Complete vehicle power compensation method and system for hybrid vehicle

Abstract

The invention discloses a whole vehicle power compensation method and system for a hybrid vehicle, and belongs to the field of new energy vehicles. The method comprises the following steps: acquiring a current battery power boundary of the BMS; judging whether the current BMS sends a power limit flag bit or not; when the BMS sends out the power limit flag bit, the whole vehicle demand power is calculated; judging whether the required power of the whole vehicle is greater than the battery power boundary or not; when the required power of the whole vehicle is larger than the battery power boundary, a vehicle engine is controlled to be started in advance, and a power reservation request is made; and after receiving the power reservation request, the engine compensates the battery power boundary according to the self condition. When the discharge power of the battery is limited, the engine is started in advance for power reservation and compensation, and the situation that under the condition that the engine cannot work in the catalyst heating period and the like, the whole vehicle driving power cannot meet the user requirement is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of new energy vehicles, and in particular, relates to a vehicle power compensation method and system for a hybrid vehicle. Background Art

[0002] As a type of new energy vehicle, PHEV (hybrid electric vehicle) has a different control strategy from traditional fuel vehicles because it involves the combination and conversion of oil and electricity. The vehicle control system, as the control center of the vehicle, bears the important task of power distribution and coordination, ensuring that the vehicle has sufficient power to meet the user's driving needs at any time and in any usage scenario, ensuring safe and reliable driving.

[0003] At present, for most PHEV models, the driving power is supplied by the battery discharge power and the engine output power at the same time, and the power request and distribution are controlled. When the power battery discharge power boundary is normal and the thermal engine state, the whole vehicle can meet the normal power output. However, in special circumstances, for example, ① at low SOC power or when the consistency deviation of the battery cell is large, the battery discharge power is limited; ② when the engine is started from cold, there is a catalyst heating process, which lasts about 1min to 2min; ③ the user has a high-power drive request. During this period, the engine output power is 0, and the single limited battery discharge power cannot meet the driving power requirements. At this time, the vehicle will have problems such as poor acceleration or failure to reach the maximum speed, which affects the driving experience and even brings safety hazards.

[0004] To this end, the present invention proposes a vehicle power compensation method and system for a hybrid vehicle. Summary of the invention

[0005] The present invention aims to overcome the shortcomings of the prior art and proposes a vehicle power compensation method and system for a hybrid vehicle to achieve the following objectives: when the battery discharge power is limited, the engine is started in advance to reserve and compensate the engine power in combination with the vehicle power demand, so as to avoid the situation where the engine cannot work during catalyst heating, etc., and the vehicle driving power cannot meet user needs.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a vehicle power compensation method for a hybrid vehicle, the method comprising the following steps in one cycle:

[0007] Step S1: Obtain the current battery power boundary P of the BMS bat ;

[0008] Step S2: Determine whether the current BMS has issued a power limit flag; if so, it indicates that the current battery power boundary P bat If it is restricted, continue to the next step; otherwise, this cycle ends;

[0009] Step S3: When the BMS sends out a power limit flag, calculate the required power of the vehicle;

[0010] Step S4: Determine whether the vehicle power requirement is greater than the battery power limit P bat ; If it is greater, continue to the next step, otherwise the loop ends;

[0011] Step S5: When the vehicle power requirement is greater than the battery power limit P bat When the vehicle engine is started in advance, a power reserve request is made;

[0012] Step S6: After receiving the power reservation request, the engine adjusts the battery power boundary P according to its own situation. bat Make compensation.

[0013] Preferably, in step S2, the judgment condition of whether the BMS issues a power limit flag includes: the BMS obtains the current battery operating condition, and judges whether the battery discharge power under the current operating condition is limited according to a pre-stored battery discharge map under different operating conditions; if limited, the BMS issues a power limit flag.

[0014] Preferably, the operating conditions include different battery SOCs, temperatures, and atmospheric pressures.

[0015] Preferably, in step S2, the judgment condition of whether the BMS issues a power limit flag includes: the BMS obtains the voltage of each single battery cell in real time and calculates the voltage difference between them, and judges whether there is a situation where the voltage difference between the single battery cells is greater than a preset voltage difference threshold. If so, it means that there is a consistent voltage deviation in the current single battery cell, and correspondingly, the BMS issues a power limit flag.

[0016] Preferably, the vehicle power compensation method for a hybrid vehicle according to claim 1 is characterized in that: in the step S2, the judgment condition of whether the BMS issues a power limit flag includes: during the battery discharge process, the BMS detects the battery voltage in real time to determine whether the current battery voltage drops to a preset undervoltage threshold. If so, the BMS limits the battery discharge power and issues a power limit flag.

[0017] Preferably, in step S3, the vehicle required power = driving power P v + Rapid acceleration power P j .

[0018] Preferably, the driving power P v And rapid acceleration power P j The calculation formula is as follows:

[0019]

[0020] Where V is the vehicle speed; η is the transmission efficiency; m is the total mass of the vehicle; g is the acceleration of gravity; f is the rolling resistance coefficient; C D represents the air resistance coefficient; A represents the windward frontal area; δ represents the vehicle rotational mass conversion coefficient; a represents the vehicle acceleration.

[0021] Preferably, in step S5, the power reserve value requested from the engine is the difference between the vehicle demand power and the battery power boundary P bat difference.

[0022] Preferably, in step S6, the compensation value of the engine is the minimum value between the power output value of its own maximum capacity and the power reserve value requested from the engine.

[0023] At the same time, based on the above-mentioned vehicle power compensation method for a hybrid vehicle, the present application also proposes a vehicle power compensation system for a hybrid vehicle, the system including a power battery, a battery management system BMS, a vehicle controller VCU, and an engine, wherein the power battery is connected to the battery management system BMS, and the vehicle controller VCU is respectively connected to the battery management system BMS and the engine; the vehicle controller VCU is used to perform vehicle power compensation according to the above-mentioned method.

[0024] The technical effect of the present invention is: under conditions of low SOC power, low temperature, large deviation in cell consistency, battery undervoltage and other conditions where the battery discharge power is limited, the present invention starts the engine in advance to reserve and compensate for power, thereby avoiding the vehicle stalling due to insufficient power during the catalyst heating process. The present invention is applicable to hybrid vehicles, which not only ensures the healthy operation of the battery, but also ensures reliable power output of the entire hybrid system. It effectively improves the reliability and safety of the hybrid system of PHEV models. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of a method for compensating vehicle power of a hybrid vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following is a further detailed description of the specific implementation of the present invention through the description of the embodiments with reference to the accompanying drawings, the purpose of which is to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation. It should be noted that the words "first", "second" and the like described in this application are only for the convenience of describing the technical solution to distinguish different components, and are not used to limit this application. In order to make the technical solution of the present invention clearer, the present invention is explained through the following embodiments.

[0027] Nowadays, with the continuous development of PHEV models, their applications in complex environments such as high and low temperatures are becoming more and more frequent. A more complete control strategy is the key to ensuring the reliable operation of the PHEV three-electric system and the core to ensuring user driving safety.

[0028] This embodiment provides a method for compensating the power of a hybrid vehicle. Figure 1 As shown, the method comprises the following steps in one cycle:

[0029] Step S1: Obtain the current battery power boundary P of the BMS (battery management system) bat ;

[0030] Step S2: Determine whether the current BMS has issued a power limit flag; if so, it indicates that the current battery power boundary P bat If it is restricted, continue to the next step; otherwise, this cycle ends;

[0031] Step S3: When the BMS sends out a power limit flag, calculate the required power of the vehicle;

[0032] Step S4: Determine whether the vehicle power requirement is greater than the battery power limit P bat ; If it is greater, continue to the next step, otherwise the loop ends;

[0033] Step S5: When the vehicle power requirement is greater than the battery power limit P bat When the vehicle engine is started in advance, a power reserve request is made;

[0034] Step S6: After receiving the power reservation request, the engine adjusts the battery power boundary P according to its own situation. bat Make compensation.

[0035] It should be noted that the above process is executed cyclically when the whole vehicle is working, so as to ensure that the hybrid vehicle has a reliable power source during driving.

[0036] Specifically, in step S2 of this embodiment, when the battery power is limited, the corresponding battery power boundary P bat will also be affected synchronously, so the battery power boundary P can be determined by the battery power limitation. bat The limited situation makes it easier to subsequently target the limited battery power boundary P bat In step S2, the judgment conditions for whether the BMS issues a power limit flag include:

[0037] (1) The BMS obtains the current battery operating condition and determines whether the battery discharge power under the current operating condition is limited according to the pre-stored battery discharge map under different operating conditions; if limited, the BMS issues a power limit flag. The operating conditions include different battery SOC (state of charge), temperature, atmospheric pressure, etc.

[0038] The battery discharge map under different working conditions is a table obtained in advance through a large amount of experimental data. It records the maximum discharge power allowed by the battery under different working conditions such as temperature, SOC, and pressure difference. Among them, under normal working conditions, the maximum discharge power allowed by the battery is relatively large, and the user's normal battery discharge power demand is far from the maximum discharge power allowed by the battery. In this case, the battery discharge power can be regarded as unrestricted. However, under harsh working conditions such as low temperature, low battery SOC, and low atmospheric pressure, in order to protect the battery, the maximum discharge power allowed by the battery is smaller. At this time, the user's normal battery discharge power demand is greater than the maximum discharge power allowed by the battery. In this case, the battery discharge power is regarded as restricted.

[0039] (2) The BMS obtains the voltage of each single cell in real time and calculates the voltage difference between them to determine whether the voltage difference between the single cells is greater than the preset voltage difference threshold. If so, it means that there is a consistency voltage deviation in the current single cell. Correspondingly, the BMS issues a power limit flag.

[0040] In a power battery pack that has been used for a period of time, individual cells may age to different degrees, causing their voltage drop rate during discharge to be inconsistent with that of other cells, resulting in a voltage difference between the cells. At this time, the BMS will limit the battery power to ensure battery safety, thereby balancing the voltage difference between the cells.

[0041] (3) In step S2, the judgment condition of whether the BMS issues a power limit flag includes: during the battery discharge process, the BMS detects the battery voltage in real time and determines whether the current battery voltage drops to a preset undervoltage threshold. If so, the BMS limits the battery discharge power and issues a power limit flag.

[0042] The undervoltage threshold refers to the limit when the battery voltage drops to a preset voltage value during the battery discharge process. This preset voltage value is the undervoltage threshold. For example, the undervoltage threshold calibrated on a lithium iron phosphate battery cell bench is 2.75V. The actual setting can be determined based on a large amount of test data under different working conditions. Once the battery voltage is lower than this threshold, the battery may not work properly, or continued use may cause damage to the battery. Therefore, when the BMS detects that the battery voltage drops to the preset undervoltage threshold, it will limit the battery discharge power to protect the battery.

[0043] In a specific implementation, there may be more conditions for the BMS to limit the battery discharge power and issue a power limit flag, which can be flexibly selected according to actual conditions, and the present invention is not limited thereto.

[0044] Specifically, in step S3 of this embodiment, the vehicle required power = driving power P v + Rapid acceleration power P j , where driving power P v And rapid acceleration power P j The calculation formula is as follows:

[0045]

[0046] Where V is the vehicle speed; η is the transmission efficiency; m is the total mass of the vehicle; g is the acceleration of gravity; f is the rolling resistance coefficient; C D represents the air resistance coefficient; A represents the windward frontal area; δ represents the vehicle rotational mass conversion coefficient; a represents the vehicle acceleration.

[0047] In this embodiment, the vehicle power requirement is divided into driving power and rapid acceleration power, which can more accurately evaluate the power requirements of the vehicle under different working conditions. Driving power is mainly used to overcome various resistances during the vehicle's driving process, and rapid acceleration power takes into account the additional power requirements of the vehicle in situations where rapid acceleration is required for emergency avoidance and other situations. The vehicle power requirement configured in this way is sufficient to meet the user's vehicle driving power requirements under most working conditions.

[0048] Further, in step S5 of this embodiment, in order to ensure that the battery power is within the current limited battery power boundary P bat Under the premise that the engine is sufficient to meet the power demand of the user. In this embodiment, the power reserve value requested to the engine is the sum of the vehicle demand power and the battery power boundary P bat The difference is: P v +P j -P bat .

[0049] In step S6 of this embodiment, after receiving the power reservation request, the engine also needs to consider its own situation, that is, the power output value of its maximum capacity. Obviously, when the power output value of its maximum capacity is less than the requested power reservation value, the engine cannot meet the request, but in order to meet the request as much as possible to improve the user's driving experience, the engine should output according to the power output value of its maximum capacity. In summary, in this embodiment, the compensation value of the engine is the minimum value between the power output value of its maximum capacity and the power reservation value requested from the engine.

[0050] At the same time, this embodiment also proposes a whole vehicle power compensation system for a hybrid vehicle according to the above method, wherein the system includes a power battery, a battery management system BMS, a whole vehicle controller VCU, and an engine, wherein the power battery is connected to the battery management system BMS, and the whole vehicle controller VCU is respectively connected to the battery management system BMS and the engine.

[0051] The battery management system BMS is used to monitor the status of the power battery in real time, including voltage, current, temperature, output power, etc. The vehicle controller VCU is used to perform vehicle power compensation according to the method of this embodiment, and issue an early engine start and power reservation request instruction to the engine; after receiving the instruction, the engine performs power compensation in combination with its own working conditions. In addition, the power compensated by the engine can be converted into electrical energy and stored in the power battery, or stored in another device battery.

[0052] The present invention is beneficial to the vehicle hybrid system in extreme situations, meeting the driving needs of the driver, allowing the PHEV model to be compensated when the battery power is limited, ensuring that the entire hybrid system operates more stably and reliably, so as to ensure a better driving experience for the entire vehicle and solve driving problems in various situations. The present invention not only ensures the healthy operation of the battery, but also ensures that the entire hybrid system has reliable power output. Under conditions of limited battery discharge power such as low SOC power, low temperature, large consistency deviation of battery cells, and battery voltage undervoltage, the present invention starts the engine in advance to reserve and compensate for power, thereby avoiding the vehicle stalling due to insufficient power during the catalyst heating process.

[0053] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for compensating vehicle power of a hybrid vehicle, characterized in that: The method comprises the following steps in one cycle: Step S1: Obtain the current battery power boundary P of the BMS bat ; Step S2: Determine whether the current BMS has issued a power limit flag; if so, it indicates that the current battery power boundary P bat If it is restricted, continue to the next step; otherwise, this cycle ends; Step S3: When the BMS sends out a power limit flag, calculate the required power of the vehicle; Step S4: Determine whether the vehicle power requirement is greater than the battery power limit P bat ; If it is greater, continue to the next step, otherwise the loop ends; Step S5: When the vehicle power requirement is greater than the battery power limit P bat When the vehicle engine is started in advance, a power reserve request is made; Step S6: After receiving the power reservation request, the engine adjusts the battery power boundary P according to its own situation. bat Make compensation.

2. The method for compensating the power of a hybrid vehicle according to claim 1, characterized in that: In step S2, the judgment condition of whether the BMS issues a power limit flag includes: the BMS obtains the current battery operating condition, and judges whether the battery discharge power under the current operating condition is limited according to a pre-stored battery discharge map under different operating conditions; if limited, the BMS issues a power limit flag.

3. The vehicle power compensation method for a hybrid vehicle according to claim 1, characterized in that: The operating conditions include different battery SOCs, temperatures, and atmospheric pressures.

4. The method for compensating the power of a hybrid vehicle according to claim 1, characterized in that: In the step S2, the judgment conditions for whether the BMS issues a power limit flag include: the BMS obtains the voltage of each single cell in real time and calculates the voltage difference between them, and judges whether there is a situation where the voltage difference between the single cells is greater than the preset voltage difference threshold. If so, it means that there is a consistent voltage deviation in the current single cell, and correspondingly, the BMS issues a power limit flag.

5. The method for compensating the power of a hybrid vehicle according to claim 1, characterized in that: The vehicle power compensation method for a hybrid vehicle according to claim 1 is characterized in that: in the step S2, the judgment condition of whether the BMS issues a power limit flag includes: during the battery discharge process, the BMS detects the battery voltage in real time, and determines whether the current battery voltage drops to a preset undervoltage threshold. If so, the BMS limits the battery discharge power and issues a power limit flag.

6. The method for compensating the power of a hybrid vehicle according to claim 1, characterized in that: In step S3, the vehicle required power = driving power P v + Rapid acceleration power P j .

7. The method for compensating the power of a hybrid vehicle according to claim 1, characterized in that: Driving power P v And rapid acceleration power P j The calculation formula is as follows: Where V is the vehicle speed; η is the transmission efficiency; m is the total mass of the vehicle; g is the acceleration of gravity; f is the rolling resistance coefficient; C D represents the air resistance coefficient; A represents the windward frontal area; δ represents the vehicle rotational mass conversion coefficient; a represents the vehicle acceleration.

8. A method for compensating vehicle power of a hybrid vehicle according to claim 1, 7 or 8, characterized in that: In step S5, the power reserve value requested from the engine is equal to the vehicle power requirement and the battery power boundary P bat difference.

9. The method for compensating the power of a hybrid vehicle according to claim 7, characterized in that: In step S6, the compensation value of the engine is the minimum value between the power output value of the engine's maximum capacity and the power reserve value requested from the engine.

10. A vehicle power compensation system for a hybrid vehicle according to the method according to any one of claims 1 to 9, characterized in that: The system includes a power battery, a battery management system BMS, a vehicle controller VCU, and an engine, wherein the power battery is connected to the battery management system BMS, and the vehicle controller VCU is respectively connected to the battery management system BMS and the engine; the vehicle controller VCU is used to perform vehicle power compensation according to the method according to any one of claims 1-9.

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