High-Frequency Stability Analysis and Impedance Optimization for an MMC-HVDC Integrated System Considering Delay Effects

• Published in: IEEE journal on emerging and selected topics in circuits and systems Vol. 12; no. 1; pp. 59 - 72
• Main Authors: Huang, Tong, Yang, Fan, Zhang, Donghui, Chen, Xin
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.03.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Control stability; Controllers; Converters; Current control; Damping; Delay; Delay effects; Delays; Frequency analysis; Frequency control; Frequency ranges; Frequency stability; high voltage direct current transmission system (HVDC); Impedance; impedance analysis method; modular multilevel converter (MMC); Optimization; Parameters; Resonant frequency; Stability analysis
• ISSN: 2156-3357; 2156-3365
• DOI: 10.1109/JETCAS.2022.3147197

Delay generated by digital control will inevitably lead to negative damping of Modular Multilevel Converter (MMC), which also has significant impacts on the high-frequency stability of the integrated system. Controller parameter optimization is an effectively method for MMC impedance optimization and high-frequency resonance suppression. This paper firstly extends the sequence impedance model of MMC by considering delay effects, and analyzes the high-frequency impedance characteristics as well as the stability of the MMC integrated system. Then, the effect of delay on the frequency range of MMC shows negative damping can be analyzed quantitatively by a vector diagram. Based on the quantified frequency range, the boundary of controller parameters can be derived. Finally, an MMC impedance optimization method that traversal all the values within the derived parameter boundaries to obtain the optimal controller parameters that maximize the phase margin of the system.