Interactions analysis and quadrature voltage compensation control for stabilizing LCC-HVDC system with multiple STATCOMs

• Published in: International journal of electrical power & energy systems 2022-11, Vol.142, p.108251, Article 108251
• Main Authors: Xia, Haitao, Zhou, Xiaoping, Hong, Lerong, Guo, Jian, Liu, Yifeng, Yin, Hanhang
• Format: Article
• Language: English
• Subjects: LCC-HVDC; Quadrature voltage compensation control; Small-signal stability; STATCOM; Trajectories of dominant poles
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2022.108251

•The interaction paths among LCC, STATCOMs and weak AC network are presented. Then, the impacts of the interactions among them on the system damping characteristic and oscillation modes are further analyzed.•A stability-enhancing control called quadrature voltage compensation control is proposed, which is easy to implement and will not slow down response speed of STATCOM.•The physical explanations on the instability caused by increasing the number of online STATCOMs are given from two physical perspectives, which help in understanding such unstable phenomenon intuitively and easily. Instability may occur in LCC-HVDC system when multiple STATCOMs operate simultaneously at the inverter station. To deeply investigate this problem, firstly a structured linear model of LCC-HVDC system with STATCOMs is presented. Then, a single-input single-output (SISO) form of the model is obtained. Based on the movement of dominant poles (MODPs) of the SISO model, the interactions at the receiving end of the system are investigated. The results reveal that the interactions between LCC and STATCOMs mainly affect the high-frequency (HF) characteristics of the system. With the increase in the number of online STATCOMs, the negative effects of the interactions on the system HF stability gradually increase, while that on low-frequency (LF) stability become weaker. In order to improve such negative interactions, a quadrature voltage compensation control (QVCC) of STATCOM is proposed in this paper. This method introduces the q-axis AC voltage into the constant AC voltage control (CAVC). The theoretical analysis indicates that the QVCC can enhance the stability of the LCC-HVDC system with multiple STATCOMs, which is verified by the simulation results conducted in PSCAD/EMTDC. Finally, the intuitive and physical explanations on the mechanism of instability caused by increasing number of online STATCOMs are given from two perspectives.