In automobiles, Start-Stop system automatically shuts down and restarts the internal combustion engine to reduce the amount of time the engine spends idling, thereby reducing fuel consumption and emissions. Traditional Start-Stop system using the battery as the storage device, there are several weaknesses such as pool charge current, performance dropping in low temperature, short battery life and relatively high cost.
Ultracapacitor (UC) is a new kind of storage device surged in recent years. It has amount of advantages with respect to battery, such as high drain current charge, high performance in low temperature, long life span, etc. In the condition when automobile braking，the Start-Stop system will regenerate more energy if using the UC as the storage device in the Start-Stop system. Furthermore, assistant acceleration can be realized when using the UC in Start-Stop system. While, the voltage of UC is very unstable as charging and discharging, so it cannot be used directly in Start-Stop system.
In order to implement the UC in Start-Stop system, the purpose of my work is to design a bidirectional high power DC/DC converter. In this project, the main work is as follow:
Analyzing the system requirement in UC Start-Stop system, and determining the specific performance indicators.
Comparing several DC/DC converter topologies with experiment and determining the most suitable topology.
Designed a 2kW power DC/DC converter prototype, and proposing the hardware and software solution. This prototype uses the TMS320F28035 as the microcontroller unit and STP75NF75 as the power MOSFET.
Prototype’s debug and performance tests have been done. The tests’ result indicates: interleaved bidirectional DC/DC converter have 2kW peak and 1.6kW continuous power conversion capability; single voltage closed loop implemented in this prototype satisfied the voltage regulation requirement in steady state; boosting the output voltage when UC discharging and step down the voltage from input for charging the UC.