The Effect ofHVDC Inverter on Subsynchronous Oscillation and Damping Controller Design

In general, it is considered that improper control parameters of HVDC rectifier station would have negative effects on subsynchronous oscillation (SSO) characteristics of turbine generator sets close to rectifier station while the inverter station has little effect on it. This paper shows that in AC/DC parallel system, both AC bus strength and the control mode of inverter side also have remarkable effect on SSO, which should be considered during the design of supplementary subsynchronous damping controller (SSDC). In this paper, H_infin robust control theory is used to design SSDC and the effect of inverter station on SSO is considered as model uncertainty. In addition, PSS including a SSO filter is used to improve the damping of electromechanical mode. Both eigenvalue analysis and the time domain simulation show that the proposed SSDC and PSS can provide satisfactory SSO damping under a wide variety of operating conditions