Micro-sector Analysis of Harmonic Instability for HVDC Systems Interconnected to Weak Grids

The increasing integration of Voltage Sourced Converter (VSC) HVDC systems and inverterbased resources (IBRs), such as offshore wind farms, has raised concerns regarding harmonic stability when connected to weak AC grids [1][2][3]. Reliable assessment is especially critical during operating conditions such as grid energisation. Impedance-based harmonic stability analysis described in [3][4][7] can rely on sector-based loci method [4][5][6], which may be overly conservative. When detailed AC network configuration data are available, case-by-case analysis of individual configurations offers higher accuracy, but it could become too complex with large numbers of configurations and frequency-dependent stability margins.