Development Of 3kW DC-DC Converter For Electric Bus Air Conditioning

The fossil fuels that are common in life are non-renewable and highly polluting,and people pay more and more attention to energy crisis and environmental protection issues.Electric vehicle technology is driven by clean energy and energy,which is widely used to alleviate the above problems.The electric vehicle realizes power supply to the vehicle equipment through the vehicle power.The vehicle power not only meets the wide output voltage range of the battery,but also meets the practical application requirements of power density,efficiency,volume and shelter.In order to meet the practical application requirements of a 3kW electric bus air conditioning system vehicle power,developed a power converter with a wide input voltage range is developed.In order to meet the needs of the wide input voltage range converter,a cascaded solution of Buck converter and LLC resonant converter is used.The intermediate bus is used to realize the cooperation between the two converters and realize the high efficiency and the wide input voltage range of the vehicle converter.The front stage uses a Buck converter structure to stabilize th e intermediate bus voltage at a fixed value by a pulse width modulation strategy.The rear stage of the vehicle power adopts the LLC resonant converter structure to obtain the desired power output through the pulse frequency modulation strategy.The paper analyzes the operating state of the inverter under different frequency modulations.The AC equivalent model of the LLC resonant converter is established.According to the equivalent circuit of the parallel machine,the output external characteristic curves of the two LLC modules of the latter stage are obtained,and the parallel current ripple and current sharing realization process are analyzed.The AC small-signal model is established by using the extended description function method,and the loop compensation design is developed.The simulation circuit model of the split resonant capacitor LLC is built in MATLAB to verify its no load performance,current sharing performance and dynamic response performance.Finally,an experimental prototype of 280~880V input and 27V/55 A output was built.The converter of performance was tested with soft start,module cut,parallel current sharing,and overcurrent protection.The experimental results show that the feasibility of this design and the validity of theoretical analysis.