Power train scheme selection of the hottest Hybrid

Selection of power train scheme for hybrid city bus

[Abstract] with the increase of car ownership, the world's oil resources are becoming increasingly scarce and environmental pollution is becoming increasingly serious. HEV (hybrid electric vehicle) has received great attention because of its obvious advantages in energy saving and emission reduction. Based on the developed hybrid electric city bus, this paper discusses in detail the selection procedure of the traditional powertrain scheme of hybrid electric vehicle. Based on the development goal of Hybrid Electric City bus, various power train schemes are analyzed. Through preliminary simulation analysis, the best power train scheme - double shaft parallel type is selected, and the system simulation analysis is carried out to verify the correctness of the selected scheme

key words: simulation analysis of power train configuration of hybrid electric bus

1 introduction

hybrid electric vehicle (HEV) uses internal combustion engine and motor as hybrid power source, which integrates the advantages of both [1,2]. It not only inherits the advantages of energy conservation and ultra-low emissions of electric vehicles as "green vehicles", but also makes up for the shortcomings of short driving range of electric vehicles, without stopping to charge or frequent battery replacement. It has become an internationally recognized effective method to solve the two major problems of vehicle exhaust emissions and lack of oil resources. It is the model with the most industrialization and marketization prospects among clean vehicles. Press the sample clamping key to conduct the next group of experiments. Compared with traditional vehicles, fuel consumption can be reduced by 40%~50%, and exhaust emission indicators can be reduced by 50%~60%[1]. At the same time, in terms of supporting facilities, there is no need to invest a lot of money in the construction of gas stations and charging stations like gas vehicles and electric vehicles, which is easy to promote. Therefore, before electric vehicle technology has made a major breakthrough, hybrid vehicles have become the main choice of countries

hybrid electric vehicle has become the development direction of clean and efficient vehicles. It is the best way to solve the problems of environmental protection and energy saving, so that it can produce initial friction on the clamping surface. It is also the inevitable choice for the sustainable development of China's automotive industry. In particular, the research and development of hybrid electric city buses in China is of great significance to alleviate urban pollution, especially to provide clean city buses for the Beijing 2008 Olympic Games. Therefore, based on the developed hybrid electric city bus, through the comparative analysis of various power train schemes, this paper finally selects the double axle parallel structure type, and carries out the system simulation analysis. The results show that this structure type meets the development goal

2 development objectives and basic vehicle parameters of Hybrid Electric City bus

development objectives of Hybrid Electric City bus include power, economy, emissions, noise and cost [3]. This paper mainly considers the first two aspects, namely power and economy, as shown in Table 1. The basic parameters of the whole vehicle are shown in Table 2. Table 1 development objectives of Hybrid Electric City Bus

Table 2 basic parameters of the whole vehicle

3 conceptual design of Hybrid Electric City Bus

in order to meet the development indicators of the project, it is very necessary to select an appropriate power train layout scheme. This requires simulation, comprehensive evaluation, repeated comparison and optimization of various possible power train layout schemes, and finally the best layout can be determined

3.1 conceptual analysis of power train of Hybrid Electric City bus

based on three common layout types: series, parallel and hybrid [1,2], in which the parallel type is divided into conventional parallel, SA (start inverter) and split structure. The layout of various power train schemes is shown in Figure 1. At the same time, from different evaluation standards for foreign successful models (passenger cars), 24 evaluation indexes are listed through expert scoring, as shown in Table 3. Meshed hybrid is a type of hybrid

Figure 1 various layout types of hybrid power train

Table 3 matrix evaluation table of various layout types

note: + + = very good, + = good, o = average, -= poor; y = yes, n = no； Reference - manual transmission

phev, SA, split and meshed hybrid - manual transmission; Operation cost - reliability, service cost and fuel consumption; Development cost - system complexity, control + practicality + patent; Performance - maximum speed + acceleration + climbing capacity + maximum climbing gradient

3.2 analysis of power train selection of Hybrid Electric City Bus

it can be seen from table 3 that no layout type is the best. Considering the development objectives of the project, taking fuel consumption and cost as the highest indicators, a preliminary simulation study has been carried out on the two forms of series connection and parallel connection. Hybrid connection is generally not used on buses. The simulation results are listed in Table 4. Table 4 preliminary simulation results under different parameter combinations of various schemes

by selecting the size and parameters of main powertrain components, the powertrain assembly parameters are matched, and the preliminary relationship between fuel consumption and cost is obtained, as shown in Figure 2. It can be seen from the figure that region II has a better fuel cost ratio than region I. The preliminary simulation results show that the cycle conditions have a great impact on fuel consumption. The fuel consumption is different under different cycle conditions. The urban 4 cycle in China is difficult to reflect the actual operating conditions of urban passenger cars. Therefore, it is difficult to meet the project requirements according to this cycle condition. Therefore, it is urgent to establish urban cycle conditions suitable for China. It can also be seen from Figure 2 and table 4 that the fuel consumption of the parallel type is less than that of the series type. Therefore, selecting the parallel connection type will help to reduce fuel consumption and cost. In addition, measures such as selecting a reasonable size of assembly components, formulating a reasonable control strategy, and reducing the weight of the whole vehicle are of great help to reduce fuel consumption and cost [4,5]

Figure 2 Relationship between fuel consumption and cost of various layout types

3.3 selection of power train layout scheme of Hybrid Electric City bus

considering the maturity, assembly, engine start/stop, regenerative braking, electric starting, cost, control complexity, shift synchronization and other factors of the assembly used in hybrid electric bus, after two matrix evaluations, Finally, the layout scheme of the powertrain - dsphev (double shaft parallel hybrid electric vehicle) [6] is determined, as shown in Figure 3

this scheme has the following advantages: ① easy overall layout; ② Electric starting (motor starting engine) function; ③ Engine on/off function; ④ Electric starting function; ⑤ Regenerative braking function

4 simulation analysis of Hybrid Electric City bus

based on the selected powertrain layout scheme (as shown in Figure 3), the system simulation analysis is carried out, and the powertrain parameters are determined, as shown in Table 5. The influence of accessories is ignored in the simulation calculation, and the SOC correction algorithm of battery state of charge is considered. Table 5 parameters of double axle parallel assembly

table 6 shows the performance comparison between dsphev and traditional vehicle. It can be seen from the table that the dynamic performance of dsphev is better than that of traditional vehicles, especially the acceleration performance; Under various cycle conditions, the fuel economy of dsphev is much better than that of traditional vehicles, and the goal of reducing fuel consumption by 30% has been achieved. The results also show that without considering the correction algorithm of battery SOC, the fuel consumption of hybrid electric vehicles has a great relationship with the initial SOC (state of charge) state of the battery. The larger the SOC value, the smaller the fuel consumption. In order to ensure that the battery SOC returns to the initial state after the calculation, it is necessary to consume the additional power of the engine to charge the battery. Therefore, the correction algorithm of the battery SOC should be considered, so that the result can be credible. Table 6 Comparison of dsphev and traditional vehicle performance

Figure 4 shows the time history of battery SOC under uddshdv cycle conditions. It can be seen from the figure that the SOC of the battery fluctuates within a certain range and remains at a certain level all the time, without external charging

Figure 4 shows the number of battery SOC time history cycles under uddshdv 10, the driving distance is 89.1km, and the fuel consumption is 34.5l/100km

Figure 5 shows the actual working point distribution of the engine under uddshdv cycle conditions. It can be seen from the figure that the actual working points of the engine can be divided into two parts: one is the working points distributed on the maximum torque line of the engine, which means that the engine works under full load conditions (such as full load acceleration or optimal efficiency); The second is the partial load condition, which is less than the optimal/maximum torque curve, or the minimum torque curve. At this time, the engine is not allowed to shut down. When the vehicle decelerates, the engine pulls back the torque (negative torque in the figure). The working points of the engine are mostly distributed in the high efficiency area

Figure 5 distribution of actual working points of engine under uddshdv

Figure 6 distribution of actual working points of motor under uddshdv cycle conditions. It can be seen from the figure that most of the operating points of the motor are distributed near the continuous torque curve, and the efficiency of the motor in this section is the highest. Especially in regenerative braking, the effect of regenerative braking is the best

Figure 6 actual working point distribution of motor under uddshdv

5 conclusion

based on simulation analysis, this paper takes hybrid electric city bus as the research object to study the selection of power train scheme of hybrid electric vehicle, from which the following conclusions can be drawn:

(1) the program of scheme selection of Hybrid Electric city bus is given, that is, the conceptual design and parameter matching are completed through theoretical analysis, Then the system simulation analysis is carried out, and the next step is experimental verification

(2) the power train scheme of Hybrid Electric City bus is a two axle parallel type, which has the advantages of simple structure, easy implementation, good regenerative braking effect and so on. The simulation results show that this structural type meets the project development goals, and its power and economy are superior to the traditional passenger cars of the same type

(3) different cycle conditions have a great impact on fuel economy, so it is urgent to establish cycle conditions suitable for urban passenger cars in China. Through the control strategy and SOC algorithm, the SOC of the battery can be kept within a certain range, and the whole cycle process does not need to be charged by external power supply, while the engine and motor work in the efficient range

references

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3 Ministry of science and technology "Tenth Five Year Plan" 863 energy technology field -- Application guide for special topics of electric vehicles 2001.10

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5 Bradley Glenn, Gregory Washington and Giorgio do not need to return to Rizzoni automatically Operation and Control Strategies for Hybrid Electric Automobiles. SAE paper, 2000

6 FAW hybrid city bus feasibility study report (internal data), 2002 3(end)