Research And Design Of Digital Average Current Control Low Surge Start Interleaved PFC

Power electronic devices are widely used to bring convenience to industrial production and daily life,but also bring harmonic pollution problems.Boost PFC converter is widely used to solve the problem of harmonic pollution due to its simple structure,easy control and wide input voltage range.However,there are some problems in practical application,such as large input inrush current,large device current stress and large input current ripple.Under the same power level,the interleaved Boost PFC topology has the advantages of reducing the current stress of the device and the input current ripple,but it can not suppress the input inrush current;at present,some commonly used input surge current suppression schemes have problems such as insignificant suppression effect in high and low temperature environments,low reliability of repeated startup,and additional loss.Therefore,this paper focuses on the problem of suppressing the input surge current,and studies the two-phase interleaved Boost PFC converter as the carrier.Firstly,based on the analysis of the working mode and circuit characteristics of the two-phase interleaved Boost PFC converter in CCM mode,the power parameters of the converter are designed,the core material of the power inductor and the number of turns of the tuning inductor are determined.The state-space averaging method is used to model the small signal of the converter,and the power level transfer function is obtained.Based on the average current control strategy with feedforward voltage,a single-cycle phase current sharing control link is added,and two independent current loop controllers are used to control each phase switch tube to achieve phase current equalization.The designed converter is simulated,and the power factor correction and phase current balance function of the converter are verified.Secondly,on the basis of analyzing the causes of surge current,a thyristor surge current suppression circuit based on phase-controlled rectifier bridge is proposed.The topology and working principle are analyzed in detail,and the working sequence of the circuit and the conduction interval of the thyristor are obtained.The charging process of the output filter capacitor is theoretically analyzed,and the relationship between the voltage step value of the output filter capacitor terminal voltage,the inrush current and the start-up time is obtained.A segmented constant inrush current start-up control strategy is developed.The output voltage is partitioned,and different voltage step values are set in different voltage level intervals.According to the voltage step value,the conduction angle of the thyristor is gradually adjusted to realize the pulse charging of the output filter capacitor and suppress the input surge current.The converter with thyristor surge suppression circuit is simulated to verify the feasibility of the circuit and the effectiveness of the control strategy.Thirdly,Again,the converter hardware and software design.In terms of hardware design,the circuit parameters are calculated according to the specific design indexes of the converter,and the domestic devices are selected.The minimum system of the main control chip and its peripheral circuit,auxiliary power supply,sampling and protection circuit and drive circuit are designed.In terms of software design,the main program,interrupt service subroutine and inductor current sampling program are designed and the program flow chart is given.Finally,a 1.8 k W experimental prototype was developed and verified by experiments.The experimental waveforms and data are analyzed by using the test platform.The experimental results verify the correctness of the theoretical analysis and the effectiveness of the control strategy.