**6. Conclusions**

With more and more wind and solar energy plants connected to power systems, grid voltages are prone to be distorted. To keep grid frequency and phase tracking accuracy during distorted and even faulty conditions without degrading dynamic performance, a hybrid filter-based PLL is proposed. By using well designed MDSCs and MAFs with narrowed window length, time delay introduced by filtering stage is reduced. The hybrid filtering stage is incorporated with a QT1-PLL structure. A comprehensive experimental study is implemented to examine the effectiveness. Test cases concerning several conditions, which are easily triggered in high renewable penetration power systems, are carried out. Experimental results illustrate that the proposed PLL can provide a more satisfactory dynamic response than other traditional methods. The filtering capability and implementation complexity are also better than the conventional DSC-based PLLs.

**Author Contributions:** T.L. and J.Y. proposed the original idea and analyzed the experimental results. Y.L. built the experimental setup and performed the experiments. T.L. wrote the full manuscript. W.G. and B.H. supervised the experiments.

**Funding:** This work was supported by scientific research fund from Liaoning Electric Power Co., Ltd., State Grid Co. of China.

**Acknowledgments:** This work was with technical assistance from Liaoning Electric Power Co., Ltd., State Grid Co. of China.

**Conflicts of Interest:** The authors declare no conflict of interest.
