A control method for optimizing charging efficiency of a P2 type hybrid vehicle

Abstract

The application provides a P2 type hybrid vehicle driving charging efficiency optimal control method, aiming at solving the problem that the P2 configuration cannot guarantee the optimal charging efficiency in the driving charging mode in the actual situation, and the control method comprises the following steps: S1, discrete engine torque and speed; S2, establishing a power distribution mode; S3, determining an optimization function with the optimal charging efficiency as the target; and S4, extracting a driving charging instantaneous efficiency optimal curve. The input variables of the control method only include the current driving demand power, the battery power state and the power assembly universal characteristic, and do not need the input of the prior working condition, thereby breaking through the traditional engine optimal control method, and the development of the above driving charging efficiency optimal control method is the key to improving the fuel economy and energy utilization efficiency of the P2 configuration hybrid vehicle.

Description

Technical Field

[0001] This invention relates to the field of hybrid vehicle control, and specifically to a control method for optimizing the charging efficiency of P2 type hybrid vehicles. Background Technology

[0002] With an increasing number of hybrid vehicles entering the market, hybrid vehicles offer greater adaptability to various operating conditions compared to traditional gasoline vehicles due to their diverse operating modes. Among the various hybrid configurations, the P2 configuration has become the mainstream structure in the market and industry today due to its advantages such as simple vehicle topology, short cost cycle, and relatively mature technology. Typical P2 hybrid vehicles include four driving modes: pure electric drive, engine direct drive, charging while driving, and combined drive. The switching between these four modes depends on the current vehicle status. The traditional control strategy adopts the idea of ​​optimizing engine efficiency, keeping the engine operating point as close to the optimal curve as possible, regardless of changes in external operating conditions, with other auxiliary power sources such as the electric motor playing a dynamic adjustment role. Therefore, without considering factors such as the battery, when the vehicle's power demand is above the optimal curve, the operation switches to combined drive mode; when the vehicle's power demand is below the optimal curve, the operation switches to charging while driving. While such a control strategy can ensure optimal engine efficiency, the overall energy utilization efficiency of the vehicle may actually decrease due to the secondary conversion of electrical energy during charging. Therefore, research on the optimal charging efficiency of P2 hybrid vehicles can effectively ensure the highest overall energy utilization rate of the vehicle, thereby improving the overall vehicle economy and fully leveraging the advantages of multiple operating modes.

[0003] In current existing technologies, such as the invention patent published on January 15, 2021 (Publication No.: CN112224210A), "Dynamic Adjustment Method for Driving Charging Power of Planetary Hybrid Vehicle and Vehicle," this invention patent provides a solution for adjusting the driving charging power of planetary hybrid vehicles. However, due to the significant differences between different hybrid system configurations, and because this method is based on the control concept of keeping the battery state constant, it cannot guarantee the best energy utilization effect of the entire vehicle. Therefore, it is not applicable to the problem of optimal driving charging efficiency for P2 configurations. Another example is the invention patent published on April 29, 2015 (Publication No.: CN104578267A), "A Driving Charging System for Pure Electric Vehicles." This invention patent's charging system only addresses the situation of pure electric vehicles charging while parked, not the driving charging mode. Furthermore, the innovation of this invention mainly includes hardware facilities such as charging equipment and charging lines, but does not include software aspects such as control algorithms. None of the above solutions propose a detailed control method for optimal driving charging efficiency for P2 configurations. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention presents a control method for optimizing the charging efficiency of P2 hybrid vehicles while in operation. This method achieves the best overall energy utilization of the vehicle during driving and charging, thus breaking through the traditional engine-optimal control concept and reducing losses caused by secondary energy conversion. This method does not require solving for the required power under specific operating conditions. Instead, it finds the operating point by traversing the universal characteristic diagram of the power source. The resulting optimal charging efficiency curve map covers a wide range, ensuring the highest energy utilization efficiency of the entire vehicle. It fully leverages the multi-operating mode characteristics of the P2 configuration and meets users' needs for driving economy.

[0005] To achieve the above objectives, the present invention employs the following technical solution.

[0006] Step 1: Discretize engine torque and speed.

[0007] The P2 hybrid vehicle operates in driving-charging mode, where the driver's required torque deviates from the engine's optimal torque curve and the engine's actual output torque T. eng It is divided into two parts. The part used to drive the entire vehicle is denoted as the driving torque demand T. drive The other part used to power the generator is denoted as the motor's required torque T. isg The P2 hybrid vehicle completes power coupling before the transmission, disregarding the influence of the transmission ratio, and sets the engine speed N. eng At the lowest stable speed N min With the highest speed N max The intervals are discretely spaced at equal intervals, and the engine torque T is... eng At minimum torque T eng_min With maximum torque T eng_max By discretizing the components at equal intervals, the engine speed sequence N is obtained. eng As shown in equation (1), the torque sequence T eng As shown in equation (2):

[0008] (1)

[0009] (2)

[0010] In the formula, dN and dT represent the engine speed deviation distance and torque deviation distance, respectively.

[0011] Step 2: Establish a power distribution method.

[0012] With the peak torque T of the drive motor isg _ maxAs a reference value, the power distribution coefficient δ ranges from 0 to 1, and is discretized into 100 parts at equal intervals with a step size of 0.01. The motor torque is then discretized using the power distribution coefficient δ to obtain the motor torque sequence T. isg As shown in equation (3), the engine torque sequence T eng With motor torque sequence T isg The difference is the torque sequence T required by the driver. drive As shown in equation (4), to prevent the power source from overloading, the method limits the torque of the power source, as shown in equation (5).

[0013] (3)

[0014] (4)

[0015] (5)

[0016] Traversing the actual engine torque T eng Engine speed n e By looking up the engine universal characteristic map, the fuel consumption rate b at the current operating point can be obtained. e Iterate through the torque T generated by the drive motor isg Drive motor speed n m By consulting the motor efficiency characteristic map, the current operating point's motor generation efficiency η can be obtained. motor ,

[0017] Step 3: Determine the optimization function with the objective of achieving the optimal charging efficiency.

[0018] The fuel consumption b at different operating points is obtained through step two. e and motor efficiency η motor According to equation (6), the fuel consumption energy Q of the engine is calculated. eng Energy generated by the motor Q isg Total driving energy demand Q drive In the formula, q represents the calorific value of the fuel oil, in MJ / kg.

[0019] (6)

[0020] The objective function of the method is to maximize the instantaneous charging efficiency, that is, to maximize the utilization of energy used for charging. The charging efficiency η is calculated according to equation (7). charge

[0021] (7)

[0022] Step 4: Extract the optimal instantaneous charging efficiency curve.

[0023] Through computer programming, all operating points are traversed, the power distribution coefficient δ is iterated, and the instantaneous charging efficiency η at each operating point is recorded. charge And record the power distribution coefficient δ that optimizes charging efficiency. opt Plot the optimal power distribution coefficient δ at each engine speed and torque in a three-dimensional coordinate system. opt The x-axis and y-axis correspond to engine torque and speed, respectively, and the z-axis is the power distribution coefficient. The projection of the image onto the xy-plane is the map of optimal instantaneous charging efficiency while driving. Connect the power distribution coefficient δ in the map. opt At the boundary point near 0, after smoothing, the optimal curve for instantaneous charging efficiency is extracted.

[0024] Compared with the prior art, the beneficial effects of this invention are as follows:

[0025] 1. The optimal control method for charging efficiency of P2 hybrid vehicles described in this invention breaks through the traditional control idea based on engine efficiency optimization, reduces energy loss caused by secondary conversion of electrical energy, and for any operating point, on the basis of meeting the power requirements of the whole vehicle, the excess torque is distributed to the motor for power generation by establishing the concept of power distribution coefficient, thereby maximizing energy utilization and improving the overall energy utilization efficiency of the whole vehicle.

[0026] 2. The optimal control method for charging efficiency of P2 hybrid vehicles described in this invention obtains the operating point and power at different times by first discretizing the engine speed and torque, and then performing a traversal solution. It does not require the traditional method of solving the required power through longitudinal dynamics based on experiments and operating conditions, and does not consider the influence of factors such as gearbox gear. This method can ensure the accuracy and breadth of the operating point coverage, save a lot of time and computational costs, and improve the portability of the algorithm. For other hybrid vehicles with different configurations, only the initial data such as the external characteristics of the power source and the vehicle parameters need to be modified to obtain a new optimal efficiency curve, further exploring the energy-saving potential of hybrid vehicles. Attached Figure Description

[0027] The following description of the embodiments, taken in conjunction with the accompanying drawings, will make the embodiments readily understood, wherein:

[0028] Figure 1 This is a flowchart illustrating the optimal control process for charging efficiency of a P2 hybrid vehicle according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the P2 type hybrid vehicle system structure according to an embodiment of the present invention; Detailed Implementation

[0030] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] The following description, with reference to the accompanying drawings, outlines a method for optimal control of charging efficiency during driving in P2 hybrid vehicles; however, the invention is not limited to these embodiments.

[0032] Reference Appendix Figure 1 The implementation of this invention patent includes the following four steps.

[0033] Step 1: Discretize engine torque and speed.

[0034] The P2 hybrid vehicle operates in driving-charging mode, where the driver's required torque deviates from the engine's optimal torque curve and the engine's actual output torque T. eng It is divided into two parts. The part used to drive the entire vehicle is denoted as the driving torque demand T. drive The other part used to power the generator is denoted as the motor's required torque T. isg See attached document Figure 2 The control method described above describes a P2 hybrid vehicle where power coupling is completed before the transmission, without considering the influence of the transmission ratio, and the engine speed N is set to... eng At the lowest stable speed N min With the highest speed N max The intervals are discretely spaced at equal intervals, and the engine torque T is... eng At minimum torque T eng_min With maximum torque T eng_max By discretizing the components at equal intervals, the engine speed sequence N is obtained. eng As shown in equation (1), the torque sequence T eng As shown in equation (2):

[0035] (1)

[0036] (2)

[0037] In the formula, dN and dT represent the engine speed deviation distance and torque deviation distance, respectively.

[0038] Step 2: Establish a power distribution method.

[0039] With the peak torque T of the drive motor isg _ maxAs a reference value, the power distribution coefficient δ ranges from 0 to 1, and is discretized into 100 parts at equal intervals with a step size of 0.01. The motor torque is then discretized using the power distribution coefficient δ to obtain the motor torque sequence T. isg As shown in equation (3), the engine torque sequence T eng With motor torque sequence T isg The difference is the torque sequence T required by the driver. drive As shown in equation (4), to prevent the power source from overloading, the method limits the torque of the power source, as shown in equation (5).

[0040] (3)

[0041] (4)

[0042] (5)

[0043] Traversing the actual engine torque T eng Engine speed n e By looking up the engine universal characteristic map, the fuel consumption rate b at the current operating point can be obtained. e Iterate through the torque T generated by the drive motor isg Drive motor speed n m By consulting the motor efficiency characteristic map, the current operating point's motor generation efficiency η can be obtained. motor ,

[0044] Step 3: Determine the optimization function with the objective of achieving the optimal charging efficiency.

[0045] The fuel consumption b at different operating points is obtained through step two. e and motor efficiency η motor According to equation (6), the fuel consumption energy Q of the engine is calculated. eng Energy generated by the motor Q isg Total driving energy demand Q drive In the formula, q represents the calorific value of the fuel oil, in MJ / kg.

[0046] (6)

[0047] The objective function of the method is to maximize the instantaneous charging efficiency, that is, to maximize the utilization of energy used for charging. The charging efficiency η is calculated according to equation (7). charge

[0048] (7)

[0049] Step 4: Extract the optimal instantaneous charging efficiency curve.

[0050] Through computer programming, all operating points are traversed, the power distribution coefficient δ is iterated, and the instantaneous charging efficiency η at each operating point is recorded. charge And record the power distribution coefficient δ that optimizes charging efficiency. opt Plot the optimal power distribution coefficient δ at each engine speed and torque in a three-dimensional coordinate system. opt The x-axis and y-axis correspond to engine torque and speed, respectively, and the z-axis is the power distribution coefficient. The projection of the image onto the xy-plane is the map of optimal instantaneous charging efficiency while driving. Connect the power distribution coefficient δ in the map. opt At the boundary point near 0, after smoothing, the optimal curve for instantaneous charging efficiency is extracted.

Claims

1. A method for optimal control of charging efficiency during driving of P2 hybrid vehicles, characterized in that... Includes the following steps: Step 1: Discretize engine torque and speed. The P2 hybrid vehicle operates in driving-charging mode, where the driver's torque demand deviates from the engine's optimal torque curve, and the engine's actual output torque T... eng It is divided into two parts. The part used to drive the entire vehicle is denoted as the driving torque demand T. drive The other part used to power the generator is denoted as the motor's required torque T. isg The P2 hybrid vehicle completes power coupling before the transmission, disregarding the influence of the transmission ratio, and sets the engine speed N. eng At the lowest stable speed N min With the highest speed N max The intervals are discretely spaced at equal intervals, and the engine torque T is... eng At minimum torque T eng_min With maximum torque T eng_max By discretizing the components at equal intervals, the engine speed sequence N is obtained. eng As shown in equation (1), the torque sequence T eng As shown in equation (2): N eng =[N eng_min :dN:N eng_max ] (1) T drive =[T eng_min :dT:T eng_max ] (2) In the formula, dN and dT represent the engine speed deviation distance and torque deviation distance, respectively. Step 2: Establish a power distribution method. With the peak torque T of the drive motor isg _ max As a reference value, the power distribution coefficient δ ranges from 0 to 1, and is discretized into 100 parts at equal intervals with a step size of 0.

01. The motor torque is then discretized using the power distribution coefficient δ to obtain the motor torque sequence T. isg As shown in equation (3), the engine torque sequence T eng With motor torque sequence T isg The difference is the torque sequence T required by the driver. drive As shown in equation (4), to prevent the power source from overloading, the method limits the torque of the power source, as shown in equation (5). T isg =T isg_max ·δ (3) T drive =T eng -T isg (4) Traversing the actual engine torque T eng Engine speed n e By looking up the engine universal characteristic map, the fuel consumption rate b at the current operating point can be obtained. e traverse the driving motor's generating torque T isg Drive motor speed n m By consulting the motor efficiency characteristic map, the current operating point's motor generation efficiency η can be obtained. motor , Step 3: Determine the optimization function with the objective of achieving the optimal charging efficiency. The fuel consumption b at different operating points is obtained through step two. e and motor efficiency η motor According to equation (6), the fuel consumption energy Q of the engine is calculated. eng Energy generated by the motor Q isg Total driving energy demand Q drive In the formula, q represents the calorific value of the fuel oil, in MJ / kg. The objective function of the method is to maximize the instantaneous charging efficiency, that is, to maximize the utilization of energy used for charging. The charging efficiency η is calculated according to equation (7). charge Step 4: Extract the optimal instantaneous charging efficiency curve. Through computer programming, all operating points are traversed, the power distribution coefficient δ is iterated, and the instantaneous charging efficiency η at each operating point is recorded. charge And record the power distribution coefficient δ that optimizes charging efficiency. opt Plot the optimal power distribution coefficient δ at each engine speed and torque in a three-dimensional coordinate system. opt The x-axis and y-axis correspond to engine torque and speed, respectively, and the z-axis is the power distribution coefficient. The projection of the image onto the xy-plane is the map of optimal instantaneous charging efficiency while driving. Connect the power distribution coefficient δ in the map. opt At the boundary point near 0, after smoothing, the optimal curve for instantaneous charging efficiency is extracted.

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