“产生效益的电力驱动”-客车和重型车辆的动力电子设备

1 前言

对于轿车混合动力系统而言,其主要目标是小型化、能力密度和节约成本等方面,而开发周期更长的商用车混合动力系统则将注意力集中在耐用和可靠性方面。这里动力电子设备扮演着重要的角色。

作为一个混合动力系统技术供应商,ZF公司能够提供全系统、子系统和单一部件。

ZF Electronics GmbH作为ZF集团中一个独立的部门主要研究电力电子学,例如逆变器和DC/DC转换器,为节省车辆节油做出贡献。

位于Upper Palatinate地区Auerbach城的该部门具有多年生产汽车电子设备的经验和能力,这也是该部门成为集团中一个成功部门的主要因素。

2 商用车辆用混合动力传动

自从丰田公司的Prius轿车上市以来,混合动力轿车开始普及并在消费者心中赢得环境-友好形象。尽管节省油耗是无容置疑的,但是精确计算出混合动力技术行驶多少里程后其效果与付出相平衡是相当困难的,反之,比较柴油机和汽油机的优劣则更容易些,其盈亏平衡点是每年行驶15,000km。

1 Introduction

Whereas for hybrid systems for passenger cars the focus is on integration with the aim of attaining compactness,power density and cost savings,the considerably longer periods commercial vehicles are in operation means that a greater technological emphasis is placed on robustness and reliability.Power electronics play an important role here.

ZF is a single-source supplier for technology for hybrid systems.ZF supplies complete hybrid systems,subsystems and also individual hybrid components.

ZF Electronics GmbH is an independent business unit within the ZF group specialising in power electronics–for example,inverters and DC/DC converters–providing product solutions that contribute to fuel economy.

Their many years of experience in producing automobile electronics and their manufacturing capacities at the Auerbach location in Upper Palatinate are the main reasons for the success of the group's industrialisation partner.

商用车辆的节能效果与投入成本之间的关系更复杂。根据文献?[1]可知,采用混合动力的城市公共汽车由于能够单独使用电力驱动(强混合动力),其试验表明可以节省燃油。平均节油率超过20%,由于年行驶里程远高于轿车,意味着混合动力系统的采购成本能快速回收。

3 商用车辆的混合动力系统

应用混合动力技术时,跨学科知识尤为重要。在一个并联混合动力系统中,电动机、动力电子设备和蓄电池都作为内燃机的补充,实际节省的燃油主要取决于上述各系统相互作用是否完美,而不是各系统本身。因此,单一供应商模式的优势更明显,例如作为独立供应商的ZF公司精通系统优化?[2]。

ZF公司的工作集中在并联混合动力方面,为用户带来最佳的经济效益[3]。

4 混合动力的动力电子设备部件

目前应用于商用车辆电力驱动的动力电子设备源自于工业电子学部分,同时并未根据商用车辆的苛刻要求进行特殊优化。

在能量密度、高环境温度、可靠性和低成本等方面的需求矛盾只能通过智能电子系统和仔细挑选元器件等来解决。

ZF电子元件业务部门的产品还包括称为ZFHyControl的高级混合动力控制单元(HCU),见图1。该项新技术被用于系统性的提高各元件的使用寿命,因而可以满足商用车辆的要求,例如：

◦结构坚固

◦设计紧凑

图1 ZF-HyControl控制器Fig.1 ZF-HyControl

2 Hybrid drives for commercial vehicles–why?

Since the launch of the Toyota Prius,hybrid cars have enjoyed growing popularity and have gained an environmentally-friendly image among customers.While undoubtedly saving fuel,calculating whether and from which mileage the effort and expense of hybrid technology really pays off is more difficult than,for example,comparing diesel vehicles with petrol-powered ones,which can pay off at a mileage of around 15,000 km a year.

The relationship between savings and initial costs is completely different for commercial vehicles.The potential cited in?[1]for reducing fuel consumption in urban buses using hybrid technology,which can run solely on electricpower(full hybrid),has now been confirmed in tests.Average fuel savings were more than 20%,which,together with a considerably higher annual mileage compared with a passenger car,mean that the cost of purchasing a hybrid drive system in a commercial vehicle can be recouped quickly.

3 Integrated hybrid drive system for commercial vehicles

Interdisciplinary system expertiseis particularly important when using hybrid technology.In a parallel hybrid system in which the electric engine,power electronics and battery all supplement the combustion engine,the actual fuel savings depend less on the components used than on the perfection of their interaction.Therefore,it is a considerable advantage for manufacturers to have a supplier–like ZF–w ho understands systematic optimisation?[2]and is a single-source provider.

ZF focuses on parallel hybrid technology,which yields an optimum economic gain for the customer?[3].

◦高效率

在客车和重型车辆中采用模块化和柔性化结构元件是使用大量相同部件进行系统结构设计的一种策略。

目前ZF-HyControl逆变器具有两种型号：中等混合动力和强混合动力。它最适用于ZF模块化混合动力系统(见图2)。与两种不同的电动机相匹配,它能够产生60或120kW的动力,其转矩为500或1,000Nm。

5 使用寿命、耐用性和可靠性

在使用寿命方面,关键元件是绝缘栅双极晶体管、功率半导体器件、二极管和中间电路电容器等。在外壳、结构和连接技术方面的创新以及系统最优化设计使得动力组件能够满足商用车辆对于环境和使用寿命之要求。

机械结构应该满足商用车辆对环境的要求。电缆布线和连接空间应该易于安装、采用坚固和耐用的夹头和螺栓联接。这意味着能够满足严酷的振动标准,并提供免于机械损伤。达到IP6K9K防护等级意味着能够外露安装。功率半导体器件在使用中其热点温度可达150℃。

但是,由于环境条件变化会产生从-40°C到+85°C的被动温度变化,材料不同的热膨胀系数将导致电气插头、底层支撑和冷却系统热端等连接点的应力变化。这些连接点的可靠性决定了动力电子设备的使用寿命,ZF-HyControl系统通过采用弹簧触点、粉末冶金和挤压工艺替代锡焊满足要求。

6 车辆高功率的控制

High Power型ZF-HyControl的中间电路能够工作在750V电压下。这是绝无仅有的,因为中间电路电容器和功率半导体器件之间的连接采用了超低电感技术。开关具有低功耗特性。切换绝缘栅双极晶体管时造成的快速电流变化(di/dt)会产生过电压,它将导致功率半导体的早期失效或损坏。低感应构形和滤波技术确保系统满足EMC指令,即便工作在高中间电路电压下。

当然,驾驶员希望强混合动力车辆能够采用电力起步而无需内燃机助力。所需要的高起步转矩意味着在电动机处于停顿状态时,逆变器必须承受极高的电流,因而动力单元承受的应变也达到最大值。智能化的电动机控制器和逆变器控制软件中的保护程序使得其能够适应电流变化,确保系统的使用寿命满足商用车的需求。

4 Power electronics hybrid components

The power electronics for electrical drives currently available for commercial vehicles originate in the industrial electronics sector,and have not been specifically optimised for the tough requirements of the commercial vehicle sector.

The conflicts of interest between power density,high ambient temperatures,reliability and low costs can only be resolved by using intelligent power electronics systems for hybrid vehicles,and carefully selecting the individual components.

The product ranges produced by the ZF electronic components business unit,which,together with the superordinate hybrid control unit(HCU),are called ZF-HyControl(see figure?1.),and were developed with this in mind.The new technology available has been used to systematically increase the service life of the individual components,thereby meeting commercial vehicle requirements,such as：

◦Sturdy construction

◦Compact design

◦High degree of efficiency

The modular and flexible component structure chosen also enables a strategy of using largely the same parts in the system construction for use in buses and HGVs.

The ZF-HyControl inverter is currently available in two versions：Medium Power and High Power.It is the optimum enhancement for theZF modular hybrid system(see figure?2.).In combination with the tw o electric engines designed and calibrated for this purpose,it provides the drive with mechanical power of 60 or 120 kW at a torque of 500 or 1,000 Nm.

5 Lifespan,sturdiness and reliability are the decisive factors

In terms of lifespan,the key components are the IGBT power semiconductor and diode and the intermediate circuit capacitor.Theinnovative housing,construction and connection technology,as well as the consistent system optimisation have pro-duced a power component that meets the high environmental and lifespan requirements of commercial vehicles.

图2 混合动力系统元件：ZF HyTronic和ZF HyTronic Lite用逆变器Fig.2 Fig.2 Hybrid system components：the inverter in focus ZF HyTronic and ZF HyTronic Lite

在动力电子设备的峰值载荷阶段或持续载荷期间,混合动力传动系统的控制器用来确保使用寿命和提高离合器、齿轮和内燃机的载荷转换。

7 仿真-成功的关键

整个混合动力系统的相互作用在车辆模拟器上进行。在开发的早期阶段,部件性能和工作点的实际和综合循环方面开展仿真的目的是测定转矩分配、转换策略和能量流管理。

能量存储单元、电动机、齿轮和逆变器的相互作用随负载(发动机转速、转矩、电流、工作点等)的变化而变化。

该方法有助于智能部件的设计和混合动力系统的持续优化和功能微调,以延长使用寿命、提高效率、性能和功能。

8 市场准备之路

理论、实践、概念、设计和仿真、操作等过程的目的是完成混合动力系统的每个部件和每个混合动力模式在试验台和整车上的试验。

目前普遍采用的微调方法能够确保满足用户关于能量效率、耐用性和可靠性等方面的要求。这点首先经实验室试验得到论证。不同车辆和不同道路的电流电子设备试验将作为车队实际环境试验的一部分。

The mechanical construction fulfils the environmental requirements for commercial vehicles.The cable routing and connection spaces for cables and cooling were designed with ease of installation,and sturdy and durable clamp and screw connections,in mind.This means that it complies with the strict vibration standards and provides protection from mechanical damage.The IP6K9K protection class it has attained means it can also be installed in exposed areas.The power semiconductors can reach temperatures of up to 150°C in their hot spots during operation.

However,passive temperature changes of between-40°C to+85°C due to climatic conditions,and the different thermal expansion coefficients of the materials,result in varying mechanical stress on the connection points of electric contacts,the substrate support and the thermal connections to the cooling system.The reliability of the these connection points is a critical factor in determining the lifespan of power electronics,and is attained in the ZF-HyControl systems by using spring contacts,powder metallurgy and pressing technology instead of soldering?[4].

9 总结

商用车辆传动系统的电气化是ZF公司的基本策略之一。ZF Electronics的动力电子设备不仅经久耐用,而且处于不断创新之中。与商用车辆的适用性体现在动力电子设备具有很大的使用范围,即使市场需求出现变化时-例如能够适应强混合动力城市公共汽车、并联和串联混合动力车辆或工作在蓄电池或燃料电池状态下。

总之,低运行成本意味着混合动力将能够为重型车辆和公共汽车带来效益。

The connection to the cooling system as well as the layout of the cooling system itself also have a significant impact on the lifespan,especially in consideration of the fact that lowering the semiconductor temperature by 10 K doubles the lifespan.

The central focus of the heat dissipation is,of course,the power semiconductor.The cooling concept integrates all heat-sensitive components of the entire inverter system in the cooling system in an appropriate manner.The layout of the cooling panel,the cooling structures and material combinations are of vital importance.Outstanding results have been achieved by optimising the structures and arrangements.A 50：50 mixture of water and glycol,as standard across the automobile industry,is used for cooling.The inverter has been designed for a coolant temperature of 60°C.

6 Mastering high vehicle power

The High Power version of the ZF-HyControl can be operated with intermediate circuit voltages of up to 750 V.This is only possible because the connection technology between the intermediate circuit capacitor and the power semiconductor have been manufactured for particularly low inductance.Switching is characterised by low power loss.The quick current changes(di/dt),which occur when switching the IGBTs,would otherwise create overvoltages,which can lead to premature failure or even the destruction of the power semiconductor.The low-induction configuration and additional filter measures also ensure adherence to EMC directives,even during operation with high intermediate circuit voltages.

Of course,drivers expect that a fully hybrid vehicle can start electrically without requiring support from the combustion engine.The high starting torque required to do so means that when the electric engine is at a standstill,the inverter is subjected to the maximum current,and the strain on the power unit is therefore also at a maximum.An intelligent electric engine controller,and sophisticated protection processes in the inverter control software,makes it adaptive to the current situation,ensuring the lifespan of the system can be guaranteed for commercial vehicles.

In peak load phases or periods of continuous load on the power electronics,the superordinate hybrid controller for the hybrid drive train undertakes a lifespan-enhancing load point shift using the clutch,gears and combustion engine.

7 Simulation–the key to success

Leaving nothing to chance,the interaction of the entire hybrid system was tested in a vehicle simulator.Early in the development process,the component behaviour and operating points were simulated for real and synthetic route cycles early in the development process using an operating concept that determines torque distribution,switching strategy and energy flow management.

The interaction between the energy storage unit,electric engine,gears and inverter is constantly changing in accordance with the various loads(engine speed,torque,current,operating point,...)

This approach facilitates an intelligent component design,as well as continual optimisation and functional fine-tuning of the interactive hybrid system units while taking service life,efficiency,performance and functional aspects into consideration.

8 The road to market-readiness

The process of reconciling theory and practice,draft and design,and simulation and operation was ultimately carried out for every hybrid system component and every hybrid model–both on the test bench as well as in various vehicle test configurations.

The progressive validation currently used for the fine-tuning process ensures that customer expectations can be met in terms of energy efficiency,sturdiness and reliability.The first evidence of this has been provided by the results from the laboratory and test benches.The power electronic tests in different vehicles on test routes are part of the preparations for the first fleet tests in a real environment.

9 Summary

The electrification of the drive train in commercial vehicles is a fundamental part of the ZF strategy.Power electronics by ZF Electronics are not just durable,but also sustainable product innovations.Their suitability for commercial vehicles means that these pow er electronics units will find a wide range of applications as an essential component for the drive concept,even when market requirements change–for example changing over from hybrid to fully-electric urban buses,in parallel and series hybrid vehicles,or in operation with batteries or fuel cells.

In any case,the low operating costs mean that the electric drive power in a hybrid drive train will pay for itself for HGVs and buses.

[1]W.Vogel,F.-D.Speck,H.-J.Domian.(2008).Beitr?ge der Getriebetechnologiezu Emissionsreduzierung und Wirtschaftlichkeit von Nutzfahrzeugen.7.Internationales CTI Symposium Innovative Fahrzeug-Getriebe.Berlin.

[2]Naunheimer,D.H.(2010).Der elektrifizierte Antriebsstrang – eine fachübergreifende Herausforderung.DKE-Tagung-Die Zukunft elektrisiert.Offenbach.

[3]S.Wallner,Dr.M.Lamke,M.Sedlacek.(01.July 2009).HyTronic – Das Hybridsystem für Verteiler-Nutzfahrzeuge basierend auf einer modularen Nkw-Getriebefamilie.VDI-Getriebetagung.Friedrichshafen.

[4]U.Scheuermann,P.Beckedahl.(11.-13.03.2008).The Road to the Next Generation Power Module–100%Solder Free Design.CIPS.Nuremberg.