LCL型三电平并网逆变器定频滞环控制研究

Research on Constant Frequency Hysteresis Control of LCL Type Three-level Grid-connected Inverter

为增强并网逆变器控制性能,降低入网电流谐波含量,提出一种基于LCL型三电平逆变器的定频滞环控制。推导桥侧电流与网侧电流关系,通过对桥侧电流的直接控制进而间接控制网侧电流。将参考电压六边形区域分为12个小平行四边形区域,实现对相间误差电流的解耦控制。根据上一周期的开关时间和环宽,实时调整下一周期环宽以实现定频控制。此外,借助扩张状态观测器进行微分跟踪,完成参考电压矢量扇区判断和桥侧参考电流估计。最后通过仿真和半实物仿真对定频滞环控制策略进行验证。

In order to enhance the control performance of grid-connected inverter and reduce the harmonic content of grid-connected current,a constant frequency hysteresis control of LCL type three-level inverter is proposed.The deduction of the relationship between bridge side current and grid side current allows for indirect control of the grid side current by directly controlling the bridge side current.To achieve the decoupling control of the phase error current,the reference voltage hexagon region is divided into 12 small parallelogram regions.According to the switching time and hysteresis width of the previous cycle,the hysteresis width of the subsequent cycle is dynamically adjusted in order to achieve constant frequency control.In addition,differential tracking is performed using the extended state observer,which allows for the determination of the reference voltage vector sector and estimation of the bridge side reference current.Finally,the constant frequency hysteresis control strategy is validated through both simulation and semi-physical simulation.