“產生效益的電力驅動”-客車和重型車輛的動力電子設備

1 前言

對于轎車混合動力系統而言,其主要目標是小型化、能力密度和節約成本等方面,而開發周期更長的商用車混合動力系統則將注意力集中在耐用和可靠性方面。這里動力電子設備扮演著重要的角色。

作為一個混合動力系統技術供應商,ZF公司能夠提供全系統、子系統和單一部件。

ZF Electronics GmbH作為ZF集團中一個獨立的部門主要研究電力電子學,例如逆變器和DC/DC轉換器,為節省車輛節油做出貢獻。

位于Upper Palatinate地區Auerbach城的該部門具有多年生產汽車電子設備的經驗和能力,這也是該部門成為集團中一個成功部門的主要因素。

2 商用車輛用混合動力傳動

自從豐田公司的Prius轎車上市以來,混合動力轎車開始普及并在消費者心中贏得環境-友好形象。盡管節省油耗是無容置疑的,但是精確計算出混合動力技術行駛多少里程后其效果與付出相平衡是相當困難的,反之,比較柴油機和汽油機的優劣則更容易些,其盈虧平衡點是每年行駛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.

商用車輛的節能效果與投入成本之間的關系更復雜。根據文獻?[1]可知,采用混合動力的城市公共汽車由于能夠單獨使用電力驅動(強混合動力),其試驗表明可以節省燃油。平均節油率超過20%,由于年行駛里程遠高于轎車,意味著混合動力系統的采購成本能快速回收。

3 商用車輛的混合動力系統

應用混合動力技術時,跨學科知識尤為重要。在一個并聯混合動力系統中,電動機、動力電子設備和蓄電池都作為內燃機的補充,實際節省的燃油主要取決于上述各系統相互作用是否完美,而不是各系統本身。因此,單一供應商模式的優勢更明顯,例如作為獨立供應商的ZF公司精通系統優化?[2]。

ZF公司的工作集中在并聯混合動力方面,為用戶帶來最佳的經濟效益[3]。

4 混合動力的動力電子設備部件

目前應用于商用車輛電力驅動的動力電子設備源自于工業電子學部分,同時并未根據商用車輛的苛刻要求進行特殊優化。

在能量密度、高環境溫度、可靠性和低成本等方面的需求矛盾只能通過智能電子系統和仔細挑選元器件等來解決。

ZF電子元件業務部門的產品還包括稱為ZFHyControl的高級混合動力控制單元(HCU),見圖1。該項新技術被用于系統性的提高各元件的使用壽命,因而可以滿足商用車輛的要求,例如：

?結構堅固

?設計緊湊

圖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

在客車和重型車輛中采用模塊化和柔性化結構元件是使用大量相同部件進行系統結構設計的一種策略。

目前ZF-HyControl逆變器具有兩種型號：中等混合動力和強混合動力。它最適用于ZF模塊化混合動力系統(見圖2)。與兩種不同的電動機相匹配,它能夠產生60或120kW的動力,其轉矩為500或1,000Nm。

5 使用壽命、耐用性和可靠性

在使用壽命方面,關鍵元件是絕緣柵雙極晶體管、功率半導體器件、二極管和中間電路電容器等。在外殼、結構和連接技術方面的創新以及系統最優化設計使得動力組件能夠滿足商用車輛對于環境和使用壽命之要求。

機械結構應該滿足商用車輛對環境的要求。電纜布線和連接空間應該易于安裝、采用堅固和耐用的夾頭和螺栓聯接。這意味著能夠滿足嚴酷的振動標準,并提供免于機械損傷。達到IP6K9K防護等級意味著能夠外露安裝。功率半導體器件在使用中其熱點溫度可達150℃。

但是,由于環境條件變化會產生從-40°C到+85°C的被動溫度變化,材料不同的熱膨脹系數將導致電氣插頭、底層支撐和冷卻系統熱端等連接點的應力變化。這些連接點的可靠性決定了動力電子設備的使用壽命,ZF-HyControl系統通過采用彈簧觸點、粉末冶金和擠壓工藝替代錫焊滿足要求。

6 車輛高功率的控制

High Power型ZF-HyControl的中間電路能夠工作在750V電壓下。這是絕無僅有的,因為中間電路電容器和功率半導體器件之間的連接采用了超低電感技術。開關具有低功耗特性。切換絕緣柵雙極晶體管時造成的快速電流變化(di/dt)會產生過電壓,它將導致功率半導體的早期失效或損壞。低感應構形和濾波技術確保系統滿足EMC指令,即便工作在高中間電路電壓下。

當然,駕駛員希望強混合動力車輛能夠采用電力起步而無需內燃機助力。所需要的高起步轉矩意味著在電動機處于停頓狀態時,逆變器必須承受極高的電流,因而動力單元承受的應變也達到最大值。智能化的電動機控制器和逆變器控制軟件中的保護程序使得其能夠適應電流變化,確保系統的使用壽命滿足商用車的需求。

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.

圖2 混合動力系統元件：ZF HyTronic和ZF HyTronic Lite用逆變器Fig.2 Fig.2 Hybrid system components：the inverter in focus ZF HyTronic and ZF HyTronic Lite

在動力電子設備的峰值載荷階段或持續載荷期間,混合動力傳動系統的控制器用來確保使用壽命和提高離合器、齒輪和內燃機的載荷轉換。

7 仿真-成功的關鍵

整個混合動力系統的相互作用在車輛模擬器上進行。在開發的早期階段,部件性能和工作點的實際和綜合循環方面開展仿真的目的是測定轉矩分配、轉換策略和能量流管理。

能量存儲單元、電動機、齒輪和逆變器的相互作用隨負載(發動機轉速、轉矩、電流、工作點等)的變化而變化。

該方法有助于智能部件的設計和混合動力系統的持續優化和功能微調,以延長使用壽命、提高效率、性能和功能。

8 市場準備之路

理論、實踐、概念、設計和仿真、操作等過程的目的是完成混合動力系統的每個部件和每個混合動力模式在試驗臺和整車上的試驗。

目前普遍采用的微調方法能夠確保滿足用戶關于能量效率、耐用性和可靠性等方面的要求。這點首先經實驗室試驗得到論證。不同車輛和不同道路的電流電子設備試驗將作為車隊實際環境試驗的一部分。

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 總結

商用車輛傳動系統的電氣化是ZF公司的基本策略之一。ZF Electronics的動力電子設備不僅經久耐用,而且處于不斷創新之中。與商用車輛的適用性體現在動力電子設備具有很大的使用范圍,即使市場需求出現變化時-例如能夠適應強混合動力城市公共汽車、并聯和串聯混合動力車輛或工作在蓄電池或燃料電池狀態下。

總之,低運行成本意味著混合動力將能夠為重型車輛和公共汽車帶來效益。

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.

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