基于k值调制三电平Boost PFC变换器的变占空比控制

Variable Duty Cycle Control Based on k-value Modulation for Three-level Boost PFC Converter

随着国家大力发展城市轨道交通,不间断电源(uninterruptible power supply,UPS)系统作为关键供电装置,具有重要的研究意义和价值。为了满足相关电能质量法规的要求,集成功率因数校正(power factor correction,PFC)输入级是保证轨道交通基础设施设备供电的UPS系统的重要要求。三电平Boost PFC在采用传统载波调制时,在一定的输入电压范围内输入电流始终为零,导致变换器功率因数校正效果较差。因此,提出一种基于k值调制的变占空比控制的方法,不仅可以解决高输入电压下传统载波调制存在的问题,且可进一步抑制输入电流的畸变从而提高输入电流波形质量。首先介绍了这种k值调制方法,分析了其原理以及k值对变换器功率因数和电感电流有效值的影响。在此基础上,结合电压平衡策略对k值进行优化,解决直流侧输出电容电压上下不均衡问题。最后,针对高输入电压下输入电流仍然严重畸变的问题,提出一种基于k值调制的可变占空比控制方法,分析了变占空比控制对变换器功率因数、输出功率、电压纹波以及电感电流峰值的影响。最后通过仿真和搭建小功率实验平台,验证了所提控制方法的正确性和有效性。

With the country’s vigorous development of urban rail transit,uninterruptible power supply(UPS)system has important research significance and value.In order to meet the requirements of the power quality regulations,the integra-tion of the power factor correction(PFC)input stage is an important requirement for UPS systems that guarantee the power supply.When the traditional carrier modulation is used,the input current of the three-level Boost PFC is always zero within a certain input voltage range,resulting in poor power factor.Therefore,this paper proposes a variable duty cycle control method based on k-value modulation,which can not only solve the problems of traditional carrier modula-tion at high input voltages,but also further suppress the distortion of input current.The k-value modulation method is first introduced,and the principle of k-value on the power factor of the converter and the effective value of the inductor current are analyzed.On this basis,the k value is optimized by combining the voltage balancing strategy to solve the problem of unbalanced voltage on the DC side.Finally,in order to solve the problem that the input current is seriously distorted at high input voltages,a variable duty cycle control method based on k-value modulation is proposed,and the influences of variable duty cycle control on the power factor,output power,voltage ripple and inductor current peak of the converter are analyzed.Finally,the correctness of the proposed methods is verified by simulation and the construction of a low-power experimental platform.