Simulation for Motor/Battery Working with High Efficiency of HEV Regenerative Braking System

　　Simulation for Motor/Battery Working with High Efficiency of HEV Regenerative Braking System
　　Regenerative braking (energy recovery braking) is an important working mode for HEV, which has a direct impact on fuel economy, emission and running security. During deceleration or braking, based on assuring vehicle braking performance, regenerative braking system can turn its electric motor into an electric generator to invert vehicle kinetic energy or potential energy into electrical energy stored into battery for recovering energy, and also supplies the whole braking forces or partial braking forces at the same time. Regenerative braking not only realizes the deceleration and braking, but also reduces fuel consumption and pollutant emission.For HEV NiMH battery, the conventional charging means aren’t fit for the characteristic of regenerative braking. Generally speaking, braking time is http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php so short that HEV can only reclaim quite limited energy using the conventional charging means and can’t exert the quick charging potential of NiMH battery. Therefore, it is necessary to research the receptivity of NiMH battery during quick charging process, and offer theoretical basis for improving the energy recovery rate further.In regenerative braking process, the braking energy recovery rate have close connection with the working condition of motor/battery. It should be assured that the joint efficiency of motor and battery is maximal in regenerative braking control strategy. So it is important to research the joint efficiency characteristic of motor and battery in regenerative braking process, and control them working efficient for improving braking energy recovery rate.Focus on the CVT Hybrid Electric Vehicle with ISG, deeply theoretical researching and experiment performance evaluation have been completed in this paper.
　　The main results are shown as follows:1. Based on analyzing NiMH battery charging characteristic, quick charging theory and the feature of regenerative braking, an optimal charging means is proposed. Through this mean, the max charge current is obtained, which can assure that the temperature rise of battery don’t exceed the specify value, and the charging receptivity of battery is determined. Based on this charging mean, the regenerative braking control strategy is proposed, finally the quick charging model of battery is modeled and simulated, whose results indicate that it can be assured to recover the braking energy maximally and charge the battery quickly and safely. 2. The operation characteristic of BLDC is analyzed. According to the performance experiment data of HEV ISG BLDC, combined with the working principle of BLDC, the mathematic model of BLDC is established. The dynamic response curve of BLDC model under specific torque aim signal is simulated and analyzed which verifies the exactitude of this BLDC model.3. According to the characteristic of the battery quick charging http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php and ISG motor generating with high efficiency, the changing rules of motor generating and battery charging efficiency are analyzed, and the joint efficiency model of motor/battery is established by which synthesis efficiency curves of battery and motor at different inputs are calculated.
　　Finally the optimal joint working curve of motor/battery is assured which establishes a basis for the regenerative braking control strategy and the performance optimum of regenerative braking system.4. Models of the parts of regenerative braking system in Matlab/Simulink environment are built. These models are simulated under the typical braking modes and the typical city driving cycles, while these models are simulated in the condition of motor/battery working together with high efficiency and motor working lonely with high efficiency. The results indicate that the braking distance and the duration of braking, using the regenerative braking control strategy and motor control strategy in this paper, can satisfy with the requirement of vehicle braking safety. Compared with the regenerative braking strategy considering the motor working lonely with high efficiency, the regenerative braking strategy considering motor/battery working together with high efficiency can increase the Ball Neodymium Magnets recovery rate further.5. According to the system configuration and parameters of CVT Hybrid Electric Vehicle with ISG, the test platform of HILS for regenerative braking system is built, and control parameters for braking system is adjusted on line. Based on the HILS, braking performance experiment for the test system is done, which establishes a basis for perfection and optimum of hybrid electric regenerative braking system.