Oscillation Damping Methods for VSC-HVDC Station using a Virtual Synchronous Machine

Application of virtual synchronous machine (VSM) is presented to damp LFOs as well as improve frequency stability of grid for a VSC based HVDC station connected to power grid. When acting as VSM, VSC-HVDC station will behave similar to the synchronous generator and can influence LFOs occurring in power system. VSC allows flexibility of control to allow design of different control methods to damp power and frequency oscillations. VSM damping strategies studied involve damping either torque or voltage amplitude. Damping method using actual grid frequency and frequency tracking ability of SRF-PLL is use for grid. Methods based on frequency derivative, power forward term and improved damping method based on grid voltage information are also presented in the paper. Damping equations, modelling and MATLAB/Simulink based simulation results with different values of damping coefficient validate the feasibility of application of these damping methods.