An ultracapacitor bank control system for an Electric Vehicle has been implemented. The purpose of this device is to allow higher accelerations and decelerations of the vehicle with minimal loss of energy, and minimal degradation of the main battery pack. The system uses an IGBT Buck-Boost converter, which is connected to the ultracapacitor bank at the Boost side, and to the main battery at the Buck side. The design has been optimized in weight and size, by using a water-cooled system for the power converter, and an aluminum inductor with air core. The ratings of the ultracapacitor are: nominal voltage: 300 Vdc; nominal current: 200 Adc; capacitance: 20 Farads. The amount of energy stored allows to have 40 kW of power during 20 seconds, which is enough to accelerate the vehicle without the help of the traction batteries. The vehicle uses a brushless dc motor with a nominal power of 32 kW, and a peak power of 53 kW. The control of the system measures the battery voltage, the battery state-of-charge, the car speed, the instantaneous currents in both the terminals (battery and ultracapacitor), and the actual voltage of the ultracapacitor. A microcomputer control based on a DSP manipulates all the variables and controls the PWM switching pattern of the IGBTs. When the car runs at high speeds, the control keeps the capacitor discharged. If the car is not running, the capacitor bank remains charged at full voltage. Medium speeds keep the ultracapacitors at medium voltages, to allow future accelerations or decelerations. The battery voltage is an indication of the car instantaneous situation. When the vehicle is accelerating, the battery voltage goes down, which is an indication for the control to take energy from the ultracapacitor. In the opposite situation (regenerative braking), the battery voltage goes up, and then the control needs to activate the Buck converter to store the kinetic energy of the vehicle inside the ultracapacitor. The measurement of the currents in both sides allows to keep the current levels inside maximum ratings. The battery state-of-charge is used to change the voltage level of the ultracapacitor at particular speeds. The car used for this experiment is a Chevrolet LUV truck, similar in shape and size to a Chevrolet S-10, which was converted to an electric vehicle at the Catholic University of Chile.
Tests results with regenerative braking based on ultracapacitors and a buck-boost converter
Versuchsergebnisse mit dem System 'regenerative Bremse, Ultrakapzität und Booster'
2001
12 Seiten, 11 Bilder, 6 Quellen
Conference paper
Storage medium
English
Tests Results with Regenerative Braking Based on Ultracapacitors and a Buck-Boost Converter
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