基于延时补偿的LCL型并网逆变器鲁棒控制策略

ROBUST CONTROL STRATEGY OF LCL-TYPE GRID-CONNECTED INVERTER BASED ON DELAY COMPENSATION

在LCL型并网逆变器控制中,为减小控制延时对有源阻尼等效虚拟阻抗的影响,提出一种基于有源阻尼内环级联超前环节的延时补偿改进控制策略。首先,建立考虑延时的数学模型,分析传统逆变侧电流反馈有源阻尼降低系统低频增益的问题,总结了延时对等效虚拟阻抗正阻尼区分布的影响规律。然后,通过在阻尼内环设计合适的增益函数,消除低频增益降低的影响;提出一种级联超前环节的延时补偿方案,对延时引入的相位滞后进行补偿,将等效正阻尼区扩展到(0,0.48fs),有效改善有源阻尼效果,显著提高了系统的稳定性和鲁棒性。最后,仿真和实验结果验证了所提方案的可行性。

In order to reduce the influence of control delay on active damped equivalent virtual impedance in LCL grid-connected inverter control,an improved control strategy based on active damped inner loop cascaded lead is proposed in this paper.Firstly,a mathematical model including the delay is established,which shows that the time delay will damage the positive frequency range of virtual impedance,threatening the stability of the inverter.Meanwhile,the mechanism of traditional inverter-side current feedback active damping lowering the low-frequency gain is analyzed.Then,an improved delay compensation scheme with a cascaded leading compensator is proposed to widen the stability region.The low-frequency gain reduction can be improved by designing a suitable gain function in the damping loop.Through the proposed delay compensation scheme,the equivalent positive damping frequency range extends to(0,0.48fs).An expected active damping performance and strong stability of the system is obtained.Simulation and experimental results verified the validity of the proposed strategy.