中文摘要：

从并网耦合端看进去的弱电网,通常被等效为阻抗与富含背景谐波的电压源相串联的形式。考虑到电网阻抗的存在,入网电流闭环控制与电网电压背景谐波前馈控制相互耦合,常见比例前馈控制会额外引入一条正反馈环路,恶化入网电流品质,甚至威胁系统稳定性。建立弱电网条件下并网逆变系统模型,明晰弱电网条件下大量谐波电流的形成机理。提出谐振前馈控制策略,衰减电网阻抗在谐振频率段的幅值响应,提高了系统的相角裕度,减小入网电流稳态误差。提出谐振前馈与谐波控制器相结合的两种控制方案,兼顾减小入网电流稳态误差与提高对弱电网感抗及其低次背景谐波的适应性。设计一台3k W并网逆变器原理样机,并通过实验验证提出控制策略的有效性。

英文摘要：

Weak grid is commonly seem as a voltage source which contains a gird impedance and background harmonics. The closed-loop control and harmonic voltage feedforward control are coupling with each other because of the existence of grid impedance. Proportion feedforward control strategy will introduce a positive feedback loop, which will worsen the quality of grid current, even threaten the stability of the system. This paper established the model of LCL-type grid-connected inverter, and elaborated the formation mechanism of resonant current under weak grid condition. The resonant feedforward control was proposed to attenuate the response of grid impedance during the resonant frequency band, and also to improve the phase margin and decrease the injected current steady state error. The proposed resonant feedforward control combined harmonic controller strategy was given, which could decrease the steady state error as well as improve the adaptability to grid impedance and low-order harmonics. A 3k W prototype is designed in the lab, and the proposed control strategy is verified by experiments.