloses a motor voltage control method and device for a hybrid vehicle. This method, designed for a single-motor, high-voltage hybrid system, uses high-voltage closed-loop control of the generator to ensure a stable high-voltage input voltage for the DC-DC converter even when battery power is limited, thereby ensuring normal power supply to the vehicle's 12V power supply system. The vehicle can also be driven directly by the engine, thereby improving system robustness. However, this technology is only applicable to hybrid systems with a single motor, two voltage platforms, and direct engine drive, and is not applicable to dual-motor, three-voltage platforms. Summary of the Invention

[0004] The purpose of the present invention is to provide a voltage control device, method and vehicle for a dual-motor hybrid power system to stabilize the voltage, ensure the safety of the power battery and enhance the environmental adaptability of the entire vehicle.

[0005] The voltage control device of the dual-motor hybrid system described in the present invention includes a power control unit (PCU), a battery management system (BMS), and a dual-motor control assembly (DPEU). The dual-motor control assembly includes a dual-motor controller and a DCDC converter connected to the dual-motor controller, a bidirectional voltage conversion unit (VCM), a generator inverter (INV1-GM), and a drive motor inverter (INV2-TM). The dual-motor controller controls the operation of the DCDC converter, the bidirectional voltage conversion unit, the generator inverter, and the drive motor inverter. The power control unit, the battery management system, and the dual-motor controller communicate via a CAN bus. The input end of the DCDC converter is connected to the output end of the power battery and the battery end (i.e., the battery side) of the bidirectional voltage conversion unit. The motor end (i.e., the motor side) of the bidirectional voltage conversion unit is connected to the generator inverter and the drive motor inverter. The power battery provides a medium voltage platform voltage U_mv. The output end of the DCDC converter provides a low voltage platform voltage U_lv (i.e., the 12V system voltage platform). The motor end of the bidirectional voltage conversion unit provides a high voltage platform voltage U_hv.

[0006] The medium-voltage platform voltage (U_mv) supplies power to the low-voltage platform via a DC-DC converter. The medium-voltage platform exchanges power with the high-voltage platform via a bidirectional voltage conversion unit. During normal operation of the dual-motor hybrid system, the low-voltage platform voltage (U_lv) is controlled by the DCDC converter to maintain 12V system stability. The medium-voltage platform voltage (U_mv) is maintained by the power battery, and its output voltage fluctuates within a certain range depending on the battery's charge and discharge power and state of charge (SOC). The high-voltage platform voltage (U_hv) exchanges power with the medium-voltage platform via a bidirectional voltage conversion unit. The high-voltage platform voltage (U_hv) is also generated by the bidirectional voltage conversion unit. The control strategy adjusts the bidirectional voltage conversion unit's energy transfer from the power battery to maintain the high-voltage platform voltage (U_hv) at the target value and maintains its stability. By dynamically boosting the medium-voltage platform voltage, the dual-motor hybrid system ensures the drive motor and generator systems operate at their highest efficiency, or by increasing the high-voltage platform voltage to increase the power of the electric drive system. However, when the battery cell temperature is extremely low or high, or abnormal, its charging and discharging capabilities will be limited. At this time, if the conventional control method is still used, the medium-voltage platform voltage cannot be effectively controlled because the bidirectional voltage conversion unit uses the high-voltage platform voltage as the target voltage and the DCDC converter uses the low-voltage platform voltage as the target voltage. In other words, the charging and discharging power of the power battery cannot be accurately controlled, which can easily lead to power battery faults and thus power interruption of the entire vehicle. More seriously, it will cause damage to the power battery or even serious accidents such as overheating and burning.

[0007] The voltage control method of the dual-motor hybrid system of the present invention adopts the voltage control device of the dual-motor hybrid system described above, and the voltage control method includes:

[0008] The battery management system estimates the current maximum allowable charging power Batt_Pmax_charge, the current maximum allowable discharge power Batt_Pmax_discharge, the battery open circuit voltage Batt_OCV and the battery internal resistance Rbatt in real time and sends them to the CAN bus.

[0009] The power control unit (after obtaining the relevant signal from the CAN bus) determines whether the current maximum allowable charging power Batt_Pmax_charge is less than the preset first power threshold, or the current maximum allowable discharge power Batt_Pmax_discharge is less than the preset second power threshold. If so, the power control unit sends a Udc_Ctl mode request to the dual-motor controller, and at the same time switches the drive motor control parameters to the Udc_Ctl parameters, and performs closed-loop control of the engine speed.

[0010] After receiving the Udc_Ctl mode request, the dual-motor controller calculates the generator target torque Tq_GM and determines whether the (power) battery is overcharged or over-discharged. If so, it sets VCM_U_batt_Tg = U_Batt - (I_Batt - P_DCDC / U_Batt) * Rbatt (implementing the battery overcharge and over-discharge protection strategy). Otherwise, (indicating that the current closed-loop voltage point of the bidirectional voltage conversion unit is set appropriately), it sets VCM_U_batt_Tg = Batt_OCV. VCM_U_batt_Tg represents the target output voltage of the bidirectional voltage conversion unit, U_Batt represents the battery-side output voltage of the bidirectional voltage conversion unit, I_Batt represents the battery-side output current of the bidirectional voltage conversion unit, and P_DCDC represents the power of the DC-DC converter. U_Batt, I_Batt, and P_DCDC are obtained by the dual-motor controller within the dual-motor control assembly.

[0011] The dual-motor controller enables the generator inverter to perform torque closed-loop control (also voltage closed-loop control) according to Tq_GM, and the dual-motor controller enables the bidirectional voltage conversion unit to perform voltage closed-loop control according to VCM_U_batt_Tg.

[0012] Preferably, the step of calculating the generator target torque Tq_GM includes:

[0013] The drive motor conversion efficiency η_TM is determined based on the acquired torque Tq_TM to be executed by the drive motor and the current drive motor speed n_TM.

[0014] The generator conversion efficiency η_GM is determined based on the acquired current generator speed n_GM.

[0015] Calculate the generator preload torque Tq_GM_TM using the formula: Tq_GM_TM = Tq_TM * n_TM / (n_GM * η_TM * η_GM). Since the driving power of the generator is much greater than the power consumption of the DCDC converter, the required torque of the generator is equivalently calculated based on the required torque of the driving motor. That is, according to the fact that the power generation power of the generator is equal to the driving power of the driving motor, the above-mentioned generator preload torque Tq_GM_TM can be obtained.

[0016] According to the obtained high-voltage platform capacitance C, high-voltage platform target voltage U_hv_tg, and high-voltage platform actual voltage U_hv_act, calculate the power deviation ΔP using the formula: ΔP = C * (U_hv_act - U_hv_tg) * (U_hv_act + U_hv_tg) / 2. C, U_hv_tg, and U_hv_act are obtained inside the dual-motor controller in the dual-motor control assembly.

[0017] Calculate the generator torque deviation Tq_GM_du (i.e., the torque deviation that the generator needs to compensate) using the formula: Tq_GM_du = ΔP / (n_GM * η_GM) * 9550.

[0018] Calculate the estimated value of the generator target torque Tq_GM_c using the formula: Tq_GM_c = Tq_GM_TM + Tq_GM_du.

[0019] If Tq_GM_min < Tq_GM_c < Tq_GM_max, then set the generator target torque Tq_GM = Tq_GM_c.

[0020] If Tq_GM_c ≤ Tq_GM_min, then set the generator target torque Tq_GM = Tq_GM_min.

[0021] If Tq_GM_c ≥ Tq_GM_max, then set the generator target torque Tq_GM = Tq_GM_max.

[0022] Among them, Tq_GM_min represents the preset minimum allowable torque of the generator, and Tq_GM_max represents the preset maximum allowable torque of the generator.

[0023] Preferably, if Batt_Pmax_charge > U_Batt * I_Batt - P_DCDC, or

[0024] Batt_Pmax_discharge > P_DCDC - U_Batt * I_Batt, it means that the battery has overcharge or over-discharge phenomenon.

[0025] Preferably, based on the acquired upcoming torque Tq_TM of the drive motor and the current speed n_TM of the drive motor, a preset drive motor conversion efficiency table is queried to obtain the drive motor conversion efficiency η_TM. The preset drive motor conversion efficiency table is a table of correspondences between upcoming torque, drive motor speed, and drive motor conversion efficiency, obtained through calibration.

[0026] Preferably, the generator conversion efficiency η_GM is obtained by querying a preset generator conversion efficiency table based on the current generator speed n_GM obtained, wherein the preset generator conversion efficiency table is a correspondence table between the generator speed and the generator conversion efficiency obtained through calibration.

[0027] The vehicle of the present invention includes the voltage control device of the dual-motor hybrid power system.

[0028] The present invention ensures the safety of the power battery through two-stage voltage closed-loop control (i.e., the generator inverter performs voltage closed-loop control according to Tq_GM, and the bidirectional voltage conversion unit performs voltage closed-loop control according to VCM_U_batt_Tg). In this mode, the entire vehicle still has a certain driving capability, which enhances the environmental adaptability of the entire vehicle. In the two-stage voltage closed-loop control, the first stage is the medium-voltage platform voltage closed-loop control, which is controlled by the bidirectional voltage conversion unit. At this time, the bidirectional voltage conversion unit operates in step-down mode, which can step down the high-voltage platform voltage to the medium-voltage platform voltage. The medium-voltage platform voltage side is the control object, stabilizing the power battery side voltage, ensuring that the power battery charge and discharge power is lower than the set value, ensuring the stability of the DCDC converter input voltage, and ensuring the stability of the 12V power supply system power supply; the other stage is the high-voltage platform voltage closed-loop control, which is performed by the generator inverter. By "equivalently preloading" the drive motor torque to the generator and high-voltage platform voltage closed-loop control, the high-voltage platform voltage is ensured to be stable, ensuring the normal operation of the drive motor, and improving the environmental adaptability of the entire vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the voltage control device of the dual-motor hybrid system in this embodiment.

[0030] Figure 2 This is a diagram of the local high-voltage architecture connecting the dual-motor control assembly and the power battery in this embodiment.

[0031] Figure 3 This is a flowchart of the execution of the battery management system in the voltage control method of the dual-motor hybrid system of this embodiment.

[0032] Figure 4 This is a flowchart of the execution of the power control unit in the voltage control method of the dual-motor hybrid system of this embodiment.

[0033] Figure 5 This is a flowchart of the execution of the dual-motor controller in the voltage control method of the dual-motor hybrid system of this embodiment. DETAILED DESCRIPTION

[0034] like Figure 1 、 Figure 2 As shown, the voltage control device of the dual-motor hybrid system in this embodiment includes a power control unit (PCU) 2, a battery management system (BMS) 3, and a dual-motor control unit (DPEU) 1. The dual-motor control unit 1 includes a dual-motor controller 10 and, connected to it, a DC-DC converter 11, a bidirectional voltage conversion unit 12, a generator inverter (INV1-GM) 13, and a drive motor inverter (INV2-TM) 14. The dual-motor controller 10 controls the operation of the DC-DC converter 11, the bidirectional voltage conversion unit 12, the generator inverter 13, and the drive motor inverter 14. The PCU 2, the BMS 3, and the dual-motor controller 10 communicate via the CAN bus. The input of the DC-DC converter 11 is connected to the output of the power battery 4 and the battery side (i.e., the battery side) of the bidirectional voltage conversion unit 12. The motor side (i.e., the motor side) of the bidirectional voltage conversion unit 12 is connected to the generator inverter 13 and the drive motor inverter 14. The power battery 4 provides a medium voltage platform voltage U_mv. The output of the DC-DC converter 11 provides a low-voltage platform voltage, U_lv. The DC-DC converter 11 converts the medium-voltage platform DC voltage into a low-voltage platform DC voltage, which powers the vehicle's 12V low-voltage platform power supply system. The motor side of the bidirectional voltage conversion unit 12 provides a high-voltage platform voltage, U_hv. In boost mode, the bidirectional voltage conversion unit 12 boosts the medium-voltage platform battery voltage to a specific value based on a boost strategy, stabilizing the high-voltage platform voltages of the generator inverter 13 and the drive motor inverter 14, ensuring optimal efficiency or maximum power for the power generation and drive systems. In buck mode, the bidirectional voltage conversion unit 12 steps down the high-voltage platform voltage to the medium-voltage platform voltage, ensuring controllable charging and discharging power of the power battery. The generator inverter 13 is responsible for controlling the generator, primarily converting the mechanical energy generated by the engine into electrical energy to provide power to the high-voltage platform. The drive motor inverter 14 controls the drive motor, primarily enabling vehicle propulsion and energy recovery. Power Control Unit 2, the system's primary controller, receives status, capability, and demand signals from each controller. Based on the driver's intent and feedback from each controller, it comprehensively evaluates and requests control modes and target values from other controllers. Battery Management System 3 primarily manages the power battery's status.

[0035] The voltage control method of the dual-motor hybrid system in this embodiment adopts the voltage control device of the dual-motor hybrid system described above. In the voltage control method, the battery management system 3 performs the following steps (see Figure 3 ):

[0036] S11. Estimate (the estimation method belongs to the prior art) the current maximum allowable charging power Batt_Pmax_charge and the current maximum allowable discharging power Batt_Pmax_discharge in real time based on the battery cell temperature, SOC and other parameters, and send them to the CAN bus, and then execute S12.

[0037] S12. Based on the real-time collected battery voltage and current, and in combination with different temperatures, the battery open circuit voltage Batt_OCV and the battery internal resistance Rbatt are estimated in real time (the estimation method belongs to the existing technology), and sent to the CAN bus, and then the process ends.

[0038] like Figure 4 As shown, in the voltage control method of the dual-motor hybrid system, the power controller 2 performs the following steps:

[0039] S21. Determine whether the current maximum allowable charging power Batt_Pmax_charge is less than a preset first power threshold, or the current maximum allowable discharging power Batt_Pmax_discharge is less than a preset second power threshold. If so, execute S22; otherwise, continue to execute S21.

[0040] S22 , sending a Udc_Ctl mode request to the dual-motor controller 10 , switching the drive motor control parameters to Udc_Ctl parameters, performing closed-loop speed control on the engine, and then ending.

[0041] like Figure 5 As shown, in the voltage control method of the dual-motor hybrid system, the dual-motor controller 10 performs the following steps:

[0042] S31. Determine whether a Udc_Ctl mode request is received. If yes, execute S32; otherwise, continue to execute S31.

[0043] S32: Calculate the generator target torque Tq_GM, and then execute S33.

[0044] The specific steps for calculating the generator target torque Tq_GM include:

[0045] Step 1: Determine the drive motor conversion efficiency η_TM based on the torque Tq_TM that the drive motor is about to execute and the current drive motor speed n_TM obtained. Specifically: Based on the torque Tq_TM that the drive motor is about to execute and the current drive motor speed n_TM obtained, query the preset drive motor conversion efficiency table to obtain the drive motor conversion efficiency η_TM; where the preset drive motor conversion efficiency table is a corresponding relationship table of the torque about to be executed, drive motor speed, and drive motor conversion efficiency obtained through calibration.

[0046] Step 2: Determine the generator conversion efficiency η_GM based on the current generator speed n_GM obtained. Specifically: Based on the current generator speed n_GM obtained, query the preset generator conversion efficiency table to obtain the generator conversion efficiency η_GM; where the preset generator conversion efficiency table is a corresponding relationship table of the generator speed and generator conversion efficiency obtained through calibration.

[0047] Step 3: Use the formula: Tq_GM_TM = Tq_TM * n_TM / (n_GM * η_TM * η_GM) to calculate the generator preload torque Tq_GM_TM. <U+

[0048] Step 4: Based on the high-voltage platform capacitance C, high-voltage platform target voltage U_hv_tg, and high-voltage platform actual voltage U_hv_act obtained, use the formula: ΔP = C * (U_hv_act - U_hv_tg) * (U_hv_act + U_hv_tg) / 2 to calculate the power deviation ΔP.

[0049] Step 5: Use the formula: Tq_GM_du = ΔP / (n_GM * η_GM) * 9550 to calculate the generator torque deviation Tq_GM_du.

[0050] Step 6: Use the formula: Tq_GM_c = Tq_GM_TM + Tq_GM_du to calculate the estimated value of the generator target torque Tq_GM_c.

[0051] Step 7: Determine the generator target torque Tq_GM. Specifically: If Tq_GM_min < Tq_GM_c < Tq_GM_max, then set Tq_GM = Tq_GM_c; if Tq_GM_c ≤ Tq_GM_min, then set Tq_GM = Tq_GM_min; if Tq_GM_c ≥ Tq_GM_max, then set Tq_GM = Tq_GM_max. Where Tq_GM_min represents the preset minimum allowable torque of the generator, and Tq_GM_max represents the preset maximum allowable torque of the generator.

[0052] S33. Determine whether Batt_Pmax_charge>U_Batt*I_Batt-P_DCDC or Batt_Pmax_discharge>P_DCDC-U_Batt*I_Batt. If so (i.e., the battery is overcharged or over-discharged), execute S34; otherwise, execute S35.

[0053] S34: Set VCM_U_batt_Tg = U_Batt - (I_Batt - P_DCDC / U_Batt) * Rbatt, and then execute S36, where VCM_U_batt_Tg represents the target output voltage of the bidirectional voltage conversion unit, U_Batt represents the battery-side output voltage of the bidirectional voltage conversion unit, I_Batt represents the battery-side output current of the bidirectional voltage conversion unit, and P_DCDC represents the power of the DCDC converter.

[0054] S35 . Set VCM_U_batt_Tg=Batt_OCV, and then execute S36 .

[0055] S36 , causing the generator inverter 13 to perform torque closed-loop control according to Tq_GM, and causing the bidirectional voltage conversion unit 12 to perform voltage closed-loop control according to VCM_U_batt_Tg, and then ending.

[0056] This embodiment also provides a vehicle, which includes the voltage control device of the dual-motor hybrid system.

Claims

1. A voltage control device for a dual-motor hybrid system, comprising a power control unit (2), a battery management system (3) and a dual-motor control assembly (1); characterized in that: The dual-motor control assembly (1) includes a dual-motor controller (10) and a DCDC converter (11), a bidirectional voltage conversion unit (12), a generator inverter (13) and a drive motor inverter (14) connected to the dual-motor controller (10). The dual-motor controller (10) controls the operation of the DCDC converter (11), the bidirectional voltage conversion unit (12), the generator inverter (13) and the drive motor inverter (14); the power control unit (2), the battery management system (3), the dual-motor controller (10) and the drive motor inverter (14) are connected to the dual-motor controller (10). ) communicates via a CAN bus, the input end of the DCDC converter (11) is connected to the output end of the power battery (4) and the battery end of the bidirectional voltage conversion unit (12), the motor end of the bidirectional voltage conversion unit (12) is connected to the generator inverter (13) and the drive motor inverter (14), the power battery (4) provides a medium voltage platform voltage U_mv, the output end of the DCDC converter (11) provides a low voltage platform voltage U_lv, and the motor end of the bidirectional voltage conversion unit (12) provides a high voltage platform voltage U_hv.

2. A voltage control method for a dual-motor hybrid system, characterized in that: Using the voltage control device according to claim 1, the method comprises: The battery management system (3) estimates the current maximum allowable charging power Batt_Pmax_charge, the current maximum allowable discharging power Batt_Pmax_discharge, the battery open circuit voltage Batt_OCV and the battery internal resistance Rbatt in real time and sends them to the CAN bus; The power control unit (2) determines whether the current maximum allowable charging power Batt_Pmax_charge is less than a preset first power threshold, or the current maximum allowable discharge power Batt_Pmax_discharge is less than a preset second power threshold. If so, a Udc_Ctl mode request is sent to the dual-motor controller (10), and the drive motor control parameter is switched to the Udc_Ctl parameter, and closed-loop speed control is performed on the engine. After receiving the Udc_Ctl mode request, the dual motor controller (10) calculates the generator target torque Tq_GM and determines whether the battery is overcharged or over-discharged. If so, it uses VCM_U_batt_Tg=U_Batt-(I_Batt-P_DCDC / U_Batt)*Rbatt, otherwise use VCM_U_batt_Tg=Batt_OCV; where VCM_U_batt_Tg represents the target output voltage of the bidirectional voltage conversion unit, U_Batt represents the battery-side output voltage of the bidirectional voltage conversion unit, I_Batt represents the battery-side output current of the bidirectional voltage conversion unit, and P_DCDC represents the power of the DCDC converter. The generator inverter (13) is made to perform torque closed-loop control according to Tq_GM, and the bidirectional voltage conversion unit (12) is made to perform voltage closed-loop control according to VCM_U_batt_Tg.

3. The voltage control method of a dual-motor hybrid system according to claim 2, characterized in that: The steps for calculating the generator target torque Tq_GM include: Determine the drive motor conversion efficiency η_TM based on the torque Tq_TM that the drive motor is about to execute and the current drive motor speed n_TM obtained; Determine the generator conversion efficiency η_GM based on the current generator speed n_GM obtained; Calculate the generator preload torque Tq_GM_TM using the formula: Tq_GM_TM = Tq_TM * n_TM / (n_GM * η_TM * η_GM); Calculate the power deviation ΔP based on the obtained high-voltage platform capacitance C, high-voltage platform target voltage U_hv_tg, and high-voltage platform actual voltage U_hv_act using the formula: ΔP = C * (U_hv_act - U_hv_tg) * (U_hv_act + U_hv_tg) / 2; Calculate the generator torque deviation Tq_GM_du using the formula: Tq_GM_du = ΔP / (n_GM * η_GM) * 9550; Calculate the estimated value of the generator target torque Tq_GM_c using the formula: Tq_GM_c = Tq_GM_TM + Tq_GM_du; If Tq_GM_min < Tq_GM_c < Tq_GM_max, then set the generator target torque Tq_GM = Tq_GM_c; If Tq_GM_c ≤ Tq_GM_min, then set the generator target torque Tq_GM = Tq_GM_min; If Tq_GM_c ≥ Tq_GM_max, then set the generator target torque Tq_GM = Tq_GM_max; Where, Tq_GM_min represents the preset minimum allowable torque of the generator, and Tq_GM_max represents the preset maximum allowable torque of the generator.

4. The voltage control method of a dual-motor hybrid system according to claim 2 or 3, characterized in that: If Batt_Pmax_charge > U_Batt * I_Batt - P_DCDC or Batt_Pmax_discharge > P_DCDC - U_Batt * I_Batt, it indicates that the battery has overcharge or over-discharge phenomena.

5. The voltage control method for a dual-motor hybrid power system according to claim 2 or 3, wherein: Query the preset drive motor conversion efficiency table based on the torque Tq_TM that the drive motor is about to execute and the current drive motor speed n_TM obtained to obtain the drive motor conversion efficiency η_TM; wherein, the preset drive motor conversion efficiency table is a corresponding relationship table of the torque about to be executed, drive motor speed, and drive motor conversion efficiency obtained through calibration; Query the preset generator conversion efficiency table based on the current generator speed n_GM obtained to obtain the generator conversion efficiency η_GM; wherein, the preset generator conversion efficiency table is a corresponding relationship table of the generator speed and generator conversion efficiency obtained through calibration.

6. A vehicle, characterized in that: Comprises a voltage control device for a dual-motor hybrid power system as described in claim 1.

Images