Stability analysis of virtual synchronous generator control in a high-voltage DC transmission system using impedance-based method

Abstract

Numerous distributed generators (DGs), which often include renewable energy sources, are connected to modern power grids through grid-connected inverters. Conventional linear model approximation methods may not be sufficient to accurately analyze the dynamic response of DGs due to the harmonics and nonlinear distortions generated by power-electronic devices. Therefore, an impedance-based stability analysis method has been adopted and applied in high-voltage direct current (HVDC) power transmission systems as a practical data-driven alternative to the linear model approximation method. However, the presence of multiple AC/DC converters and the non-negligible ground capacitance of DC transmission lines increases the difficulty of analyzing the entire HVDC system. Previous studies have mostly focused on the stability of either the generator-side system or the load-side AC system. In this study, impedance-based analyses were performed on the generator-side AC system, DC transmission line, and load-side AC system to evaluate the entire HVDC system when the generator-side AC system was weak. Additionally, an advanced inverter control method called the virtual synchronous generator (VSG) control method, which can result in grid stabilizing effects, was introduced to the load-side AC system. The analysis results demonstrate that the VSG control significantly enhances the stability of HVDC transmission systems as compared with the conventional power control methods.

Keywords

• HVDC transmission
• Modular multilevel converter
• Marginally stable
• Offshore wind farm
• Virtual synchronous generator