一种Boost PFC电路改进VOT控制策略研究

Research on an Improved VOT Control Strategy of Boost PFC Circuit

为了解决恒定导通时间(COT)控制策略下负向谐振电流和输入滤波电容引起功率因数(PF)和总谐波失真(THD)性能变差的问题,提出一种改进变导通时间(VOT)的控制策略。通过自适应增加导通时间以抵消负向谐振电流,减小相位差,使电感平均电流在工频周期内接近正弦波,并分析其工作原理与控制过程。结合主电路设计关键参数,研制1台额定功率320 W的样机,进行COT控制策略和改进VOT控制策略的对比实验。计算机仿真和实验结果表明,改进VOT控制策略在265 V高电压输入20%负载工作时,PF值由0.726提升至0.801,THD由27.92%降低至18.4%;在40%~100%负载时满足PF>0.9、THD<15%的要求,验证所提控制策略的有效性。

In order to solve the problem of poor performance of PF and THD caused by negative resonant current and input filter capacitor under constant on time(COT)control strategy,an improved variable on time(VOT)control strategy is proposed.The operating principle and operating process of making the average inductance current approach to the sine wave in the power frequency cycle by adaptively increasing the conduction time to offset the negative resonant current and reducing the phase difference are analyzed in detail.The main circuit is combined for key parameter design,a prototype with rated power of 320 W is developed.The comparative experiment of COT control strategy and improved VOT control strategy is carried out.The computer simulation and experimental results show that the PF of the improved VOT control strategy is increased from 0.726 to 0.801,and the THD is reduced from 27.92%to 18.4%when the 265 V high voltage input 20%load is working.At 40%~100%load,the requirements of PF>0.9 and THD<15%are met,which verifies the effectiveness of the proposed control strategy.