三相降压型PFC时延补偿的预测算法研究

Research on Prediction Algorithm to Compensate Time Delay of a Three-phase Buck-type PFC

在采用数字信号处理器(DSP)处理功率因数校正(PFC)电路控制环路信号时,主要有3个环节的延时:控制环路采样延时、DSP计算延时、PWM波产生延时。时延会减少环路带宽并降低环路稳定性,需加以补偿。以一种三相降压型PFC为例,讨论电流内环时延对电路稳定性的影响。研究线性预测和Smith预测两种时延补偿的预测算法,并通过仿真对两种方法进行对比。最后通过10 kW样机验证线性预测算法的鲁棒性和有效性。

Three main sources of time delays in the control loop for power factor correction（PFC） can be identified for the implementation on a digital signal processor（DSP）：the delay time due to the sampling of the control quantities,the one due to the calculation time of the DSP,the one due to the sample-and-hold function of the pulsewidth modulator.The delays can reduce the achievable control bandwidth or diminish the closed-loop system stability,thus it need to be compensated.Using the three-phase Buck-type PFC as an example,the influence of the time delay on the stability of the inner current control loop is discussed.The prediction algorithm of two prediction methods for time delay compensation of the linear prediction and the Smith prediction,are comparatively evaluated.The control performance and the effect of the delay times and the prediction methods are shown by simulation results.The robustness and effectiveness of the linear prediction is testified on a 10 kW prototype.