The Impact of High Voltage Direct Current Inverter Side on Subsynchronous Oscillation and Robust Control Design

Based on complex torque coefficient method and eigenvalue analysis, the subsynchronous oscillation(SSO) damping characteristics of an AC/DC parallel system were studied.The result shows that both AC bus strength and the control mode of inverter side have a remarkable effect on SSO damping. H_∞ robust control theory was used to design a supplementary subsynchronous damping controller (SSDC), the variation of system magnitude-frequency characteristics caused by the variation of inverter AC short-circuit impedance and the change of inverter control modes are considered as the uncertainty of system model, and the design of SSDC can be converted to a problem of mixed sensitivity in H_∞ robust control theory. The eigenvalue analysis and time-domain simulation show that the proposed SSDC has good robust performance.