Hybrid vehicle engine output power level transition control method

Abstract

This invention provides a method for controlling the power level transition of a hybrid electric vehicle engine. Based on the engine's transition threshold and the maximum adjustment capability of the high-voltage battery, the engine's power level is adjusted. As the total power demand of the drive motor and high-voltage battery changes, the engine's power level does not change immediately. Instead, it adjusts and compensates for the drive motor's power demand based on the degree of change in total power demand, prioritizing the use of the high-voltage battery to adjust and compensate, resulting in a step-like increase or decrease in the engine's power level. The advantages of this invention are that it keeps the engine's power level stable, reducing dynamic engine adjustments while meeting the drive motor's power requirements, thereby reducing dynamic fuel consumption and improving NVH performance, reducing vehicle vibration.

Description

Technical Field

[0001] This invention relates to the field of hybrid electric vehicle technology, and more specifically, to a method for controlling the transition of the output power level of a hybrid electric vehicle engine. Background Technology

[0002] Currently, in practical market applications, non-plug-in hybrid electric vehicles (HEVs) mainly fall into two categories: series-parallel configurations, such as Honda's iMMD; and power-split configurations, such as Toyota's THS. In series mode of either series or series-parallel configurations, the engine generates electricity through a generator, which then powers the drive motor to power the vehicle. Ideally, in series mode, the generator's output power would perfectly match the drive motor's power requirements. However, considering differences in hardware performance, calculation deviations, and measurement errors, such an ideal energy flow diagram cannot be achieved in practice. Therefore, a high-voltage battery is needed to regulate and compensate throughout the process. This results in three degrees of freedom that can be adjusted: the engine's operating point, the high-voltage battery's operating point, and the drive motor's operating point. Different control methods will produce different efficiency outputs.

[0003] Current solutions from various parties focus on static fuel consumption as the control target, while some mention considering the SOC (State of Charge, the ratio of remaining battery capacity to its fully charged capacity) of the high-voltage battery and appropriately charging it. However, none of these solutions address the dynamic characteristics of the engine. When the engine is dynamically adjusting, its fuel consumption is significantly higher than the static fuel consumption. Clearly, a lower fuel consumption rate equates to better fuel economy. Therefore, in actual driving conditions, the fuel consumption will be much higher than the value calculated using static fuel consumption.

[0004] Invention Patent Content

[0005] To address the aforementioned technical problems, this invention provides a method for controlling the transition of the output power level of a hybrid electric vehicle engine. This method fully utilizes the characteristics of the high-voltage battery to adjust and compensate for the power demand of the drive motor, and employs a torque-following control method to reduce fluctuations in the engine's output power and minimize dynamic losses, thereby optimizing the overall energy consumption of the system.

[0006] The present invention solves the technical problem by adopting the following technical solution:

[0007] A method for controlling the transition of the output power level in a hybrid electric vehicle engine includes the following steps:

[0008] S1. Set the transition threshold for adjusting the engine's output power;

[0009] S2. When the total power demand of the drive motor and high-voltage battery changes, compare the change in total power demand with the transition threshold:

[0010] S21. When the change in total power demand exceeds the transition threshold, adjust the engine's output power to meet the changes in the drive motor's power demand and the high-voltage battery's power demand; or

[0011] S22. When the change in total power demand is less than the transition threshold, assuming the engine output power remains constant, calculate the pre-adjustment amount Wa of the high-voltage battery to adjust the power demand of the drive motor to meet the change in the power demand of the drive motor, and compare the pre-adjustment amount Wa of the high-voltage battery with the maximum power Wb that the high-voltage battery can provide:

[0012] When the high-voltage battery pre-adjustment amount Wa is less than or equal to the maximum power Wb that the high-voltage battery can provide, the engine's output power remains unchanged. The high-voltage battery adjusts the drive motor's required power according to the high-voltage battery pre-adjustment amount Wa to meet the changes in the drive motor's required power; or

[0013] When the pre-adjustment amount Wa of the high-voltage battery is greater than the maximum power Wb that the high-voltage battery can provide, the high-voltage battery adjusts the power required by the drive motor according to the maximum power Wb that the high-voltage battery can provide, and adjusts the output power of the engine to make up for the difference between the pre-adjustment amount Wa of the high-voltage battery and the maximum power Wb that the high-voltage battery can provide, so as to meet the change in the power required by the drive motor.

[0014] S23. When the change in total power demand equals the jump threshold, adjust the output power of the engine according to step S21 to meet the changes in the power demand of the drive motor and the high-voltage battery; or adjust the power demand of the drive motor through the high-voltage battery according to step S22, or adjust the power demand of the drive motor through the high-voltage battery and the engine together to meet the changes in the power demand of the drive motor.

[0015] Furthermore, the transition threshold for the engine's output power is adjusted according to the vehicle's operating mode and speed setting. The transition threshold is set to 0.1-20kW, or in sport driving mode, the transition threshold is set to 0 for medium-high speed and high speed.

[0016] Furthermore, the transition threshold is set to 0.5-10kW.

[0017] Furthermore, the transition thresholds for the vehicle at idle, low speed, and medium speed are greater than or equal to the transition thresholds for the vehicle at medium-high speed and high speed, resulting in faster engine response and meeting the vehicle's power requirements at medium-high speed and high speed.

[0018] Furthermore, in normal driving mode and economy driving mode, the transition threshold at low and medium speeds is 1-3 times that at medium and high speeds and high speeds.

[0019] Furthermore, the specific method for adjusting the engine's output power is as follows:

[0020] S1′ Find the initial operating point A corresponding to the current engine power on the optimal fuel economy curve;

[0021] S2′ When the engine's initial operating point A is within the optimal fuel consumption range, and the vehicle speed is between 20km / h and 120km / h, the engine's output power is controlled using a torque-following method to reduce engine speed fluctuations. Specifically:

[0022] S21′, When the engine's standby output power increases:

[0023] (1) Find the maximum power value W1 in the region with the same speed as the initial operating point A within the optimal fuel consumption range;

[0024] (2) Compare the engine's output power with the maximum power value W1:

[0025] When the engine's output power is less than or equal to the maximum power value W1, the engine speed is kept constant, the engine torque increases accordingly, and the engine's operating point moves from the initial operating point A to the operating point B that meets the engine's output power requirement.

[0026] When the engine's required output power exceeds the maximum power value W1, on the optimal fuel economy curve, the engine's operating point shifts from the initial operating point A to the operating point C that meets the engine's required output power; or

[0027] S22′, When the engine's standby output power decreases:

[0028] (1) Find the minimum power value W2 that is the same as the initial operating point A speed in the region with the optimal fuel consumption;

[0029] (2) Compare the engine's output power with the minimum power value W2:

[0030] When the engine's output power is greater than or equal to the minimum power value W2, the engine speed is kept constant, the engine torque decreases accordingly, and the engine's operating point moves from the initial operating point A to the operating point D that meets the engine's output power requirement.

[0031] When the engine's required output power is less than the minimum power value W2, on the optimal fuel economy curve, the engine's operating point moves from the initial operating point A to the operating point E that meets the engine's required output power; or

[0032] S3′ When the engine's initial operating point A is outside the optimal fuel consumption region, the engine's output power is controlled using a power follower method, specifically:

[0033] The engine's operating point moves from the initial operating point A on the optimal fuel economy curve to the operating point F that meets the engine's power output requirements.

[0034] Furthermore, the engine is a turbocharged engine.

[0035] Furthermore, when the engine's initial operating point A is within the optimal specific fuel consumption range and the vehicle speed is greater than 120 km / h, a power following control method is adopted.

[0036] Furthermore, when the power demand of the drive motor decreases while the output power of the engine remains constant, the high-voltage battery increases its charging capacity, decreases its discharging capacity, or changes from discharging to charging to meet the change in the power demand of the drive motor.

[0037] When the power demand of the drive motor increases while the output power of the engine remains constant, the high-voltage battery increases its discharge, decreases its charging, or changes from charging to discharging to meet the change in the power demand of the drive motor.

[0038] Furthermore, the method for obtaining the required power of the high-voltage battery is as follows:

[0039] The high-voltage battery controller (BMS) collects the current state of charge (SOC) value of the high-voltage battery, and the vehicle control unit (HCU) receives the current SOC value of the high-voltage battery and obtains the required power of the high-voltage battery based on the current SOC value.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) Select different series control methods according to the vehicle's dynamic operating conditions to reduce engine speed fluctuations, reduce fuel consumption increase under dynamic operating conditions, and achieve optimization in the actual cycle.

[0042] (2) The engine’s output power is controlled by the energy level transition method to keep the engine’s output power stable. While meeting the power requirements of the drive motor, the engine’s dynamic adjustment is reduced, thereby reducing the engine’s dynamic fuel consumption loss and bringing better NVH performance, and reducing vehicle vibration.

[0043] (3) By adopting torque following control method, the control of the optimal fuel consumption point is changed to the control of the optimal fuel consumption area, which further reduces the speed fluctuation of the engine and obtains better dynamic fuel consumption, thereby achieving the goal of optimal fuel consumption under cyclic conditions. Attached Figure Description

[0044] Figure 1 This is the ideal series energy flow diagram of the present invention.

[0045] Figure 2 This is the energy flow diagram for pure electric driving according to the present invention.

[0046] Figure 3 This is a series energy flow diagram for charging the high-voltage battery of the present invention.

[0047] Figure 4 This is a series energy flow diagram of the high-voltage battery during discharge according to the present invention.

[0048] Figure 5 This is a schematic diagram illustrating the engine start-up threshold under different SOCs according to the present invention.

[0049] Figure 6 This is a logic diagram of the engine output power level transition control method of the present invention.

[0050] Figure 7 This is a schematic diagram of the energy level transition adjustment for the output power of the engine of the present invention.

[0051] Figure 8 This is a schematic diagram illustrating the specific fuel consumption selection in the engine output power control method of the present invention.

[0052] Figure 9 This is a schematic diagram illustrating the adjustment of the engine when its output power is increased according to the present invention.

[0053] Figure 10 This is a schematic diagram illustrating the adjustment when the engine output power of the present invention is reduced.

[0054] Figure 11 This is a schematic diagram of the vehicle speed selection range for the engine output power control method of the present invention.

[0055] In the diagram: 1-Engine; 2-Generator; 3-Drive motor; 4-High-voltage battery. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0057] This invention provides a method for controlling the transition of the output power level in a hybrid electric vehicle engine, such as... Figure 6 As shown, it includes the following steps:

[0058] S1. Set the threshold for adjusting the output power of engine 1;

[0059] S2. When the total power demand of the drive motor 3 and the high-voltage battery 4 changes, the change in total power demand is compared with the transition threshold:

[0060] S21. When the change in total power demand exceeds the transition threshold, the output power of engine 1 is adjusted to meet the changes in power demand of drive motor 3 and high-voltage battery 4; or

[0061] S22. When the change in total power demand is less than the transition threshold, assuming that the output power of engine 1 remains constant, calculate the pre-adjustment amount Wa of high-voltage battery 4 to adjust the power demand of drive motor 3 to meet the change in power demand of drive motor 3, and compare the pre-adjustment amount Wa of high-voltage battery 4 with the maximum power Wb that high-voltage battery 4 can provide:

[0062] When the pre-adjustment amount Wa of the high-voltage battery 4 is less than or equal to the maximum power Wb that the high-voltage battery 4 can provide, the output power of the engine 1 remains unchanged, and the high-voltage battery 4 adjusts the required power of the drive motor 3 according to the pre-adjustment amount Wa of the high-voltage battery 4 to meet the change in the required power of the drive motor 3; or

[0063] When the pre-adjustment amount Wa of the high-voltage battery 4 is greater than the maximum power Wb that the high-voltage battery 4 can provide, the high-voltage battery 4 adjusts the power required by the drive motor 3 according to the maximum power Wb that the high-voltage battery 4 can provide, and adjusts the output power of the engine 1 to make up for the difference between the pre-adjustment amount Wa of the high-voltage battery 4 and the maximum power Wb that the high-voltage battery 4 can provide, so as to meet the change in the power required by the drive motor 3.

[0064] S23. When the change in total demand power equals the jump threshold, adjust the output power of engine 1 according to step S21 to meet the change in demand power of drive motor 3 and high voltage battery 4; or adjust the demand power of drive motor 3 through high voltage battery 4 according to step S22, or adjust the demand power of drive motor 3 through high voltage battery 4 and engine 1 together to meet the change in demand power of drive motor 3.

[0065] The required power of drive motor 3 is the vehicle's power demand. The change in the required power of drive motor 3 can be obtained based on the driver's driving operations. When the current SOC value of high-voltage battery 4 is less than or greater than a set target SOC value (for example, the target SOC value can be set to 30%-90% depending on road conditions), high-voltage battery 4 generates a charging or discharging demand. The required power of high-voltage battery 4 is the power required for charging or discharging under the current SOC, and is a calibration value. It can be obtained according to methods commonly used by those skilled in the art. Preferably, for example, a baseline value of the required power of high-voltage battery 4 is first obtained. This baseline value can be obtained using software simulation or based on the required power of high-voltage battery 4 in older vehicle models. Then, the baseline value is corrected according to "GB / T 19753-2021 Test Method for Energy Consumption of Light Hybrid Electric Vehicles" to obtain the calibration value. For example, if the current SOC value of high-voltage battery 4 is 30% and the target SOC value is 70%, then high-voltage battery 4 needs to be charged. At this time, the charging power of high-voltage battery 4 is the required power of high-voltage battery 4. The high-voltage battery controller (BMS) collects the current state of charge (SOC) value of the high-voltage battery 4, and the vehicle control unit (HCU) receives the current SOC value of the high-voltage battery 4. Based on the current SOC value of the high-voltage battery 4, it obtains the power required for charging or discharging the high-voltage battery 4 at the current SOC. The actual charging or discharging power of the high-voltage battery 4 during operation is the power required for the high-voltage battery 4 to achieve energy balance among the engine 1, the high-voltage battery 4, and the drive motor 3, and to meet the power requirements of the drive motor 3.

[0066] When the energy flow of engine 1, high-voltage battery 4, and drive motor 3 reaches equilibrium, the power relationship in this equilibrium state is: Engine 1's output power + High-voltage battery 4's actual power = Drive motor 3's required power. Assuming the engine 1's output power and drive motor 3's required power are positive, the high-voltage battery 4's charging power requirement is negative, and its discharging power requirement is positive. Relative to engine 1, assuming the high-voltage battery 4's actual power remains constant while the drive motor 3's required power changes, or vice versa, the change in required power that increases the engine 1's output power due to the high-voltage battery 4's power requirement is positive, and the change in required power that decreases the engine 1's output power is negative. For example, when the power demand of drive motor 3 increases, the change in power demand of drive motor 3 is positive; when the power demand of drive motor 3 decreases, the change in power demand of drive motor 3 is negative. Similarly, when the power demand of high-voltage battery 4 increases for charging, decreases for discharging, or changes from discharging to charging, its power demand change is positive; and when the power demand of high-voltage battery 4 increases for discharging, decreases for charging, or changes from charging to discharging, its power demand change is negative. The total change in power demand is the sum of the changes in power demand of drive motor 3 and high-voltage battery 4, and the total change in power demand is the absolute value of the sum of these two changes.

[0067] In a hybrid electric vehicle, in series mode, when the power demand of the drive motor 3 is less than the starting threshold of the engine 1, it operates on pure electric power. In this case, the high-voltage battery 4 supplies power to the drive motor 3, and the energy flow direction is as follows: Figure 2 As shown. When the power demand of the drive motor 3 is greater than or equal to the starting threshold of the engine 1, the engine 1 operates, driving the generator 2 to generate electricity. The generator 2 supplies power to the drive motor 3. The starting threshold of the engine 1 is a calibration value, which can be obtained according to methods commonly used by those skilled in the art. Preferably, for example, a baseline value of the starting threshold of the engine 1 is first obtained. The baseline value can be obtained using software simulation or based on the starting threshold of the engine 1 of an older vehicle model. Then, the baseline value is corrected according to "GB / T 19753-2021 Test Method for Energy Consumption of Light Hybrid Electric Vehicles" to obtain the calibration value. For example, for a certain vehicle model, such as... Figure 5The figure shows the calibration values ​​of the high-voltage battery 4 at different SOCs and vehicle speeds. The horizontal axis represents vehicle speed, and the vertical axis represents the power demand of the drive motor 3. When the power demand of the drive motor 3 is less than the starting threshold of the engine 1, that is, when the power demand of the drive motor 3 is below the calibration curve, pure electric driving is used. When the power demand of the drive motor 3 is greater than or equal to the starting threshold of the engine 1, that is, when the power demand of the drive motor 3 is above the calibration curve (inclusive), the engine 1 starts.

[0068] After engine 1 starts working, when the output power of generator 2 just meets the power requirement of drive motor 3, the energy flow direction is as follows: Figure 1 As shown, the ideal state of the series mode is achieved. However, considering differences in hardware performance, calculation deviations, and measurement errors, such an ideal energy flow diagram cannot actually be achieved, and high-voltage battery 4 is needed for adjustment and compensation. When the output power of generator 2 is greater than the required power of drive motor 3, that is, when the power of engine 1 is greater than the required power of drive motor 3, generator 2 supplies power to drive motor 3 and simultaneously charges high-voltage battery 4. The excess energy of generator 2 is absorbed by high-voltage battery 4, and its energy flow direction is as follows. Figure 3 As shown. When the output power of generator 2 is less than the required power of drive motor 3, that is, when the power of engine 1 is less than the required power of drive motor 3, high-voltage battery 4 discharges, and together with generator 2, supplies power to drive motor 3. The insufficient energy of generator 2 is supplemented by high-voltage battery 4, and its energy flow direction is as follows. Figure 4As shown. When the high-voltage battery 4 charges or discharges to adjust the power demand of the drive motor 3, the energy flow among the generator 2, high-voltage battery 4, and drive motor 3 reaches a balance, that is, the energy flow among the engine 1, high-voltage battery 4, and drive motor 3 reaches a balance. When the energy flow among the engine 1, high-voltage battery 4, and drive motor 3 reaches a balance, preferably, the power demand of both the high-voltage battery 4 and the drive motor 3 must be met simultaneously. At this time, the power demand of the high-voltage battery 4 is its actual charging or discharging power. However, when the engine 1 is operating, it may not be able to meet the power demand of the high-voltage battery 4. In this case, the actual power of the high-voltage battery 4 is the charging or discharging power when the power demand of the drive motor 3 is prioritized. When the power demand of the drive motor 3 changes, or the power demand of the high-voltage battery 4 changes, or when both the power demand of the drive motor 3 and the power demand of the high-voltage battery 4 change, the output power of the engine 1 needs to be adjusted to restore balance among the three to meet the changing power demand of the drive motor 3, thereby satisfying the vehicle's driving requirements. For example, if the SOC of the high-voltage battery 4 is too low, or the vehicle's acceleration decreases causing a sudden decrease in the power demand of the drive motor 3, or if the SOC of the high-voltage battery 4 is too high, or the vehicle's acceleration increases causing a sudden increase in the power demand of the drive motor 3, the output power of the engine 1 needs to be adjusted.

[0069] During vehicle operation, to maintain a stable output power for engine 1, an energy level transition control method is employed to increase or decrease the output power of engine 1 in a step-like manner. The required output power of engine 1 is controlled based on the degree of change in the total power demand of drive motor 3 and high-voltage battery 4. A transition threshold for the output power of engine 1 needs to be set to determine whether adjustment of the output power of engine 1 is necessary to follow changes in the total power demand.

[0070] When the change in total power demand exceeds the threshold, the output power of engine 1 needs to be adjusted to match the change in total power demand, so as to simultaneously meet the changes in power demand of drive motor 3 and high-voltage battery 4.

[0071] When the change in total demand power is less than the threshold, it is first assumed that the output power of engine 1 remains constant. The pre-adjustment amount Wa of high voltage battery 4 can be calculated to meet the change in demand power of drive motor 3 when the demand power of drive motor 3 is adjusted by high voltage battery 4. Then, the pre-adjustment amount Wa of high voltage battery 4 is compared with the maximum power Wb that high voltage battery 4 can provide.

[0072] When the pre-adjustment amount Wa of the high-voltage battery 4 is less than or equal to the maximum power Wb that the high-voltage battery 4 can provide, the high-voltage battery 4 can provide sufficient charging and discharging capacity. At this time, keeping the output power of the engine 1 constant, the high-voltage battery 4 adjusts the power demand of the drive motor 3 according to the pre-adjustment amount Wa of the high-voltage battery 4 to meet the changes in the power demand of the drive motor 3. When the power demand of the drive motor 3 decreases, the high-voltage battery 4 can increase the charging amount, decrease the discharging amount, or change from discharging to charging to meet the changes in the power demand of the drive motor 3. When the power demand of the drive motor 3 increases, the high-voltage battery 4 can increase the discharging amount, decrease the charging amount, or change from charging to discharging to meet the changes in the power demand of the drive motor 3.

[0073] When the pre-adjustment amount Wa of the high-voltage battery 4 is greater than the maximum power Wb that the high-voltage battery 4 can provide, if the high-voltage battery 4 is used only to adjust the power required by the drive motor 3 to meet the change in the power required by the drive motor 3, it will exceed the adjustment capability of the high-voltage battery 4. At this time, the high-voltage battery 4 adjusts the power required by the drive motor 3 according to the maximum power Wb that the high-voltage battery 4 can provide in order to provide the maximum adjustment capability of the high-voltage battery 4. At the same time, it is necessary to adjust the output power of the engine 1 to make up for the difference between the pre-adjustment amount Wa of the high-voltage battery 4 and the maximum power Wb that the high-voltage battery 4 can provide in order to meet the change in the power required by the drive motor 3.

[0074] When the change in total power demand equals the threshold, the output power of engine 1 can be adjusted according to the steps where the change in total power demand is greater than the threshold, in order to meet the changes in power demand of drive motor 3 and high-voltage battery 4. Preferably, according to the steps where the change in total power demand is less than the threshold, high-voltage battery 4 is used first to adjust the power demand of drive motor 3, so as to maintain the stability of engine 1's operating condition and reduce engine speed fluctuations.

[0075] Based on the varying degrees of change in the total power demand of the drive motor 3 and the high-voltage battery 4, the output power of the engine 1 is adjusted using an energy level transition control method, such as... Figure 7 As shown, as the total power demand changes, the output power of engine 1 does not change immediately. During a certain period of time or during the entire driving process of the vehicle, the output power of engine 1 increases or decreases in a stepwise manner. This can effectively improve the dynamic adjustment damage of engine 1, reduce the dynamic fuel consumption loss of engine 1, and bring better NVH performance, thereby reducing vehicle vibration.

[0076] Preferably, the transition threshold of the engine 1's output power can be adjusted according to the vehicle's operating mode and speed. This transition threshold is set to 0.1-20kW, for example, it can be set to 0.5kW, 1kW, 2kW, 3kW, 5kW, 10kW, 15kW, etc.; or in sport driving mode, the transition threshold at medium-high speed and high speed is set to 0. To overcome small fluctuations in the engine 1's output power, preferably, the transition threshold is set to 0.5-10kW. Vehicle speeds are generally classified into low speed (<30km / h), medium speed (30-70km / h), medium-high speed (70-120km / h), and high speed (>120km / h). It should be noted that in this embodiment, the speed classification is only illustrative and not limiting; other speed ranges can be used depending on the specific vehicle. For vehicles with driving mode selection, the driving modes generally include Normal mode, Sport mode, and Eco mode. The transition thresholds at idle, low, and medium speeds are greater than or equal to the transition thresholds at medium-high and high speeds. As vehicle speed increases, the transition thresholds decrease, accelerating engine response and meeting the vehicle's power demands. Preferably, in Normal and Eco modes, the transition thresholds at low and medium speeds are 1-3 times higher than those at medium-high and high speeds; in Sport mode, the transition thresholds at medium-high and high speeds are 0, better meeting the vehicle's power requirements.

[0077] To facilitate understanding of this invention, a specific vehicle model is used as an example to describe the transition threshold for adjusting the output power of engine 1. Table 1 shows the transition thresholds for adjusting the output power of engine 1 under different driving modes and vehicle speeds.

[0078] Table 1 Transition thresholds for engine output power adjustment

[0079] Normal Sport Eco Idle speed 3kW 2kW 5kW Low speed (<30km / h) 3kW 1kW 5kW Medium speed (30-70km / h) 3kW 0.5kW 5kW Medium to high speed (70-120km / h) 3kW 0 3kW High speed (>120km / h) 3kW 0 3kW

[0080] As shown in Table 1, in Normal mode, the transition threshold is the same at all vehicle speeds, and the response speed of engine 1 is the same at different vehicle speeds. In Sport and Eco modes, at medium-high and high speeds, engine 1 responds faster as the total power demand changes. In particular, for medium-high and high speeds in Sport mode, the transition threshold for engine 1 power change is 0, and the output power of engine 1 changes promptly with the change in total power demand.

[0081] To facilitate understanding of this invention, the following example illustrates how the output power of engine 1 is adjusted when the total demand power changes, with a transition threshold of 3kW, a certain equilibrium state, an output power of 12kW for engine 1, a discharge demand power and actual discharge power of high-voltage battery 4 of 8kW, and a demand power of 20kW for drive motor 3. The specific details are shown in Table 2.

[0082] Table 2 Adjustment of Engine Output Power

[0083]

[0084] When the energy flow of engine 1, high-voltage battery 4, and drive motor 3 reaches equilibrium, the power relationship in this equilibrium state is: Engine 1's output power + High-voltage battery 4's actual power = Drive motor 3's required power. When high-voltage battery 4 is charging, its charging power requirement is negative; when high-voltage battery 4 is discharging, its discharging power requirement is positive. When the drive motor 3's required power increases, the change in its required power is positive; when the drive motor 3's required power decreases, the change in its required power is negative. When high-voltage battery 4's charging power requirement increases, its discharging power requirement decreases, or it changes from discharging to charging, its required power change is positive; when high-voltage battery 4's discharging power requirement increases, its charging power requirement decreases, or it changes from charging to discharging, its required power change is negative. The total change in required power is the sum of the changes in drive motor 3's required power and high-voltage battery 4's required power, and the total change in required power is the absolute value of the sum of these two changes.

[0085] When the power demand of drive motor 3 increases by 6kW to 26kW and the power demand of high voltage battery 4 increases by 2kW to 10kW, the total power demand increases by 4kW, which is greater than the transition threshold, and the output power of engine 1 is increased to 16kW.

[0086] When the discharge power demand of the high-voltage battery 4 remains unchanged at 8kW, and the power demand of the drive motor 3 increases by 2kW to 22kW, the total power demand increases by 2kW. At this time, it is necessary to assume that the output power of the engine 1 remains unchanged at 12kW. The pre-adjustment amount Wa of the high-voltage battery 4 to adjust the power demand of the drive motor 3 to meet the change in the power demand of the drive motor 3 is calculated to be 10kW. When the maximum power Wb that the high-voltage battery 4 can provide at this time is 7kW, the high-voltage battery 4 can only provide a maximum discharge power of 7kW. In order to meet the power demand of the drive motor 3 of 22kW, the engine 1 needs to provide an additional 3kW of power. Therefore, the actual discharge power of the high-voltage battery 4 is 7kW, and the output power of the engine 1 is 15kW to meet the power demand of the drive motor 3 of 22kW. When the maximum power Wb that the high-voltage battery 4 can provide at this time is 11kW, keeping the output power of the engine 1 unchanged at 12kW, the change in the power demand of the drive motor 3 can be met by adjusting only the high-voltage battery 4. The actual discharge power of the high-voltage battery 4 is the pre-adjustment amount of 10kW.

[0087] When the power demand of drive motor 3 decreases by 5kW to 15kW and the power demand of high-voltage battery 4 decreases by 1kW to 7kW, the total power demand decreases by 4kW, which is greater than the transition threshold. Therefore, the output power of large engine 1 is reduced to 8kW.

[0088] When it is necessary to adjust the output power of engine 1, the specific method for adjusting the output power of engine 1 is as follows:

[0089] S1′, Find the initial operating point A corresponding to the current power of engine 1 on the optimal fuel economy curve;

[0090] S2′ When the initial operating point A of engine 1 is within the optimal fuel consumption range, and the vehicle speed is between 20km / h and 120km / h, the output power of engine 1 adopts a torque following control method to reduce the speed fluctuation of engine 1, specifically:

[0091] S21′, When the output power of engine 1 increases:

[0092] (1) Find the maximum power value W1 in the region with the same speed as the initial operating point A within the optimal fuel consumption range;

[0093] (2) Compare the output power of engine 1 with the maximum power value W1:

[0094] When the output power of engine 1 is less than or equal to the maximum power value W1, the speed of engine 1 is kept constant, the torque of engine 1 increases accordingly, and the operating point of engine 1 moves from the initial operating point A to the operating point B that meets the output power requirement of engine 1.

[0095] When the required output power of engine 1 is greater than the maximum power value W1, on the optimal fuel economy curve, the operating point of engine 1 moves from the initial operating point A to the operating point C that meets the required output power of engine 1; or

[0096] S22′, When the output power of engine 1 decreases:

[0097] (1) Find the minimum power value W2 that is the same as the initial operating point A speed in the region with the optimal fuel consumption;

[0098] (2) Compare the output power of engine 1 with the minimum power value W2:

[0099] When the output power of engine 1 is greater than or equal to the minimum power value W2, the speed of engine 1 is kept constant, the torque of engine 1 decreases accordingly, and the operating point of engine 1 moves from the initial operating point A to the operating point D that meets the output power requirement of engine 1.

[0100] When the required output power of engine 1 is less than the minimum power value W2, on the optimal fuel economy curve, the operating point of engine 1 moves from the initial operating point A to the operating point E that meets the required output power of engine 1; or

[0101] S3′ When the initial operating point A of engine 1 is outside the optimal specific fuel consumption region, the output power of engine 1 adopts the power follower control method, specifically:

[0102] The operating point of engine 1 moves from the initial operating point A on the optimal fuel economy curve to the operating point F that meets the power output requirements of engine 1.

[0103] In a hybrid electric vehicle, in series mode, the operating point of engine 1 can be freely selected, unaffected by vehicle speed, and the engine speed can be adjusted without restriction. For example... Figure 8The diagram shows the universal characteristic curve of an engine, with engine speed on the horizontal axis and engine torque on the vertical axis. The curve has a region with the lowest fuel consumption (the innermost ring), where fuel consumption is minimized. Especially for engines like turbocharged engines 1, whose optimal fuel economy region changes slowly, the static specific fuel consumption difference is small at medium speeds and loads, forming an optimal specific fuel consumption region. When the required output power of engine 1 needs adjustment, two control methods are used based on the current operating point of engine 1 within the range shown on the universal characteristic curve. When the initial operating point A of engine 1 is within the optimal specific fuel consumption region, and the vehicle speed is between 20 km / h and 120 km / h, the required output power of engine 1 uses torque following control to keep the engine speed as constant as possible, adjusting the engine torque to meet the required output power and reducing engine speed fluctuations. When the initial operating point A of engine 1 is outside the optimal specific fuel consumption region, the required output power of engine 1 uses power following control. Within the optimal fuel consumption range, the control for the optimal fuel consumption point is changed to the control for the optimal fuel consumption range, so that engine 1 operates near the optimal fuel economy point, reducing the speed fluctuation of engine 1, keeping the operating point of engine 1 as stable as possible, and obtaining better dynamic fuel consumption, thereby achieving the optimal global energy consumption under actual operating conditions.

[0104] When using the torque follower control method, based on the current operating point of engine 1, the maximum power value W1 or minimum power value W2 that is the same as the initial operating point A speed in the optimal fuel consumption region is obtained. It is then determined whether controlling the speed of engine 1 to remain unchanged and only adjusting the torque of engine 1 can meet the output power of engine 1 in the optimal fuel consumption region.

[0105] When the output power of engine 1 increases, such as Figure 9 As shown, the output power of engine 1 is compared with the maximum power value W1:

[0106] When the output power of engine 1 is less than or equal to the maximum power value W1, it indicates that the engine is in the optimal fuel consumption region. By keeping the engine speed constant and adjusting only the torque of engine 1, the required output power can be achieved. Therefore, the engine speed can be kept constant while the torque of engine 1 increases accordingly. The operating point of engine 1 moves from the initial operating point A to the required operating point B that satisfies the required output power of engine 1. The required operating point B is located within the optimal fuel consumption region.

[0107] When the desired output power of engine 1 is greater than the maximum power value W1, the adjustment amount of the desired output power of engine 1 is relatively large. This indicates that within the optimal fuel economy region, keeping the engine speed constant and only adjusting the torque of engine 1 is insufficient to meet the desired output power adjustment. Therefore, to meet the desired output power adjustment of engine 1, on the optimal fuel economy curve, the operating point of engine 1 shifts from the initial operating point A to the required operating point C that satisfies the desired output power of engine 1. The required operating point C can be located within or outside the optimal fuel economy region.

[0108] When the output power of engine 1 decreases, such as Figure 10 As shown, the output power of engine 1 is compared with the minimum power value W2:

[0109] When the desired output power of engine 1 is greater than or equal to the minimum power value W2, it indicates that within the optimal fuel consumption region, keeping the engine speed constant and adjusting only the torque of engine 1 is sufficient to meet the desired output power. Therefore, the engine speed can be kept constant, and the torque of engine 1 will decrease accordingly. The operating point of engine 1 will move from the initial operating point A to the required operating point D that meets the desired output power of engine 1, and the required operating point D is located within the optimal fuel consumption region.

[0110] When the desired output power of engine 1 is less than the minimum power value W2, the adjustment amount of the desired output power of engine 1 is relatively large. This indicates that within the optimal fuel economy region, keeping the engine speed constant and only adjusting the torque of engine 1 is insufficient to meet the desired output power adjustment. Therefore, to meet the desired output power adjustment of engine 1, on the optimal fuel economy curve, the operating point of engine 1 moves from the initial operating point A to the required operating point E that meets the desired output power of engine 1. The required operating point E can be located within or outside the optimal fuel economy region.

[0111] When the initial operating point A of engine 1 is outside the optimal fuel consumption region, engine 1 operates on the optimal fuel economy curve at the system's optimal torque and speed points. It moves along the optimal fuel economy curve following the total power demand, from the initial operating point A to the operating point F that meets the required output power of engine 1, thus achieving optimal fuel economy. When the required output power of engine 1 increases, the operating point of engine 1 moves to the right along the optimal fuel economy curve from the initial operating point A to the operating point F that meets the required output power of engine 1, as shown below. Figure 9 As shown. When the required output power of engine 1 decreases, the operating point of engine 1 shifts from the initial operating point A to the left along the optimal fuel economy curve to the operating point F that meets the required output power of engine 1, as shown. Figure 10 As shown, the demand operating point F can be located within the optimal specific fuel consumption region or outside the optimal specific fuel consumption region.

[0112] As a preferred option, combined with Figure 8 and Figure 11 As shown, when the total power demand changes and it is necessary to adjust the output power of engine 1, different control methods for the output power of engine 1 can be used to adjust the output power of engine 1 according to the current vehicle speed and the magnitude of the total power demand. For example... Figure 11 As shown, the system can be divided into four zones based on vehicle speed and total power demand. At low speeds and low power demand (zone ①), pure electric operation is used, and engine 1 is not operating. At medium speeds and medium-high speeds with medium power demand (zone ②), engine 1 operates. Specifically, the output power of engine 1 is adjusted using either torque-following control or power-following control, depending on the zone where engine 1's initial operating point A is located. When engine 1's initial operating point A is within the optimal fuel consumption zone, torque-following control is used; when engine 1's initial operating point A is outside the optimal fuel consumption zone, demand-power-following control is used. When the total power demand is at a high power level (zone ③), or when the vehicle is at a high speed (zone ④), demand-power-following control is prioritized. For example, when the vehicle speed is greater than 120 km / h and adjustment of engine 1's output power is needed, even if engine 1's initial operating point A is within the optimal fuel consumption zone, demand-power-following control is used to promptly meet the vehicle's power requirements.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the transition of the output power level in a hybrid electric vehicle engine, characterized in that, Includes the following steps: S1. Set the transition threshold for adjusting the engine's output power; S2. When the total power demand of the drive motor and high-voltage battery changes, compare the change in total power demand with the transition threshold: S21. When the change in total power demand exceeds the threshold, the output power of the engine is adjusted to meet the changes in the power demand of the drive motor and the high-voltage battery. S22. When the change in total power demand is less than the transition threshold, assuming the engine output power remains constant, calculate the pre-adjustment amount Wa of the high-voltage battery to adjust the power demand of the drive motor to meet the change in the power demand of the drive motor, and compare the pre-adjustment amount Wa of the high-voltage battery with the maximum power Wb that the high-voltage battery can provide: When the pre-adjustment amount Wa of the high-voltage battery is less than or equal to the maximum power Wb that the high-voltage battery can provide, the output power of the engine remains unchanged. The high-voltage battery adjusts the power demand of the drive motor according to the pre-adjustment amount Wa of the high-voltage battery to meet the change in the power demand of the drive motor. When the pre-adjustment amount Wa of the high-voltage battery is greater than the maximum power Wb that the high-voltage battery can provide, the high-voltage battery adjusts the power required by the drive motor according to the maximum power Wb that the high-voltage battery can provide, and adjusts the output power of the engine to make up for the difference between the pre-adjustment amount Wa of the high-voltage battery and the maximum power Wb that the high-voltage battery can provide, so as to meet the change in the power required by the drive motor. S23. When the change in total power demand equals the jump threshold, adjust the output power of the engine according to step S21 to meet the changes in the power demand of the drive motor and the high-voltage battery; or adjust the power demand of the drive motor through the high-voltage battery according to step S22, or adjust the power demand of the drive motor through the high-voltage battery and the engine together to meet the changes in the power demand of the drive motor.

2. The hybrid electric vehicle engine power output level transition control method according to claim 1, characterized in that, The transition threshold for the engine's output power is adjusted according to the vehicle's operating mode and speed setting. The transition threshold is set to 0.1-20kW. In sport driving mode, the transition threshold is set to 0 for medium-high speed and high speed.

3. The hybrid electric vehicle engine power output level transition control method according to claim 2, characterized in that, The transition threshold is set to 0.5-10kW.

4. The hybrid electric vehicle engine power output level transition control method according to claim 2, characterized in that, The transition thresholds for vehicles at idle, low speed, and medium speed are greater than or equal to the transition thresholds for vehicles at medium-high speed and high speed.

5. The hybrid electric vehicle engine power output level transition control method according to claim 2, characterized in that, In normal and economy driving modes, the transition threshold at low and medium speeds is 1-3 times that at medium and high speeds and high speeds.

6. The hybrid electric vehicle engine power output level transition control method according to any one of claims 1-5, characterized in that, The specific method for adjusting the engine's output power is as follows: S1′ Find the initial operating point A corresponding to the current engine power on the optimal fuel economy curve; S2′ When the engine's initial operating point A is within the optimal fuel consumption range, and the vehicle speed is between 20km / h and 120km / h, the engine's output power is controlled using a torque-following method to reduce engine speed fluctuations. Specifically: S21′, When the engine's standby output power increases: (1) Find the maximum power value W1 in the region with the same speed as the initial operating point A within the optimal fuel consumption range; (2) Compare the engine's output power with the maximum power value W1: When the engine's output power is less than or equal to the maximum power value W1, the engine speed is kept constant, the engine torque increases accordingly, and the engine's operating point moves from the initial operating point A to the operating point B that meets the engine's output power requirement. When the engine's output power is greater than the maximum power value W1, on the optimal fuel economy curve, the engine's operating point moves from the initial operating point A to the operating point C that meets the engine's output power requirement. S22′, When the engine's standby output power decreases: (1) Find the minimum power value W2 that is the same as the initial operating point A speed in the region with the optimal fuel consumption; (2) Compare the engine's output power with the minimum power value W2: When the engine's output power is greater than or equal to the minimum power value W2, the engine speed is kept constant, the engine torque decreases accordingly, and the engine's operating point moves from the initial operating point A to the operating point D that meets the engine's output power requirement. When the engine's output power is less than the minimum power value W2, on the optimal fuel economy curve, the engine's operating point moves from the initial operating point A to the operating point E that meets the engine's output power requirement. S3′ When the engine's initial operating point A is outside the optimal fuel consumption region, the engine's output power is controlled using a power follower method, specifically: The engine's operating point moves from the initial operating point A on the optimal fuel economy curve to the operating point F that meets the engine's power output requirements.

7. The hybrid electric vehicle engine power output level transition control method according to claim 6, characterized in that, The engine is a turbocharged engine.

8. The hybrid electric vehicle engine power output level transition control method according to claim 6, characterized in that, When the engine's initial operating point A is within the optimal fuel consumption range and the vehicle speed is greater than 120 km / h, the power following control method is adopted.

9. The hybrid electric vehicle engine power output level transition control method according to claim 1, characterized in that, When the power demand of the drive motor decreases and the output power of the engine remains unchanged, the high-voltage battery increases its charging amount, decreases its discharging amount, or changes from discharging to charging in order to meet the change in the power demand of the drive motor. When the power demand of the drive motor increases while the output power of the engine remains constant, the high-voltage battery increases its discharge, decreases its charging, or changes from charging to discharging to meet the change in the power demand of the drive motor.

10. The method for controlling the transition of the output power level of a hybrid electric vehicle engine according to claim 1, characterized in that, The method for obtaining the required power of a high-voltage battery is as follows: The high-voltage battery controller (BMS) collects the current state of charge (SOC) value of the high-voltage battery, and the vehicle control unit (HCU) receives the current SOC value of the high-voltage battery and obtains the required power of the high-voltage battery based on the current SOC value.

Images