Study On Cause Of Subsynchronous Oscillation Caused By HVDC And The Integrated Damping Control Strategy

Under the background of the unbalanced distribution of energy resources and electrical load and the trend of the interlink of power system, the High-Voltage Direct-Current(HVDC) transmission technology has been widely applied. As a result, an increasing attention is paid to the Subsynchronous Oscillation (SSO) caused by HVDC. For the security operation of the steam turbine unit, the study of the countermeasures of the SSO caused by HVDC is of great significance.Focusing on the study of the Countermeasures of the SSO caused by HVDC, the inhibiting and the design principle of the supplementary subsynchronous damping controller (SSDC) on the grid side is discussed. On the basis of the study of the control loop of SSDC, theoretical derivation of electric damping is proposed. The affecting factors of the damping effect are also analyzed. Basing on the typical HVDC with series compensation system, wideband SSDC is designed and the effectiveness of which is verified by time-domain simulation method.On the generator side, the inhibiting and the design principle of the supplementary excitation damping controller (SEDC) and the static var generator(SVG) are discussed. On the basis of the study of the control loop of SEDC and SVG, theoretical derivation of electric damping is proposed respectively. The affecting factors of the damping effect are also analyzed. Basing on the same system, SEDC and SVG are designed and the effectiveness of which are verified by time-domain simulation method.Considering that the damping ability of the countermeasures is insufficient which may happen in actual application, a strategy is proposed to damp the SSO caused by HVDC by using SSDC on the grid side and SEDC and SVG on the generator side, the mechanism is also analyzed. Basing on the theoretical derivation, an equivalent index on damping capacity is proposed, which is verified by time-domain simulation method.