并网光伏逆变器鲁棒分数阶滑模控制设计

Robust fractional-order sliding-mode control design of grid-connected photovoltaic inverters

本文设计了一款基于扰动观测器的鲁棒分数阶滑模控制(POFO–SMC)来实现光伏逆变器的最大功率跟踪(MPPT).首先,将光伏逆变器的非线性、参数不确定性以及未建模动态聚合成一个扰动,并通过扰动观测器对其进行在线估计.随后,采用分数阶滑模控制(FOSMC)对该扰动估计进行实时完全补偿,从而实现不同工况下全局一致的控制性能.同时,POFO–SMC采用扰动实时估计而非传统滑模控制(SMC)中所使用的扰动上限值进行补偿,因此可有效解决传统SMC过于保守的缺点,使得控制成本更为合理.最后,POFO–SMC无需精确的系统模型,仅需测量光伏逆变器的q轴电流和直流侧电压,因此易于硬件实现.本文进行了两个算例的研究,即光照强度变化和电网电压跌落.仿真结果表明,与传统PI控制、反馈线性化控制(FLC)、SMC和FOSMC相比,POFO–SMC在各类工况下均具有最好的动态特性及最高的鲁棒性.基于dSpace的硬件在环实验(HIL)验证了其硬件可行性.

In this paper,a perturbation observer based robust fractional-order sliding mode control(POFO–SMC)is designed to realize the maximum power point tracking(MPPT)of photovoltaic(PV)inverters.Firstly,the nonlinearities,parameter uncertainties and unmodelled dynamics of the PV inverter are aggregated into a perturbation and then estimated online by the perturbation observer.Moreover,the perturbation estimate is fully compensated in the real-time by fractional-order sliding-mode control(FOSMC),such that a global consistent control performance can be achieved under different operation conditions.In addition,POFO–SMC replaces the upper bound of perturbation by its real-time estimation,thus the over-conservativeness of SMC could be avoided.Lastly,POFO–SMC does not require an accurate PV system model while only the measurement of q-axis current and direct current(DC)voltage is needed,which is easy to be implemented in practice.Two case studies are carried out,e.g.,solar irradiation variation and power grid voltage drop.Simulation results verify that the POFO–SMC outperforms the conventional PI control,feedback linearization control(FLC),SMC and FOSMC under different operation conditions.A hardware-in-loop(HIL)test based on dSpace is undertaken to validate the implementation feasibility of the proposed approach.