A Comprehensive Performance Evaluation Method for Series Hybrid Power Systems in Heavy-Duty Vehicles

Abstract

This invention discloses a comprehensive performance evaluation method for a series hybrid power system in heavy-duty vehicles. Through analysis of the target object and theoretical analysis, four indicators are proposed to evaluate the dynamic performance and coupling characteristics of the system: engine-generator torque coordination, front-to-rear power chain power coordination, main and auxiliary power source energy supply coordination, and the proportion of energy deficit in the main power source. Combined with four static indicators—average / maximum fluctuation rate of engine speed and average / maximum fluctuation rate of bus voltage—a comprehensive performance evaluation method is constructed using the analytic hierarchy process (AHP) and fuzzy comprehensive evaluation method, achieving the evaluation of the system's static, dynamic, and coupling characteristics. Even when significant changes in vehicle load cause strong dynamic changes in the system state, the proposed comprehensive performance evaluation method still demonstrates good evaluation results, solving the problem that static indicators and single-component indicators cannot effectively evaluate the overall system performance.

Description

Technical Field

[0001] This invention belongs to the field of hybrid vehicles, specifically relating to a comprehensive performance evaluation method for a series hybrid power system for heavy-duty vehicles. Background Technology

[0002] Hybrid vehicles represent a major direction for the transformation and upgrading of the global automotive industry and its green development. Heavy-duty vehicles, as a key force in engineering operations, unstructured road transportation, and military applications, play a vital role in social development and national defense. Therefore, the transition to hybrid powertrains in heavy-duty vehicles has become a major development trend. Series hybrid powertrain systems are one of the main powertrain configurations used in heavy-duty vehicles. However, different structural parameters, control methods, and road excitations make the system characteristics of this configuration increasingly complex, and the system performance is difficult to compare and evaluate. How to evaluate the overall performance of hybrid powertrain systems has become an important issue. Therefore, researching comprehensive performance evaluation methods suitable for series hybrid powertrain systems in heavy-duty vehicles is a primary task at present.

[0003] Current comprehensive performance evaluation methods for series hybrid power systems in heavy-duty vehicles are mainly extensions of performance evaluation methods for mechanical transmission systems or medium- and light-duty hybrid power systems, such as static, single-component indicators like voltage ripple coefficient, efficiency, mass power density, and volumetric power density. However, compared to mechanical transmission vehicles or medium- and light-duty vehicles, heavy-duty vehicle series hybrid power systems are characterized by complex operating environments, high overall vehicle power levels, small battery energy proportions, and more prominent electromechanical coupling characteristics. Under conditions of significant power fluctuations and intense dynamic changes in system state, static and single-component indicators are insufficient to assess the overall system performance. Furthermore, evaluating the performance of components such as the drive motor only reflects the performance of individual components and cannot reflect the system performance resulting from the high electromechanical coupling characteristics. To address these issues and accurately evaluate the comprehensive performance of heavy-duty vehicle hybrid power systems, this invention proposes a comprehensive performance evaluation method for series hybrid power systems suitable for heavy-duty vehicles. Summary of the Invention

[0004] In order to solve the technical problems existing in the background art, the present invention aims to provide a comprehensive performance evaluation method for heavy-duty vehicle series hybrid power systems.

[0005] To solve the technical problem, the technical solution of the present invention is as follows:

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

[0007] Evaluation indices were constructed to analyze the characteristics of the series hybrid power system of heavy-duty vehicles. Static, dynamic, and coupling characteristic indices were derived through theoretical research. The analytic hierarchy process (AHP) was used to assign weights to the indices, and the consistency of the weights was checked. If the weights were not reasonable, they were recalculated; if they were reasonable, a comprehensive evaluation was conducted. Based on the fuzzy comprehensive evaluation method, scores and comments were calculated according to the indices and weights.

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

[0009] The evaluation indicators for the construction include:

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

[0011] Coupling characteristic indicators, coordination of main and auxiliary power sources: based on the smoothness of the total power curve, it measures the synergistic power supply effect of the generator and battery; proportion of energy deficit of main power source: assesses whether the generator can meet the needs of the drive motor;

[0012] Static indicators: Combining four static indicators—engine speed, 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 heavy-duty vehicle series hybrid systems, the engine is decoupled from external operating conditions. The system requires the engine to provide stable power, and maintaining a stable engine speed is a prerequisite for providing stable power. Therefore, whether the engine speed can remain stable is an important indicator for measuring the overall performance of the system. The dynamic changes in engine speed can be given by Newton's laws of motion, as shown below:

[0016]

[0017] Where J is the sum of the rotational inertia of the engine and generator, ω e T is the engine speed. e Tg These are the engine torque and the generator torque, respectively. According to the torque-speed relationship, the essence of maintaining stable engine speed is the coordinated operation of the engine and generator; the smaller the torque difference between the two, the more stable the speed. Further differentiating both sides of equation (1), the influence of dynamic torque changes on speed is shown below:

[0018]

[0019] A dynamic index for evaluating engine speed is established using the dynamic changes in engine and generator torque; the requirement that the instantaneous fluctuation rate of engine speed within t0 seconds be less than n% can be expressed as:

[0020]

[0021] Where, ω ref Let D be the desired engine speed, and D be the integration domain; substituting equation (2) into equation (3), we get:

[0022]

[0023] Since the chosen t0 is relatively small, the above formula is... Approximating a constant, we further obtain:

[0024]

[0025] This indicator means that in order to make the instantaneous fluctuation rate of engine speed less than n%, it is necessary to... Less than n;

[0026] Power coordination between front and rear power chains:

[0027] In heavy-duty vehicle series hybrid power systems, the bus voltage is the energy conversion platform. The energy generated by the engine generator set is transferred to the downstream power chain via the bus. When the voltage is too low, the rated power of the drive motor cannot be fully utilized, resulting in the drive motor not achieving normal operating efficiency. When the drive motor is running, it will also generate additional current surges due to insufficient voltage, which will affect the normal operation of the drive motor. Therefore, whether the bus voltage can be kept stable is an important indicator for measuring the overall performance of the system.

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

[0029]

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

[0031] According to the voltage-current relationship, the essence of maintaining a 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 differentiating both sides of the above equation, the influence of dynamic changes in DC current on the bus voltage is shown below:

[0032]

[0033] A dynamic index for evaluating bus voltage is established using the dynamic changes in DC current of the engine and generator; 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 Let D be the desired engine speed, and D be the integration domain; substituting equation (7) into equation (8), we get:

[0036]

[0037] Since the chosen t0 is relatively small, the above formula is... Approximating a constant, we further obtain:

[0038]

[0039] This indicator means that in order to ensure the instantaneous fluctuation rate of the bus voltage is less than n%, it is necessary to... Less than n.

[0040] Furthermore, the coupling characteristic indicators specifically include:

[0041] Coordination of main and auxiliary power sources:

[0042] In a series hybrid power system for heavy-duty vehicles, the generator provides high power as the primary power source, while the battery, with its rapid response, serves as a secondary power source to supplement the power supply. The coordination between these two power sources determines the quality of the primary power supply and affects the stability of the bus voltage. The main role of the battery as a power source is to fill valleys, that is, to assist the generator in outputting more stable power. From the power curve perspective, the total power curve of the generator and battery needs to be smoother than the generator's power curve. Therefore, the smoothness of the total power supply is used to establish an evaluation index for the coordination of the primary and secondary 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 dividing the integral of the absolute value of the second derivative of the curve by the length of the integration domain, as shown below:

[0044]

[0045] Among them, P sum For the total power, P g For generator power, α sum For the smoothness of the total power curve, α g The generator power curve smoothness is represented by t1 and t2, which are the start and end times of the integration domain, respectively.

[0046]

[0047] Among them, β is the coordination index of power supply from the main and auxiliary power sources; the smoothness of a straight line is 0, while the smoothness of a step curve is infinitely large, 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 this index is to 0, the better; when the total power curve is smoother than the generator power curve, this index reaches the ideal state and is set to 0.

[0048] Percentage of energy deficit from primary power sources:

[0049] In a series hybrid power system for heavy-duty vehicles, the engine-generator set serves as the primary power source, providing most of the energy. The energy storage device acts as an emergency measure, shaving off peak loads and filling valleys for a limited period of time. The goal is for the engine-generator set to meet the power demand of the drive motor most of the time. The portion of the time when the energy provided by the engine-generator set is less than the required energy is called the deficit. Therefore, this paper proposes to evaluate the quality of the engine-generator set's energy supply performance by using the proportion of the primary power source's energy deficit.

[0050] Considering that generator power accounts for most of the power in the front power chain and drive motor power accounts for most of the power in the rear power chain, this indicator focuses on the generator and drive motor. The main power source energy deficit 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 main power source energy deficit reflects the quality of matching between the engine generator set and the drive motor, and is expressed as the ratio of the proportion of main power source energy deficit to the total load energy demand over a period of time.

[0051] First, calculate the power deficit of the main power source, using the following formula:

[0052]

[0053] Among them, P g P m These represent the generator power and drive motor power, ΔP q The power deficit of the main power source is calculated; then the power is integrated, and the proportion of the power deficit of the main power source is calculated, as shown in the following formula:

[0054]

[0055] The smaller this indicator is, the better the power supply effect of the engine generator set.

[0056] Furthermore, the static indicators specifically include:

[0057] To evaluate the overall performance of the system, four static indicators are added to the above dynamic indicators: maximum engine speed fluctuation rate, average engine speed fluctuation rate, maximum bus voltage fluctuation rate, and average bus voltage fluctuation rate.

[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, and t1 and t2 are the start and end times of the selected time period;

[0063] The maximum fluctuation rate of the bus voltage is:

[0064]

[0065] The average fluctuation rate of the bus voltage is:

[0066]

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

[0068] Furthermore, the analytic hierarchy process (AHP) is used to assign weights to the indicators, and the resulting weights are subjected to a consistency test, including:

[0069] Construct the judgment matrix: Using the 1-9 scale method, perform pairwise comparisons based on the relative importance of the indicators to construct the judgment matrix A;

[0070] Calculate the weights: Multiply the judgment matrix A by its row elements, then calculate... The power of n is the order of matrix A. Calculate the relative weights of each index; normalize the weight results to form the weight matrix W.

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

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

[0073] Furthermore, the analytic hierarchy process (AHP) is used to assign weights to the indicators, and the resulting weights are subjected to a consistency test, including:

[0074] First, a 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] Based on the meaning of the 1-9 scale, each indicator is compared pairwise to construct a judgment matrix, providing a foundation 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, main and auxiliary power source power supply coordination, main power source energy deficit ratio, engine-generator torque coordination, and front and rear power chain power coordination. Based on the above indicator order, 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, compared with the second indicator, the maximum fluctuation rate of engine speed, the first indicator, the average fluctuation rate of engine speed, is slightly more important than the second indicator, so the scale is 2.

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

[0079] Multiply the judgment matrix A by its row elements, then calculate... The power of n is the order of matrix A, i.e., the number of indices is 8;

[0080]

[0081] Among them, a ij To determine the data in the i-th row and j-th column of matrix A; the calculated data will be... Normalization yields 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] To ensure that the judgment matrix A and the weight matrix W are logically consistent, i.e., without contradictions or unreasonable ordering, a further consistency check is needed. First, the largest eigenvalue of A is calculated using the following formula:

[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 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 a factor set for comprehensive evaluation, which is a set composed of various factors that affect the evaluation object, represented by U:

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

[0095] Establish an evaluation set for comprehensive evaluation, which is a set composed of various results that the evaluator may give to the evaluation object, 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 i1Then, the result of the single-factor evaluation of the i-th element is represented by a fuzzy set as: R i ={r i1 r i2 r i3 r i4 r i5}, using 5 single-factor evaluation sets R i The fuzzy comprehensive evaluation matrix R is formed by rows. 8×5 ;

[0104] Membership degrees are defined using trapezoidal functions, 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 ​​obtained as follows:

[0115]

[0116] To take all factors into account, the final score B is obtained by multiplying the weights, the fuzzy comprehensive evaluation matrix, and the evaluation score matrix; B = W T ·R·v.

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

[0118] 1. The present invention provides a comprehensive performance evaluation method for a series hybrid power system applicable to heavy-duty vehicles. Through analysis of the analysis object and theoretical analysis, two indicators for evaluating dynamic and coupling performance are proposed: engine-generator torque coordination and front-to-back power chain power coordination. This solves the problem that static indicators are not effective in evaluating the dynamic and coupling characteristics of the system.

[0119] 2. The present invention provides a comprehensive performance evaluation method for a series hybrid power system applicable to heavy-duty vehicles. Through analysis of the analysis object and theoretical analysis, it proposes two indicators for evaluating dynamic performance: the coordination of power supply from the secondary power source and the proportion of energy deficit from the primary power source. This solves the problem that static indicators are not effective in evaluating the dynamic characteristics of the system.

[0120] 3. The present invention provides a comprehensive performance evaluation method for series hybrid power systems applicable to heavy-duty vehicles. Through analysis of the analysis object and theoretical analysis, four dynamic indicators are proposed: engine-generator torque coordination, front and rear power chain power coordination, main and auxiliary power source energy supply coordination, and the proportion of energy deficit in the main power source. At the same time, four static indicators are combined with the average / maximum fluctuation rate of engine speed and the average / maximum fluctuation rate of bus voltage. The analytic hierarchy process and fuzzy comprehensive evaluation method are used to systematically analyze these indicators to obtain a score and evaluation of the system's comprehensive performance, which solves the problem that traditional evaluation methods have poor effects on the comprehensive performance evaluation of systems. Attached Figure Description

[0121] Figure 1 A flowchart illustrating the usage scheme of the comprehensive performance evaluation method of this invention;

[0122] Figure 2 Experimental data group 1 curve graph;

[0123] Figure 3 A schematic diagram of a scheme for establishing a comprehensive performance evaluation method for series hybrid power systems of heavy-duty vehicles. Detailed Implementation

[0124] The specific implementation of the present invention is described below with reference to embodiments:

[0125] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0126] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0127] Example 1:

[0128] This invention discloses a comprehensive performance evaluation method for a series hybrid power system in heavy-duty vehicles. It utilizes four dynamic indicators: engine-generator torque coordination, front-to-rear power chain power coordination, main and auxiliary power source energy supply coordination, and the proportion of energy deficit in the main power source. Simultaneously, it incorporates four static indicators: average / maximum engine speed fluctuation rate and average / maximum bus voltage fluctuation rate. The method employs the analytic hierarchy process (AHP) and fuzzy comprehensive evaluation to calculate the overall system performance score and evaluation. Two indicators are used to evaluate dynamic and coupling performance: front-to-rear power chain power coordination and engine-generator torque coordination. Front-to-rear power chain power coordination is calculated using the power change rate between the generator and drive motor, and is used to assess the stability of the bus voltage. Generator torque coordination is calculated using the torque change rate between the engine and generator, and is used to assess the stability of engine speed. Two indicators are used to evaluate dynamic performance: main and auxiliary power source energy supply coordination and the proportion of energy deficit in the main power source. Main and auxiliary power source energy supply coordination is calculated using the power of the generator and battery, and is used to assess the degree of coordination between the generator and battery. The percentage of energy deficit from the main power source is calculated using the total power of the generator and drive motor, and is used to evaluate the quality of the coordination between the system's energy supply and consumption.

[0129] This invention provides a comprehensive performance evaluation method for series hybrid power systems applicable to heavy-duty vehicles, the usage of which is as follows: First, select a heavy-duty vehicle as the evaluation object, which 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. Second, conduct real-vehicle tests or simulation tests using the selected vehicle, and obtain operating data: engine speed, bus voltage, engine torque, generator torque, generator power, total drive motor power, battery discharge power, and data segment length. Third, calculate indicators based on vehicle parameters and operating data. Fourth, calculate a fuzzy evaluation matrix based on the indicators. Fifth, calculate the final score based on weights, a scoring matrix, and the fuzzy evaluation matrix. Sixth, obtain the comprehensive performance evaluation and score for the selected vehicle.

[0130] To illustrate the calculation of the above usage scheme, the first step is to select a vehicle simulation model with the following parameters: engine and generator shaft inertia of 0.7 kg·m. 2 The supercapacitor value is 6×10 -6 F, sampling time is 0.01 seconds. The second step is to use this vehicle model for simulation testing. The data segment length is 20 seconds, and the images of other data are shown below.

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

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

[0133]

[0134] Using bus voltage data, 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 derivative of engine torque and the first derivative of generator torque. The average difference of the torque change rate within each second is calculated, and then the maximum value among all average values ​​is selected. The engine-generator torque coordination is then calculated according to the following formula.

[0137]

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

[0139]

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

[0141]

[0142] Using the generator power and total drive motor power data, calculate the proportion of energy deficit from the main power source according to the following formula.

[0143]

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

[0145] Table 1. Indicators of Experimental Data Group 1

[0146] index numerical values engine speed average fluctuation 1.18％ Maximum fluctuation of engine speed 3.83％ Average fluctuation of bus voltage 0.64％ Maximum fluctuation rate of bus voltage 3.07％ Coordination of main and auxiliary power sources 2.50％ Active power source energy deficit ratio 0.00％ Engine-generator torque coordination 37.41％ Power coordination between front and rear power chains 3.09％

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

[0148]

[0149] Each element in the matrix is ​​a trapezoidal membership function with an index as the independent variable. The trapezoidal membership functions and the boundary points in the functions are shown in Table 2 below.

[0150]

[0151] Table 2. Boundary points in the trapezoidal membership function

[0152]

[0153]

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

[0155]

[0156] The fifth step is to calculate the final score based on the weights, the scoring matrix, and the fuzzy evaluation matrix. W represents the weights, and v represents the score, with specific values ​​shown below.

[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 a comprehensive performance evaluation and score for the object.

[0162] B = 3.15

[0163] The comments and scores correspond as follows: 0 for Excellent; 1 for Good; 2 for Average; 3 for Poor; and 4 for Very Poor. Therefore, the comment for this assessment is Poor.

[0164] Example 2:

[0165] This invention designs a comprehensive performance evaluation method for series hybrid power systems suitable for heavy-duty vehicles. First, evaluation indicators are established, and the characteristics of the series hybrid power system in heavy-duty vehicles are analyzed. Static indicators, dynamic indicators, and coupling characteristic indicators are derived through theoretical research. Then, the analytic hierarchy process (AHP) is used to assign weights to the indicators, and the consistency of the weights is checked. If the weights are unreasonable, they are recalculated; if they are reasonable, a comprehensive evaluation is performed. Finally, the fuzzy comprehensive evaluation method is used to calculate scores and comments based on the indicators and weights. A schematic diagram of the scheme is shown below. Figure 3 As shown.

[0166] This paper analyzes a series hybrid power system for heavy-duty vehicles. This configuration transmits power through a high-voltage microgrid consisting of an engine-generator set, a power battery, and a drive motor. The generator requires stable engine operation to generate electricity, and the drive motor requires a stable voltage from the generator to operate normally. The operating status of the engine-generator set and the high-voltage microgrid determines the overall performance of the series hybrid power system. Therefore, the paper identifies indicators based on engine speed and bus voltage stability. Then, for engine speed stability, a dynamic indicator of engine-generator torque coordination is proposed; for bus voltage stability, a dynamic indicator of front-to-back power chain power coordination is proposed; and coupling characteristic indicators include the energy supply coordination of the main and auxiliary power sources and the proportion of energy deficit in the main power source. The calculation process for each indicator is described in detail below.

[0167] 1) Engine-generator torque coordination

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

[0169]

[0170] Where J is the sum of the rotational inertia of the engine and generator, ω e T is the engine speed. e T g These represent engine torque and generator torque, respectively. According to the torque-speed relationship, the essence of maintaining stable engine speed is the coordinated operation of the engine and generator; the smaller the torque difference between the two, the more stable the speed. Further differentiating both sides of the above equation, the influence of dynamic torque changes on speed is shown below.

[0171]

[0172] Dynamic indices for evaluating engine speed are established using the dynamic changes in engine and generator torque. The requirement that the instantaneous fluctuation rate of engine speed within seconds t0 be less than n% can be expressed as:

[0173]

[0174] Where, ω ref Let D be the desired engine speed, and D be the integration domain. Substituting equation (22) into equation (23), we get:

[0175]

[0176] Since the chosen t0 is relatively small, the above formula is... Approximating a constant, we further obtain:

[0177]

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

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

[0180] In heavy-duty vehicle series hybrid power systems, the bus voltage serves as the energy conversion platform. The energy generated by the engine-generator set is transferred to the downstream power chain via the bus. When the voltage is too low, the rated power of the drive motor cannot be fully utilized, resulting in the drive motor failing to achieve normal operating efficiency. Furthermore, insufficient voltage can cause additional current surges in the drive motor during operation, further affecting its normal operation. Therefore, maintaining a stable bus voltage is a crucial indicator for evaluating the overall system performance.

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

[0182]

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

[0184] According to the voltage-current relationship, the essence of maintaining a 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 differentiating both sides of the above equation, the influence of dynamic changes in DC current on the bus voltage is shown below.

[0185]

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

[0187]

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

[0189]

[0190] Since the chosen t0 is relatively small, the above formula is... Approximating a constant, we further obtain:

[0191]

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

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

[0194] In a series hybrid power system for heavy-duty vehicles, the generator serves as the primary power source due to its high power output, while the battery, with its rapid response, acts as a secondary power source to supplement the power supply. The coordination between these two power sources determines the quality of the primary power supply and affects the stability of the bus voltage. The main role of the battery as a power source is to "fill the valleys," that is, to assist the generator in outputting more stable power. From the perspective of power curves, the total power curve of the generator and battery needs to be smoother than the generator's power curve. Therefore, the smoothness of the total power supply is used to establish an evaluation index for the coordination of the primary and secondary power sources. The calculation process for the index is as follows.

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

[0196]

[0197] Among them, P sum For the total power, P g For generator power, α sum For the smoothness of the total power curve, α g Let t1 and t2 represent the smoothness of the generator power curve, and t1 and t2 represent the start and end times of the integration domain, respectively.

[0198]

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

[0200] 4) Proportion of energy deficit from primary power sources

[0201] In heavy-duty vehicle series hybrid systems, the engine-generator set serves as the primary power source, providing most of the energy. Energy storage devices act as an emergency measure, shaving off peak demand for a limited period. This necessitates that the engine-generator set meet the power requirements of the drive motor most of the time. The portion of the time when the engine-generator set provides less energy than required is called a power deficit. Therefore, this paper proposes using the proportion of the primary power source energy deficit to evaluate the effectiveness of the engine-generator set's power supply.

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

[0203] First, calculate the power deficit of the main power source, using the following formula:

[0204] ΔP=PP

[0205] gm

[0206]

[0207] Among them, P g P m These represent the generator power and drive motor power, ΔP q The power deficit is calculated as follows: The power is then integrated, and the proportion of the power deficit in the main power source is calculated using the following formula:

[0208]

[0209] The smaller this indicator is, the better the power supply effect of the engine generator set.

[0210] 5) Static Indicators

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

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

[0213]

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

[0215]

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

[0217] The maximum fluctuation rate of the bus voltage is:

[0218]

[0219] The average fluctuation rate of the bus voltage is:

[0220]

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

[0222] The calculation methods for each indicator are given above. However, among multiple indicators, the degree of influence of each indicator on the overall characteristics may vary. To improve the accuracy of the evaluation and make the results more consistent with reality, it is necessary to assign weights to each indicator. Weighting helps to quantify the contribution of different indicators, reflect the importance of each indicator, and allow more important indicators to occupy a larger share in the overall evaluation. The Analytic Hierarchy Process (AHP) is used to assign weights to the above indicators. First, a judgment matrix is ​​constructed using the 1-9 scale method. The 1-9 scale method can quantify the relative importance of decision factors through a 1-9 scale, making it possible to compare and analyze factors that are difficult to measure with data. The meaning of each scale is shown in the table below.

[0223] Table 3 1-9 Scale Method

[0224]

[0225] Based on the meaning of the 1-9 scale, each indicator is compared pairwise to construct a judgment matrix, providing a foundation for subsequent weight calculation and decision analysis. The indicators proposed in this 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, main and auxiliary power source power supply coordination, main power source energy deficit ratio, engine-generator torque coordination, and front-to-back power chain power coordination. The judgment matrix is ​​constructed according to the above indicator order 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 second indicator, the maximum fluctuation rate of engine speed, the first indicator, the average fluctuation rate of engine speed, is slightly more important than the second indicator, so the scale is 2.

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

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

[0230]

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

[0232]

[0233] The weight matrix W is 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 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:

[0236]

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

[0238]

[0239] According to the order of the 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 the judgment matrix A is considered to be within the allowable range, and there are no logical errors 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, denoted by U:

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

[0248] (2) Establish a comprehensive evaluation set, which is a set of all possible outcomes that evaluators may make regarding the evaluated object, denoted by V:

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

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

[0251] Its corresponding evaluation score matrix v is:

[0252] v =

[01234] T (28)

[0253] (3) Construct the weight matrix for each factor. The weights obtained using the analytic hierarchy process are denoted 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] Let r be the membership degree of the i-th element in the factor set U to the 1-th element in the evaluation set V. i1 Then, the result of the single-factor evaluation of the i-th element is represented by a fuzzy set as: R i ={r i1 r i2 r i3 r i4 r i5}, using 5 single-factor evaluation sets R i The fuzzy comprehensive evaluation matrix R is formed by rows. 8×5 .

[0257] Membership degrees are defined using trapezoidal functions, 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 ​​obtained as follows:

[0268]

[0269] To take into account all factors, the final score B is obtained by multiplying the weights, the fuzzy comprehensive evaluation matrix, and the evaluation score matrix.

[0270] B = W T ·R·v(36)

[0271] Furthermore, this invention provides a comprehensive performance evaluation method for a series hybrid power system for heavy-duty vehicles. The method for calculating weights and final scores is not limited to the specific scheme proposed in this paper. For example, the calculation of weights is not limited to the analytic hierarchy process of this invention, but can also use the entropy weight method, expert survey method, chain ratio scoring method, etc. The method for calculating final scores is not limited to the fuzzy comprehensive evaluation method of this invention, but can also use the artificial neural network method, grey relational analysis method, etc.

[0272] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, 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 magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0273] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0274] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The 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 operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device 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 have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

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

Claims

1. A method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles, characterized in that, The method includes: Evaluation indicators were constructed to analyze the characteristics of the series hybrid power system of heavy-duty vehicles. Static indicators, dynamic indicators, and coupling characteristic indicators were derived through theoretical research. The analytic hierarchy process (AHP) was used to assign weights to the indicators, and the consistency of the weights was checked. If the weights were unreasonable, they were recalculated; if they were reasonable, a comprehensive evaluation was conducted. Based on the fuzzy comprehensive evaluation method, scores and comments were calculated according to the indicators and weights. The series hybrid power system of heavy 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 needs the engine to work stably to generate electricity, and the drive motor needs 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 overall performance of the series hybrid power system. Therefore, the index is constructed from the perspective of engine speed and bus voltage stability. The evaluation indicators for the construction include: Dynamic indicators, engine-generator torque coordination: assess the stability of engine speed by the dynamic changes in engine and generator torque; front and rear power chain power coordination: assess the energy transfer effect based on bus voltage stability and the coordination of generator and drive motor current. Coupling characteristic indicators, coordination of main and auxiliary power sources: based on the smoothness of the total power curve, it measures the synergistic power supply effect of the generator and battery; proportion of energy deficit of main power source: assesses whether the generator can meet the needs of the drive motor; Static indicators: Combining four static indicators—engine speed, maximum and average fluctuation rate of bus voltage—to measure the stability of the system under different operating conditions.

2. The method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles according to claim 1, characterized in that, The dynamic indicators specifically include: Engine-generator torque coordination: In heavy-duty vehicle series hybrid systems, the engine is decoupled from external operating conditions. The system requires the engine to provide stable power, and maintaining a stable engine speed is a prerequisite for providing stable power. Therefore, whether the engine speed can remain stable is an important indicator for measuring the overall performance of the system. The dynamic changes in engine speed can be given by Newton's laws of motion, as shown below: Where J is the sum of the rotational inertia of the engine and generator, ω e T is the engine speed. e T g These are the engine torque and the generator torque, respectively. According to the torque-speed relationship, the essence of maintaining stable engine speed is the coordinated operation of the engine and generator; the smaller the torque difference between the two, the more stable the speed. Further differentiating both sides of equation (1), the influence of dynamic torque changes on speed is shown below: A dynamic index for evaluating engine speed is established using the dynamic changes in engine and generator torque; the requirement that the instantaneous fluctuation rate of engine speed within t0 seconds be less than n% can be expressed as: D={(t',t)|0≤t'≤t0,0≤t≤t0} (3) Where, ω ref Let D be the desired engine speed, and D be the integration domain; substituting equation (22) into equation (23), we get: Since the chosen t0 is relatively small, the above formula is... Approximating a constant, we further obtain: This indicator means that in order to make the instantaneous fluctuation rate of engine speed less than n%, it is necessary to... Less than n; Power coordination between front and rear power chains: In heavy-duty vehicle series hybrid power systems, the bus voltage is the energy conversion platform. The energy generated by the engine generator set is transferred to the downstream power chain via the bus. When the voltage is too low, the rated power of the drive motor cannot be fully utilized, resulting in the drive motor not achieving normal operating efficiency. When the drive motor is running, it will also generate additional current surges due to insufficient voltage, which will affect the normal operation of the drive motor. Therefore, whether the bus voltage can be kept stable is an important indicator for measuring the overall performance of the system. Considering that the generator power accounts for the majority of the power in the front power chain and the drive motor power accounts for the majority of the power in the rear power chain, for ease of calculation, the current of the generator and the drive motor are used to calculate the dynamic change of the bus voltage according to the relationship between capacitor voltage and current, as shown below: Where C is the capacitance value of the supercapacitor, u bus For the bus voltage, i g i m These are the DC current of the generator and the DC current of the drive motor, respectively. According to the voltage-current relationship, the essence of maintaining a 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 differentiating both sides of the above equation, the influence of dynamic changes in DC current on the bus voltage is shown below: A dynamic index for evaluating bus voltage is established using the dynamic changes in DC current of the engine and generator; the instantaneous fluctuation rate of the bus voltage within t0 seconds is required to be less than n%, which can be expressed as: D={(t',t)|0≤t'≤t0,0≤t≤t0} (8) Among them, u ref Let D be the desired bus voltage, and D be the integration domain; substituting equation (27) into equation (28), we get: Since the chosen t0 is relatively small, the above formula is... Approximating a constant, we further obtain: This indicator means that in order to ensure the instantaneous fluctuation rate of the bus voltage is less than n%, it is necessary to... Less than n.

3. The method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles according to claim 1, characterized in that, The coupling characteristic indicators specifically include: Coordination of main and auxiliary power sources: In a series hybrid power system for heavy-duty vehicles, the generator provides high power as the primary power source, while the battery, with its rapid response, serves as a secondary power source to supplement the power supply. The coordination between these two power sources determines the quality of the primary power supply and affects the stability of the bus voltage. The main role of the battery as a power source is to fill valleys, that is, to assist the generator in outputting more stable power. From the power curve perspective, the total power curve of the generator and battery needs to be smoother than the generator's power curve. Therefore, the smoothness of the total power supply is used to establish an evaluation index for the coordination of the primary and secondary 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 dividing the integral of the absolute value of the second derivative of the curve by the length of the integration domain, as shown below: Among them, P sum For the total power, P g For generator power, α sum For the smoothness of the total power curve, α g The generator power curve smoothness is represented by t1 and t2, which are the start and end times of the integration domain, respectively. Among them, β is the coordination index of power supply from the main and auxiliary power sources; the smoothness of a straight line is 0, while the smoothness of a step curve is infinitely large, 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 this index is to 0, the better; when the total power curve is smoother than the generator power curve, this index reaches the ideal state and is set to 0. Percentage of energy deficit from primary power sources: In a series hybrid power system for heavy-duty vehicles, the engine-generator set serves as the primary power source, providing most of the energy. The energy storage device acts as an emergency measure, shaving off peak loads and filling valleys for a limited period of time. The goal is for the engine-generator set to meet the power demand of the drive motor most of the time. The portion of the time when the energy provided by the engine-generator set is less than the required energy is called the deficit. Therefore, this paper proposes to evaluate the quality of the engine-generator set's energy supply performance by using the proportion of the primary power source's energy deficit. Considering that generator power accounts for most of the power in the front power chain and drive motor power accounts for most of the power in the rear power chain, this indicator focuses on the generator and drive motor. The main power source energy deficit 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 main power source energy deficit reflects the quality of matching between the engine generator set and the drive motor, and is expressed as the ratio of the proportion of main power source energy deficit to the total load energy demand over a period of time. First, calculate the power deficit of the main power source, using the following formula: ΔP=P g -P m Among them, P g P m These represent the generator power and drive motor power, ΔP q The power deficit of the main power source is calculated; then the power is integrated, and the proportion of the power deficit of the main power source is calculated, as shown in the following formula: The smaller this index is, the better the energy supply effect of the engine generator set.

4. The method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles 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 fluctuation rate of the engine speed, the average fluctuation rate of the engine speed, the maximum fluctuation rate of the bus voltage, and the average fluctuation rate of the bus voltage; The maximum fluctuation rate of the engine speed is: The average fluctuation rate 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 fluctuation rate of the bus voltage is: The average fluctuation rate 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.

5. The method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles 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 to make pairwise comparisons according to the relative importance of the indicators and construct the judgment matrix A; Calculate the weights: Multiply the judgment matrix A by its row elements, then calculate... The power of n is the order of matrix A. Calculate the relative weights of each index; normalize the weight results 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.

6. The method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles according to claim 5, 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, respectively: the average fluctuation rate of the engine speed, the maximum fluctuation rate of the engine speed, the average fluctuation rate of the bus voltage, the maximum fluctuation rate of the bus voltage, the energy supply coordination of the main and auxiliary power sources, the proportion of the energy shortage 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 fluctuation rate of the engine speed, is compared with the second indicator, the maximum fluctuation rate 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: Multiply the judgment matrix A by its row elements, then calculate... The power of n is the order of matrix A, i.e., the number of indices is 8; Among them, a ij To determine the data in the i-th row and j-th column of matrix A; the calculated data will be... Normalization yields the weight matrix: The obtained weight matrix W is as follows: W＝[0.09 0.17 0.13 0.07 0.13 0.05 0.18 0.17] T (22) To ensure that the above judgment matrix A and the 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. Therefore, the obtained weights can be used for calculation.

7. The method for comprehensive performance evaluation of a series hybrid power system for heavy-duty vehicles according to claim 1, characterized in that, The fuzzy comprehensive evaluation method is used to calculate scores and comments, specifically including: Establish a comprehensive evaluation factor set, which is a set of various factors affecting the evaluation object, denoted by U: U={u1 u2 u3 u4 u5 u6 u7 u8}(26) Establish a comprehensive evaluation set, which is a set of all possible outcomes that evaluators may make regarding the evaluated object, denoted by V: V = {v1 v2 v3 v4 v5} = {Excellent Good Average Poor Very Poor} (27) Its corresponding evaluation score matrix v is: v＝[01234] T (28) Construct a weight matrix for each factor, and denot the weights using the analytic hierarchy process (AHP). W＝[0.230.280.140.170.030.050.030.07] T (29) Perform a single-factor fuzzy evaluation to obtain the evaluation matrix: Let r be the membership degree of the i-th element in the factor set U to the 1-th element in the evaluation set V. i1 Then, the result of the single-factor evaluation of the i-th element is represented by a fuzzy set as: R i ={r i1 r i2 r i3 r i4 r i5 }, using 5 single-factor evaluation sets R i The fuzzy comprehensive evaluation matrix R is formed by rows. 8×5 ; Membership degrees are defined using trapezoidal functions, 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 ​​obtained as follows: To take all factors into account, the final score B is obtained by multiplying the weights, the fuzzy comprehensive evaluation matrix, and the evaluation score matrix; B = W T ·R·v.

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