Interleaved Boost PFC Converter Without Electrolytic Capacitor

With the wide application of switching power supply,people pay more attention to the power quality.In order to reduce the current harmonics,improve the power quality and improve the grid side power factor,active power factor correction(APFC)technology is proposed.In many APFC topologies,Boost converter is simple in structure and easy to control,but it has the problems of large input current ripple and low power level,so its application field is limited.The Boost circuit with interleaved parallel structure can increase the equivalent switching frequency,improve the power level and reduce the input current ripple.Due to the high failure rate,short service life and limited application environment,the removal of electrolytic capacitors has become a research trend.Therefore,this paper focuses on the problem of de electrolytic capacitor,focusing on the research of interleaved Boost PFC.Secondly,in order to remove the electrolytic capacitor,the Buck bidirectional Buck/ Boost decoupling circuit is studied,and the AC current control strategy under DC steady state is proposed.The topology of Buck bidirectional Buck / Boost decoupling circuit is given,and its working principle is analyzed,which is to absorb the reactive power of DC bus by increasing the fluctuation of decoupling capacitor voltage.Then the parameters of the decoupling circuit are designed,the model is established,and the PI control is used to simulate it.In order to eliminate the static error of PI control,this paper proposes the AC current control strategy of Buck bidirectional Buck / Boost decoupling circuit under DC steady state.On this basis,modern control algorithm is used to improve the performance.Then this paper studies the cooperative control of PFC system without electrolytic capacitor,and proposes a load switching control strategy based on load power feedforward.This paper studies the cooperative control of PFC system without electrolytic capacitor under different types of loads,including resistive load,single-phase inverter load and multi-phase inverter load.In order to solve the problems of DC bus voltage drop and long steady-state time in the process of load switching,a load switching control strategy based on load power feedforward is proposed.Finally,an experimental platform is built and verified.First,the hardware selection and software design.Experiments on interleaved PFC Converters with different electrolytic capacitors are carried out to verify the function of electrolytic capacitors in absorbing reactive power in steady state.The effectiveness of decoupling circuit and alternating current control strategy is verified by the experiment of PFC system without electrolytic capacitor.