扩大级联H桥光伏逆变器运行范围的控制策略

CONTROL STRATEGY FOR EXTENDING OPERATION RANG OF CASCADED H-BRIDGE PHOTOVOLTAIC INVERTER

受遮挡或组件表面灰尘等影响,若级联H桥光伏逆变器的H桥单元之间功率差异较大,则功率较大H桥模块可能会过调制,导致电网电流性能变差甚至系统不能正常运行。为此,提出一种改进型三次谐波补偿策略控制策略,能够在光伏组件之间输出功率严重不平衡的条件下确保系统单位功率因数运行,且并网电流的THD能够满足要求。此外,搭建Matlab/Simulink仿真模型以及数字样机系统,仿真结果和实验结果都验证了所提方法的有效性。

Affected by partial occlusion or surface dust of modules,if the power difference among H-bridge units of cascaded H-bridge(CHB)photovoltaic(PV)inverter is large,the H-bridges with large powers may be over-modulation,resulting in distorted grid current and that the system cannot operate normally.Based on this,an improved third harmonic compensation strategy is proposed,which can ensure that the system operates at unity power factor under the heavy power imbalance conditions and the THD of grid current can meet the requirements.In addition,the simulation based on Matlab/Simulink and the digital prototype are built.The simulation and experimental results all verify the effectiveness of the proposed method.