摘要
三段式不对称空间矢量脉宽调制(SVPWM)可以有效地抑制三相Buck整流器扇区切换引起的不规则直流链电流纹波,从而降低输入电流总谐波畸变率(THD)。根据矢量作用顺序的不同,可组成多种不对称脉宽调制(PWM)序列,通常认为它们具有等效的矢量合成效果。然而,在相同输入条件、不同的不对称PWM序列的直流链电流纹波特性存在显著差异,进而影响输入电流THD。该文分析了两种不对称PWM调制序列的直流链电流纹波特性,得出对应不同输入电压相序的最优不对称PWM序列。通过相序自适应调制策略,对随机接入的输入电压相序均可实现低直流链电流纹波和低输入电流THD,有效解决了不对称调制的不对称性带来的电流畸变问题。最后设计了一台1 kW的实验样机,验证了理论分析的正确性。
The input current total harmonic distortion(THD)of a three-phase buck rectifier is closely related to the modulation strategy.Space vector pulse width modulation(SVPWM)is widely used in three-phase buck rectifiers due to its simple digital implementation and flexible strategy.The three-segment asymmetric SVPWM has two different PWM sequences,which are generally considered to have equivalent vector synthesis effects.However,due to the influence of parasitic capacitances,the order of vector action affects the harmonic composition.Under the same input voltage conditions,these two asymmetric PWM sequences exhibit different DC chain current ripple characteristics.In addition,when the phase sequence of the input voltage changes,the corresponding DC chain current ripple changes accordingly,which leads to significant differences in the input currents of the three-phase buck rectifier.To deal with above issues,this paper proposes a phase sequence adaptive modulation strategy,which suppresses the DC chain current ripple and input current distortion caused by the asymmetry of the modulation technology.This paper analyzes the operating modes of the two asymmetric PWM sequences in sector 12 when the input voltage is in positive phase sequence,the changes of the difference between the upper and lower inductor currents,the charging and discharging conditions of the parasitic capacitances C_(ps)and C_(ns),and derives the formula for the input current.The analysis and derivation results show that there are significant differences in the DC chain current ripple characteristics of these two asymmetric PWM sequences and their impacts on the input current.When the input voltage is in positive phase sequence,compared with the asymmetric PWM sequence 1,the DC chain current and its ripple of the three-phase buck rectifier with the asymmetric PWM sequence 2 increase significantly.When the input voltage is in negative phase sequence,the asymmetric PWM sequence 2 has more advantages.For asymmetric modulation technology,the DC chain current and its ripple of the three-phase Buck rectifier are significantly affected by the phase sequence of the input voltage,and the change of phase sequence will cause obvious distortion of the input current.This paper optimizes the phase shift in the digital implementation process and proposes a phase sequence adaptive modulation strategy to realize the logical matching between the input voltage phase sequence and the PWM sequence.To verify the analysis results,a 1 kW experimental prototype is designed.The experimental results show that when the asymmetric PWM sequence 1 modulation strategy is adopted,the input current THD of the three-phase buck rectifier is low(1.2%)under positive phase sequence input,while the input current is obviously distorted with a THD of 3.3%under negative phase sequence input.With the proposed phase sequence adaptive modulation strategy,both the DC chain current ripple and input current of the three-phase buck rectifier have no obvious distortion under either positive or negative phase sequence input,and the input current THD is low(1.2%)in both cases.In addition,when the input voltage phase sequence is unknown,the system can judge the input voltage phase sequence according to whether the sector is increasing and change the PWM sequence accordingly to achieve adaptation,thus suppressing the DC chain current ripple and input current distortion.
作者
陈欣
谢飞
许建平
Chen Xin;Xie Fei;Xu Jianping(Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle Ministry of Education School of Electrical Engineering Southwest Jiaotong University,Chengdu 610031 China;Chengdu Siwei Power Electronic Technology Co.Ltd,Chengdu 610065 China)
出处
《电工技术学报》
北大核心
2026年第3期738-748,共11页
Transactions of China Electrotechnical Society
基金
国家自然科学基金资助项目(52477198)。
关键词
三相Buck整流器
不对称调制
直流链电流纹波
输入电流畸变
输入相序
Three-phase Buck rectifier
asymmetric modulation
DC chain current ripple
input current distortion
input phase sequence
