DOI:10.35833/MPCE.2021.000417 Small-signal Stability Analysis and Improvement with Phase-shift Phase-locked Loop Based on Back Electromotive Force Observer for VSC-HVDC in Weak Grids Page view: 3        Net amount: 54 Author: Yongqing Meng1,Haibo Wang2,Ziyue Duan1,Feng Jia1,Zhengchun Du1,Xiuli Wang1 Author Affiliation: 1.the State Key Laboratory of Electrical Insulation and Power Equipment, Shaanxi Province Key Laboratory of Smart Grid, Xi’an Jiaotong University, Xi’an 710049, China;2.the State Grid Henan Electric Power Corporation Maintenance Company, Zhengzhou 450000, China Foundation: This work was supported by the National Natural Science Foundation of China (No. 51677142) and the National Key R&D Program of China (No. 2016YFB0900600). Abstract: Voltage source converter based high-voltage direct current (VSC-HVDC) transmission technology has been extensively employed in power systems with a high penetration of renewable energy resources. However, connecting a voltage source converter (VSC) to an AC weak grid may cause the converter system to become unstable. In this paper, a phase-shift phase-locked loop (PS-PLL) is proposed wherein a back electromotive force (BEMF) observer is added to the conventional phase-locked loop (PLL). The BEMF observer is used to observe the voltage of the infinite grid in the stationary αβ frame, which avoids the problem of inaccurate observations of the grid voltage in the dq frame that are caused by the output phase angle errors of the PLL. The VSC using the PS-PLL can operate as if it is facing a strong grid, thus enhancing the stability of the VSC-HVDC system. The proposed PS-PLL only needs to be properly modified on the basis of a traditional PLL, which makes it easy to implement. In addition, because it is difficult to obtain the exact impedance of the grid, the influence of short-circuit ratio (SCR) estimation errors on the performance of the PS-PLL is also studied. The effectiveness of the proposed PS-PLL is verified by the small-signal stability analysis and time-domain simulation. Keywords: Phase-locked loop (PLL) ; small-signal model ; stability improvement ; voltage source converter based high-voltage direct current (VSC-HVDC) ; weak grid Received:June 29, 2021               Online Time:2023/05/23 View Full Text       Download reader