Electricity balance control system and method based on WLTC working condition

Abstract

A power balance control system and method based on WLTC working condition, comprising: an input module, a SOC (battery power) storage module, a dynamic energy calculation module, a power balance identification module, a power balance penalty module and a power balance torque distribution module. The present invention aims at GB18352 National VI regulations requiring that the power of the transition cycle and the confirmation cycle need to meet the energy change amount Δ of the WLTC driving cycle Eress Less than the total energy E of the entire driving cycle total The 0.5% error can avoid differences in driver's driving operations and test benches, and improve the robustness of the test.

Description

Technical Field

[0001] The present invention relates to a technology in the field of vehicle power control, specifically a power balance control system and method based on the WLTC working condition based on the GB18753 National VI emission cycle. Background Art

[0002] As emission requirements become increasingly stringent, vehicle manufacturers face increasing pressure to meet the increasing national regulations. Starting from National VI, regulations gradually increase the requirements for the battery balance of PHEV and HEV vehicles. The energy change of the WLTC driving cycle is required to be Δ Eress Less than the total energy E of the entire driving cycle total Different driving habits and different rotation speeds will have a greater impact on the robustness of the test results, causing the power to exceed the regulatory requirements and leading to test failure.

[0003] The defects and shortcomings of the existing power balance control methods are as follows: the existing WLTC power balance control methods are mostly based on the SOC feedback from the high-voltage battery controller BMS for power balance calculation, but the SOC feedback from the BMS is the integral settlement result of the high-voltage battery current based on time, and cannot feedback the actual energy of the high-voltage system. The actual energy of the high-voltage system is the integral result of the power of the high-voltage battery system based on time.

[0004] The SOC fed back by the BMS cannot truly reflect the actual energy status of the battery. After the battery is frequently charged and discharged, the SOC is prone to jump. If the SOC is used to calculate the power balance, it is easy to cause the experimental results to exceed the regulatory requirements and the experiment to fail. Summary of the invention

[0005] The present invention aims at GB18352 National VI regulations requiring that the power of the transition cycle and the confirmation cycle must meet the energy change Δ of the WLTC driving cycle Eress Less than the total energy E of the entire driving cycle total A power balance control system and method based on WLTC working condition is proposed, which can avoid the differences in driver's driving operation and test bench and improve the robustness of the test.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention relates to a power balance control system based on a WLTC working condition, comprising: an input module, a SOC (battery power) storage module, a dynamic energy calculation module, a power balance identification module, a power balance penalty module and a power balance torque distribution module, wherein: the dynamic energy calculation module monitors the battery power in real time, and performs closed-loop control of the battery power in the WLTC ultra-high speed section, and performs dynamic torque compensation of the engine according to the difference between the power at the beginning of the driving cycle and the power in the closed-loop control section in which the WLTC ultra-high speed section is activated, so as to achieve energy balance of the entire driving cycle; the SOC storage module determines whether the battery power SOC is in a balanced range when the whole vehicle is powered on, and stores it in a VCU In EEprom, it is used as the initial SOC value for dynamic energy calculation; the dynamic energy calculation module integrates the time according to the current and voltage of the BMS (battery management system) fed back in real time on the CAN during vehicle operation, calculates the total battery energy change BMS_Energy, and divides BMS_Energy by the total capacity of the battery to calculate the SOC change corresponding to the energy change; the power balance identification module sets the SOC closed-loop flag in the ultra-high-speed section, and the VCU detects that the current vehicle speed is greater than the upper limit of the vehicle speed threshold. If the above conditions are met, the VCU activates the closed loop once, and when the vehicle speed is lower than the lower limit of the vehicle speed threshold, the closed-loop control is exited; the power balance penalty calculation module will call the torque penalty coefficient once each time the VCU closed-loop flag is activated, and obtain different engine torque penalty coefficients SOC_FA according to the SOC difference calculated by the dynamic energy calculation module; the power balance torque distribution module VCU obtains the torque penalty coefficient by looking up the table according to the SOC difference. When the torque penalty coefficient obtained by looking up the table is equal to 0, the VCU looks up the original engine torque distribution strategy, and the engine torque directly drives the wheel end, and the motor does not generate electricity or assist. When the torque penalty coefficient is less than 0, the VCU looks up the table to correct the engine torque distribution strategy, and uses the power generation compensation VCU_Charge_MAP*SOC_FAC + engine torque original MAP*(1-SOC_FAC) to distribute the engine torque. When SOC_FAC is greater than 0, the VCU looks up the table to correct the engine torque distribution strategy, and uses the discharge compensation VCU_Discharge_MAP*SOC_FAC + engine torque original MAP*(1-SOC_FAC) to distribute the engine torque. The above functions are used to achieve dynamic coordination of SOC and ensure the balance of vehicle energy.

[0008] The VCU (vehicle control unit) in the input module receives basic vehicle parameter information to provide information input for the subsequent dynamic energy calculation module.

[0009] The basic vehicle parameter information includes: current vehicle speed, power battery SOC and current and voltage values, vehicle high voltage state, accelerator pedal and brake pedal opening.

[0010] The original engine torque distribution strategy in the power balancing torque distribution module is based on the engine universal characteristic curve to determine the optimal working load point range of the engine, and determines the engine torque under each gear according to the output shaft speed and the wheel end required torque.

[0011] The power generation compensation VCU_Charge_MAP in the power balance torque distribution module is based on the original engine torque distribution strategy to increase a certain amount of engine torque, so that more power generation torque is distributed to the motor.

[0012] The discharge compensation VCU_Discharge_MAP in the power balancing torque distribution module is based on reducing a certain amount of engine torque on the basis of the original engine torque distribution strategy, so that the motor needs to consume electrical energy to meet the required torque at the wheel end.

[0013] Technical Effects

[0014] The technical effects of the present invention include:

[0015] 1. By using the integral value of the battery's charge and discharge current and voltage over time during vehicle driving, the battery's energy changes are calculated in real time, and the control of battery power changes is more accurate, thereby avoiding the failure of the entire energy balance control due to inaccurate battery power SOC feedback due to differences in the battery's own state. In addition, the SOC based on BMS feedback is the integral settlement result of the high-voltage battery current based on time, and cannot feedback the actual energy of the high-voltage system. This system calculates the power balance through the integral result of the high-voltage battery power based on time, and the test has high credibility.

[0016] 2. Closed-loop control is adopted in the ultra-high-speed section. The corresponding engine torque penalty coefficient is obtained by looking up the table according to the current SOC change, and the engine torque is compensated to achieve the entire WLTC power balance. Since the present invention adopts closed-loop control in the final stage of the WLTC test, it can avoid the influence of driver operation differences and test benches, and the control robustness is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the present invention;

[0018] Figure 2 A schematic diagram of an embodiment.

[0019] Figure 3 The following are the test results of the embodiments. DETAILED DESCRIPTION

[0020] like Figure 1As shown, a power balance control system based on the WLTC working condition involved in this embodiment includes: an input module, an SOC storage module, a dynamic energy calculation module, a power balance identification module, a power balance penalty module and a power balance torque distribution module.

[0021] The input module includes vehicle status information obtained by the vehicle controller VCU, motor controller MCU, transmission controller TCU, engine management system EMS, battery management system BMS, etc. The vehicle controller VCU interacts with each unit controller through the vehicle communication CAN network, receives the current basic parameter information of the vehicle, such as the current vehicle speed, power battery SOC and current and voltage values, total battery capacity, vehicle high voltage state, accelerator pedal and brake pedal opening, current engine gear and motor gear, etc., and provides software input information for other modules.

[0022] The SOC storage module includes determining whether the battery power SOC is in a balanced range when the vehicle is powered on, and normalizing the real SOC within the available power range of the battery as the SOC initial value for dynamic energy calculation, and storing it in the VCU EEprom.

[0023] The dynamic energy calculation module includes a battery instantaneous power calculation module, a power calculation module, and a dynamic energy calculation module. The battery instantaneous power calculation module multiplies the current and voltage of the BMS fed back in real time on the CAN during vehicle operation to obtain the battery charge and discharge power at each moment. The power calculation module integrates the battery charge and discharge power obtained by the battery instantaneous power calculation module over time to calculate the total battery energy change BMS_Energy. The dynamic energy calculation module divides BMS_Energy by the total capacity of the battery to calculate the SOC change corresponding to the energy change.

[0024] The power balance identification module sets the SOC closed-loop flag in the ultra-high-speed section. When the VCU detects that the current vehicle speed is greater than the upper speed threshold, the VCU activates the closed loop once if the above conditions are met. When the vehicle speed is lower than the lower speed threshold or exceeds a certain time, the closed-loop control is exited.

[0025] The power balance penalty calculation module will call the torque penalty coefficient each time the VCU closed-loop flag is activated, and obtain different engine torque penalty coefficients SOC_FAC by looking up the table according to the SOC difference calculated by the dynamic energy calculation module.

[0026] The power balancing torque distribution module VCU obtains the torque penalty coefficient SOC_FAC by looking up the table according to the difference in SOC. When the torque penalty coefficient obtained by looking up the table is equal to 0, VCU looks up the original engine torque distribution strategy, and the engine torque directly drives the wheel end, and the motor does not generate electricity or assist. When the torque penalty coefficient is less than 0, VCU looks up the table to correct the engine torque distribution strategy, and adopts the power generation compensation VCU_Charge_MAP*(-SOC_FAC)+engine torque original MAP*(1+SOC_FAC) to distribute the engine torque. When SOC_FAC is greater than 0, VCU looks up the table to correct the engine torque distribution strategy, and adopts the discharge compensation VCU_Discharge_MAP*SOC_FAC+engine torque original MAP*(1-SOC_FAC) to distribute the engine torque. The above functions realize the dynamic coordination of SOC and ensure the balance of vehicle energy.

[0027] The original engine torque distribution strategy in the power balancing torque distribution module is based on the engine universal characteristic curve to determine the optimal working load point range of the engine, and determines the engine torque in each gear according to the speed and wheel-end demand torque shift line.

[0028] The power generation compensation VCU_Charge_MAP in the power balance torque distribution module is based on the original engine torque distribution strategy to increase a certain amount of engine torque, so that more power generation torque is distributed to the motor.

[0029] The discharge compensation VCU_DisCharge_MAP in the power balancing torque distribution module is based on reducing a certain amount of engine torque on the basis of the original engine torque distribution strategy, so that the motor needs to consume electrical energy to meet the required torque at the wheel end.

[0030] The motor torque calculation module in the power balance torque distribution module is equal to the current wheel end demand torque minus the torque transmitted to the wheel end by the engine torque and then divided by the current motor gear ratio, that is, (wheel end demand torque-engine transmitted to wheel end torque) / motor gear ratio.

[0031] like Figure 1 As shown, the present embodiment relates to a power balance control method based on the WLTC working condition of the above system, which specifically includes:

[0032] Step 1, SOC storage: VCU detects that the driver activates the current driving cycle, and the high-voltage battery SOC is within a certain range [A-2, A+2]. VCU stores the actual BMS_ACT_SOC received by the battery at this time = A in VCU EEprom;

[0033] Step 2: Dynamic energy calculation: Starting from the moment the driver presses the PEPS vehicle power-on enable button, the VCU integrates the BMS actual current BMS_Current and BMS actual voltage BMS_Voltage received through the CAN communication network to calculate the total battery energy BMS_Energy, and divides BMS_Energy by the total capacity of the battery to calculate the SOC change Δ corresponding to the energy. SOC , electricity consumption is negative and power generation is positive.

[0034] Step 3: SOC closed-loop identification: According to the requirements of CS mode power balance in WLTC regulations Δ Eress / E fuelcs Less than 4%, so VCU sets the flag to activate closed-loop control in the ultra-high speed section. When VCU detects that the current vehicle speed is greater than 120kph, the above conditions are met and VCU activates the closed loop once. When the vehicle speed is less than 100kph or lasts for 30s, it exits SOC closed-loop identification.

[0035] Step 4: Calculation of SOC closed-loop penalty coefficient: Each time the VCU closed-loop flag is activated, the torque penalty coefficient will be called once. Different coefficients SOC_FAC will be penalized according to the size of the SOC difference calculated by the dynamic energy calculation module to compensate for the increase or decrease of torque.

[0036] Step 5: SOC closed-loop torque compensation: VCU looks up the torque penalty coefficient based on the SOC difference. SOC difference Δ SOC =[-2-1.5 1 1 1.5 2] Look up the table SOC_FAC = [-1-0.5 0 0 0.5 1]. When SOC_FAC is equal to 0, VCU looks up the original engine torque distribution strategy, the engine torque can directly meet the wheel end torque demand, and the motor does not generate electricity or assist. When SOC_FAC is less than 0, VCU looks up the table to correct the engine torque distribution strategy, and uses the power generation compensation VCU_Charge_MAP*(-SOC_FAC)+engine torque original MAP*(1+SOC_FAC) to distribute the engine torque. At this time, the motor torque is equal to the wheel end demand torque minus the engine torque transmitted to the wheel end torque and then divided by the motor gear ratio. When SOC_FAC is greater than 0, VCU looks up the table to correct the engine torque distribution strategy, and uses discharge compensation VCU_Discharge_MAP*SOC_FAC+engine torque original MAP*(1-SOC_FAC) to distribute the engine torque. Similarly, the motor torque at this time is equal to the wheel end demand torque minus the engine torque transmitted to the wheel end torque and then divided by the motor gear ratio. The above functions realize the dynamic coordination of SOC and ensure the balance of vehicle energy.

[0037] like Figure 2As shown, the WLTC test is carried out in accordance with GBT 19753-2013 light hybrid electric vehicle energy consumption test method. The test room temperature should be set to 23℃ with an allowable deviation of ±5℃. Before starting, the vehicle is placed indoors at a temperature of 20℃ to 30℃ for at least 6 hours until the engine oil temperature and coolant temperature are within the range of 23℃±2℃.

[0038] like Figure 2 As shown, through the above-mentioned control system and method based on WLTC power balance, the SOC closed-loop control is activated 4 times in the WLTC ultra-high speed section. When the difference of SOC is greater than 0, the SOC_FAC coefficient obtained by looking up the table in the closed-loop activation stage 2 is 0.5, and the actual torque of the engine is equal to the original engine torque in the gear 6 * (1-0.5) + the engine torque value under the discharge compensation MAP * 0.5. At this time, the motor torque is equal to the wheel-end demand torque minus the torque transmitted to the wheel end by the engine and then divided by the motor gear ratio. When the difference of SOC is less than 0, the SOC_FAC coefficient obtained by looking up the table in the closed-loop activation stage 3 is -0.3, and the actual torque of the engine is equal to the original engine torque in the gear 6 * (1-0.3) + the engine torque value under the discharge compensation MAP * 0.3. At this time, the motor torque is equal to the wheel-end demand torque minus the torque transmitted to the wheel end by the engine and then divided by the motor gear ratio. The SOC_FAC coefficient obtained by looking up the table in the 4th stage of closed-loop activation is -0.9, and the actual torque of the engine is equal to the original engine torque in the 6th gear * (1-0.9) + the engine torque value under the discharge compensation MAP * 0.9. At this time, the motor torque is equal to the wheel end demand torque minus the torque transmitted to the wheel end by the engine divided by the motor gear ratio. The test results show that the CS power balance requirements can be met after the entire test, and the fuel consumption index is also relatively ideal.

[0039] Compared with the prior art, the performance indicators of the control system and method are improved in that: through the control system and method, not only the WLTC National VI emission requirements are met, but also the requirements of CS mode power balance are met. Eress / E fuelcs The requirement of less than 4% is met, and the test results are highly consistent after tests by different testers, indicating that the control system and method have good robustness and strong applicability.

[0040] like Figure 3 As shown, by comparing with 10 groups of tests in the prior art, according to the requirements of CS mode power balance Δ Eress / E fuelcs Under the requirement of less than 4% (i.e. the power consumption in the table must be less than the energy consumption limit), the use of the control system and method of the present invention can significantly improve the robustness and success of the test.

[0041]

[0042] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A power balance control system based on WLTC working condition, characterized in that: include: Input module, SOC storage module, dynamic energy calculation module, power balance identification module, power balance penalty module and power balance torque distribution module, wherein: the dynamic energy calculation module monitors the battery power in real time, and performs closed-loop control of the battery power in the WLTC ultra-high speed section, and performs dynamic compensation of the engine torque according to the difference between the power at the beginning of the driving cycle and the power in the closed-loop control section with the WLTC ultra-high speed section activated, so as to achieve energy balance of the entire driving cycle; the SOC storage module determines whether the battery power SOC is in the balance range when the whole vehicle is powered on, and stores it in the VCU EEprom as the SOC initial value for dynamic energy calculation; the dynamic energy calculation module integrates the time according to the current and voltage of the BMS fed back in real time on the CAN during the operation of the vehicle, calculates the total energy change BMS_Energy of the battery, and divides BMS_Energy by the total capacity of the battery to calculate the SOC change corresponding to the energy change; the power balance identification module sets the SOC closed-loop flag in the ultra-high speed section, and the VCU Detect that the current vehicle speed is greater than the upper speed threshold. If the above conditions are met, VCU activates the closed loop once. When the vehicle speed is lower than the lower speed threshold, the closed loop control is exited. The power balance penalty calculation module will call the torque penalty coefficient every time the VCU closed-loop flag is activated. According to the SOC difference calculated by the dynamic energy calculation module, different engine torque penalty coefficients SOC_FA are obtained by looking up the table. The power balance torque distribution module VCU looks up the torque penalty coefficient according to the SOC difference. When the torque penalty coefficient obtained from the table is equal to 0, VCU looks up the original engine torque distribution strategy, and the engine torque directly drives the wheel end, and the motor does not generate electricity or assist. When the torque penalty coefficient is less than 0, VCU looks up the table to correct the engine torque distribution strategy, and uses the power generation compensation VCU_Charge_MAP*SOC_FAC+engine torque original MAP*(1-SOC_FAC) to distribute the engine torque. When SOC_FAC is greater than 0, VCU The engine torque distribution strategy is corrected by looking up the table, and the discharge compensation VCU_Discharge_MAP*SOC_FAC+engine torque original MAP*(1-SOC_FAC) is used to distribute the engine torque. The dynamic coordination of SOC is achieved through the above functions to ensure the balance of vehicle energy.

2. The power balance control system based on WLTC working condition according to claim 1 is characterized in that: The VCU in the input module receives basic vehicle parameter information to provide information input for the subsequent dynamic energy calculation module; The basic vehicle parameter information includes: current vehicle speed, power battery SOC and current and voltage values, vehicle high voltage state, accelerator pedal and brake pedal opening.

3. The power balance control system based on WLTC working condition according to claim 1 is characterized in that: The original engine torque distribution strategy in the power balancing torque distribution module is based on the engine universal characteristic curve to determine the optimal working load point range of the engine, and determines the engine torque under each gear according to the output shaft speed and the wheel end required torque.

4. The power balance control system based on WLTC working condition according to claim 1 is characterized in that: The power generation compensation VCU_Charge_MAP in the power balance torque distribution module is based on the original engine torque distribution strategy to increase a certain amount of engine torque, so that more power generation torque is distributed to the motor.

5. The power balance control system based on WLTC working condition according to claim 1 is characterized in that: The discharge compensation VCU_Discharge_MAP in the power balancing torque distribution module is based on reducing a certain amount of engine torque on the basis of the original engine torque distribution strategy, so that the motor needs to consume electrical energy to meet the required torque at the wheel end.

Images