电力电子技术

在三相并网逆变器中,无差拍控制简单实用、动态响应速度快,但是难以实现零稳态误差控制,并且会导致并网电流谐波含量增大。针对以上问题,利用比例谐振(PR)控制器对于特定频率谐波抑制能力强的优势,采用无差拍控制器复合PR控制器控制并网电流,可以在保证动态响应速度的前提下大大减小系统稳态误差。首先建立三相四桥臂并网逆变器模型,然后利用电流权重控制方法将系统降为一阶系统。根据内模原理设计了PR控制器,对高次谐波进行谐振补偿,降低了并网电流总谐波畸变率(THD)含量。实验结果表明所提控制策略可以取得较快的动态响应速度和较好的稳态性能。

In the three-phase grid-connected inverter,the deadbeat control is very simple,practical and has fast dynamic response,but it s difficult to achieve zero steady-state error control,and it will lead to the increase of harmonic content of grid-connected current.Aiming at the above problems,the advantage that proportional resonance(PR) controller has a very strong suppression ability for the specified frequency harmonic is used,and the grid-connected current is controlled by a deadbeat controller combined with a PR controller,the steady-state error of the system will be greatly reduced on the premise of ensuring the dynamic response speed.Firstly,a three-phase four-leg grid-connected inverter model is established,then the current weight control method is used to reduce the system to a first-order system.According to the principle of internal mode,a PR controller is designed.Resonance compensation is carried out for the multiple harmonics to reduce total harmonic distortion(THD) content of grid-connected current.Experimental results show that the proposed control strategy can achieve faster dynamic response speed and better steady-state performance.