A method for controlling energy of a range extended hybrid electric vehicle

Abstract

The application provides a range-extending hybrid electric vehicle energy control method, comprising the following steps: obtaining the specific fuel consumption values corresponding to different output powers of an engine at different rotating speeds according to the universal characteristics of the engine and a generator; selecting the working condition point with the lowest specific fuel consumption value according to the value of the engine output power, and forming a working condition point set; obtaining the output power and rotating speed of the engine according to the running working condition when the vehicle is running, and matching the working condition point with the lowest specific fuel consumption value corresponding to the output power in the working condition point set when the output power is less than a set power threshold, and correcting the running working condition by using the working condition point. The application can increase the electric quantity balance of the hybrid electric vehicle and improve the energy utilization efficiency of the electric vehicle.

Description

Technical Field

[0001] This invention relates to the technical field of hybrid vehicle control, specifically to an energy control method for a range-extended hybrid electric vehicle. Background Technology

[0002] Range-extended hybrid electric vehicles (REEVs) use an engine to drive a generator, converting the energy of fuel into mechanical energy, which is then converted into electrical energy and input into the battery. The battery acts as an intermediate energy storage device, transferring electrical energy to the drive motor, which in turn converts the electrical energy into mechanical energy to drive the vehicle. The energy control principle of REEVs is to maintain the power required for vehicle operation equal to the engine's power output as much as possible, while minimizing the use of the battery for energy transfer. This is because there is efficiency loss when energy enters and leaves the battery. However, current hybrid electric vehicles experience large fluctuations in power demand under different operating conditions, often causing rapid changes in engine operating conditions. This necessitates the battery to quickly absorb the electrical energy generated by the engine, which can lead to reduced energy utilization efficiency and an inability to achieve battery balance over extended periods. Therefore, effective energy control of electric vehicles under different operating conditions is of great significance. Summary of the Invention

[0003] This invention provides an energy control method for range-extended hybrid electric vehicles, which solves the problem that existing hybrid electric vehicles have low energy utilization efficiency due to power changes under different operating conditions and cannot achieve power balance over a long period of time. This method can increase the power balance of hybrid electric vehicles and improve the energy utilization efficiency of electric vehicles.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] An energy control method for a range-extended hybrid electric vehicle includes:

[0006] Based on the universal characteristics of the vehicle engine and generator, obtain the specific fuel consumption value corresponding to the engine at different speeds and different output powers.

[0007] Based on the engine output power value, select the operating point with the lowest fuel consumption value and form a set of operating points;

[0008] When the vehicle is in motion, the engine output power and speed are obtained according to the operating conditions. When the output power is less than a set power threshold, the operating condition point with the lowest specific fuel consumption value corresponding to the output power is matched in the set of operating condition points, and the operating condition is corrected based on the operating condition point.

[0009] Preferred options also include:

[0010] The SOC value of the power battery is obtained. If the current battery SOC value is greater than the first set value but less than 100%, the vehicle is determined to be driving in pure electric mode. The engine is started only when the required driving power is greater than the maximum discharge power allowed by the power battery, in order to supplement the insufficient discharge power of the power battery.

[0011] Preferred options also include:

[0012] If the current SOC value is less than the first set value, the vehicle will operate in a mode where the power battery and engine drive simultaneously.

[0013] Preferred options also include:

[0014] When the current SOC value is less than the first set value and greater than the second set value, it is determined whether the vehicle is in high-speed or urban driving conditions.

[0015] If the vehicle is in high-speed operation, the vehicle adopts power following mode, matching the corresponding operating point according to the power required for the vehicle's driving, so that the engine generates electricity at the operating point matched by the set of operating points, thereby balancing the power required for the vehicle's driving and the power generated by the engine.

[0016] Preferred options also include:

[0017] When the vehicle is operating at high speed, if the power required for driving is 0, the engine speed will be gradually adjusted to a minimum of 1000 rpm, and the generator will reverse-drive the engine and provide a small amount of power to maintain the engine speed.

[0018] Preferred options also include:

[0019] If the vehicle is in urban conditions, it will use a constant power generation mode, where the engine generates electricity at a set power, and the power battery will output power to supplement the insufficient power.

[0020] Preferred options also include:

[0021] If the current SOC value is less than the second set value and greater than the third set value, the vehicle adopts the power following mode and the bottoming-out power generation mode. When the driver presses the accelerator pedal, the engine generates electricity in the power following mode. When the driver releases the accelerator pedal, the engine generates electricity at the operating point with the lowest fuel consumption value corresponding to the lowest speed.

[0022] Preferred options also include:

[0023] When the vehicle is in power following mode and bottom-up power generation mode, if it is in high-speed operation, the engine continuously generates electricity to increase the SOC value to a value greater than the second set value; if it is in urban operation, the engine continuously generates electricity to increase the SOC value to a value greater than the first set value.

[0024] Preferably, determining whether the vehicle is in high-speed or urban driving conditions includes:

[0025] The vehicle speed is obtained, and it is determined whether the speed is greater than a set speed threshold. If so, it is determined whether the duration of the speed being greater than the set speed threshold is greater than a set time threshold. If so, it is determined to be a high-speed condition.

[0026] When the duration of the vehicle speed being greater than the set vehicle speed threshold is less than the set time threshold, it is determined whether the number of parking operations or braking decelerations within the set historical time period is greater than the set number threshold. If so, it is determined to be an urban driving condition.

[0027] Preferably, determining whether the vehicle is in high-speed or urban driving conditions further includes:

[0028] When the vehicle speed is less than the set vehicle speed threshold, it is determined whether the vehicle speed is less than the set vehicle speed threshold by more than a set time threshold. If so, it is determined to be an urban driving condition. If not, it is determined whether the number of parking operations or braking decelerations within a set historical time period is greater than a set number threshold. If so, it is determined to be an urban driving condition.

[0029] This invention provides an energy control method for a range-extended hybrid electric vehicle (REEV). It identifies the operating point with the lowest specific fuel consumption value to form an operating point set. During vehicle operation, the method matches the operating point with the lowest specific fuel consumption value corresponding to the output power from this set, and uses this operating point to correct the operating conditions. This addresses the problem of low energy utilization efficiency and the inability to achieve battery balance over extended periods in existing hybrid electric vehicles due to power variations under different operating conditions. The method improves battery balance and energy utilization efficiency in hybrid electric vehicles. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0031] Figure 1 A schematic diagram of an energy control method for a range-extended hybrid electric vehicle provided by the present invention.

[0032] Figure 2 This is an engine universal characteristic diagram provided in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the energy control logic for an electric vehicle provided in an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of the logic for judging urban and highway operating conditions provided in an embodiment of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the embodiments of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and implementation methods.

[0036] To address the problem of low energy utilization efficiency caused by power variation under different operating conditions in current hybrid electric vehicles, this invention provides an energy control method for range-extended hybrid electric vehicles. This method solves the problem of low energy utilization efficiency caused by power variation under different operating conditions in existing hybrid electric vehicles, which makes it impossible to achieve battery balance over a long period of time. It can increase battery balance in hybrid electric vehicles and improve the energy utilization efficiency of electric vehicles.

[0037] like Figure 1 As shown, an energy control method for a range-extended hybrid electric vehicle includes:

[0038] S1: Based on the universal characteristics of the vehicle engine and generator, obtain the specific fuel consumption value corresponding to the engine at different speeds and different output powers;

[0039] S2: Select the operating point with the lowest fuel consumption value based on the engine output power value, and form a set of operating points;

[0040] S3: When the vehicle is in motion, the engine output power and speed are obtained according to the operating conditions. When the output power is less than a set power threshold, the operating condition point with the lowest specific fuel consumption value corresponding to the output power is matched in the set of operating condition points, and the operating condition is corrected based on the operating condition point.

[0041] Specifically, the basic principle of a range-extended hybrid electric vehicle (REEV) is that when the driver presses the accelerator pedal, the vehicle controller determines the total drive power required by the vehicle based on the pedal's opening. This total drive power is provided by the battery and the engine. The engine's MAP (Maximum Power Output) is as follows: Figure 2 As shown in the figure, the contour lines represent the engine's specific fuel consumption, expressed in g / kWh, which is the weight of fuel consumed to produce 1 kWh of work. The formula for converting engine torque to power is: P represents power, T represents torque, and n represents rotational speed.

[0042] Based on the universal characteristics of the engine and generator, the specific fuel consumption value Ge corresponding to the different power output P of the engine at different speeds n is calculated by interpolation, where Ge = Φ(n, P).

[0043] Select the operating points with the lowest specific fuel consumption when P = P1, P2, ..., P10 (P1, P2, ..., P10 = 10, 20, ..., 90) to form the set of operating points H = {(n1, P1, Ge1), (n2, P2, Ge2), (n3, P3, Ge3), ..., (n10, P10, Ge10)}, where n1 ≤ n2 ≤ n3 ≤ ... ≤ n10.

[0044] If, at a certain operating point, the output power Pi is less than the threshold P0, then the operating point is corrected. A point with the lowest fuel consumption within the range of Pi ± δP is found to replace it, and the reduced power is compensated by the power battery. This method, through operating point correction, ensures stable power demand for vehicle operation and maintains battery balance over a long period.

[0045] In practical applications, when the battery's SOC is high and the vehicle is operating in pure electric mode, the power battery provides all the driving power. When the power battery's output power is insufficient, the engine starts, driving the generator to generate electricity and supplement the power battery's insufficient output power. When the battery's SOC is low, the engine needs to start to drive the generator to generate electricity and charge the power battery simultaneously.

[0046] like Figure 3 As shown, the method also includes: obtaining the SOC value of the power battery; if the current battery SOC value is greater than a first set value and less than 100%, then the vehicle is determined to be driving in pure electric mode, and the engine is started only when the required driving power is greater than the maximum discharge power allowed by the power battery, in order to supplement the insufficient discharge power of the power battery.

[0047] The method also includes: if the current SOC value is less than the first set value, then driving in a mode where the power battery and engine drive simultaneously.

[0048] The method further includes: when the current SOC value is less than the first set value and greater than the second set value, determining whether the vehicle is in high-speed or urban driving conditions. If the vehicle is in high-speed driving conditions, the vehicle adopts a power following mode, matching the corresponding driving point in the set of driving points according to the power required for the entire vehicle's driving, so that the engine generates electricity at the driving point matched by the set of driving points, thereby balancing the power required for the entire vehicle's driving and the power generated by the engine.

[0049] In practical applications, the power follower mode means that the engine generates electricity at the operating point corresponding to the set of operating points, thus balancing the power demanded by the vehicle and the power generated by the engine. This mode can maintain a balance of electricity for a relatively long period of time and is suitable for high-speed driving conditions.

[0050] The method also includes: when the vehicle is in high-speed operation, if the power required for driving is 0, the engine speed is gradually adjusted to a minimum speed of 1000 rpm, and the generator reverse-drives the engine and provides a small amount of power to maintain the engine speed.

[0051] The method also includes: if the vehicle is in urban conditions, the vehicle adopts a constant power generation mode, in which the engine generates electricity at a set power, and the power battery outputs power to supplement the deficiency.

[0052] In practical applications, the constant power charging mode, regardless of the vehicle's power demand, selects a suitable operating point where the engine generates electricity at a constant power. In one embodiment, this is achieved at 1000 rpm, 14.66 kW, and 216.6 g / kWh. The selection of this operating point should be constrained by the continuous charging power allowed by the battery, seeking a point with lower engine speed (better NVH performance) and lower fuel consumption. This mode is suitable for urban driving, where the vehicle's power output fluctuates significantly, but the total energy consumption is low, allowing for gradual recharging to maintain battery balance.

[0053] The method also includes: if the current SOC value is less than the second set value and greater than the third set value, the vehicle adopts a power following mode and a bottoming-out power generation mode. When the driver presses the accelerator pedal, the engine generates electricity in the power following mode. When the driver releases the accelerator pedal, the engine generates electricity at the operating point with the lowest fuel consumption value corresponding to the lowest speed.

[0054] The method further includes: when the vehicle is in power following mode and bottom-up power generation mode, if it is in high-speed operation, the engine continuously generates electricity to increase the SOC value to a value greater than the second set value; if it is in urban operation, the engine continuously generates electricity to increase the SOC value to a value greater than the first set value.

[0055] like Figure 3 As shown, several SOC thresholds are set: SOC1 > SOC2 > SOC3. Segment 1: When the SOC is between 100% and SOC1, the vehicle operates in pure electric mode. The engine only starts generating electricity to compensate for insufficient battery discharge power when the required drive power exceeds the maximum allowable discharge power of the battery. Segment 2: When the SOC is between SOC1 and SOC2, if in high-speed conditions, it enters power-following mode; if in urban conditions, it enters constant power generation mode. Segment 3: When the SOC is between SOC2 and SOC3, it is considered that the battery charge is nearing its lower limit, and it enters power-following + bottom-support generation mode.

[0056] To employ different energy control strategies, range-extended electric vehicles (REEVs) are categorized based on whether they are operating in urban or highway conditions. To improve fuel economy, the engine's power output should be kept as stable as possible, as fluctuations in engine power output can reduce fuel efficiency. In urban driving conditions, due to acceleration and deceleration, the vehicle's power demand fluctuates significantly, but the overall energy demand is relatively low. In highway driving conditions, the vehicle speed is more stable, the vehicle's power demand fluctuates less, but the overall energy demand is higher.

[0057] like Figure 4 As shown, further, determining whether the vehicle is in high-speed or urban driving conditions includes:

[0058] The vehicle speed is obtained, and it is determined whether the speed is greater than a set speed threshold. If so, it is determined whether the duration of the speed being greater than the set speed threshold is greater than a set time threshold. If so, it is determined to be a high-speed condition.

[0059] When the duration of the vehicle speed being greater than the set vehicle speed threshold is less than the set time threshold, it is determined whether the number of parking operations or braking decelerations within the set historical time period is greater than the set number threshold. If so, it is determined to be an urban driving condition.

[0060] Furthermore, the determination of whether the vehicle is in high-speed or urban driving conditions also includes:

[0061] When the vehicle speed is less than the set vehicle speed threshold, it is determined whether the vehicle speed is less than the set vehicle speed threshold by more than a set time threshold. If so, it is determined to be an urban driving condition. If not, it is determined whether the number of parking operations or braking decelerations within a set historical time period is greater than a set number threshold. If so, it is determined to be an urban driving condition.

[0062] Therefore, this invention provides an energy control method for a range-extended hybrid electric vehicle. Besides considering the SOC value of the power battery, energy control also needs to be performed based on specific driving conditions. By obtaining the operating point with the lowest specific fuel consumption, a set of operating points is formed. During vehicle operation, the operating point with the lowest specific fuel consumption corresponding to the output power is matched from this set, and the operating condition is corrected based on this operating point. This solves the problem of low energy utilization efficiency caused by power changes under different operating conditions in existing hybrid electric vehicles, which prevents them from achieving battery balance over a long period. It increases the battery balance of hybrid electric vehicles and improves their energy utilization efficiency.

[0063] The structure, features, and effects of the present invention have been described in detail above with reference to the embodiments shown in the figures. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall be within the protection scope of the present invention as long as they do not exceed the spirit covered by the specification and figures.

Claims

1. An energy control method for a range-extended hybrid electric vehicle, characterized in that, include: Based on the universal characteristics of the vehicle engine and generator, obtain the specific fuel consumption value corresponding to the engine at different speeds and different output powers. Based on the engine output power value, select the operating point with the lowest fuel consumption value and form a set of operating points; When the vehicle is in motion, the engine output power and speed are obtained according to the operating conditions. When the output power is less than a set power threshold, the operating condition with the lowest specific fuel consumption value corresponding to the output power is matched in the set of operating condition points. The operating condition is then corrected using the operating condition with the lowest specific fuel consumption value. The excess or insufficient power is compensated by the power battery. The SOC value of the power battery is obtained. If the current battery SOC value is greater than the first set value and less than 100%, the vehicle is determined to be driving in pure electric mode. The engine is started only when the required driving power is greater than the maximum discharge power allowed by the power battery, in order to supplement the insufficient discharge power of the power battery. If the current SOC value is less than the first set value, the vehicle will be driven in a mode where the power battery and engine drive simultaneously. When the current SOC value is less than the first set value and greater than the second set value, it is determined whether the vehicle is in high-speed or urban driving conditions. If the vehicle is in high-speed operation, the vehicle adopts power following mode, matching the corresponding operating point in the set of operating points according to the power required for the vehicle's driving, so that the engine generates electricity at the operating point matched by the set of operating points, thereby balancing the power required for the vehicle's driving and the power generated by the engine. If the current SOC value is less than the second set value and greater than the third set value, the vehicle adopts the power following mode and the bottoming-out power generation mode. When the driver presses the accelerator pedal, the engine generates electricity in the power following mode. When the driver releases the accelerator pedal, the engine generates electricity at the operating point with the lowest fuel consumption value corresponding to the lowest speed.

2. The energy control method for a range-extended hybrid electric vehicle according to claim 1, characterized in that, Also includes: When the vehicle is operating at high speed, if the power required for driving is 0, the engine speed will be gradually adjusted to a minimum of 1000 rpm, and the generator will reverse-drive the engine and provide a small amount of power to maintain the engine speed.

3. The energy control method for a range-extended hybrid electric vehicle according to claim 2, characterized in that, Also includes: If the vehicle is in urban conditions, it will use a constant power generation mode, where the engine generates electricity at a set power, and the power battery will output power to supplement the insufficient power.

4. The energy control method for a range-extended hybrid electric vehicle according to claim 3, characterized in that, Also includes: When the vehicle is in power follow mode and bottom-out power generation mode, if it is in high-speed operation, the engine will continuously generate electricity to increase the SOC value to a value greater than the second set value. If operating in urban conditions, continuous power generation will raise the SOC value to a level greater than the first set value.

5. The energy control method for a range-extended hybrid electric vehicle according to claim 4, characterized in that, The determination of whether the vehicle is in high-speed or urban driving conditions includes: The vehicle speed is obtained, and it is determined whether the speed is greater than a set speed threshold. If so, it is determined whether the duration of the speed being greater than the set speed threshold is greater than a set time threshold. If so, it is determined to be a high-speed condition. When the duration of the vehicle speed being greater than the set vehicle speed threshold is less than the set time threshold, it is determined whether the number of parking operations or braking decelerations within the set historical time period is greater than the set number threshold. If so, it is determined to be an urban driving condition.

6. The energy control method for a range-extended hybrid electric vehicle according to claim 5, characterized in that, The determination of whether the vehicle is in high-speed or urban driving conditions also includes: When the vehicle speed is less than the set vehicle speed threshold, it is determined whether the vehicle speed is less than the set vehicle speed threshold by more than a set time threshold. If so, it is determined to be an urban driving condition. If not, it is determined whether the number of parking operations or braking decelerations within a set historical time period is greater than a set number threshold. If so, it is determined to be an urban driving condition.

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