Research On High Power Density Single-phase AC-DC Converter

Single-phase AC-DC converters are widely used.However,bus capacitor volume limits the increase in power density,and the dynamic response of PFC converter is poor due to loop bandwidth.Consequently,to improve power density and dynamic response,the research on control strategy and design method for PFC converter and active storage unit(ASU)is carried out in this thesis.The influence of reference distortion and the limitation of dynamic response are analyzed in PFC converter with traditional average current control.Then,this thesis proposes dual feedforward improved average control(DFIAC).In DFIAC,sinusoidal waveform reference generated by controller is used to reduce reference distortion;input and load feedforward branches are employed to improve dynamic response through theoretical deduction.Based on analysis of second harmonic energy,the relationship between input current of ASU and bus capacitance is established.According to the relationship,adaptive control strategy of ASU is proposed.By configuring bus capacitance and second harmonic current(SHC)absorption,the power density and efficiency are balanced.Because current reference of ASU is obtained by real-time calculation method,the control implementation of proposed adaptive control is simplified.For verifying the proposed DFIAC and adaptive control strategy,an 1.3kW three-channel interleaved Boost PFC prototype with ASU is designed and built in the laboratory.Experimental results show that DFIAC can significantly improve the dynamic response of PFC under input or load transient,speed up the phase-shedding speed,improve PF and THD of input current.On the condition of line frequency or load change,the adaptive control strategy can regulate the SHC absorption of ASU adaptively.Compared with the full absorption control,the efficiency is increased by 1.9%.Meanwhile,the volume of bus capacitor is reduced by 35% compared with the method that only capacitor is employed.According to the application requirements of pulse load,the thesis analyzes the harmonic current of DC bus in the single-phase AC-DC converter.Through the analysis,ASU is introduced to reduce DC bus capacitance,and the control method of ASU's input side is proposed.Also,the analysis of ASU control challenge and comparison of three nonlinear control strategies is implemented.Based on analysis and comparison,current open-loop control is adopted to meet the requirement of dynamic response.Furthermore,current open-loop control is extended and the theoretical duty cycle is derived.The key waveform of ASU is deduced to design ASU in single-phase AC-DC converter with pulse load.With consideration of phase-shift between input voltage and pulsed load,the ASU design method is proposed.A 360 W average power,1800 W peak power and electrolytic capacitor-less prototype is fabricated.The experiment results verify the proposed control strategy and design method.With the use of ASU,the total volume of energy storage component on the DC bus is reduced by 82.6%.Because SiC MOSFET has the benefits of short drive delay and low switching loss,SiC MOSFET is used to increase ASU's switching frequency for removing ferrite core of ASU's inductor and reducing volume.Compared with the 50 kHz IGBT ASU prototype,the volume of inductor is decreased by 54% in SiC prototype.