CN109910867B - Engine working point optimization method of series-parallel hybrid vehicle - Google Patents

Abstract

The invention discloses a method for optimizing the working point of an engine of a series-parallel hybrid vehicle, which comprises the following steps: step 1, collecting an engine rotating speed parameter and a motor torque parameter; step 2, under the condition that the engine rotating speed parameter is not changed, the corresponding engine oil consumption and the corresponding ISG motor power consumption are calculated by changing the magnitude of the motor torque parameter; step 3, under the condition that the torque parameter of the motor is not changed, calculating the corresponding oil consumption of each engine and the electricity consumption of the ISG motor by changing the rotating speed parameter of the engine; step 4, obtaining transverse comparison data; step 5, longitudinal comparison data are obtained; and 6, determining an optimal working point for starting the engine and an optimal charging working point under the engine series working mode according to the transverse comparison data obtained in the step 4 and the longitudinal comparison data obtained in the step 5. The method has the advantages of simple rule, comprehensive search range and wide applicability, and can be suitable for optimizing energy management strategies such as series-parallel hybrid power and series hybrid power.

Description

Engine working point optimization method of series-parallel hybrid vehicle

Technical Field

The invention relates to the technical field of vehicle engines, in particular to an engine working point optimization method of a series-parallel hybrid vehicle.

Background

The series-parallel hybrid power system has better dynamic property and fuel economy, integrates the advantages of a series hybrid power vehicle and a parallel hybrid power vehicle, is developed and popularized more quickly, and is particularly widely applied to the field of motor buses. At present, most of the series-parallel connection type structures in China adopt a single-shaft or multi-shaft series-parallel connection type system, namely, an engine is connected with an ISG motor and then is connected with a driving motor and an energy source through a clutch device.

In the starting process of the engine, different from the traditional starting method, the torque control of the ISG motor is adopted to drive the starting process of the engine. In the working process of a hybrid vehicle, particularly in the working process of a hybrid vehicle, in order to ensure the fuel economy, an engine can be started and stopped frequently according to an energy management strategy, and a certain degree of energy waste can be caused in the process. Similarly, in the area of series operation, because the process from fuel to power generation exists, the working efficiency and the setting of the power generation working point greatly affect the fuel economy of the whole process, and therefore, how to measure the quality of one series power generation working point also becomes an important problem.

At present, most of solutions to the two problems are determined by a comparison method of working condition circulation and actual road tests, and the method is not only inaccurate, but also consumes time and energy.

Disclosure of Invention

It is an object of the present invention to provide a method for optimizing the engine operating point of a series-parallel hybrid vehicle which overcomes or at least alleviates at least one of the above-mentioned drawbacks of the prior art.

In order to achieve the above object, the present invention provides a method for optimizing an engine operating point of a series-parallel hybrid vehicle, including:

step 1, collecting an engine rotating speed parameter and a motor torque parameter;

step 2, under the condition that the engine rotating speed parameters are not changed, the engine oil consumption and the ISG motor power consumption corresponding to the motor torque parameters and the unchanged engine rotating speed parameters are calculated by changing the sizes of the motor torque parameters;

step 3, under the condition that the motor torque parameter is not changed, calculating the oil consumption of each engine and the electricity consumption of the ISG motor corresponding to each engine rotating speed parameter and the unchanged motor torque parameter by changing the size of the engine rotating speed parameter;

step 4, obtaining transverse comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

step 5, obtaining longitudinal comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and 6, determining an optimal working point for starting the engine and an optimal charging working point under the engine series working mode according to the transverse comparison data obtained in the step 4 and the longitudinal comparison data obtained in the step 5.

Further, in step 1, the engine speed parameter includes an unloading speed, and the motor torque parameter includes a motor starting torque;

the step 4 specifically includes:

step 41, calculating the starting weight of each motor torque corresponding to each motor starting torque and the unchanged unloading rotating speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

step 42, taking the motor starting torque corresponding to the minimum value in the motor torque starting weights calculated in the step 41 as an optimal motor starting torque, wherein the optimal motor starting torque is the transverse comparison data;

the step 5 specifically includes:

step 51, calculating the unloading rotation speed starting weight corresponding to the unloading rotation speed and the unchanged motor starting torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and step 52, taking the unloading rotating speed corresponding to the minimum value in the unloading rotating speed starting weights calculated in the step 51 as an optimal unloading rotating speed, wherein the optimal unloading rotating speed is the longitudinal comparison data.

Further, the calculation formula of "calculating each motor torque start weight corresponding to each motor start torque and the unchanged unloaded rotation speed" in step 41 and/or "calculating each unloaded rotation speed start weight corresponding to each unloaded rotation speed and the unchanged motor start torque" in step 51 is as follows (1):

H＝(αf_c+βp_c)(1+γt+τn_a) (1)

in the formula (1), α, β, γ and τ are all weight coefficients, f_cFor engine start-up fuel consumption, p_cFor starting ISG motorElectric quantity, t is engine starting time, n_aThe rotational speed is overshot.

Further, the step 6 specifically includes:

step 61, obtaining the minimum value C in the motor torque starting weight value obtained in the step 42_αAnd the minimum value L in each unloading rotating speed starting weight value obtained in the step 52_αIf the following formula (2) is satisfied, the formula (1) is used to calculate the starting weight M corresponding to the optimal motor starting torque a 'obtained in the step 42 and the optimal unloading rotation speed B' obtained in the step 52, and then C_α、L_αAnd minimum value min (C) of M_a,L_aM) the corresponding motor starting torque and unloading rotating speed are the optimal working points for starting the engine;

|C_a-L_a|≤Δ (2)

step 62, obtaining the minimum value C in the motor torque starting weight value obtained in the step 42_αAnd the minimum value L in each unloading rotating speed starting weight value obtained in the step 52_αIn the case where the following expression (3) is satisfied, the following two cases are included:

the first case: if C_aLess than L_αIf yes, the optimal motor starting torque a' obtained in step 42 is the motor starting torque in the optimal operating point for starting the engine; repeating the step 5 on the premise that the optimal motor starting torque A' is not changed, and performing longitudinal search by changing the unloading rotating speed to obtain the optimal unloading rotating speed serving as the unloading rotating speed in the optimal working point for starting the engine;

the second case: if C_aGreater than L_αIf yes, the optimal unloading rotation speed B' obtained in step 52 is the unloading rotation speed in the optimal working point for starting the engine; on the premise that the optimal unloading rotating speed B' is not changed, repeating the step 4, and performing transverse search by changing the motor starting torque to obtain the optimal motor starting torque as the motor starting torque in the optimal working point for starting the engine;

|C_a-L_a|＞Δ (3)

the numerical value of Delta in the formulae (2) and (3) is represented by C_αAnd L_αAnd (4) determining.

Further, Δ in the formula (2) and the formula (3) satisfies:

Δ＝5％·min(C_a,L_a) Wherein: min (C)_a,L_a) Is C_αAnd L_αMinimum value of (1).

Further, in the step 1, the engine speed parameter includes a power generation speed, and the motor torque parameter includes a power generation torque;

the step 4 specifically includes:

step 41, calculating each oil-electricity ratio corresponding to each power generation rotation speed and the unchanged power generation torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

step 42, setting the power generation rotation speed corresponding to the minimum value in the oil-to-electricity ratios calculated in the step 41 as an optimal power generation rotation speed, wherein the optimal power generation rotation speed is the transverse comparison data;

the step 5 specifically includes:

step 51, calculating each oil-electricity ratio corresponding to each power generation torque and the unchanged power generation rotating speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and a step 52 of setting, as an optimal power generation torque, the power generation torque corresponding to the minimum value of the oil-to-electricity ratios calculated in the step 51, the optimal power generation torque being the vertical comparison data.

Further, the calculation formula of "calculating each of the oil-to-electricity ratios corresponding to each of the power generation torques and the unchanged power generation rotational speed" in step 41 and/or "calculating each of the oil-to-electricity ratios corresponding to each of the power generation rotational speeds and the unchanged power generation torques" in step 51 is the following formula (5):

in the formula (5), f_cIs at the time of fixationConsumption of engine oil, p, during period t_cThe generated energy of the ISG motor in a fixed time period t.

Further, the step 6 specifically includes:

step 61, obtaining the minimum value eta of the oil-electricity ratio values obtained in the step 42_nAnd the minimum value eta of the oil-electricity ratio values obtained in the step 52_TWhen the following expression (6) is satisfied, the optimum power generation torque T obtained in step 42 is calculated by expression (5)_g' and the optimum power generation rotation speed n obtained in the step 52_e' corresponding oil-to-electricity ratio eta, minimum eta in each oil-to-electricity ratio_nMinimum value eta of each oil-electricity ratio_TMinimum value min (η) of and η_n,η_TEta) the corresponding generating torque and generating speed are the optimal charging working points in the engine series working mode;

|η_n-η_T|≤Δ (6)

step 62, minimum value eta in each oil-electricity ratio_nAnd the minimum value eta of each oil-electricity ratio_TIn the case where the following expression (7) is satisfied, the following two cases are included:

the first case: if eta_nLess than η_TThen, the optimum generating torque T obtained in said step 42 is obtained_g' is the generated torque in the optimal charging operating point in the engine series operating mode; then the optimal power generation torque T is obtained_gOn the premise of no change, repeating the step 5, and performing longitudinal search by changing the power generation rotating speed to obtain the optimal power generation rotating speed as the power generation rotating speed in the optimal charging operating point in the engine series operating mode;

the second case: if eta_nGreater than η_TThen the optimum power generation rotation speed n obtained in the step 52_e' is the power generation rotating speed in the optimal charging working point in the engine series working mode; on the premise that the optimal power generation rotating speed is not changed, repeating the step 4, and performing transverse search by changing the power generation torque to obtain the optimal power generation torque as the power generation torque in the optimal charging working point under the engine serial working mode;

|η_n-η_T|＞Δ (7)

the numerical value of Δ in the formulae (6) and (7) is represented by η_nAnd η_TAnd (4) determining.

Further, Δ in the formula (6) and the formula (7) satisfies:

Δ＝5％·min(η_n,η_T) Wherein: min (. eta.)_n,η_T) Is eta_nAnd η_TMinimum value of (1).

Further, in the step 1, the engine rotation speed parameter further includes a power generation rotation speed, and the motor torque parameter further includes a power generation torque;

in step 2, the engine rotation speed parameter further comprises the power generation rotation speed, and the motor torque parameter further comprises the power generation torque;

the step 4 specifically includes:

step 41, calculating each oil-electricity ratio corresponding to each power generation torque and the unchanged power generation rotation speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

a step 42 of setting, as an optimal power generation torque, the power generation torque corresponding to the minimum value of the oil-to-electricity ratios calculated in the step 41, the optimal power generation torque being the lateral comparison data;

the step 5 specifically includes:

step 51, calculating each oil-electricity ratio corresponding to each power generation rotation speed and the unchanged power generation torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

step 52, taking the power generation rotation speed corresponding to the minimum value in the oil-to-electricity ratios calculated in the step 51 as an optimal power generation rotation speed, wherein the optimal power generation rotation speed is the longitudinal comparison data;

the step 6 specifically includes:

step 61, obtaining the minimum value eta of the oil-electricity ratio values obtained in the step 42_nAnd the minimum value eta of the oil-electricity ratio values obtained in the step 52_TIn the case where the following formula (6) is satisfied, the step is calculated by the formula (5)42 the optimum power generation torque T_g' and the optimum power generation rotation speed n obtained in the step 52_e' corresponding oil-to-electricity ratio eta, minimum eta in each oil-to-electricity ratio_nMinimum value eta of each oil-electricity ratio_TMinimum value min (η) of and η_n,η_TEta) the corresponding generating torque and generating speed are the optimal charging working points in the engine series working mode;

|η_n-η_T|≤Δ (6)

step 62, minimum value eta in each oil-electricity ratio_nAnd the minimum value eta of each oil-electricity ratio_TIn the case where the following expression (7) is satisfied, the following two cases are included:

the first case: if eta_nLess than η_TThen, the optimum generating torque T obtained in said step 42 is obtained_g' is the generated torque in the optimal charging operating point in the engine series operating mode; then the optimal power generation torque T is obtained_gOn the premise of no change, repeating the step 5, and performing longitudinal search by changing the power generation rotating speed to obtain the optimal power generation rotating speed as the power generation rotating speed in the optimal charging operating point in the engine series operating mode;

the second case: if eta_nGreater than η_TThen the optimum power generation rotation speed n obtained in the step 52_e' is the power generation rotating speed in the optimal charging working point in the engine series working mode; on the premise that the optimal power generation rotating speed is not changed, repeating the step 4, and performing transverse search by changing the power generation torque to obtain the optimal power generation torque as the power generation torque in the optimal charging working point under the engine serial working mode;

|η_n-η_T|＞Δ (7)

the numerical value of Δ in the formulae (6) and (7) is represented by η_nAnd η_TAnd (4) determining.

The method has the advantages of simple rule, comprehensive search range and wide applicability, and can be suitable for optimizing energy management strategies such as series-parallel hybrid power and series hybrid power.

Drawings

FIG. 1 is a speed schematic for an engine start process provided by the present invention.

FIG. 2 is a speed schematic of the engine entering a series operating mode.

FIG. 3 is a method diagram of the present invention relating to engine start operating point optimization.

FIG. 4 is a method diagram of the present invention relating to engine series operating point optimization.

FIG. 5a is a graph of instantaneous fuel consumption during start-up as a function of time with the abscissa representing time (unit 10)^-4s), the ordinate represents the instantaneous fuel consumption (in L/h);

FIG. 5b is a graph showing the variation of instantaneous power consumption with time during startup, with the abscissa representing time (unit is 10)^-4s), the ordinate represents the instantaneous fuel consumption (in W · s);

FIG. 6a is a graph showing the fuel consumption during power generation in the series operating mode as a function of time, with the abscissa representing time (unit 10)^-4s), the ordinate represents the instantaneous fuel consumption (in L/h);

FIG. 6b is a graph showing the change of electricity consumption with time during power generation in the series operating mode, with the abscissa representing time (unit is 10)^-4s), the ordinate represents the instantaneous fuel consumption (in W · s).

Detailed Description

In the drawings, the same or similar reference numerals are used to denote the same or similar elements or elements having the same or similar functions. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In the description of the present invention, the terms "central", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be construed as limiting the scope of the present invention.

The method for optimizing the engine operating point of the series-parallel hybrid vehicle provided by the embodiment comprises the following steps:

step 1, collecting an engine rotating speed parameter and a motor torque parameter;

step 2, under the condition that the engine rotating speed parameters are not changed, the engine oil consumption and the ISG motor power consumption corresponding to the motor torque parameters and the unchanged engine rotating speed parameters are calculated by changing the sizes of the motor torque parameters;

step 3, under the condition that the motor torque parameter is not changed, calculating the oil consumption of each engine and the electricity consumption of the ISG motor corresponding to each engine rotating speed parameter and the unchanged motor torque parameter by changing the size of the engine rotating speed parameter;

step 4, obtaining transverse comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

step 5, obtaining longitudinal comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and 6, determining an optimal working point for starting the engine and an optimal charging working point under the engine series working mode according to the transverse comparison data obtained in the step 4 and the longitudinal comparison data obtained in the step 5.

The method for optimizing the working point of the engine of the series-parallel hybrid vehicle is suitable for a single-shaft or multi-shaft series-parallel hybrid vehicle (a series hybrid is also suitable), and can be used for measuring the optimal working point of the engine during starting and the optimal charging working point of a series working mode. The specific measurement method is described below for different conditions.

First, a method for determining an optimal engine start operating point in an engine start phase (as shown in fig. 3) will be described, the method including:

in step 1, according to the dynamic parameters of the engine, such as the torque of the friction motor and the like and debugging experience, the initial value A of the starting torque of the motor (the motor is in a torque control mode) required by starting is preliminarily calculated, and after the torque of the motor is applied, the rotating speed of the engine is controlledWhen the value reaches the initial value B of the rotating speed, the starting torque of the motor is removed to obtain engine parameters in the whole starting process, wherein the engine parameters comprise the starting time t of the engine and the starting oil consumption f of the engine_cAnd ISG motor starting power consumption p_cAnd overshooting of speed n_a. The engine parameter obtaining method comprises the following steps:

as shown in fig. 1, the engine start time t is obtained by: the engine start time t is set from the engine start time t₀Until the engine speed stabilizes at time t₂The specific value of the engine start time t can be read by an engine message. Wherein: engine speed stabilization time t₂Refers to the moment t when the engine speed is basically stable₁And then, after a plurality of continuous periods (for example, 5 periods), the engine speed is stabilized at the moment that the fluctuation amplitude (the fluctuation amplitude can be set to 3r/min or 5r/min, for example) of the idle speed value is stabilized. Fuel consumption f for starting engine_cThe method of obtaining (1), comprising: calculating the oil consumption value of the instantaneous oil consumption value within the engine starting time t by utilizing an integral method according to the instantaneous oil consumption value read by the engine message within the engine starting time t, namely the engine starting oil consumption f_c. About ISG motor starting power consumption p_cThe method of obtaining (1), comprising: according to the ISG motor torque (hereinafter, both referred to as the motor torque) and the engine speed read by the ISG motor message, the power consumption value within the engine starting time t is obtained, namely the ISG motor starting power consumption p_c. About overshooting speed n_aThe obtained mode is a rotation speed difference from the maximum rotation speed point to the idle speed value.

In step 1, the engine speed parameter includes an unloaded speed (collectively referred to as "unloaded engine speed"), and the motor torque parameter includes a motor start torque (collectively referred to as "motor start torque of the ISG motor").

In step 2, the engine rotation speed parameter further includes the unloading rotation speed, and the motor torque parameter further includes the motor starting torque.

In step 2, "under the condition that the engine speed parameter is not changed, by changing the magnitude of the motor torque parameter" specifically means by changing a motor starting torque value. That is, only the motor startup torque value is changed on the basis of the unload rotation speed value B. For example: on the basis of the initial value A of the motor starting torque, a is changed up and down respectively, and the obtained motor starting torque can be A + a, A-a, A +2a, A-2a and the like. The temperature of the engine is approximately guaranteed to be kept at a certain value during each starting experiment of changing parameters.

In step 2, "calculating the engine oil consumption and the ISG motor power consumption corresponding to each of the motor torque parameters and the unchanged engine speed parameter" specifically means that under the condition that the unloading speed value and the motor starting torque are determined, the corresponding engine oil consumption and the corresponding ISG motor power consumption are calculated by using a known method. For example: the required quantities for this embodiment include: the unloading method comprises the steps that the motor starting torque is A, the unloading rotating speed value is B, corresponding engine oil consumption and ISG motor power consumption, the unloading rotating speed value is B, corresponding motor starting torque is A + a, corresponding engine oil consumption and ISG motor power consumption, unloading rotating speed value is B, corresponding motor starting torque is A-a, corresponding engine oil consumption and ISG motor power consumption, unloading rotating speed value is B, corresponding motor starting torque is A +2a, corresponding engine oil consumption and ISG motor power consumption, and unloading rotating speed value is B, corresponding motor starting torque is A-2a, corresponding engine oil consumption and ISG motor power consumption and the like.

In step 4, the step of obtaining transverse comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 2 specifically comprises the following steps:

as shown in fig. 3, a specific implementation of S13 is described below by way of a specific embodiment, see the two left columns of fig. 3. And step 41, calculating the starting weight of each motor torque corresponding to each motor starting torque and the unchanged unloading rotating speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 2. That is, based on the changed values of the motor start torques, the motor torque start weight C corresponding to the motor start torque values is calculated by the formula (1)_iN, n is large 1A natural number at 5. Taking n as 5 as an example: initial motor torque starting weight C corresponding to initial motor starting torque value A₁The first motor torque starting weight C corresponding to the first motor starting torque value A + a₂The second motor torque starting weight C corresponding to the second motor starting torque value A-a₃The third motor torque starting weight C corresponding to the third motor starting torque value A +2a₄The fourth motor torque starting weight C corresponding to the fourth motor starting torque value A-2a₅。

H＝(αf_c+βp_c)(1+γt+τn_a) (1)

In the formula (1), α, β, γ, and τ are all weight coefficients. Wherein: alpha and beta are main factors for measuring the cost value of the starting process, the two factors are the multiple relation between the alpha and the beta determined according to the equivalent oil quantity value of consumed unit electric quantity, generally, the alpha can be 1, the beta is about 3, and the calculation is needed according to the use characteristic of the engine. γ and τ are small, both secondary factors, and both are less than 1. If the engine is started for a time t and the speed n is overshot_aThe influence is small, namely the values of gamma and tau are smaller than the set threshold value and can be ignored.

And 42, taking the motor starting torque corresponding to the minimum value in the motor torque starting weights calculated in the step 41 as an optimal motor starting torque, wherein the optimal motor starting torque is the transverse comparison data. The minimum value of the torque starting weight values of the motors is represented as C_α＝min(C₁,C₂,...,C_n) At this time, C_αThe corresponding motor starting torque a' is taken as an optimal motor starting torque, which is the lateral comparison data. The unloading speed value is still B.

In step 3, "under the condition that the motor torque parameter is not changed, the change of the engine speed parameter" specifically means: on the basis of the initial value A of the starting torque of the motor, only the rotating speed value of the unloading engine is changed. For example: on the basis of the initial value B of the engine speed, a is changed up and down respectively, and the obtained unloaded engine speed can be B + a, B-a, B +2a, B-2a and the like. The temperature of the engine is approximately guaranteed to be kept at a certain value during each starting experiment of changing parameters.

In step 3, "calculating the engine oil consumption and the ISG motor power consumption corresponding to each engine speed parameter and the unchanged motor torque parameter" specifically means that under the condition that the unloading speed value and the motor starting torque are determined, the corresponding engine oil consumption and the corresponding ISG motor power consumption are calculated by using a known method. For example: the required quantities for this embodiment include: the method comprises the steps that the starting torque of a motor is A, the unloading rotating speed value is B and corresponds to engine oil consumption and ISG motor power consumption, the starting torque of the motor is A, the unloading rotating speed value is B + a and corresponds to engine oil consumption and ISG motor power consumption, the starting torque of the motor is A, the unloading rotating speed value is B-a and corresponds to engine oil consumption and ISG motor power consumption, the starting torque of the motor is A, the unloading rotating speed value is B +2a and corresponds to engine oil consumption and ISG motor power consumption, the starting torque of the motor is A, the unloading rotating speed value is B-2a and corresponds to engine oil consumption and ISG motor power consumption, and the like.

In the step 5, the step of obtaining longitudinal comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 3 specifically includes:

as shown in fig. 3, a specific implementation of S13 is described below by way of a specific embodiment, see the two columns on the right side of fig. 3. And step 51, calculating the unloading rotation speed starting weight corresponding to each unloading rotation speed and the unchanged motor starting torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 3. That is, according to each of the unloaded engine speed values obtained by the change, the unloaded engine speed start weight L corresponding to each of the unloaded engine speed values is calculated by using the formula (1)_iN is a natural number greater than 5. Taking n as 5 as an example: initial unloading rotating speed starting weight L corresponding to initial unloading engine rotating speed value B₁The first unloading engine speed value B + a corresponds to the first unloading engine speed starting weight L₂The second unloading rotating speed starting weight L corresponding to the second unloading engine rotating speed value B-a₃And a third unloaded engine speed starting weight L corresponding to the third unloaded engine speed value B +2a₄Fourth unloaded engine speed value B-2a pairThe corresponding fourth unloading rotation speed starting weight L₅。

And step 52, taking the unloading rotating speed corresponding to the minimum value in the unloading rotating speed starting weights calculated in the step 51 as an optimal unloading rotating speed, wherein the optimal unloading rotating speed is the longitudinal comparison data. The minimum value of the unloading rotation speed starting weight values is expressed as L_α＝min(L₁,L₂,...,L_n) At this time, L_αAnd taking the corresponding unloaded engine rotating speed B' as the optimal unloaded rotating speed for longitudinal comparison, wherein the optimal unloaded rotating speed is the longitudinal comparison data, and the starting torque of the motor is still A at the moment.

The step 6 specifically includes:

step 61, obtaining the minimum value C in the motor torque starting weight value obtained in the step 42_αAnd the minimum value L in each unloading rotating speed starting weight value obtained in the step 52_αIf the following formula (2) is satisfied, that is, if the two values are close to each other, the optimal motor starting torque a 'obtained in the step 42 and the starting weight M corresponding to the optimal unloading rotation speed B' obtained in the step 52 are calculated by using the formula (1), then C_α、L_αAnd minimum value min (C) of M_a,L_aM) the corresponding motor starting torque and unloading rotating speed are the optimal working points for starting the engine;

|C_a-L_a|≤Δ (2)

in the formula (2), Δ ═ 5% · min (C)_a,L_a) As a relatively close signature, wherein: min (C)_a,L_a) Is C_αAnd L_αMinimum value of (1).

Step 62, obtaining the minimum value C in the motor torque starting weight value obtained in the step 42_αAnd the minimum value L in each unloading rotating speed starting weight value obtained in the step 52_αIn the case where the following expression (3) is satisfied, that is, the two values are far apart, the following two cases are included:

the first case: if C_aLess than L_αThen the optimal motor starting torque A' obtained in step 42 is the optimal engine starting torqueStarting torque of the motor in the starting point; and repeating the step 5 on the premise that the optimal motor starting torque A' is not changed, and performing longitudinal search by changing the unloading rotating speed to obtain the optimal unloading rotating speed serving as the unloading rotating speed in the optimal working point for starting the engine.

The second case: if C_aGreater than L_αIf yes, the optimal unloading rotation speed B' obtained in step 52 is the unloading rotation speed in the optimal working point for starting the engine; on the premise that the optimal unloading rotating speed B' is not changed, repeating the step 4, and performing transverse search by changing the motor starting torque to obtain the optimal motor starting torque as the motor starting torque in the optimal working point for starting the engine;

|C_a-L_a|＞Δ (3)

in the formula (2), Δ ═ 5% · min (C)_a,L_a) As a relatively close signature, wherein: min (C)_a,L_a) Is C_αAnd L_αMinimum value of (1).

Next, a description will be given of a method (shown in fig. 4) of determining an optimal operating point for charging in the series engine operating mode, the method including:

according to the required power P in vehicle passing, wherein the required power P comprises dynamic required power and vehicle accessory power), selecting an economic area with lower fuel consumption rate in an engine Map characteristic diagram, and finding an operating point meeting the following formula (4):

in the formula (4), n_e(r/min) is an engine power generation rotation speed (hereinafter simply referred to as "power generation rotation speed"), T_g(N.m) is the ISG motor-corresponding generating torque (hereinafter simply referred to as "generating torque"), P_charge(kW) is the generated power to be stored in the energy storage element, and P (kW) is the power demanded by the vehicle.

As shown in FIG. 2, a fixed time t (e.g. a fixed time t) is taken during which the engine enters the operation of stable power generation from the start20s), from the Map of the engine, the range of the engine power generation rotation speed with high efficiency is determined as n_sTo n_lCorrespondingly, the range corresponding to the motor generating torque corresponding to each engine generating rotation speed operating point is T_gs(n)To T_gl(n)。

The method is determined by a mode of determining the starting working point of the engine, namely, the method of longitudinal comparison and transverse comparison are respectively adopted for searching, but the judgment index is changed, the generation rotating speed and the generation torque are respectively controlled to be unchanged by working within a fixed time t, and the other quantity is changed to obtain the fuel quantity f consumed within the fixed time t_c(L) the amount of electricity generated is p_c(kW · h), a concept of the fuel-electric ratio is expressed by formula (5), and the fuel-electric ratio η for generating 1kW · h of electric power per unit of the fuel-electric ratio is:

in the formula (5), f_cFor the consumption of engine oil, p, over a fixed period of time t_cThe generated energy of the ISG motor in a fixed time period t.

The smaller the fuel-to-electric ratio η, the more efficient and economical the conversion of oil to electricity.

In step 1, the engine rotation speed parameter includes a power generation rotation speed (collectively referred to as "engine power generation rotation speed"), and the motor torque parameter includes a power generation torque (collectively referred to as "ISG motor-corresponding power generation torque").

In step 2, the engine rotation speed parameter further includes the power generation rotation speed, and the motor torque parameter further includes the power generation torque.

In step 2, "under the condition that the engine speed parameter is not changed, the value of the motor torque parameter is changed" specifically means that the power generation speed value is n_eOn a constant basis, only the generating torque T is changed_g. For example: at the initial value T of the power generation torque_gOn the basis of the above formula, the upper part and the lower part are respectively changed by T, and the obtained starting power generation torque of the motor can be T_g+T、T_g-T、T_g+2T、T_g-2T, etc. The temperature of the engine is approximately guaranteed to be kept at a certain value during each starting experiment of changing parameters.

In step 2, "calculating the engine oil consumption and the ISG motor power consumption corresponding to each of the motor torque parameters and the unchanged engine speed parameter" specifically means that the engine oil consumption and the ISG motor power consumption are calculated by using a known method under the condition that the power generation speed value and the power generation torque are determined. For example: the required quantities for this embodiment include: generating speed n_eThe value of the generated torque is T_gCorresponding engine oil consumption, ISG motor power consumption and generating speed n_eThe value of the generated torque is T_g+ T corresponding engine oil consumption, ISG motor power consumption and generating speed n_eThe value of the generated torque is T_g-engine and ISG motor power consumption for T, generating speed n_eThe value of the generated torque is T_g+2T engine oil consumption and ISG motor power consumption, and generating speed n_eThe value of the generated torque is T_g-engine oil consumption and ISG motor power consumption for 2T.

In step 4, the step of obtaining transverse comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 2 specifically comprises the following steps:

as shown in fig. 4, a specific implementation of S13 is described below by way of a specific embodiment, see the two left columns of fig. 4. And step 41, calculating each oil-electricity ratio corresponding to each power generation rotating speed and the unchanged power generation torque according to each engine oil consumption and the ISG motor power consumption obtained in the step 2. That is, the oil-to-electric ratio η between the respective generated torque values and the constant generated rotation speed is calculated by the equation (5) for the respective generated torque values_TiN is a natural number greater than 5. Taking n as 5 as an example: initial value T of generating torque_gAnd an initial value n of the generating speed_eCorresponding initial oil-to-electric ratio eta_T1First value of generating torque T_g+ T and initial value n of generating speed_eCorresponding first oil-to-electric ratio eta_T2Second value of generated torque T_g-T and initial value n of the generator speed_eCorrespond toSecond oil-to-electric ratio η_T3Third value of generated torque T_g+2T and initial value n of generating speed_eCorresponding third oil-to-electric ratio eta_T4Fourth value of generated torque T_g-2T and initial value n of generating speed_eCorresponding fourth oil-to-electric ratio eta_T5。

And 42, setting the power generation rotation speed corresponding to the minimum value in the oil-to-electricity ratios calculated in the step 41 as an optimal power generation rotation speed, wherein the optimal power generation rotation speed is the transverse comparison data. "minimum value among the oil-to-electricity ratios" is expressed as η_n＝min(η_n1,η_n2,..,) at which the minimum η among the oil-to-electricity ratios is equal to_nCorresponding value n of generating speed_e' as an optimum power generation rotation speed, which is the lateral comparison data. The power generation torque value at this time is still T_gAnd is not changed.

In step 3, "under the condition that the motor torque parameter is not changed, the change of the engine speed parameter" specifically means: when the power generation torque value is T_gOn the basis of no change, only the generating speed n is changed_e. For example: at the initial value n of the generating rotation speed_eOn the basis of (1), n is respectively changed from top to bottom, and the obtained generating rotating speed can be n_e+n、n_e-n、n_e+2n、n_e-2n, etc.

In step 3, "calculating the engine oil consumption and the ISG motor power consumption corresponding to each engine speed parameter and the unchanged motor torque parameter" specifically means that the corresponding engine oil consumption and the ISG motor power consumption are calculated by using a known method under the condition that the power generation torque value and the power generation speed are determined. For example: the required quantities for this embodiment include: the value of the generating torque is T_gAnd a power generation rotation speed n_eCorresponding engine oil consumption and ISG motor power consumption, and generating torque value T_gAnd a power generation rotation speed n_eThe engine oil consumption and the ISG motor power consumption corresponding to + n, and the generating torque value is T_gAnd a power generation rotation speed n_e-n corresponding engine and ISG motor power consumption, and the power generation torque value is T_gAnd a power generation rotation speed n_e+2n engineThe oil consumption and the ISG motor power consumption and the power generation torque value are T_gAnd a power generation rotation speed n_e-2n corresponding engine oil consumption and ISG motor power consumption, etc.

The step 5 specifically includes: the step of obtaining longitudinal comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 3 specifically comprises the following steps:

as shown in fig. 4, a specific implementation of step 5 is described below by using a specific embodiment, which is shown in the two columns on the right side of fig. 4. And step 51, calculating each oil-electricity ratio corresponding to each power generation torque and the unchanged power generation rotating speed according to each engine oil consumption and ISG motor power consumption obtained in the step 3. That is, the oil-to-electric ratio η corresponding to each power generation rotation speed value and the constant power generation torque is calculated by the formula (5) based on each power generation rotation speed value obtained by the change_niN is a natural number greater than 5. Taking n as 5 as an example: initial value n of generating speed_eAnd an initial value T of the power generation torque_gCorresponding initial oil-to-electric ratio eta_n1First value of generator speed n_e+ n and initial value of generating torque T_gCorresponding first oil-to-electric ratio eta_n2Second value of generated rotational speed n_e-n and an initial value of the generation torque T_gCorresponding second oil-to-electric ratio eta_n3Third value of generated rotational speed n_e+2n and initial value of generating torque T_gCorresponding third oil-to-electric ratio eta_n4Fourth value of generated rotational speed n_e-2n and an initial value of the generation torque T_gCorresponding fourth oil-to-electric ratio eta_n5。

And a step 52 of setting, as an optimal power generation torque, the power generation torque corresponding to the minimum value of the oil-to-electricity ratios calculated in the step 51, the optimal power generation torque being the vertical comparison data. In S24, "minimum value among the oil-to-electricity ratios" is represented by η_T＝min(η_T1,η_T2,..,) at which the minimum η among the oil-to-electricity ratios is equal to_TCorresponding power generation rotating speed value T_g' optimal value of generating rotation speed for lateral comparison, where the value of generating rotation speed is still n_eAnd is not changed. That is, when the power generation rotation speed n_eWhen not changed, the generating torque is T_gWhenObtaining the minimum value eta of each oil-electricity ratio_T。

The step 6 specifically includes:

step 61, obtaining the minimum value eta of the oil-electricity ratio values obtained in the step 42_nAnd the minimum value eta of the oil-electricity ratio values obtained in the step 52_TIn the case where the following formula (6) is satisfied, i.e., the minimum value η among the oil-to-electricity ratios_nAnd the minimum value eta of each oil-electricity ratio_TAre relatively close. Calculating the optimum power generation rotation speed n obtained in the step 42 by using the formula (5)_e' and the optimum power generation torque T obtained in the step 52_g' corresponding oil-to-electricity ratio eta, minimum eta in each oil-to-electricity ratio_nMinimum value eta of each oil-electricity ratio_TMinimum value min (η) of and η_n,η_TEta) the corresponding generating torque and generating speed are the optimal charging working points in the engine series working mode;

|η_n-η_T|≤Δ (6)

in the formula (6), Δ ═ 5% · min (η)_n,η_T) Is used as a relatively close mark. min (. eta.)_n,η_T) Is eta_nAnd η_TMinimum value of (1).

Step 62, minimum value eta in each oil-electricity ratio_nAnd the minimum value eta of each oil-electricity ratio_TIn the case where the following expression (7) is satisfied, that is, the two values are far apart, the following two cases are included:

the first case: if eta_nLess than η_TThen the optimum power generation rotation speed n obtained in said step 42_e' is the power generation rotating speed in the optimal charging working point in the engine series working mode; then the optimal power generation rotating speed n_eOn the premise of' unchanging, repeating the step 5, and performing longitudinal search by changing the generating torque to obtain the optimal generating torque as the generating torque in the optimal charging operating point in the engine series operating mode.

The second case: if eta_nGreater than η_TThen the optimum power generation torque T obtained in the step 52 is obtained_g' is the engine stringGenerating torque in an optimal charging operating point in a combined operating mode; on the premise that the optimal power generation torque is not changed, repeating the step 4, and performing transverse search by changing the power generation rotating speed to obtain the optimal power generation rotating speed as the power generation rotating speed in the optimal charging working point under the engine serial working mode;

|η_n-η_T|＞Δ (7)

in the formula (7), Δ ═ 5% · min (η)_n,η_T) Is used as a relatively close mark. min (. eta.)_n,η_T) Is eta_nAnd η_TMinimum value of (1).

If the mode is a multi-working-point mode, the operation selection can be repeated for the rest working points.

In the embodiment, an optimization method is established, firstly, transverse and longitudinal analyses are respectively carried out by a control variable method, effective quantitative measurement indexes are selected, and two optimal values are obtained by comparison; and finally, through further judgment and analysis, the overall optimal value and the optimal working point can be obtained through cross comparison. The advantages embodied are as follows:

1. the method has simple rule, and the quantitative concepts of the weight function and the oil-electricity ratio are used for comparison, so that the calculation accuracy is ensured.

2. The method has comprehensive search range, does not need to carry out more verification, can obtain accurate qualitative relation on the basis of ensuring certain experimental conditions, and provides the basis for establishing the working point.

3. The method is wide in applicability and can be suitable for optimizing energy management strategies such as series-parallel hybrid power and series hybrid power. Meanwhile, the method can be referred to for the establishment of other working conditions such as the working curve of the engine and the like, which are not limited to the starting and series working conditions mentioned above. The method has the advantages of simple measurement and easy calculation, and can be used as a link for the later optimization development of the energy management strategy of the hybrid vehicle.

Based on the above system, the following explains the optimization effect of the present invention on the optimal operating point for engine start and the optimal operating point for charging in the engine series operating mode of an actual vehicle by specific embodiments:

the vehicle parameters used are shown in table 1, the ambient temperature in the experiment was about 20 degrees, and the engine temperature was 70 ± 2 degrees celsius.

TABLE 1 Main parameters of hybrid vehicle

Vehicle mass	m(kg)	16500
			Rated power and speed of engine	ne(r/min)	2300
Maximum power of engine	Pe(kW)	160
			Maximum power of ISG motor	P(kW)	135
Maximum torque of ISG motor	N(N·m)	850
			Maximum rotation speed of ISG motor	n(mm)	3100
Radius of wheel	r(mm)	0.5

1) The ISG motor torque of the engine is 350 N.m according to the initial value, and the engine rotating speed is 550r/min during unloading. In the actual calculation, instantaneous oil consumption data and rotating speed data reported by an engine, and rotating speed and motor torque data of an ISG motor are adopted. The idle speed of the engine is 650 r/min.

2) And performing transverse calculation. First, the motor starting torque is 350N · m constant, and the rotational speeds for starting unloading are 600, 550,500,450,400,350, six groups, respectively, and the data obtained are shown in the following table:

since the overshoot rotational speed is not much affected, the weighting factor of the overshoot rotational speed may be approximately 0.

It can be basically obviously seen that as the unloading rotating speed is increased, the oil consumption is gradually reduced, and the power consumption is gradually increased, but the increase of the oil consumption is more obvious, and the power consumption increase proportion is less. In addition, 550r/min is obviously seen, and after the speed is increased to 600r/min, the power consumption and the oil consumption are not good.

If 500r/min is unloaded, and the oil consumption is reduced by 15 percent and the power consumption is increased by 6 percent when 550r/min is unloaded, the effect is improved. Analysis at this set, the initial unload at 550r/min was the best.

2) The longitudinal comparison was carried out, with the unloading speed set at 550r/min and the motor starting torques set at 300N · m, 350N · m, 400N · m, 450N · m, respectively, and the data obtained are shown in table 3:

this group has found that when the starting torque of the electric machine is increased, the fuel consumption is significantly reduced and the power consumption is also reduced considerably. Compared with the current 500r/min unloading and 350 N.m motor torque, the oil consumption of the red part is improved by 22.3 percent, and the power consumption is improved by 17.6 percent. It can be seen that this method is preferable in that the unloading speed becomes higher and the motor torque becomes higher.

3) The horizontal direction and the vertical direction are comprehensively compared.

It can be seen that as shown in table 4, it is still the best red, although the power consumption is reduced by 5.3%, but the fuel consumption is increased by 10%, and of course, the 400N · m is much better than the current method when unloading at 500 r/min.

3) The horizontal direction and the vertical direction are comprehensively compared.

It can be seen that as shown in table 4, which is still the best red, although the power consumption is reduced by 5.3%, the fuel consumption is increased by 10%, and of course, 400Nm is much better than the current method when unloading at 500 r/min.

Therefore, by comparison, the final conclusion is easily reached: the best effect is achieved by adopting the unloading rotation speed of 550r/min and the motor starting torque of 450 N.m, then the unloading rotation speed of 500r/min and the motor starting torque of 400 N.m, and then the unloading rotation speed of 500r/min and the motor starting torque of 350 N.m (the current starting mode).

And (3) calculating the acceleration time of the motor from 0 to 500r/min because the motor torque is overlarge during starting and the motor is damaged by too fast acceleration. The correspondence is as follows:

has no problem and can be selected practically.

Referring to fig. 5a and 5b, 550r/min unload, 450N · m motor starting torque is best.

Example of operating Point selection for series charging

1) The initial SOC ranges from 25% to 26.5%, the engine is never started every time, the charging time is 20s when the engine enters a working point, the time of each experiment is basically maintained at a fixed level, the time is long, and the rotation speed and the power generation torque of the ISG motor are selected in power consumption calculation.

Since the Map characteristic Map of the engine and the operating point mode should be closely related to each other, first, the engine economy point 1200r/min power generation rotation speed and the 400N · m power generation torque are selected from the Map characteristic Map.

2) Firstly, transverse comparison is carried out, the torque of the charging motor is made to be 400 N.m, the working rotating speed of the engine is respectively 1100r/min, 1150r/min,1200r/min,1250r/min and 1300r/min, and the obtained data are shown in the following table:

motor torque (N.m)	400	400	400	400	400
						Engine speed (r/min)	1100	1150	1200	1250	1300
Speed regulation and chargingElectric time(s)	21.44875	21.52905	21.6542	21.7005	21.73855
						Charging time(s)	20	20	20	20	20
Overshoot speed (r/min)	1103	1159	1205	1257	1308
						Instantaneous highest oil consumption (L/h)	13.55	14	14.5	16.75	16.75
Oil consumption (L/3600)	230.1988	240.5558	249.9698	270.7313	281.3122
						Charge (kW. h)	709300	736960	770720	818820	855210
Oil-to-electricity ratio (L/KW. h)	0.3245	0.3264	0.3243	0.3306	0.3289

It can be seen that the currently adopted approach, i.e. 1200r/min, 400N · m, is optimal.

3) For the following longitudinal comparison, the operating speed of the engine was set at 1200r/min, and the motor torques for power generation were set at 350N · m, 400N · m, and 450N · m, respectively, and the data obtained were as follows:

motor torque (N.m)	350	400	450
				Engine speed (r/min)	1200	1200	1200
Speed regulation + charging time(s)	21.8336	21.6542	21.5836
				Charging time(s)	20	20	20
Overshoot speed (r/min)	1205	1205	1206
				Instantaneous highest oil consumption (L/h)	13.3	14.5	17.2
Oil consumption (L/3600)	232.2194	249.9698	293.47
				Charge (kW. h)	705320	770720	859730
Oil-to-electricity ratio (L/KW. h)	0.3292	0.3243	0.3414

It can be seen more clearly that the baseline method in the longitudinal comparison is also optimal.

4) And (5) verifying the method. Although the calculation result does not need to be verified in the method, in order to better prove the accuracy of the method, several sets of cross-comparisons are performed as follows:

the torque of the power generation motor is increased, the power generation rotating speed is reduced, or the torque of the power generation motor is reduced, the power generation rotating speed is increased, the oil consumption of the two methods is far greater than the found optimal point after being combined, and reference is made to fig. 6a and fig. 6 b.

Finally, it should be pointed out that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Those of ordinary skill in the art will understand that: modifications can be made to the technical solutions described in the foregoing embodiments, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. An engine operating point optimization method of a series-parallel hybrid vehicle, characterized by comprising:

step 1, collecting an engine rotating speed parameter and a motor torque parameter;

step 2, under the condition that the engine rotating speed parameters are not changed, the engine oil consumption and the ISG motor power consumption corresponding to the motor torque parameters and the unchanged engine rotating speed parameters are calculated by changing the sizes of the motor torque parameters;

step 3, under the condition that the motor torque parameter is not changed, calculating the oil consumption of each engine and the electricity consumption of the ISG motor corresponding to each engine rotating speed parameter and the unchanged motor torque parameter by changing the size of the engine rotating speed parameter;

step 4, obtaining transverse comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

step 5, obtaining longitudinal comparison data according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and 6, determining an optimal working point for starting the engine and an optimal charging working point under the engine series working mode according to the transverse comparison data obtained in the step 4 and the longitudinal comparison data obtained in the step 5.

2. The engine operating point optimization method of a series-parallel hybrid vehicle according to claim 1, characterized in that in step 1, the engine speed parameter includes an unloading speed, and the motor torque parameter includes a motor starting torque;

the step 4 specifically includes:

step 41, calculating the starting weight of each motor torque corresponding to each motor starting torque and the unchanged unloading rotating speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

step 42, taking the motor starting torque corresponding to the minimum value in the motor torque starting weights calculated in the step 41 as an optimal motor starting torque, wherein the optimal motor starting torque is the transverse comparison data;

the step 5 specifically includes:

step 51, calculating the unloading rotation speed starting weight corresponding to the unloading rotation speed and the unchanged motor starting torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and step 52, taking the unloading rotating speed corresponding to the minimum value in the unloading rotating speed starting weights calculated in the step 51 as an optimal unloading rotating speed, wherein the optimal unloading rotating speed is the longitudinal comparison data.

3. The method for optimizing the engine operating point of the series-parallel hybrid vehicle according to claim 2, wherein the calculation formula of "calculating each motor torque start weight corresponding to each of the motor start torques and the constant unload rotation speeds" in step 41 and/or "calculating each unload rotation speed start weight corresponding to each of the unload rotation speeds and the constant motor start torques" in step 51 is as follows (1):

H＝(αf_c+βp_c)(1+γt+τn_a) (1)

in the formula (1), α, β, γ and τ are all weight coefficients, f_cFor engine start-up fuel consumption, p_cFor starting the ISG motor, power consumption, t is engine starting time, n_aThe rotational speed is overshot.

4. The engine operating point optimization method of a series-parallel hybrid vehicle according to any one of claims 2 to 3, characterized in that the step 6 specifically includes:

step 61, obtaining the minimum value C in the motor torque starting weight value obtained in the step 42_αAnd the minimum value L in each unloading rotating speed starting weight value obtained in the step 52_αIf the following formula (2) is satisfied, the formula (1) is used to calculate the starting weight M corresponding to the optimal motor starting torque a 'obtained in the step 42 and the optimal unloading rotation speed B' obtained in the step 52, and then C_α、L_αAnd minimum value min (C) of M_a,L_aM) the corresponding motor starting torque and unloading rotating speed are the optimal working points for starting the engine;

|C_a-L_a|≤Δ (2)

step 62, obtaining the minimum value C in the motor torque starting weight value obtained in the step 42_αAnd the minimum value L in each unloading rotating speed starting weight value obtained in the step 52_αIn the case where the following expression (3) is satisfied, the following two cases are included:

the first case: if C_aIs less thanL_αIf yes, the optimal motor starting torque a' obtained in step 42 is the motor starting torque in the optimal operating point for starting the engine; repeating the step 5 on the premise that the optimal motor starting torque A' is not changed, and performing longitudinal search by changing the unloading rotating speed to obtain the optimal unloading rotating speed serving as the unloading rotating speed in the optimal working point for starting the engine;

the second case: if C_aGreater than L_αIf yes, the optimal unloading rotation speed B' obtained in step 52 is the unloading rotation speed in the optimal working point for starting the engine; on the premise that the optimal unloading rotating speed B' is not changed, repeating the step 4, and performing transverse search by changing the motor starting torque to obtain the optimal motor starting torque as the motor starting torque in the optimal working point for starting the engine;

|C_a-L_a|＞Δ (3)

the numerical value of Delta in the formulae (2) and (3) is represented by C_αAnd L_αAnd (4) determining.

5. The engine operating point optimizing method of a series-parallel hybrid vehicle according to claim 4, characterized in that Δ in the equations (2) and (3) satisfies:

Δ＝5％·min(C_a,L_a) Wherein: min (C)_a,L_a) Is C_αAnd L_αMinimum value of (1).

6. The engine operating point optimizing method of a series-parallel hybrid vehicle according to claim 1, characterized in that in step 1, the engine speed parameter includes a power generation speed, and the motor torque parameter includes a power generation torque;

the step 4 specifically includes:

step 41, calculating each oil-electricity ratio corresponding to each power generation torque and the unchanged power generation rotation speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

a step 42 of setting, as an optimal power generation torque, the power generation torque corresponding to the minimum value of the oil-to-electricity ratios calculated in the step 41, the optimal power generation torque being the lateral comparison data;

the step 5 specifically includes:

step 51, calculating each oil-electricity ratio corresponding to each power generation rotation speed and the unchanged power generation torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

and step 52, setting the power generation rotation speed corresponding to the minimum value in the oil-to-electricity ratios calculated in the step 51 as an optimal power generation rotation speed, wherein the optimal power generation rotation speed is the longitudinal comparison data.

7. The engine operating point optimizing method of the series-parallel hybrid vehicle according to claim 6, wherein the calculation formula of "calculating each of the oil-to-electric ratios corresponding to each of the power generation torques and the constant power generation rotational speed" in step 41 and/or "calculating each of the oil-to-electric ratios corresponding to each of the power generation rotational speeds and the constant power generation torques" in step 51 is the following formula (5):

in the formula (5), f_cFor the consumption of engine oil, p, over a fixed period of time t_cThe generated energy of the ISG motor in a fixed time period t.

8. The engine operating point optimization method of a series-parallel hybrid vehicle according to any one of claims 6 and 7, characterized in that the step 6 specifically includes:

step 61, obtaining the minimum value eta of the oil-electricity ratio values obtained in the step 42_nAnd the minimum value eta of the oil-electricity ratio values obtained in the step 52_TWhen the following expression (6) is satisfied, the optimum power generation torque T obtained in step 42 is calculated by expression (5)_g' and the optimum power generation rotation speed n obtained in the step 52_e' corresponding oil-to-electricity ratio eta, minimum value of each oil-to-electricity ratioη_nMinimum value eta of each oil-electricity ratio_TMinimum value min (η) of and η_n,η_TEta) the corresponding generating torque and generating speed are the optimal charging working points in the engine series working mode;

|η_n-η_T|≤Δ (6)

step 62, minimum value eta in each oil-electricity ratio_nAnd the minimum value eta of each oil-electricity ratio_TIn the case where the following expression (7) is satisfied, the following two cases are included:

the first case: if eta_nLess than η_TThen, the optimum generating torque T obtained in said step 42 is obtained_g' is the generated torque in the optimal charging operating point in the engine series operating mode; then the optimal power generation torque T is obtained_gOn the premise of no change, repeating the step 5, and performing longitudinal search by changing the power generation rotating speed to obtain the optimal power generation rotating speed as the power generation rotating speed in the optimal charging operating point in the engine series operating mode;

the second case: if eta_nGreater than η_TThen the optimum power generation rotation speed n obtained in the step 52_e' is the power generation rotating speed in the optimal charging working point in the engine series working mode; on the premise that the optimal power generation rotating speed is not changed, repeating the step 4, and performing transverse search by changing the power generation torque to obtain the optimal power generation torque as the power generation torque in the optimal charging working point under the engine serial working mode;

|η_n-η_T|＞Δ (7)

the numerical value of Δ in the formulae (6) and (7) is represented by η_nAnd η_TAnd (4) determining.

9. The engine operating point optimizing method of a series-parallel hybrid vehicle according to claim 8, characterized in that Δ in the formula (6) and the formula (7) satisfies:

Δ＝5％·min(η_n,η_T) Wherein: min (. eta.)_n,η_T) Is eta_nAnd η_TMinimum value of (1).

10. The engine operating point optimization method of a series-parallel hybrid vehicle according to claim 5, wherein in step 1, the engine speed parameter further includes a power generation speed, and the motor torque parameter further includes a power generation torque;

the step 4 specifically includes:

step 41, calculating each oil-electricity ratio corresponding to each power generation torque and the unchanged power generation rotation speed according to the engine oil consumption and the ISG motor power consumption obtained in the step 2;

a step 42 of setting, as an optimal power generation torque, the power generation torque corresponding to the minimum value of the oil-to-electricity ratios calculated in the step 41, the optimal power generation torque being the lateral comparison data;

the step 5 specifically includes:

step 51, calculating each oil-electricity ratio corresponding to each power generation rotation speed and the unchanged power generation torque according to the engine oil consumption and the ISG motor power consumption obtained in the step 3;

step 52, taking the power generation speed moment corresponding to the minimum value in the oil-to-electricity ratios obtained by the calculation in the step 51 as an optimal power generation speed, wherein the optimal power generation speed is the longitudinal comparison data;

the step 6 specifically includes:

step 61, obtaining the minimum value eta of the oil-electricity ratio values obtained in the step 42_nAnd the minimum value eta of the oil-electricity ratio values obtained in the step 52_TWhen the following expression (6) is satisfied, the optimum power generation torque T obtained in step 42 is calculated by expression (5)_g' and the optimum power generation rotation speed n obtained in the step 52_e' corresponding oil-to-electricity ratio eta, minimum eta in each oil-to-electricity ratio_nMinimum value eta of each oil-electricity ratio_TMinimum value min (η) of and η_n,η_TEta) the corresponding generating torque and generating speed are the optimal charging working points in the engine series working mode;

|η_n-η_T|≤Δ (6)

step 62, minimum value eta in each oil-electricity ratio_nAnd the minimum value eta of each oil-electricity ratio_TIn the case where the following expression (7) is satisfied, the following two cases are included:

the first case: if eta_nLess than η_TThen, the optimum generating torque T obtained in said step 42 is obtained_g' is the generated torque in the optimal charging operating point in the engine series operating mode; then the optimal power generation torque T is obtained_gOn the premise of no change, repeating the step 5, and performing longitudinal search by changing the power generation rotating speed to obtain the optimal power generation rotating speed as the power generation rotating speed in the optimal charging operating point in the engine series operating mode;

the second case: if eta_nGreater than η_TThen the optimum power generation rotation speed n obtained in the step 52_e' is the power generation rotating speed in the optimal charging working point in the engine series working mode; on the premise that the optimal power generation rotating speed is not changed, repeating the step 4, and performing transverse search by changing the power generation torque to obtain the optimal power generation torque as the power generation torque in the optimal charging working point under the engine serial working mode;

|η_n-η_T|＞Δ (7)

the numerical value of Δ in the formulae (6) and (7) is represented by η_nAnd η_TAnd (4) determining.

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