两级式单相逆变器二次纹波电流的抑制与动态特性的改善

Suppression of the Second Harmonic Current and Improvement of the Dynamic Performance for Two-stage Single-phase Inverters

两级式单相逆变器的瞬时输出功率以两倍输出频率脉动,使得前级DC-DC变换器和输入源产生二次纹波电流。前级DC-DC变换器采用电压电流双闭环控制能有效抑制二次纹波电流,但要求电压外环的截止频率很低,这将导致负载跳变时系统动态特性较差。从阻抗的角度出发,分析电感电流内环抑制前级DC-DC变换器和输入源中二次纹波电流的机理;提出在前级DC-DC变换器中引入含有两倍输出电压频率陷波器的负载电流前馈,该方法可在不增大二次纹波电流的情况下,显著改善负载跳变时的动态特性;最后,通过实验结果证明所提出的控制策略的有效性。

The instantaneous output power of two-stage single-phase inverter pulsates at twice the output frequency, generating the second harmonic current （SHC） in the front-end DC-DC converter and the input DC voltage source. Dual loop control strategy can suppress SHC effectively, but at the expense of a very low voltage loop crossover frequency, which will result in poor dynamic performance during load transient. This paper analyzes the mechanism how inner current loop suppresses the SHC from the viewpoint of output impedance, and then proposes a modified load current feed-forward with a double output frequency notch filter inserted, which could improve the dynamic performance without magnifying SHC. Finally, experimental results are given to verify the effectiveness of the proposed control strategy.