输入电压不平衡时三相PFC整流器改进单周期控制策略研究

Modified One-Cycle Controlled Three-Phase PFC Rectifier under Unbalanced Input-Voltage Conditions

三相PFC变换器的单周期控制因其控制简单,无需乘法器及采样输入电压受到广泛重视。当输入不平衡时,三相PFC整流器直流侧输出电压将产生两倍于输入电源频率的脉动,该脉动信号经过传统单周期控制环路作用最终导致变换器输入电流产生较大幅值的三次谐波分量,影响输入电流品质。文章通过详细分析输入不平衡时,单周期控制的三相PFC整流器输入输出特性,提出在传统单周期控制策略中引入谐振控制器,从而可以有效抑制输入不平衡引起的单周期控制的三相PFC整流器输入电流中的三次谐波分量,进而大大改善输入电流品质。本文给出了谐振控制器的设计方法,建立了新的控制策略下的系统传递函数并分析了满足系统稳定性要求的设计准则。最后通过仿真与实验验证了所提出的改进单周期控制策略对于输入不平衡时,改善三相PFC输入电流品质的有效性。

The one-cycle control(OCC) strategy used in the PFC circuit is widely researched because of simple circuit and needless of the multiplier and sampling input voltage. The output voltage of three-phase PFC converter would contain low frequency ripple whose frequency is twice that of the rectifier's input source voltage under unbalanced input voltage conditions. This ripple signal would cause the input current containing a large amplitude of three-order harmonic component under the OCC control strategy and the THD(total harmonic distortion) of input currents would be increased. The input and output characteristic of OCC three-phase PFC converter is detailed analyzed in this paper, and the resonant is proposed to introduce in the conventional OCC control strategy for restraining the three-order harmonic component which exists in the input currents under the unbalanced input voltage conditions. The design of resonant and system control transfer function is also shown in the paper. At last, the effectiveness of proposed new control strategy to reduce the OCC three-phase PFC rectifier's input current THD under the unbalanced input voltage is verified by simulation and experimental results.