Comprehensive performance evaluation method for tandem hybrid power system of heavy vehicle

Abstract

The invention discloses a comprehensive performance evaluation method for a tandem type hybrid power system of a heavy vehicle. Four indexes capable of evaluating the dynamic performance and the coupling characteristic of the system, namely engine and generator torque coordination, front and back power chain power coordination, main and auxiliary power source energy supply coordination and main power source energy vacancy proportion, are provided, and four static indexes, namely engine speed average / maximum fluctuation ratio and bus voltage average / maximum fluctuation ratio, are combined. A comprehensive performance evaluation method is constructed by using an analytic hierarchy process and a fuzzy comprehensive evaluation method, and evaluation of static, dynamic and coupling characteristics of the system is realized. When the dynamic change of the system state is relatively strong due to the large change of the vehicle load, the comprehensive performance evaluation method still has a relatively good evaluation effect, and the problem that the comprehensive performance of the system cannot be effectively evaluated by a static index and a single-component index is solved.

Description

Technical Field

[0001] The invention belongs to the field of hybrid vehicles, and in particular relates to a comprehensive performance evaluation method for a series hybrid power system of a heavy-duty vehicle. Background Art

[0002] Hybrid vehicles are one of the main directions for the transformation and upgrading of the global automotive industry and green development. As a key force in engineering operations, non-structural road transportation and military applications, heavy-duty vehicles play an important role in social development and national defense construction. Therefore, the transformation of heavy-duty vehicles into hybrid vehicles has become the current main development trend. The series hybrid system is one of the main power system configurations used in heavy-duty vehicles, but different structural parameters, control methods and road excitations make the system characteristics of this configuration gradually complex and the system performance difficult to compare and evaluate. How to evaluate the comprehensive performance of the hybrid system has become an important issue. Therefore, it is the current priority to carry out research on comprehensive performance evaluation methods suitable for series hybrid systems of heavy-duty vehicles.

[0003] The current comprehensive performance evaluation method of the series hybrid power system of heavy-duty vehicles is mainly based on the performance evaluation method of mechanical transmission systems or medium- and light-duty hybrid power systems, such as static and single-component indicators such as voltage ripple factor, efficiency, mass power density and volume power density. However, compared with mechanical transmission vehicles or medium- and light-duty vehicles, the series hybrid power system of heavy-duty vehicles has the characteristics of complex driving environment, high vehicle power level, small battery energy ratio and more prominent electromechanical coupling characteristics. In the working conditions where the power changes greatly and the system state changes dynamically more strongly, it is difficult for static indicators and single-component indicators to evaluate the comprehensive performance of the system. At the same time, the evaluation of the performance of components such as drive motors can only reflect the performance of individual components, and cannot reflect the system performance brought about by high electromechanical coupling characteristics. In order to solve the above problems and accurately evaluate the comprehensive performance of the hybrid power system of heavy-duty vehicles, the present invention proposes a comprehensive performance evaluation method for a series hybrid power system suitable for heavy-duty vehicles. Summary of the invention

[0004] The present invention aims to solve the technical problems existing in the background technology and provides a comprehensive performance evaluation method for a series hybrid power system of a heavy-duty vehicle.

[0005] In order to solve the technical problem, the technical solution of the present invention is:

[0006] A method for evaluating the comprehensive performance of a heavy-duty vehicle series hybrid power system, the method comprising:

[0007] Construct evaluation indicators, analyze the characteristics of the series hybrid power system of heavy-duty vehicles, and obtain static indicators, dynamic indicators and coupling characteristic indicators through theoretical research; use the hierarchical analysis method to weight the indicators, and perform a consistency check on the obtained weights. If they are unreasonable, recalculate them; if they are reasonable, conduct a comprehensive evaluation; based on the fuzzy comprehensive evaluation method, calculate the scores and comments according to the indicators and weights.

[0008] Furthermore, the series hybrid system of heavy-duty vehicles is analyzed. The system transmits power through a high-voltage microgrid composed of an engine generator set, a power battery, and a drive motor. The generator requires the engine to work stably to generate electricity, and the drive motor requires the generator to provide a stable voltage to work normally. The operating status of the engine generator set and the high-voltage microgrid determines the comprehensive performance of the series hybrid system. Therefore, the indicators are constructed from the perspective of engine speed and bus voltage stability.

[0009] The construction evaluation indicators include:

[0010] Dynamic indicators, engine generator torque coordination: evaluate the stability of engine speed through the dynamic changes of engine and generator torque; front and rear power chain power coordination: evaluate the energy transfer effect based on bus voltage stability and the coordination of generator and drive motor current;

[0011] Coupling characteristic indicators, coordination of energy supply between main and auxiliary power sources: based on the smoothness of the total power curve, measure the synergistic energy supply effect of the generator and the battery; energy shortage ratio of the main power source: evaluate whether the generator can meet the needs of the drive motor;

[0012] Static indicators: Combine the four static indicators of engine speed and maximum and average fluctuation rate of bus voltage to measure the stability of the system under different operating conditions.

[0013] Furthermore, the dynamic indicators specifically include:

[0014] Engine generator torque coordination:

[0015] In the series hybrid system of heavy-duty vehicles, the engine is decoupled from the external working conditions. The system requires the engine to provide stable power, and the stable engine speed is the premise for it to provide stable power. Therefore, whether the engine speed can be kept stable is an important indicator to measure the overall performance of the system; the dynamic change of the engine speed can be given according to Newton's laws of motion, as shown below:

[0016]

[0017] Where J is the sum of the moments of inertia of the engine and generator, ω e is the engine speed, T e , Tg are the engine torque and the generator torque respectively. According to the torque-speed relationship, the essence of maintaining a stable engine speed is the coordinated operation of the engine and the generator. The smaller the torque difference between the two, the more stable the speed. Further deriving both sides of the above formula (1), the influence of the dynamic change of torque on the speed is as follows:

[0018]

[0019] The dynamic changes of the engine and generator torque are used to establish a dynamic index for evaluating the engine speed; the instantaneous fluctuation rate of the engine speed within t0 seconds is required to be less than n%, which can be expressed as:

[0020]

[0021] Among them, ω ref is the expected engine speed, D is the integration domain; Substituting formula (2) into formula (3), we get:

[0022]

[0023] The selected t0 is small, so Approximately a constant, further obtained:

[0024]

[0025] The meaning of this indicator is: In order to make the instantaneous fluctuation rate of engine speed less than n%, it is necessary is less than n;

[0026] Front and rear power chain power coordination:

[0027] In the series hybrid system of heavy-duty vehicles, the bus voltage is the platform for energy conversion. The energy generated by the engine generator set is transmitted to the rear power chain through the bus. When the voltage is too low, the rated power of the drive motor cannot be fully utilized, resulting in the drive motor being unable to achieve normal operating efficiency. When the drive motor is running, additional current shocks will also be generated due to insufficient voltage, thus affecting the normal operation of the drive motor. Therefore, whether the bus voltage can remain stable is an important indicator for measuring the overall performance of the system.

[0028] Considering that the generator power accounts for most of the front power chain power, and the drive motor power accounts for most of the rear power chain power, for the convenience of calculation, the current of the generator and the drive motor is used to calculate the dynamic change of the bus voltage according to the relationship between the capacitor voltage and current, as shown below:

[0029]

[0030] Where C is the capacitance of the supercapacitor, u bus is the bus voltage, ig 、i m are the generator DC current and the drive motor DC current respectively,

[0031] According to the voltage-current relationship, the essence of maintaining stable bus voltage is the coordinated operation of the generator and the drive motor. The smaller the DC current difference between the two, the more stable the bus voltage. Further deriving both sides of the above equation, the influence of the dynamic change of DC current on the bus voltage is as follows:

[0032]

[0033] The dynamic changes of the DC current of the engine and the generator are used to establish the dynamic index for evaluating the bus voltage; the instantaneous fluctuation rate of the bus voltage within t0 seconds is required to be less than n%, which can be expressed as:

[0034]

[0035] Among them, u ref is the expected engine speed, D is the integration domain; Substituting equation (7) into equation (8), we get:

[0036]

[0037] The selected t0 is small, so Approximately a constant, further obtained:

[0038]

[0039] The meaning of this indicator is: In order to make the instantaneous fluctuation rate of bus voltage less than n%, it is necessary Less than n.

[0040] Furthermore, the coupling characteristic index specifically includes:

[0041] Coordination of energy supply between main and auxiliary power sources:

[0042] In the series hybrid system of heavy-duty vehicles, the generator is used as the main power source because it can provide high power, and the battery is used as the auxiliary power source to supplement the energy due to its fast response characteristics. The coordination between the two power sources also determines the quality of the front power supply and affects the stability of the bus voltage; the main function of the battery as a power source is to fill the valley, that is, to assist the generator to output more stable power. From the power curve, the total power curve of the generator and the battery needs to be smoother than the power curve of the generator. Therefore, the smoothness of the total power supply is used to establish the evaluation index of the coordination of the main and auxiliary power sources. The index calculation process is as follows:

[0043] First, the smoothness of the total power curve and the generator power curve is calculated by using the integral of the absolute value of the second derivative of the curve divided by the length of the integration domain, as shown below:

[0044]

[0045] Among them, P sum is the total power, P g is the generator power, α sum is the smoothness of the total power curve, α g is the smoothness of the generator power curve, t1 and t2 are the start time and end time of the integration domain respectively;

[0046]

[0047] Among them, β is the coordination index of the energy supply of the main and auxiliary power sources; the smoothness of the straight line is 0, and the smoothness of the step curve is infinite, so the smaller the value of α, the smoother the curve; when the generator power curve is smoother than the total power curve, the closer the index is to 0, the better; when the total power curve is smoother than the generator power curve, the index reaches the ideal state and is set to 0;

[0048] Main power source energy shortage ratio:

[0049] In the heavy-duty vehicle series hybrid system, the engine generator set provides most of the energy as the main power source, and the energy storage device is used as an emergency measure to reduce peak loads and fill valleys in a small part of the time. The engine generator set is required to meet the power demand of the drive motor most of the time. The part where the energy provided by the engine generator set is less than the required energy in a period of time is the shortage; therefore, the energy shortage ratio of the main power source is proposed to evaluate the quality of the energy supply effect of the engine generator set;

[0050] Considering that the generator power accounts for most of the power of the front power chain, and the drive motor power accounts for most of the power of the rear power chain, this indicator focuses on the generator and the drive motor. The energy shortage of the main power source is the difference between the energy consumed and the energy provided when the energy provided by the generator is less than the energy required by the drive motor. The proportion of the main power source energy shortage reflects the matching quality of the engine generator set and the drive motor, and is expressed by the ratio of the main power source energy shortage proportion to the total load demand energy over a period of time;

[0051] First, calculate the power shortage of the main power source, the formula is as follows:

[0052]

[0053] Among them, P g , P m are the generator power and the drive motor power respectively, ΔP q The power shortage of the main power source is then integrated to calculate the energy shortage ratio of the main power source. The formula is as follows:

[0054]

[0055] The smaller the index is, the better the energy supply effect of the engine generator set is.

[0056] Furthermore, the static indicators specifically include:

[0057] In order to evaluate the comprehensive performance of the system, four static indicators are added on the basis of the above dynamic indicators: maximum fluctuation rate of engine speed, average fluctuation rate of engine speed, maximum fluctuation rate of bus voltage and average fluctuation rate of bus voltage;

[0058] The maximum fluctuation rate of engine speed is:

[0059]

[0060] The average fluctuation rate of engine speed is:

[0061]

[0062] Where ω is the engine speed, t1 and t2 are the start and end times of the selected time period;

[0063] The maximum bus voltage fluctuation is:

[0064]

[0065] The average bus voltage fluctuation is:

[0066]

[0067] Among them, u is the bus voltage, t1 and t2 are the start and end times of the selected time period.

[0068] Furthermore, the analytic hierarchy process is used to weight the indicators and the obtained weights are checked for consistency, including:

[0069] Construct judgment matrix: Use 1-9 scaling method to compare two indicators according to their relative importance and construct judgment matrix A;

[0070] Calculate the weight: Take the product of the judgment matrix A by row elements, and then find The power, n is the order of matrix A, calculate the relative weight of each indicator; normalize the weight result to form the weight matrix W;

[0071] Consistency test: Calculate the maximum eigenvalue of the judgment matrix A, calculate the consistency ratio and test the consistency ratio according to the consistency index formula and the random consistency index, and confirm the consistency of the judgment matrix;

[0072] Application weights: If the consistency check passes, a weight matrix is ​​used for comprehensive evaluation.

[0073] Furthermore, the analytic hierarchy process is used to weight the indicators and the obtained weights are checked for consistency, including:

[0074] First, the judgment matrix is ​​constructed using the 1-9 scaling method; the 1-9 scaling method quantifies the relative importance of decision factors through a 1-9 scale;

[0075] According to the meaning of the 1-9 scale, each indicator is compared in pairs to construct a judgment matrix to provide a basis for subsequent weight calculation and decision analysis; the proposed indicators are ranked from 1 to 8 as follows: average engine speed fluctuation rate, maximum engine speed fluctuation rate, average bus voltage fluctuation rate, maximum bus voltage fluctuation rate, coordination of main and auxiliary power sources, energy shortage ratio of main power source, engine generator torque coordination and front and rear power chain power coordination; according to the above indicator sequence, the judgment matrix is ​​constructed as follows:

[0076]

[0077] The meaning of this matrix is ​​that the data in the i-th row and j-th column is the scale of the i-th indicator to the j-th indicator. For example, the first indicator, the average fluctuation rate of engine speed, is slightly more important than the second indicator, the maximum fluctuation rate of engine speed, and the scale is 2.

[0078] Then, the judgment matrix is ​​sorted hierarchically, that is, the importance of each factor in the decision is quantified, and the weight of each indicator is calculated; the calculation process is as follows:

[0079] Take the product of the judgment matrix A by row elements, and then find power, n is the order of matrix A, that is, the number of indicators 8;

[0080]

[0081] Among them, a ij is the data of the i-th row and j-th column of the judgment matrix A; the calculated Normalize and get the weight matrix:

[0082]

[0083] The weight matrix W is obtained as follows:

[0084] W=[0.090.170.130.070.130.050.180.17] T (twenty two)

[0085] In order to ensure that the above judgment matrix A and weight matrix W are logically self-consistent, that is, there is no contradiction or unreasonable sorting, it is necessary to further check their consistency; first calculate the maximum eigenvalue of A, the calculation formula is:

[0086]

[0087] Calculate the C.I. according to the consistency index C.I. formula:

[0088]

[0089] According to the order of the judgment matrix A, look up the table to obtain the random consistency index R.I.; calculate the consistency ratio C.R. to get:

[0090]

[0091] C.R. is less than 0.1, indicating that the consistency degree of the judgment matrix A is considered to be within the allowable range, and there is no logical error such as A > B, B > C, but A < C. Therefore, the obtained weights can be used for calculation.

[0092] Furthermore, use the fuzzy comprehensive evaluation method to calculate the scores and comments, specifically including:

[0093] Establish the factor set of the comprehensive evaluation, which is a set composed of various factors affecting the evaluation object, and is represented by U:

[0094] U = {u1 u2 u3 u4 u5 u6 u7 u8}(26)

[0095] Establish the evaluation set of the comprehensive evaluation, which is a set composed of various results that the evaluator may give to the evaluation object, and is represented by V:

[0096] V = {v1 v2 v3 v4 v5}

[0097] = {excellent good medium poor very poor}(27)

[0098] The corresponding evaluation score matrix v is:

[0099] v = [0 1 2 3 4] T (28)

[0100] Construct the weight matrix of each factor, and use the weights obtained by the analytic hierarchy process, represented by W:

[0101] W = [0.23 0.28 0.14 0.17 0.03 0.05 0.03 0.07] T (29)

[0102] Conduct single-factor fuzzy evaluation to obtain the evaluation matrix:

[0103] Let the membership degree of the i-th element in the factor set U to the first element in the evaluation set V be r i1, then the result of the single factor evaluation of the i-th element is expressed by fuzzy set: R i = {r i1 r i2 r i3 r i4 r i5}, with 5 single factor evaluation sets R i The rows form the fuzzy comprehensive evaluation matrix R 8×5 ;

[0104] Use the trapezoidal function to define the membership, u i The membership function for v1 is:

[0105]

[0106] u i The membership function for v2 is:

[0107]

[0108] u i The membership function for v3 is:

[0109]

[0110] u i The membership function for v4 is:

[0111]

[0112] u i The membership function for v5 is:

[0113]

[0114] The fuzzy comprehensive evaluation matrix is ​​as follows:

[0115]

[0116] In order to take all factors into consideration, the weight, fuzzy comprehensive evaluation matrix and evaluation score matrix are multiplied to obtain the final score B; B = W T ·R·v.

[0117] Compared with the prior art, the advantages of the present invention are:

[0118] 1. The scheme of the present invention provides a comprehensive performance evaluation method for a series hybrid power system suitable for heavy-duty vehicles. Through analysis of the object and theoretical analysis, two indicators for evaluating dynamic and coupling performance, namely engine generator torque coordination and front and rear power chain power coordination, are proposed, which solves the problem that static indicators have poor evaluation effect on the dynamic characteristics and coupling characteristics of the system.

[0119] 2. The present invention provides a comprehensive performance evaluation method for a series hybrid power system suitable for heavy-duty vehicles. Through analysis of the object and theoretical analysis, two indicators for evaluating dynamic performance, namely the coordination of energy supply from the auxiliary power source and the proportion of energy shortage from the main power source, are proposed, which solves the problem that static indicators have poor effect on evaluating the dynamic characteristics of the system.

[0120] 3. The scheme of the present invention provides a comprehensive performance evaluation method for a series hybrid power system suitable for heavy-duty vehicles. Through analysis of the object and theoretical analysis, four dynamic indicators are proposed, namely, engine generator torque coordination, front and rear power chain power coordination, main and auxiliary power source energy supply coordination, and main power source energy shortage ratio. At the same time, four static indicators, namely, engine speed average / maximum fluctuation rate and bus voltage average / maximum fluctuation rate, are combined. The hierarchical analysis method and fuzzy comprehensive evaluation method are used to systematically analyze these indicators to obtain the score and comments of the system comprehensive performance, thus solving the problem that the traditional evaluation method has poor effect on the evaluation of the system comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0121] Figure 1 , a flowchart of the use scheme of the comprehensive performance evaluation method of the present invention;

[0122] Figure 2 , curve graph of test data set 1;

[0123] Figure 3 , a scheme diagram for establishing a comprehensive performance evaluation method for a series hybrid power system of a heavy-duty vehicle. DETAILED DESCRIPTION

[0124] The specific implementation mode of the present invention is described below in conjunction with embodiments:

[0125] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0126] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0127] Embodiment 1:

[0128] The present invention discloses a comprehensive performance evaluation method for a series hybrid power system of a heavy-duty vehicle. The method uses four dynamic indicators, namely, engine generator torque coordination, front and rear power chain power coordination, main and auxiliary power source energy supply coordination, and main power source energy shortage ratio. The method also combines four static indicators, namely, engine speed average / maximum fluctuation rate, bus voltage average / maximum fluctuation rate, to calculate the score and comments of the system comprehensive performance using the analytic hierarchy process and the fuzzy comprehensive evaluation method. Two indicators for evaluating dynamic and coupling performance are the front and rear power chain power coordination and the engine generator torque coordination. The front and rear power chain power coordination is calculated by the power change rate of the generator and the drive motor, and is used to evaluate the stability of the bus voltage. The generator torque coordination index is calculated by the torque change rate of the engine and the generator, and is used to evaluate the stability of the engine speed. Two indicators for evaluating dynamic performance are the main and auxiliary power source energy supply coordination and the main power source energy shortage ratio. The main and auxiliary power source energy supply coordination is calculated using the generator and battery power, and is used to evaluate the coordination degree of the generator and battery coordinated work. The energy shortage ratio of the main power source is calculated using the total power of the generator and the drive motor, and is used to evaluate the coordination between the system's energy supply and consumption.

[0129] The present invention provides a comprehensive performance evaluation method for a series hybrid power system suitable for heavy-duty vehicles, and its usage scheme is as follows. The first step is to select a series hybrid power system heavy-duty vehicle as an evaluation object. The object can be an actual vehicle or a simulation model, and obtain vehicle parameters: engine and generator shaft inertia, supercapacitor capacitance, controller sampling time or simulation step size. The second step is to use the object vehicle to conduct a real vehicle test or a simulation test, and obtain operating data: engine speed, bus voltage, engine torque, generator torque, generator power, drive motor total power, battery discharge power and data segment time length. The third step is to calculate indicators based on vehicle parameters and operating data. The fourth step is to calculate a fuzzy evaluation matrix based on the indicators. The fifth step is to calculate the final score based on the weight, scoring matrix and fuzzy evaluation matrix. The sixth step is to obtain a comprehensive performance comment and score for the object.

[0130] Take an example to illustrate the calculation of the above usage scenario. In the first step, select a vehicle simulation model. The vehicle parameters of the vehicle are: the inertia of the engine and generator shaft is 0.7kg·m 2 , the supercapacitor value is 6×10 -6 F, the sampling time is 0.01 seconds. The second step is to use the vehicle model to conduct simulation tests. In its operating data, the data segment time length is 20 seconds. The images of other operating data are shown below.

[0131] The third step is to calculate indicators based on vehicle parameters and operating data.

[0132] Using the engine speed data, calculate the maximum and average engine speed fluctuations according to the following formula.

[0133]

[0134] Use the bus voltage data to calculate the maximum and average bus voltage fluctuations according to the following formula.

[0135]

[0136] The engine-generator torque coordination is calculated using the first-order derivative of the engine torque and the first-order derivative of the generator torque. The average value of the difference in torque change rate within each second is calculated, and then the maximum value of all average values ​​is selected to calculate the engine-generator torque coordination according to the following formula.

[0137]

[0138] The power coordination of the front and rear power chains is calculated using the first-order derivative of the generator power and the first-order derivative of the total power of the drive motor. The average value of the difference in power change rate within each second is calculated, and then the maximum value of all average values ​​is selected to calculate the power coordination of the front and rear power chains according to the following formula.

[0139]

[0140] Using the generator power and battery discharge power data, calculate the coordination of the main and auxiliary power sources according to the following formula.

[0141]

[0142] Use the generator power and the total drive motor power data to calculate the main power source energy shortage ratio according to the following formula.

[0143]

[0144] The indicators calculated from this segment of data are shown in Table 1 below.

[0145] Table 1 Indicators of test data set 1

[0146] index Numeric Average engine speed fluctuation rate 1.18％ Maximum engine speed fluctuation rate 3.83％ Average bus voltage fluctuation rate 0.64％ Maximum bus voltage fluctuation rate 3.07％ Coordination of energy supply between main and auxiliary power sources 2.50％ Energy shortage ratio of main power source 0.00％ Engine Generator Torque Coordination 37.41％ Front and rear power chain power coordination 3.09％

[0147] The fourth step is to calculate the fuzzy evaluation matrix according to the indicators. The fuzzy comprehensive evaluation matrix R is calculated using the above indicators as follows.

[0148]

[0149] Among them, each element in the matrix is ​​a trapezoidal membership function with the indicator as the independent variable. The trapezoidal membership function and the dividing points in the function are shown in Table 2 below.

[0150]

[0151] Table 2 Cut-off points in trapezoidal membership function

[0152]

[0153]

[0154] The fuzzy comprehensive evaluation matrix R calculated based on the indicators and trapezoidal membership function is shown below.

[0155]

[0156] Step 5: Calculate the final score based on the weight, score matrix and fuzzy evaluation matrix. W is the weight and v is the score. The specific values ​​are as follows.

[0157] W=[0.230.280.140.170.030.050.030.07] T

[0158] v =

[01234] T

[0159] The final score is calculated using the following formula.

[0160] B=W T ·R·v

[0161] The sixth step is to obtain the comprehensive performance evaluation and score of the object.

[0162] B=3.15

[0163] The corresponding evaluation scores are: 0 is excellent; 1 is good; 2 is fair; 3 is poor; 4 is very poor. Therefore, the evaluation score for this evaluation is poor.

[0164] Embodiment 2:

[0165] The present invention designs a comprehensive performance evaluation method for a series hybrid power system suitable for heavy-duty vehicles. First, an evaluation index is established to analyze the characteristics of the series hybrid power system of heavy-duty vehicles, and static indexes, dynamic indexes and coupling characteristic indexes are obtained through theoretical research; then, the hierarchical analysis method is used to assign weights to the indexes, and the obtained weights are checked for consistency. If they are unreasonable, they are recalculated; if they are reasonable, a comprehensive evaluation is performed; finally, the fuzzy comprehensive evaluation method is used to calculate the scores and comments based on the indexes and weights. The schematic diagram of the scheme is shown in the figure. Figure 3 shown.

[0166] The series hybrid system of heavy-duty vehicles is analyzed. This configuration transmits power through a high-voltage microgrid composed of an engine generator set, a power battery and a drive motor. The generator requires the engine to work stably to generate electricity, and the drive motor requires the generator to provide a stable voltage to work normally. The operating status of the engine generator set and the high-voltage microgrid determines the comprehensive performance of the series hybrid system. Therefore, the indicators are pointed out starting from the engine speed and bus voltage stability. Then, a dynamic indicator engine generator torque coordination is proposed for engine speed stability, and a dynamic indicator front and rear power chain power coordination is proposed for bus voltage stability, as well as coupling characteristic indicators main and auxiliary power source energy supply coordination and main power source energy shortage ratio. Next, the calculation process of each indicator is described in detail.

[0167] 1) Engine-generator torque coordination

[0168] In the heavy-duty vehicle series hybrid system, the engine is decoupled from the external working conditions. The system requires the engine to provide stable power, and the engine speed is kept stable as a prerequisite for providing stable power. Therefore, whether the engine speed can be kept stable is an important indicator for measuring the overall performance of the system. The dynamic change of the engine speed can be given according to Newton's laws of motion, as shown below.

[0169]

[0170] Where J is the sum of the moments of inertia of the engine and generator, ω e is the engine speed, T e , T g They are the engine torque and the generator torque respectively. According to the torque-speed relationship, it can be seen that the essence of maintaining a stable engine speed is the coordinated operation of the engine and the generator. The smaller the torque difference between the two, the more stable the speed. Further deriving both sides of the above equation, the influence of the dynamic change of torque on the speed is shown below.

[0171]

[0172] The dynamic changes of engine and generator torque are used to establish a dynamic index for evaluating engine speed. The requirement that the instantaneous fluctuation rate of engine speed within t0 seconds is less than n% can be expressed as:

[0173]

[0174] Among them, ω ref is the expected engine speed, and D is the integration domain. Substituting equation (22) into equation (23), we get:

[0175]

[0176] The selected t0 is small, so Approximately a constant, further obtained:

[0177]

[0178] This indicator means that in order to make the instantaneous fluctuation rate of engine speed less than n%, it is necessary Less than n.

[0179] 2) Power coordination between front and rear power chains

[0180] In the series hybrid system of heavy-duty vehicles, the bus voltage is the platform for energy conversion. The energy generated by the engine generator set is transmitted to the rear power chain through the bus. When the voltage is too low, the rated power of the drive motor cannot be fully utilized, resulting in the drive motor being unable to achieve normal operating efficiency; when the drive motor is running, additional current shocks will also be generated due to insufficient voltage, thus affecting the normal operation of the drive motor. Therefore, whether the bus voltage can remain stable is an important indicator for measuring the overall performance of the system.

[0181] Since the generator power accounts for most of the front power chain power and the drive motor power accounts for most of the rear power chain power, for the convenience of calculation, the current of the generator and the drive motor is used to calculate the dynamic change of the bus voltage according to the relationship between the capacitor voltage and current, as shown below.

[0182]

[0183] Where C is the capacitance of the supercapacitor, u bus is the bus voltage, i g 、i m are the generator DC current and the drive motor DC current respectively;

[0184] According to the voltage-current relationship, the essence of maintaining stable bus voltage is the coordinated operation of the generator and the drive motor. The smaller the DC current difference between the two, the more stable the bus voltage. Further deriving both sides of the above equation, the influence of the dynamic change of DC current on the bus voltage is shown below.

[0185]

[0186] The dynamic changes of the DC current of the engine and generator are used to establish the dynamic index for evaluating the bus voltage. The requirement that the instantaneous fluctuation rate of the bus voltage within t0 seconds is less than n% can be expressed as:

[0187]

[0188] Among them, u ref is the expected engine speed, and D is the integration domain. Substituting equation (27) into equation (28), we get:

[0189]

[0190] The selected t0 is small, so Approximately a constant, further obtained:

[0191]

[0192] This indicator means that in order to make the bus voltage instantaneous fluctuation rate less than n%, it is necessary Less than n.

[0193] 3) Coordination of energy supply between main and auxiliary power sources

[0194] In the series hybrid system of heavy-duty vehicles, the generator is used as the main power source because it can provide high power, and the battery is used as the auxiliary power source to supplement the energy due to its fast response characteristics. The coordination between these two power sources also determines the quality of the front power supply and affects the stability of the bus voltage. The main function of the battery as a power source is to "fill the valley", that is, to assist the generator to output more stable power. From the power curve, the total power curve of the generator and the battery needs to be smoother than the power curve of the generator. Therefore, the smoothness of the total power supply is used to establish the evaluation index of the coordination of the main and auxiliary power sources. The index calculation process is as follows.

[0195] First, the smoothness of the total power curve and the generator power curve is calculated using the method of integrating the absolute value of the second derivative of the curve divided by the length of the integration domain, as shown below.

[0196]

[0197] Among them, P sum is the total power, P g is the generator power, α sum is the smoothness of the total power curve, α g is the smoothness of the generator power curve, t1 and t2 are the start time and end time of the integration domain respectively.

[0198]

[0199] Among them, β is the coordination index of the energy supply of the main and auxiliary power sources. The smoothness of the straight line is 0, and the smoothness of the step curve is infinite, so the smaller the value of α, the smoother the curve. When the generator power curve is smoother than the total power curve, the closer the index is to 0, the better; when the total power curve is smoother than the generator power curve, the index reaches the ideal state and is set to 0.

[0200] 4) Proportion of energy shortage of main power source

[0201] In the heavy-duty vehicle series hybrid system, the engine generator set provides most of the energy as the main power source, and the energy storage device is used as an emergency measure to reduce peak loads and fill valleys in a small part of the time. This requires the engine generator set to meet the power demand of the drive motor most of the time. The part where the energy provided by the engine generator set is less than the required energy in a period of time is the shortage. Therefore, the energy shortage ratio of the main power source is proposed to evaluate the quality of the energy supply effect of the engine generator set.

[0202] Since the generator power accounts for most of the power of the front power chain and the drive motor power accounts for most of the power of the rear power chain, for the convenience of calculation, this indicator focuses on the generator and the drive motor. The energy shortage of the main power source is the difference between the energy consumed and the energy provided when the energy provided by the generator is less than the energy required by the drive motor. The proportion of the main power source energy shortage reflects the quality of the matching between the engine generator set and the drive motor, and is expressed by the ratio of the main power source energy shortage proportion to the total load demand energy over a period of time.

[0203] First, calculate the power shortage of the main power source, the formula is as follows:

[0204] ΔP=PP

[0205] gm

[0206]

[0207] Among them, P g , P m are the generator power and the drive motor power respectively, ΔP q The power shortage of the main power source is then integrated to calculate the energy shortage ratio of the main power source. The formula is as follows:

[0208]

[0209] The smaller the index is, the better the energy supply effect of the engine generator set is.

[0210] 5) Static indicators

[0211] In order to evaluate the comprehensive performance of the system, four static indicators are added on the basis of the above dynamic indicators: maximum fluctuation rate of engine speed, average fluctuation rate of engine speed, maximum fluctuation rate of bus voltage and average fluctuation rate of bus voltage.

[0212] The maximum fluctuation rate of engine speed is:

[0213]

[0214] The average fluctuation rate of engine speed is:

[0215]

[0216] Among them, ω is the engine speed, and t1 and t2 are the start and end times of the selected time period.

[0217] The maximum bus voltage fluctuation is:

[0218]

[0219] The average bus voltage fluctuation is:

[0220]

[0221] Among them, u is the bus voltage, t1 and t2 are the start and end times of the selected time period.

[0222] The calculation methods of each indicator are given above, but among multiple indicators, the degree of influence of each indicator on the comprehensive characteristics may be different. In order to improve the accuracy of the evaluation and make the results more in line with the actual situation, it is necessary to weight each indicator. Weighting helps to quantify the contribution of different indicators, reflect the importance of each indicator, and make more important indicators occupy a larger share in the comprehensive evaluation. The above indicators are weighted using the hierarchical analysis method. First, the judgment matrix is ​​constructed using the 1-9 scaling method. The 1-9 scaling method can quantify the relative importance of decision factors through a 1-9 scale, so that factors that are difficult to measure with data can be compared and analyzed. Among them, the meaning of each scale is shown in the following table.

[0223] Table 3 1-9 scaling method

[0224]

[0225] According to the meaning of the 1-9 scale, each index is compared in pairs to construct a judgment matrix, which provides a basis for subsequent weight calculation and decision analysis. The indexes proposed by the present invention are ranked from 1 to 8 as follows: average engine speed fluctuation rate, maximum engine speed fluctuation rate, average bus voltage fluctuation rate, maximum bus voltage fluctuation rate, coordination of energy supply between main and auxiliary power sources, energy shortage ratio of main power source, coordination of engine generator torque, and coordination of power of front and rear power chains. According to the above index sequence, the judgment matrix is ​​constructed as shown below.

[0226]

[0227] The meaning of this matrix is ​​that the data in the i-th row and j-th column is the scale of the i-th indicator to the j-th indicator. For example, compared with the first indicator, the average fluctuation rate of engine speed, and the second indicator, the maximum fluctuation rate of engine speed, the former is slightly more important than the latter, and the scale is 2.

[0228] Then, the judgment matrix is ​​sorted hierarchically, that is, the importance of each factor in the decision is quantified, and the weight of each indicator is calculated. The calculation process is as follows:

[0229] Multiply the elements of judgment matrix A row by row, and then calculate the nth power, where n is the order of matrix A, that is, the number of indicators, which is 8.

[0230]

[0231] where a ij is the data in the i-th row and j-th column of judgment matrix A. Normalize the calculated to obtain the weight matrix:

[0232]

[0233] The weight matrix W is obtained as follows.

[0234] W = [0.09 0.17 0.13 0.07 0.13 0.05 0.18 0.17] T (22)

[0235] To ensure that the above judgment matrix A and weight matrix W are logically consistent, that is, there is no contradictory or unreasonable ranking, it is necessary to further conduct a consistency test on them. First, calculate the largest eigenvalue of A, and the calculation formula is:

[0236]

[0237] Calculate C.I. according to the consistency index C.I. formula:

[0238]

[0239] According to the order of judgment matrix A, look up the table to obtain the random consistency index R.I., and the value table and R.I. are as follows:

[0240] Table 4 R.I. value table

[0241]

[0242] Calculate the consistency ratio C.R. to get:

[0243]

[0244] C.R. is less than 0.1, indicating that the consistency degree of judgment matrix A is considered within the allowable range, and there is no logical error such as A > B, B > C, but A < C. Therefore, the obtained weights can be used for calculation.

[0245] After obtaining the indicators and weights, in order to systematically analyze this multi-dimensional information and provide a comprehensive evaluation result, the fuzzy comprehensive evaluation method is used to calculate the scores and comments.

[0246] (1) Establish a comprehensive evaluation factor set, which is a set of various factors that affect the evaluation object, represented by U:

[0247] U={u1 u2 u3 u4 u5 u6 u7 u8}(26)

[0248] (2) Establish an evaluation set for comprehensive evaluation, which is a set of various possible results that the evaluator may make on the evaluation object, represented by V:

[0249] V={v1 v2 v3 v4 v5}

[0250] ={Excellent Good Average Poor Very Poor}(27)

[0251] The corresponding evaluation score matrix v is:

[0252] v =

[01234] T (28)

[0253] (3) Construct the weight matrix of each factor, and use the weight obtained by the hierarchical analysis method, represented by W:

[0254] W=[0.230.280.140.170.030.050.030.07] T (29)

[0255] (4) Perform single factor fuzzy evaluation to obtain the evaluation matrix

[0256] Suppose the membership degree of the i-th element in the factor set U to the first element in the evaluation set V is r i1 , then the result of the single factor evaluation of the i-th element is expressed by fuzzy set: R i = {r i1 r i2 r i3 r i4 r i5}, with 5 single factor evaluation sets R i The rows form the fuzzy comprehensive evaluation matrix R 8×5 .

[0257] Use the trapezoidal function to define the membership, u i The membership function for v1 is:

[0258]

[0259] u i The membership function for v2 is:

[0260]

[0261] u iThe membership function for v3 is:

[0262]

[0263] u i The membership function for v4 is:

[0264]

[0265] u i The membership function for v5 is:

[0266]

[0267] The fuzzy comprehensive evaluation matrix is ​​as follows:

[0268]

[0269] In order to take all factors into consideration, the weight, fuzzy comprehensive evaluation matrix and evaluation score matrix are multiplied to obtain the final score B.

[0270] B=W T ·R·v(36)

[0271] Furthermore, the present invention provides a comprehensive performance evaluation method for a heavy-duty vehicle series hybrid power system, wherein the method for calculating weights and final scores is not limited to the specific scheme proposed in the article. For example, the calculation of weights is not limited to the hierarchical analysis method of the present invention, and entropy weight method, expert survey method, year-on-year scoring method, etc. may also be used. The final score calculation method is not limited to the fuzzy comprehensive evaluation method of the present invention, and artificial neural network method, grey correlation method, etc. may also be used.

[0272] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0273] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0274] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0275] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0276] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

[0277] Many other changes and modifications may be made without departing from the concept and scope of the present invention.It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A method for evaluating the comprehensive performance of a heavy-duty vehicle series hybrid power system, characterized in that: The method comprises: Construct evaluation indicators, analyze the characteristics of the series hybrid power system of heavy-duty vehicles, and obtain static indicators, dynamic indicators and coupling characteristic indicators through theoretical research; use the hierarchical analysis method to weight the indicators, and perform a consistency check on the obtained weights. If they are unreasonable, recalculate them; if they are reasonable, conduct a comprehensive evaluation; based on the fuzzy comprehensive evaluation method, calculate the scores and comments according to the indicators and weights.

2. A comprehensive performance evaluation method for a heavy-duty vehicle series hybrid power system according to claim 1, characterized in that: The series hybrid system of heavy-duty vehicles is analyzed. The system transmits power through a high-voltage microgrid composed of an engine generator set, a power battery, and a drive motor. The generator requires the engine to work stably to generate electricity, and the drive motor requires the generator to provide a stable voltage to work normally. The operating status of the engine generator set and the high-voltage microgrid determines the comprehensive performance of the series hybrid system. Therefore, the indicators are constructed from the perspective of engine speed and bus voltage stability. The construction evaluation indicators include: Dynamic indicators, engine generator torque coordination: evaluate the stability of engine speed through the dynamic changes of engine and generator torque; front and rear power chain power coordination: evaluate the energy transfer effect based on bus voltage stability and the coordination of generator and drive motor current; Coupling characteristic indicators, coordination of energy supply between main and auxiliary power sources: based on the smoothness of the total power curve, measure the synergistic energy supply effect of the generator and the battery; energy shortage ratio of the main power source: evaluate whether the generator can meet the needs of the drive motor; Static indicators: Combine the four static indicators of engine speed and maximum and average fluctuation rate of bus voltage to measure the stability of the system under different operating conditions.

3. A comprehensive performance evaluation method for a heavy-duty vehicle series hybrid power system according to claim 1, characterized in that: The dynamic indicators specifically include: Engine generator torque coordination: In the series hybrid system of heavy-duty vehicles, the engine is decoupled from the external working conditions. The system requires the engine to provide stable power, and the stable engine speed is the premise for it to provide stable power. Therefore, whether the engine speed can be kept stable is an important indicator to measure the overall performance of the system; the dynamic change of the engine speed can be given according to Newton's laws of motion, as shown below: Where J is the sum of the moments of inertia of the engine and generator, ω e is the engine speed, T e , T g are the engine torque and the generator torque respectively. According to the torque-speed relationship, the essence of maintaining a stable engine speed is the coordinated operation of the engine and the generator. The smaller the torque difference between the two, the more stable the speed. Further deriving both sides of the above formula (1), the influence of the dynamic change of torque on the speed is as follows: The dynamic changes of the engine and generator torque are used to establish a dynamic index for evaluating the engine speed; the instantaneous fluctuation rate of the engine speed within t0 seconds is required to be less than n%, which can be expressed as: Among them, ω ref is the expected engine speed, D is the integration domain; Substituting equation (22) into equation (23), we get: The selected t0 is small, so Approximately a constant, further obtained: The meaning of this indicator is: In order to make the instantaneous fluctuation rate of engine speed less than n%, it is necessary is less than n; Front and rear power chain power coordination: In the series hybrid system of heavy-duty vehicles, the bus voltage is the platform for energy conversion. The energy generated by the engine generator set is transmitted to the rear power chain through the bus. When the voltage is too low, the rated power of the drive motor cannot be fully utilized, resulting in the drive motor being unable to achieve normal operating efficiency. When the drive motor is running, additional current shocks will also be generated due to insufficient voltage, thus affecting the normal operation of the drive motor. Therefore, whether the bus voltage can remain stable is an important indicator for measuring the overall performance of the system. Considering that the generator power accounts for most of the front power chain power, and the drive motor power accounts for most of the rear power chain power, for the convenience of calculation, the current of the generator and the drive motor is used to calculate the dynamic change of the bus voltage according to the relationship between the capacitor voltage and current, as shown below: Where C is the capacitance of the supercapacitor, u bus is the bus voltage, i g 、i m are the generator DC current and the drive motor DC current respectively, According to the voltage-current relationship, the essence of maintaining stable bus voltage is the coordinated operation of the generator and the drive motor. The smaller the DC current difference between the two, the more stable the bus voltage. Further deriving both sides of the above equation, the influence of the dynamic change of DC current on the bus voltage is as follows: The dynamic changes of the DC current of the engine and the generator are used to establish the dynamic index for evaluating the bus voltage; the instantaneous fluctuation rate of the bus voltage within t0 seconds is required to be less than n%, which can be expressed as: Among them, u ref is the expected engine speed, D is the integration domain; Substituting equation (27) into equation (28), we get: The selected t0 is small, so Δi in the above formula is approximated as a constant, and further obtained: The meaning of this indicator is: In order to make the instantaneous fluctuation rate of bus voltage less than n%, it is necessary Less than n.

4. A method for comprehensive performance evaluation of a heavy-duty vehicle series hybrid power system according to claim 1, characterized in that: The coupling characteristic index specifically includes: Coordination of energy supply between main and auxiliary power sources: In the series hybrid system of heavy-duty vehicles, the generator is used as the main power source because it can provide high power, and the battery is used as the auxiliary power source to supplement the energy due to its fast response characteristics. The coordination between the two power sources also determines the quality of the front power supply and affects the stability of the bus voltage; the main function of the battery as a power source is to fill the valley, that is, to assist the generator to output more stable power. From the power curve, the total power curve of the generator and the battery needs to be smoother than the power curve of the generator. Therefore, the smoothness of the total power supply is used to establish the evaluation index of the coordination of the main and auxiliary power sources. The index calculation process is as follows: First, the smoothness of the total power curve and the generator power curve is calculated by using the integral of the absolute value of the second derivative of the curve divided by the length of the integration domain, as shown below: Among them, P sum is the total power, P g is the generator power, α sum is the smoothness of the total power curve, α g is the smoothness of the generator power curve, t1 and t2 are the start time and end time of the integration domain respectively; Among them, β is the coordination index of the energy supply of the main and auxiliary power sources; the smoothness of the straight line is 0, and the smoothness of the step curve is infinite, so the smaller the value of α, the smoother the curve; when the generator power curve is smoother than the total power curve, the closer the index is to 0, the better; when the total power curve is smoother than the generator power curve, the index reaches the ideal state and is set to 0; The proportion of energy shortage of main power source: In the heavy-duty vehicle series hybrid system, the engine generator set provides most of the energy as the main power source, and the energy storage device is used as an emergency measure to reduce peak loads and fill valleys in a small part of the time. The engine generator set is required to meet the power demand of the drive motor most of the time. The part where the energy provided by the engine generator set is less than the required energy in a period of time is the shortage; therefore, the energy shortage ratio of the main power source is proposed to evaluate the quality of the energy supply effect of the engine generator set; Considering that the generator power accounts for most of the power of the front power chain, and the drive motor power accounts for most of the power of the rear power chain, this indicator focuses on the generator and the drive motor. The energy shortage of the main power source is the difference between the energy consumed and the energy provided when the energy provided by the generator is less than the energy required by the drive motor. The proportion of the main power source energy shortage reflects the matching quality of the engine generator set and the drive motor, and is expressed by the ratio of the main power source energy shortage proportion to the total load demand energy over a period of time; First, calculate the power shortage of the main power source, the formula is as follows: ΔP=P g -P m Among them, P g , P m are the generator power and the drive motor power respectively, ΔP q The power shortage of the main power source is then integrated to calculate the energy shortage ratio of the main power source. The formula is as follows: The smaller the index is, the better the energy supply effect of the engine generator set is.

5. A comprehensive performance evaluation method for a heavy-duty vehicle series hybrid power system according to claim 1, characterized in that: The static indicators specifically include: To evaluate the comprehensive performance of the system, four static indicators are added on the basis of the above dynamic indicators: the maximum volatility of the engine speed, the average volatility of the engine speed, the maximum volatility of the bus voltage, and the average volatility of the bus voltage; The maximum volatility of the engine speed is: The average volatility of the engine speed is: Where ω is the engine speed, and t1 and t2 are the start and end times of the selected time period; The maximum volatility of the bus voltage is: The average volatility of the bus voltage is: Where u is the bus voltage, and t1 and t2 are the start and end times of the selected time period.

6. A method for comprehensive performance evaluation of a heavy-duty vehicle series hybrid power system according to claim 1, characterized in that: Use the analytic hierarchy process to assign weights to the indicators and conduct a consistency test on the obtained weights, including: Construct a judgment matrix: Use the 1-9 scale method, make pairwise comparisons according to the relative importance of the indicators, and construct the judgment matrix A; Calculate the weight: Take the product of the judgment matrix A by row elements, and then find The power, n is the order of matrix A, calculate the relative weight of each indicator; normalize the weight result to form the weight matrix W; Consistency test: Calculate the maximum eigenvalue of the judgment matrix A, and calculate the consistency ratio and test the consistency ratio according to the consistency index formula and the random consistency index to confirm the consistency of the judgment matrix; Apply weights: If the consistency test passes, use the weight matrix for comprehensive evaluation.

7. A method for evaluating the comprehensive performance of a heavy-duty vehicle series hybrid power system according to claim 6, characterized in that: Use the analytic hierarchy process to assign weights to the indicators and conduct a consistency test on the obtained weights, including: First, construct a judgment matrix using the 1-9 scale method; the 1-9 scale method quantifies the relative importance of decision-making factors through a scale of 1-9; According to the meaning of the 1-9 scale, make pairwise comparisons of each indicator to construct a judgment matrix, providing a basis for subsequent weight calculation and decision analysis; sort the proposed indicators, from 1 to 8 are: the average volatility of the engine speed, the maximum volatility of the engine speed, the average volatility of the bus voltage, the maximum volatility of the bus voltage, the energy supply coordination of the main and auxiliary power sources, the proportion of the energy deficit of the main power source, the torque coordination of the engine generator, and the power coordination of the front and rear power chains; according to the above indicator order, the judgment matrix is constructed as follows: The meaning of this matrix is that the data in the i-th row and j-th column is the scale of the i-th indicator to the j-th indicator. For example, when the first indicator, the average volatility of the engine speed, is compared with the second indicator, the maximum volatility of the engine speed, the former is slightly more important than the latter, and the scale is 2; Then, conduct a hierarchical single sorting of the judgment matrix, that is, quantify the importance of each factor in the decision-making, and calculate the weight of each indicator; the calculation process is as follows: Take the product of the judgment matrix A by row elements, and then find power, n is the order of matrix A, that is, the number of indicators 8; Among them, a ij is the data of the i-th row and j-th column of the judgment matrix A; the calculated Normalize and get the weight matrix: The obtained weight matrix W is as follows: W＝[0.090.170.130.070.130.050.180.17] T (22) To ensure that the above judgment matrix A and weight matrix W are logically self-consistent, that is, there are no contradictions or unreasonable rankings, it is necessary to further conduct a consistency test on it; first calculate the maximum eigenvalue of A, and the calculation formula is: Calculate C.I. according to the consistency index C.I. formula: According to the order of the judgment matrix A, look up the table to obtain the random consistency index R.I.; calculate the consistency ratio C.R. to get: C.R. is less than 0.1, indicating that the consistency degree of the judgment matrix A is considered within the allowable range, and there are no logical errors such as A > B, B > C, but A < C, so the obtained weights can be used for calculation.

8. A method for evaluating comprehensive performance of a heavy-duty vehicle series hybrid power system according to claim 1, characterized in that: Use the fuzzy comprehensive evaluation method to calculate the score and comments, specifically including: Establish a comprehensive evaluation factor set, which is a set of various factors that affect the evaluation object, represented by U: U={u1 u2 u3 u4 u5 u6 u7 u8} (26) Establish an evaluation set for comprehensive evaluation, which is a set of various possible results that the evaluator may make on the evaluation object, represented by V: V={v1 v2 v3 v4 v5}={excellent, good, moderate, poor, very poor} (27) The corresponding evaluation score matrix v is: v＝[0 1 2 3 4] T (28) Construct the weight matrix of each factor, and use the weight obtained by the hierarchical analysis method, represented by W: W＝[0.23 0.28 0.14 0.17 0.03 0.05 0.03 0.07] T (29) Perform single factor fuzzy evaluation and obtain the evaluation matrix: Suppose the membership degree of the i-th element in the factor set U to the first element in the evaluation set V is r i1 , then the result of the single factor evaluation of the i-th element is expressed by fuzzy set: R i = {r i1 r i2 r i3 r i4 r i5 }, with 5 single factor evaluation sets R i The rows form the fuzzy comprehensive evaluation matrix R 8×5 ; Use the trapezoidal function to define the membership, u i The membership function for v1 is: u i The membership function for v2 is: u i The membership function for v3 is: u i The membership function for v4 is: u i The membership function for v5 is: The fuzzy comprehensive evaluation matrix is ​​as follows: In order to take all factors into consideration, the weight, fuzzy comprehensive evaluation matrix and evaluation score matrix are multiplied to obtain the final score B; B = W T ·R·v.

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