based SRM Drive Control Strategy for Regenerative Braking in

电动汽车能量回收

A Neural Network Based SRM Drive Control Strategy for Regenerative Braking in EV and HEVHongwei Gao

Yimin Gao

Mehrdad Ehsani

Texas A&M University, Dept. of Electrical Engineering College Station, TX 77843-3128, USA Phone: 979-845-7562lFax: 979-845- 1976Abstract-The characteristicsof the regenerative braking in EV and HEV are analyzed in this paper. A neural network based SRM drive control strategy is developed for satisfying the requirements of regenerative braking in EV and HEV when SRM is chosen as the power source of EV and HEV. The energy recovery efficiency of the proposed control strategy is also evaluated.

11. BRAKE SYSTEM OPERATING AND CHARACTERISTICS

I. INTRODUCTION

Regenerative braking is an effective approach to extend the operating rang of an electric vehicle (EV) and improve the fuel economy of a self-sustained hybrid electric vehicle (HEV),especially for the vehicle that mainly runs in urban areas. For example, a 1500 kg passenger car, running at a speed of 7 0 k d h (44mph), stores about 300k.J (0.083 KW.h) kinetic energy. If all the kinetic energy can be recovered and reused to propel the vehicle, the recovered energy can support the vehicle to run about 1.8 km (1.1 miles). However, without regenerative braking, most of the kinetic energy is converted into heat during fictional braking. Braking power in an emergent braking is huge. For example, a 1500 kg passenger car with a deceleration of 0.6g (6m/s2) at a initial speed of lOOkm/h (60 mph), the braking power is about 250 KW. It is obvious that the electric regenerative braking system cannot handle such large braking power. Therefore, a mechanical friction braking system must be attached with the electric regenerative brake system for the safety reason. Due to its low-cost and rugged construction, reliable inverter topology, simple control strategy, and high efficiency at wide speed range, switched reluctance motor drive is considered promising as the propulsion power source of EV and HEV. However, development of the SRM drive control strategy for satisfying the requirement of regenerative braking in EV and HEV remains a research problem. In this paper, the distribution of the braking force of the vehicle is briefly explained in section 11. The distributionof the braking power and energy at different vehicle speed for a typical urban driving cycle is reviewed in section 1 1 An 1. artificial neural network based SRM drive control strategy for satisfying the requirement of regenerative braking in EV and HEV is presented in section IV.Energy recovery efficiency of the proposed SRM drive control strategy is also evaluated. Section V concludes the paper.

Reference[ 11 indicates that parallel-hybridized braking system with a fr relationship between electrical regenerative u braking force and mechanical friction braking force for an EV and HEV has a simple construction and control strategy. It is also effective to absorb most of the braking energy in typical urban driving. The

configuration of the braking system is shown in Fig.1. The regenerative braking only exists in the front wheels. The braking torque on the front wheels is the combination of regenerative braking torque produced by the electric braking system and the frictional braking torque produced by the mechanical braking system. The relationship of the regenerative and frictional braking forces on the front wheels is shown in Fig.2 for a 1500kg passenger car. In Fig. 2, Fbh, Fbrrand j represents the mechanical braking force on the front wheels, the electrical braking force on the front wheels, the braking force on the rear wheels, and the deceleration, respectively. Curve A, B, and C shows the ideal braking force distribution between the front wheels and the rear wheels, the practical braking force distribution between the front wheels and the rear wheels in case without regenerative braking system, and the practical braking force distribution between the front wheels and the rear wheels in case with regenerative braking system, respectively. When the deceleration of the vehicle is less than O.lg, only regenerative braking is invoked; otherwise both the regenerative and frictional braking system produce braking torque on the front wheels. The regenerative braking force at various decelerations is shown in Fig.3.Master Force

Fig.1 Configurationof the braking system

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电动汽车能量回收

(25mph), the braking force is almost constant. This speedbraking force characteristic well matches that of the electric motor. Fig.5 shows the distribution of braking energy along with the vehicle speed. It indicates that about 85% of recoverable braking energy is distributed in the speed range of higher than 15km/h (9.4mph). This fact implies that at very low speed, the energy recovery efficiency is not a concern for the electric braking system. At high speed, the electric motor should produce the required braking torque with high energy recovery efficiency. In fact, all the urban driving cycles share the same braking power (force) and energy distribution characteristics as mentioned above. Table 1 lists some key numbers for typical urban driving cycles.Braking force on the front wheels, kN,Fig.2 Braking forces on the front and rear wheels along

w. CONTROL STRATEGY OF SRM DRIVE FOR REGENERATIVEBRAKINGAs shown in Fig. 1, during braking, the driver applies a force on the braking pedal, which represents the desired deceleration. After receiving this braking signal from the force sensor on the pedal, the SRM drive system should produce corresponding braking torque according to the designed braking force distribution shown in Fig. 2.

Braking deceleration, gFig.3 Regenerative braking force along with the vehicle deceleration

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