A Novel Modulated Model-Free Predictive Control for LC-Filtered Grid-Forming Inverters with Double-Difference Updating
Cungang Hu, Wanlun Xu, Zheng Yin, Tao Rui, Zhenbin Zhang, Geye Lu, Wenping Cao, Pinjia Zhang
Abstract
The parametric uncertainties have a great effect on the output voltage of grid-forming inverters when they are operated under conventional modulated model predictive control (MPC). To address this known issue, a novel modulated model-free predictive control (MFPC) is proposed in this article. First, a new look-up table (LUT) formed by capacitor voltage differences and inductor current differences of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -filter is designed for voltage-current predictions. Then, the state-space equations of different voltage vectors are established and reconstructed to update each voltage-current difference in the LUT per control period. Next, the duration of each voltage vector and the voltage prediction are calculated based on the updated voltage differences, so as to remove the impact of parameter variation on duration calculation and prediction calculation, enabling their robustness. Finally, the practicality of the proposed approach is demonstrated experimentally under both ideal and mismatched parameters. In comparison with conventional modulated MPC, the proposed modulated MFPC not only achieves comparable voltage performance, but also exhibits greater robustness.