一种基于谐波补偿的级联H桥光伏并网逆变器控制策略

Control strategy for cascaded H-bridge photovoltaic grid-connected inverter based on harmonic compensation

级联H桥光伏并网逆变器受输入功率的影响,功率大的单元易出现过调制现象,进而诱发并网电流畸变。为此提出了一种新型谐波补偿控制策略。通过引入适当的3、5次谐波至过调制单元中,以保持其调制波峰值始终为1;同时引入反向的谐波至剩余各单元中,以抵消过调制单元中引入的谐波成分。与传统3次谐波补偿法相比,所提控制策略使逆变器过调制能力提高了33.55%,进一步扩宽了其稳定域运行范围。在各单元输入功率极度不平衡时,系统仍可稳定运行。通过仿真和实验证明了所提控制策略的可行性和有效性。

Affected by the input power,the units with higher power in the cascaded H-bridge photovoltaic grid-connected inverter may over-modulate,thereby resulting in grid-connected current distortion.Concerning this issue,a novel harmonic compensation control strategy is proposed.By introducing the appropriate third and fifth harmonics into the over-modulated unit,the peak value of its modulation wave is always 1.At the same time,the reverse harmonics are introduced to the remaining units to counteract the effects of harmonics.Compared with the traditional third-harmonic compensation strategy,the proposed control strategy increases the inverter’s over-modulation capability by 33.55%,further expanding its stability domain operating range.When the input power of each unit is severely unbalanced,the system still operates steadily.Finally,simulations and experiments prove the effectiveness and feasibility of the proposed control strategy.