Analysis of oscillation modes in a VSC-HVDC system

Harmonic instability may occur when a controlled voltage source converter interacts with the local power grid in a power system. In this paper, oscillation modes are analyzed in a voltage source converter based high voltage direct current (VSC-HVDC) system. The impedance models that are seen from the point of common coupling (PCC) for the rectifier ac system are also derived. The output impedance models consider the parameters of the inner current control loop and the outer power control loop. The obtained impedance models are then used to analysis the oscillation modes of the system. Simulation is built in the time-domain program (PSCAD/EMTDC) and the results validate the analysis.