混合动力环卫车动力系统总体方案设计与控制策略分析外文翻译资料

Energy management strategy for a parallel hybrid electric

vehicle equipped with a battery/ultra-capacitor

hybrid energy storage system

Abstract: To solve the low power density issue of hybrid electric vehicular batteries, a combination of batteries and ultra-capacitors (UCs) could be a solution. The high power density feature of UCs can improve the performance of battery/UC hybrid energy storage systems (HESSs). This paper presents a parallel hybrid electric vehicle (HEV) equipped with an internal combustion engine and an HESS. An advanced energy management strategy (EMS), mainly based on fuzzy logic, is proposed to improve the fuel economy of the HEV and the endurance of the HESS. The EMS is capable of determining the ideal distribution of output power among the internal combustion engine, battery, and UC according to the propelling power or regenerative braking power of the vehicle. To validate the effectiveness of the EMS, numerical simulation and experimental validations are carried out. The results indicate that EMS can effectively control the power sources to work within their respective efficient areas. The battery load can be mitigated and prolonged battery life can be expected. The electrical energy consumption in the HESS is reduced by 3.91% compared with that in the battery only system. Fuel consumption of the HEV is reduced by 24.3% compared with that of the same class conventional vehicles under Economic Commission of Europe driving cycle.

1 Introduction

The large number of automobiles used around the world has produced and continues to cause serious environmental and human survival problems. Dealing with the air pollution, global warming, and rapidly diminishing oil resources has become the primary concern of modern people. The next-generation vehicles have been developed, which are more efficient, cleaner, and safer. Pure electric, hybrid electric (HEV), and fuel cell (FC) vehicles have been proposed as representatives of future vehicles for the replacement of conventional vehicles (Ehsani et al., 2009).

Although pure electric and FC vehicles are more environmentally friendly (Chan, 2002), they both face technical difficulties and require a large number of infrastructure improvements (Tanoue et al., 2008). Thus, these vehicle types are not likely to be widely

used in the short term. By contrast, HEVs have recently captured widespread attention because of their relatively similar technologies to conventional vehicles and good adaptability to existing infrastructures (Xiong et al., 2009a).

An HEVrsquo;s power train consists of different components, such as the internal combustion engine (ICE) and electric motor (EM). Thus, an energy storage system (ESS) is needed in HEV to satisfy the electric power requirement of the EM. In practice, different kinds of batteries have been selected as the normal ESS (Jung et al., 2002; Karden et al., 2007; Vasebi et al., 2007). However, their relatively low power density hinders batteries from performing well to meet the high electric power requirements of HEVs in some modes, such as pure electric acceleration and regenerative braking.

The features of some energy storage components are shown in Table 1 (Wu et al., 2012). Compared with batteries, ultra-capacitors (UCs) have low energy density but high power density. The specific features of UC enable energy to be stored and released without chemical reaction, thus the energy can be absorbed and released immediately with low losses. Therefore, UC is capable of meeting the instantaneous high power demand of EM. According to different features of batteries and UCs, a battery/UC-based hybrid ESS (HESS) can be constructed. In HESS, the battery only needs to meet the average power requirement of the electric power system during HEV driving, whereas the UC is employed to make up for the fluctuations in electrical power demand. The combination of the two electrical sources can mitigate battery workload, which will improve battery working efficiency and extend battery life expectancy. Moreover, the high power density of UCs makes HESS more effective in absorbing regenerated power during vehicle braking. Notably, the efficiency of HESS also depends on other factors, such as power interface efficiency and the regenerative ratio. However, UC energy efficiency is significantly higher than that of the battery, and power interface efficiency normally has a high value. We can thus employ HESS to obtain better energy efficiency than traditional ESS.

This paper emphasizes the EMS design for a parallel HEV equipped with HESS. The EMS for different schemes of HEVs equipped with HESS has recently been explored. Several methods, such as logic threshold, fuzzy logic, and a low-pass filter method, have been applied in this area. Three strategies are studied for the distribution of power between batteries and UCs, and the “filtration strategy” can maintain the current stresses significantly lower than that of the other two strategies (Allegre et al., 2009). A power-flow management for a Series HEV using HESS is proposed to satisfy the vehicle load demand and improve dynamic performance, but the fuel efficiency is not evaluated (Yoo et al., 2008). A fuzzy logic control strategy has been employed in an FC/UC hybrid vehicle, and the strategy is capable of determining the desired FC power and can maintain the DC voltage around the nominal value (Kisacikoglu et al., 2009). Nevertheless, an EMS that could satisfy the complexity of combination of ICE and HESS has not been well addressed in previous study.

HEVs are highly nonlinear systems, and drive loads and driving conditions cannot be explicitly predicted and described. Thus, intelligent controllers have been widely used in HEV control. Previous studies demonstrate that fuzzy logic control could be successfully appli

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