A power generation control method for a range extender of a series hybrid vehicle

Abstract

The application belongs to the technical field of range extender assembly power generation, and particularly relates to a power generation control method for a series hybrid vehicle range extender, which comprises the following steps: high-voltage ready on the whole vehicle, driver controls the whole vehicle driving, judges whether the battery discharge power is >20KW and the battery peak charging power is >10KW, if not, VCU controls APU power generation power according to the power following control strategy, VCU calculates the vehicle weight according to the information collected by the load sensor, according to the whole vehicle load, the whole vehicle load state is set as three load states of empty load, half load and full load, each load state corresponds to a group of power generation power points, according to the SOC size, the SOC interval is divided, the low, medium and high SOC interval flag bits are output, the optimal operating speed corresponding to the target power generation power point is inquired according to the APU efficiency map, and VCU controls APU to generate power at a constant power, so that the problems of possible overcharging of the battery caused by too large power generation power of APU fixed point power generation strategy and large APU noise are solved.

Description

Technical Field

[0001] This invention belongs to the field of range extender assembly power generation technology. Specifically, this invention relates to a power generation control method for a series hybrid vehicle range extender. Background Technology

[0002] Series hybrid electric vehicles are equipped with lithium batteries, electric drive systems, and range extenders (hereinafter referred to as "APUs") that can replenish their own power at any time. The power generation control of APUs usually adopts a fixed-point power generation strategy, which improves the overall vehicle's economic efficiency by making the APU work in the high-efficiency range as much as possible. Once the APU is started, it will always be in the power generation state to avoid the APU idling and wasting fuel, which would affect the economy. However, there are also problems such as excessive power generation leading to overcharging of the battery and loud APU noise.

[0003] However, existing batteries may overcharge during parking and charging, which can seriously damage the battery's health and lifespan. In addition, in winter, when the ambient temperature is low, the battery cell temperature will drop, preventing the battery from reaching full power charging and reducing charging efficiency. Summary of the Invention

[0004] This invention provides a power generation control method for series hybrid vehicle range extenders, proposing a three-stage fixed-point power generation strategy. The power generation point is dynamically adjusted based on the vehicle's load status and battery SOC. The optimal power generation speed is controlled according to the APU's efficiency map for different target power outputs, while simultaneously considering battery charging and discharging capabilities to avoid overcharging and over-discharging damage. This achieves the best balance between vehicle economy, comfort, safety, and power, solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a power generation control method for a series hybrid vehicle range extender, comprising the following steps:

[0006] Step S10: High voltage is ready for the entire vehicle;

[0007] Step S20: The driver controls the vehicle to drive.

[0008] Step S21: Determine whether the battery discharge power is greater than 20KW and the battery peak charging power is greater than 10KW. If not, the VCU controls the APU power generation power according to the power follower control strategy. If yes, proceed to step S22.

[0009] Step S22: The VCU calculates the vehicle weight based on the information collected by the load sensor;

[0010] Step S23: Based on the vehicle load, the vehicle load status is set to three load states: no load, half load, and full load. Each load state corresponds to a set of power generation points.

[0011] Step S24: Divide the SOC interval according to the SOC size;

[0012] Step S25: Output the low, medium, and high SOC interval flags;

[0013] Step S26: Based on the preset power generation map, query the constant power generation point according to the load status flag and the SOC interval flag.

[0014] Step S27: Query the optimal operating speed corresponding to the target power generation point based on the APU efficiency map;

[0015] In step S28, the VCU controls the APU to generate electricity at a constant power.

[0016] Preferably, in step S23, the unloaded state range is 2900-3500 kg, the half-loaded state range is 3400-4600 kg, and the fully loaded state range is 4500-6100 kg.

[0017] Preferably, in step S24, for each group of power generation points under different load conditions, the power generation points are set according to the different battery SOC. Three groups of power generation points are set according to the SOC size. Therefore, the three load conditions of the whole vehicle correspond to three SOC sizes, with a total of three groups and nine power generation points, and a constant power generation map is established.

[0018] Preferably, the SOC interval is divided into a low SOC interval, a medium SOC interval, and a high SOC interval, with numerical ranges of 0%-25%, 20%-50%, and 45%-95%, respectively.

[0019] Preferably, a hysteresis control interval is added to both the load state division and the SOC interval division. When the vehicle weight and SOC are within the hysteresis control interval, the current power generation point is maintained. When the vehicle changes from the overlapping area to the independent area, the power generation corresponding to the area is executed.

[0020] Preferably, in step S27, the generator control unit performs speed control based on the real-time query of the optimal operating speed of the APU. The optimal operating speed obtained in real-time is the target speed. The generator control unit performs closed-loop speed control through PI based on the target operating speed. The engine control unit queries the target control torque based on the optimal target operating speed and the power generation point. When there is a deviation between the power generation output and the target power generation, step S28 is followed to ensure that the power generation accuracy meets the design requirements.

[0021] Preferably, the specific method for VCU controlling APU to perform constant power generation in step S28 is as follows: VCU calculates the actual power generation of APU in real time based on the actual current and bus voltage fed back by APU, and feeds the actual power generation back to engine control unit. When there is a deviation between the actual power generation and the target power generation, the engine torque is dynamically adjusted to ensure the stability of constant power generation. The adjustment method is to reduce the engine torque when the actual power generation is greater than the target power generation, and increase the engine torque when the actual power generation is less than the target power generation. Engine torque adjustment can be achieved through air-fuel ratio control, which is achieved by adjusting the throttle opening or enriching / leaning the fuel injection based on the theoretical air-fuel ratio.

[0022] The beneficial effects of adopting the above technical solutions are:

[0023] 1. A three-stage fixed-point power generation strategy is proposed. The power generation point is dynamically adjusted according to the vehicle load status and battery SOC. Based on the efficiency map of APU, the optimal efficiency power generation speed is controlled for different target power generation. At the same time, the charging and discharging capacity of the battery is taken into account to avoid overcharging and over-discharging damage to the battery, so as to achieve the best balance of vehicle economy, comfort, safety and power.

[0024] 2. Power follower control is adopted, which solves the problems of battery overcharging and damage caused by the low allowable charging capacity of the battery when it is close to or fully charged, or under low temperature conditions, and battery over-discharge when the battery's discharge capacity is insufficient. Attached Figure Description

[0025] Figure 1 This is the overall flowchart provided by the present invention. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0027] Specifically, such as Figure 1 As shown, a power generation control method for a series hybrid vehicle range extender includes the following steps:

[0028] Step S10: High voltage is ready for the entire vehicle;

[0029] Step S20: The driver controls the vehicle to drive.

[0030] Step S21: Determine whether the battery discharge power is greater than 20KW and the battery peak charging power is greater than 10KW. If not, the VCU controls the APU power generation power according to the power follower control strategy. If yes, proceed to step S22.

[0031] Step S22: The VCU calculates the vehicle weight based on the information collected by the load sensor;

[0032] Step S23: Based on the vehicle load, set the vehicle load status to no load (3000kg), half load (4500kg) and full load (6000kg), with each load status corresponding to one set of power generation points;

[0033] Step S24: Divide the SOC range according to the SOC size. For each group of power generation points under different load conditions, set the power generation points according to the different battery SOC. Set three groups of power generation points according to the SOC size. Therefore, the three load conditions of the whole vehicle correspond to three SOC sizes, with a total of three groups and nine power generation points. Establish a constant power generation map.

[0034] Step S25: Output low, medium and high SOC interval flags. The SOC intervals are divided into low SOC interval, medium SOC interval and high SOC interval, with numerical ranges of 0%-25%, 20%-50% and 45%-95%, respectively.

[0035] Step S26: Based on the preset power generation map, query the constant power generation point based on the load status flag and SOC interval flag. Add hysteresis control intervals to both load status division and SOC interval division. When the vehicle weight and SOC are within the hysteresis control interval, maintain the current power generation point. When the vehicle changes from an overlapping area to an independent area, execute the power generation corresponding to the area.

[0036] Step S27: Query the optimal operating speed corresponding to the target power generation point according to the APU efficiency map. The generator control unit performs speed control based on the real-time query of the optimal APU operating speed. The optimal operating speed obtained in real-time is the target speed. The generator control unit performs closed-loop speed control through PI based on the target operating speed. The engine control unit queries the target control torque based on the optimal operating target speed and the power generation point. When there is a deviation between the power generation output and the target power generation, step S28 is followed to ensure that the power generation accuracy meets the design requirements.

[0037] Step S28: The VCU controls the APU to generate constant power. The specific method for the VCU to control the APU to generate constant power is as follows: Based on the actual current and bus voltage fed back by the APU, the VCU calculates the actual power generated by the APU in real time and feeds the actual power generated back to the engine control unit. When there is a deviation between the actual power generated and the target power generated, the engine torque is dynamically adjusted to ensure the stability of constant power generation. The adjustment method is as follows: when the actual power generated is greater than the target power generated, the engine torque is reduced; when the actual power generated is less than the target power generated, the engine torque is increased. The engine torque adjustment can be achieved through air-fuel ratio control, which is achieved by adjusting the throttle opening or enriching / leaning the fuel injection based on the theoretical air-fuel ratio.

[0038] To prevent fluctuations in vehicle weight acquisition signals and SOC fluctuations from the BMS from causing fluctuations in the generator power point, which in turn cause torque fluctuations and noise steps when the engine switches speeds, hysteresis control intervals are added to both load state division and SOC interval division to avoid fluctuation problems. The unloaded interval is 2900-3500kg, the half-loaded interval is 3400-4600kg, and the full-loaded interval is 4500-6100kg. When the vehicle weight and SOC are in the overlapping area of ​​the classification (within the hysteresis interval), the current generator power point is maintained. When changing from the overlapping area to an independent area, the generator power corresponding to the area is executed. The SOC intervals are divided as follows: 0%-25% (low SOC interval), 20%-50% (medium SOC interval), and 45%-95% (high SOC interval).

[0039] It should be noted that when the battery is close to or fully charged, or under low temperature conditions, the battery's allowable charging capacity is relatively low, and overcharging is prone to occur. In order to prevent the battery from being damaged by overcharging, power follow control needs to be used at this time. In addition, when the battery's discharge capacity is insufficient, power follow control also needs to be used to ensure the vehicle's power performance and avoid battery over-discharge.

[0040] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A power generation control method for a series hybrid vehicle range extender, characterized in that, Includes the following steps: Step S10: High voltage is ready for the entire vehicle; Step S20: The driver controls the vehicle to drive. Step S21: Determine whether the battery discharge power is greater than 20KW and the battery peak charging power is greater than 10KW. If not, the VCU controls the APU power generation power according to the power follower control strategy. If yes, proceed to step S22. Step S22: The VCU calculates the vehicle weight based on the information collected by the load sensor; Step S23: Based on the vehicle load, the vehicle load status is set to three load states: no load, half load, and full load. Each load state corresponds to a set of power generation points. Step S24: Divide the SOC range according to the SOC size. For each group of power generation points under different load conditions, set the power generation points according to the different battery SOC. Set three groups of power generation points according to the SOC size. Therefore, the three load conditions of the whole vehicle correspond to three SOC sizes, with a total of three groups and nine power generation points. Establish a constant power generation map. Step S25: Output the low, medium, and high SOC interval flags; Step S26: Based on the preset power generation map, query the constant power generation point according to the load status flag and the SOC interval flag. Step S27: Query the optimal operating speed corresponding to the target power generation point based on the APU efficiency map; Step S28: The VCU controls the APU to generate electricity at a constant power. Hysteresis control intervals are added to both load condition division and SOC interval division. When the vehicle weight and SOC are within the hysteresis control interval, the current power generation point is maintained. When the vehicle changes from an overlapping area to an independent area, the power generation corresponding to the area is executed.

2. The power generation control method for a series hybrid vehicle range extender according to claim 1, characterized in that: In step S23, the unloaded state range is 2900-3500kg, the half-loaded state range is 3400-4600kg, and the full-loaded state range is 4500-6100kg.

3. The power generation control method for a series hybrid vehicle range extender according to claim 1, characterized in that: The SOC range is divided into a low SOC range, a medium SOC range, and a high SOC range, with numerical ranges of 0%-25%, 20%-50%, and 45%-95%, respectively.

4. The power generation control method for a series hybrid vehicle range extender according to claim 1, characterized in that: In step S27, the generator control unit performs speed control based on the real-time query of the optimal operating speed of the APU. The optimal operating speed obtained in real-time is the target speed. The generator control unit performs closed-loop speed control through PI based on the target operating speed. The engine control unit queries the target control torque based on the optimal target operating speed and the power generation point. When there is a deviation between the power generation output and the target power generation, step S28 is followed to ensure that the power generation accuracy meets the design requirements.

5. The power generation control method for a series hybrid vehicle range extender according to claim 1, characterized in that: The specific method for VCU to control APU for constant power generation in step S28 is as follows: VCU calculates the actual power generation of APU in real time based on the actual current and bus voltage fed back by APU, and feeds the actual power generation back to engine control unit. When there is a deviation between the actual power generation and the target power generation, the engine torque is dynamically adjusted to ensure the stability of constant power generation. The adjustment method is to reduce the engine torque when the actual power generation is greater than the target power generation, and increase the engine torque when the actual power generation is less than the target power generation. Engine torque adjustment can be achieved through air-fuel ratio control, which is achieved by adjusting the throttle opening or enriching / leaning the fuel injection based on the theoretical air-fuel ratio.

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